JP5656710B2 - Mobile hearth furnace and screw conveyor replacement method - Google Patents

Description

  The present invention relates to a moving hearth furnace such as a rotary hearth furnace and a method for replacing a screw conveyor.

  A rotary hearth furnace, which is one of mobile hearth furnaces, is a furnace that supplies a workpiece to the hearth while rotating the hearth in one direction and continuously heats the workpiece. In the technical field such as iron making, a rotary hearth furnace is used as a reducing furnace for obtaining reduced added iron (DRI) with high added value by heating and reducing iron ore, iron making waste, and the like (for example, Patent Document 1). reference).

  FIG. 1 is a perspective view showing a schematic structure of a rotary hearth furnace. As shown in FIG. 1, the rotary hearth furnace 1 has a hearth 2 whose planar shape is formed in an annular shape (doughnut shape), for example, and the hearth 2 is rotated in one direction in a horizontal plane by a driving device (not shown). To do. The upper surface side of the hearth 2 is surrounded by a furnace body 3 having a rectangular cross-sectional shape, for example, and a space (inner furnace space) 31 surrounded by the furnace body 3 becomes a processing space for heating an object to be processed. Therefore, a plurality of heating devices 32 for heating the inside of the furnace space 31 are arranged on the outer peripheral side and inner peripheral side surfaces of the furnace body 3. The heating device 32 is, for example, a burner, and when used as a reduction furnace, the combustion conditions and the amount of air blown into the furnace are adjusted so that a reduction combustion region is formed in the furnace space 31. Air or the like blown into the furnace is discharged outside the furnace through an exhaust duct 33 connected to the upper surface of the furnace body 3.

  On the upper surface of the furnace body 3, a supply device 4 for dropping and supplying an object to be processed onto the hearth is disposed. The object to be processed is, for example, a pellet or briquette formed by mixing a carbonaceous material with iron ore, iron making waste, or the like. As the supply device 4, for example, a vibration-type supply device 4 is used. A screw conveyor 5 for discharging the heat-treated object is disposed along the width direction of the hearth 2 in the furnace body 3. The screw conveyor 5 conveys the object to be processed on the hearth to the outer peripheral side of the furnace by rotating screw blades, and drops and supplies it to the recovery device 61 through the discharge port 6.

  In the case of the rotary hearth furnace 1, the screw conveyor 5 exposed to a high temperature atmosphere in the furnace is likely to be deteriorated. Therefore, the screw conveyor 5 generally has a water-cooled structure inside the rotating shaft and uses screw blades made of a material having heat resistance and wear resistance. However, it is difficult to completely prevent the screw conveyor 5 from deteriorating, and work for inspecting and replacing the screw conveyor 5 is required. Depending on the size of the furnace, it is not an easy task to replace the screw conveyor 5 exceeding at least several hundred kg.

  In Patent Document 2, openings larger than the screw blades are formed on both sides of the furnace body 3, the openings are closed with a lid when the heat treatment is performed, and the lid is removed when the screw conveyor 5 is replaced. Thus, a rotary hearth furnace capable of “extracting” and “incorporating” the screw conveyor 5 is disclosed.

  However, in the structure of Patent Document 2, there is a concern that high temperature gas in the furnace may be ejected outside the furnace when the lid is removed, which is dangerous for workers. Therefore, in order to perform the replacement work safely, it is necessary to extinguish the burner and cool the furnace temperature to a temperature that does not hinder the work. Cooling the furnace each time the screw conveyor 5 is inspected or replaced has the following problems.

  That is, empirically, when the burner is extinguished at about 1300 ° C., the temperature suddenly decreases at a rate of about 150 to 200 ° C./h, and cracks and the like often occur in the refractory constituting the furnace body. Therefore, in order to cool the furnace while preventing damage to the furnace body, it is necessary to cool it over a long time at a speed of about 50 to 80 ° C./h. Similarly, when the apparatus is restarted after the screw conveyor 5 is replaced, it is necessary to heat it over a long period of time.

  Therefore, it may take about 2.5 to 3 days from empirically cooling the furnace from about 1300 ° C. to replacing the screw conveyor 5 and then raising the temperature again and starting the operation. Thus, in the conventional rotary hearth furnace 1, in addition to the difficulty of replacing the screw conveyor 5, it takes a long time to cool and raise the temperature of the furnace when replacing the screw conveyor 5, and the operation rate is lowered. There is a problem of inviting.

No. 2007-116878 JP 2001-304766 A

  That is, the present invention has been made in order to solve the above-mentioned problems mentioned as an example, and the purpose thereof is a mobile hearth furnace capable of safely and easily replacing the screw conveyor. It is in providing the replacement method of a screw conveyor.

  Another object of the present invention is to provide a mobile hearth furnace and a screw conveyor replacement method that can replace the screw conveyor without cooling the inside of the furnace to near room temperature. Desirably, the screw conveyor can be replaced without stopping a heating device such as a burner.

  A mobile hearth furnace according to the present invention includes a mobile hearth, a furnace body that forms a furnace space on the upper surface side of the furnace floor, a heating device that heats the furnace space, and a furnace hearth in the furnace body. In a mobile hearth furnace including a screw conveyor disposed on the upper surface side, the screw conveyor formed on the upper surface of the furnace body is wider than the diameter of the screw blades along the axial direction of the screw conveyor. A cylindrical member having an opening for carrying it out and a semicircular or larger arc-shaped cross section larger than the diameter of the screw blade, the outer peripheral surface of which is the longitudinal edge opposite to the opening The screw conveyor is disposed on the center of the semicircle or arc and is rotatable about the center of rotation. As positioned in a distant state, characterized in that and a lifting device for raising and lowering the relative screw conveyor to the upper surface of the rotary hearth.

  The screw cover is rotatable to a position where the outer peripheral surface passes from the one longitudinal edge of the opening to the lower side of the screw conveyor and straddles the other longitudinal edge of the opening, When the cross-sectional shape of the cylindrical member is a semicircle, it can rotate at least 180 °. A seal mechanism for sealing the longitudinal gap is disposed in the longitudinal gap between the screw cover and the furnace body, and the longitudinal gap between the screw cover and the furnace body is hermetically sealed.

  The screw cover is disposed so that the center thereof is positioned on the rotating shaft, and further includes a disk-shaped side wall member connected to both ends of the cylindrical member, and the disk-shaped side wall is formed. It can be set as the structure rotatably supported by the some rotating roller arrange | positioned so that the outer peripheral surface of a member may be contact | connected.

  The side wall member is disposed outside the side surface of the furnace body, and a hole through which the rotation shaft of the screw conveyor passes is formed at the center thereof, and further, from the through hole in the plane of the side wall member to the outer peripheral edge. It is possible to form a divided structure in which a part of the crossing is detachable.

  The through hole is along a trajectory along which the rotation axis of the screw conveyor moves when the screw conveyor is raised from a position positioned when the heat treatment is performed to a height that is positioned when the heat treatment is carried out. It can be shaped. For example, when the screw conveyor is moved up and down in the vertical direction, the through hole is made into a long hole. In this case, it is possible to further include a seal cover that is disposed on the outer surface of the side wall member and closes the through hole.

  The screw conveyor replacement method of the present invention uses any one of the above-described mobile hearth furnaces, the position where the screw conveyor is carried out of the furnace while the opening is closed without stopping the heating device. The screw cover is rotated until the screw conveyer is removed / installed.

  When replacing the screw conveyor, the screw conveyor, the bearing mechanism for supporting the screw conveyor, and the seal cover may be replaced as one unit.

  The mobile hearth furnace according to the present invention has an opening for carrying the screw conveyor out of the furnace on the upper surface of the furnace body forming the space inside the furnace, and the opening can be opened and closed with a rotatable screw cover. The configuration. The screw cover is a cylindrical member having a semicircular or larger arc-shaped cross section larger than the diameter of the screw blade.

  If comprised in this way, a screw conveyor can be rapidly carried out of a furnace only by raising a screw conveyor to the inside area | region of the rotating screw cover, and rotating a screw cover to a predetermined angle. And since the space in a furnace and the exterior of a furnace are interrupted | blocked by the screw cover, the replacement | exchange operation | work of a screw conveyor can be performed safely and easily. As a result, it is not necessary to cool the inside of the furnace to near room temperature, and it is possible to replace the screw conveyor without stopping the heating device such as a burner, and it is possible to minimize a reduction in operating rate. .

It is a perspective view which shows roughly the whole structure of a rotary hearth furnace. It is a longitudinal cross-sectional view of the rotary hearth furnace according to embodiment of this invention. It is a perspective view which shows the screw cover of the said rotary hearth furnace. It is process drawing which shows the procedure which replaces | exchanges the screw conveyor of the said rotary hearth furnace. It is process drawing which shows the other example of the sealing structure of the said rotary hearth furnace. The other example of the sealing structure of the said rotary hearth furnace is shown. It is process drawing which shows the procedure which replaces | exchanges the screw conveyor of the said rotary hearth furnace. It is process drawing which shows the procedure which replaces | exchanges the screw conveyor of the said rotary hearth furnace.

  Hereinafter, a mobile hearth furnace according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings by taking a rotary hearth furnace as an example. However, the technical scope of the present invention is not construed as being limited by the embodiments described below.

  The rotary hearth furnace 1 of the present embodiment is a hearth in which the planar shape is formed in an annular shape (for example, a ring shape or a donut shape), similar to the conventional rotary hearth furnace 1 shown in FIG. 2. A furnace body 3 surrounding the upper surface side of the hearth 2 to form a furnace space 31, a heating device 32 such as a burner, a supply device 4 for charging the workpiece onto the hearth 4, a heat-treated workpiece Are provided with a screw conveyor 5, a discharge port 6 for discharging the object to be processed, and an exhaust duct 33.

  FIG. 2 is a longitudinal sectional view of the rotary hearth furnace 1 according to the present embodiment. The hearth 2 constitutes a rotating carriage having wheels 21 disposed on the lower surface. For example, the wheel 21 travels on a rail 22 disposed so that the planar shape is an annular shape. Rotates continuously in the direction. A refractory material such as brick is laid on the upper surface side of the hearth 2 exposed to a high temperature atmosphere, and a hearth material is laid on the upper surface. As the hearth material, for example, magnesium oxide or dolomite material can be used. In addition, although illustration is abbreviate | omitted, a motor etc. can be used for the drive device which rotates a hearth, for example.

  A furnace space 31 for heat-treating an object to be processed includes a furnace body 3 having a U-shaped cross section having an upper surface wall 3A having a ring shape and a side wall 3B forming an inner periphery and an outer periphery of the furnace body. It is formed by arranging so as to surround the upper surface side. And the clearance gap between the side surface of the hearth 2 rotated at the time of execution of heat processing, and the side wall 3B of the stationary furnace body 3 is sealed with the water sealing apparatus 35. FIG.

  The screw conveyor 5 disposed on the upper surface of the hearth 2 includes a rotating shaft (main shaft) 51 disposed along the width direction of the hearth 2 and a continuous screw blade 52 disposed on the outer peripheral surface of the main shaft 51. Have. When the planar shape of the hearth 2 is a donut shape, the screw conveyor 5 is arrange | positioned along the radial direction of the hearth 2, for example. The screw blades 52 may be fixed to the main shaft 51 by welding or the like, or may be detachable from the main shaft 51 by fixing means such as bolts. If the screw blades 52 can be detached from the main shaft 51, only the deteriorated screw blades 52 can be replaced when the screw conveyor 5 is replaced.

  The rotating shafts 53 on both ends of the screw conveyor 5 extend through the side surface of the furnace body 3 and extend outside the furnace, and are rotatably supported by bearing boxes 54 as bearing mechanisms. And the drive device (not shown) which rotates the screw conveyor 5 is connected with the any one rotating shaft 53 extended out of the furnace. For example, a motor or the like can be used as the driving device.

  The bearing box 54 is supported by a lifting device 55, and the screw conveyor 5 is lifted and lowered relative to the hearth 2 by the lifting device 55. At this time, it is preferable that both the lifting devices 55 are operated synchronously so that the screw conveyor 5 moves up and down while maintaining a horizontal posture. As the lifting device 55, for example, a cylinder device that expands and contracts using fluid pressure such as air pressure or hydraulic pressure can be used. The raising / lowering amount can be controlled using a sensor such as an encoder. Although FIG. 2 is a structure which raises / lowers the screw conveyor 5, the structure which a hearth side raises / lowers may be sufficient. The bearing box 54 and the lifting device 55 are detachably connected by a fixing means such as a bolt, for example, and the connection is released when the screw conveyor 5 is replaced.

  The screw conveyor 5 is heated to a high temperature as the furnace space 31 is heated. The rotary hearth furnace 1 of the present embodiment is preferably configured so that the screw conveyor 5 can be inspected and replaced without stopping the heating device 32 such as a burner. Safety will be reduced. Therefore, for example, a flow path (not shown) for passing cooling water is formed inside the main shaft 51.

  The screw conveyor 5 is positioned in the height direction by the elevating device 55 so that the screw blades 52 are in contact with the hearth material on the upper surface of the hearth during the heat treatment. In addition to the height adjustment at the time of performing this heat treatment, in this embodiment, the lifting device 55 is also used when the screw conveyor 5 is exposed outside the furnace.

  As shown in FIG. 3, the rotary hearth furnace 1 of the present embodiment has an opening 7 for exposing the screw conveyor 5 to the outside of the furnace at a position above the screw conveyor 5 on the upper surface of the furnace body. . The opening 7 on the upper surface of the furnace body has a substantially rectangular planar shape. The longitudinal direction of the opening 7 extends from the inner peripheral end to the outer peripheral end of the upper surface of the furnace body, and the width in the short direction is at least wider than the diameter of the screw blade 52. Furthermore, the opening 7 on the upper surface of the furnace body communicates with the opening 71 on the side surface of the furnace body cut out in a semicircular shape, for example. The opening 71 on the side surface of the furnace body only needs to have a shape that allows the rotary shaft 53 to be separated upward when the screw conveyor 5 is lifted upward in order to replace the screw conveyor 5, and may not be particularly semicircular. .

  The opening 7 is provided with a screw cover 8 that blocks the opening 7 and carries the screw conveyor 5 out of the furnace. The screw cover 8 includes a cylindrical member (cover body) 81 having an inner diameter that is larger than the diameter of the screw blade 52 and a side wall member 82 connected to both ends of the cover body 81. The center of the semicircle is rotatably arranged with the rotation axis (virtual rotation axis) 81a. The cover main body 81 is arranged so that the outer peripheral surface thereof straddles the edge portion 7a in the longitudinal direction of the opening portion 7 that opposes, thereby closing the opening portion 7 on the upper surface of the furnace body. More specifically, a slight gap (for example, 5 to 10 mm) is provided between the outer peripheral surface of the cover body 81 and the edge 7a of the opening 7, and the opening 7 is airtight by providing a seal structure in this gap. (See FIGS. 4A and 4B). As a seal structure, a seal member 72 such as a ceramic fiber rope is typically disposed in the gap as shown in FIG. 4A. However, as shown in FIG. 4B, the outer peripheral surface of the cover body 81 and the edge 7a of the opening 7 It is also possible to arrange a movable seal plate 101 between them. When the heat treatment is performed and when the screw conveyor 5 is replaced, the seal plate 101 is brought into close contact with the cover body 81 and the opening 7 is hermetically closed, and the seal plate 101 is moved by the cylinder 102 when the screw cover 8 is rotated. By providing a gap with 81, the screw cover 8 can be made rotatable. Furthermore, after the screw cover 8 is rotated 180 degrees, the seal plate 101 can be pressed against the cover main body to close the opening 7 in an airtight manner. A heat insulating sealing material 103 such as a ceramic fiber is attached to the inner surface side of the seal plate 101 to enhance the airtightness and heat insulating property of the seal portion (see FIG. 4C). A plurality of cylinders 102 for opening and closing the seal plate 101 may be arranged in the width direction of the cover main body 81 to move the seal plate 101 open and close. The cylinders 102 may be operated by coupling (see FIG. 4C).

  The side wall members 82 connected to both ends of the cover main body 81 are arranged so as to be in contact with or biased to the side of the furnace body via a sealing member 73 such as a ceramic fiber rope, for example. The opening 71 whose side surface is notched is closed. The side wall member 82 is a disk member having a circular outer periphery, and is disposed so that, for example, the center thereof is located on the rotation axis of the cover body 81 (that is, the center of a semicircle) 81a. A plurality of small-diameter rotating rollers 83 are arranged so as to contact the outer peripheral side surface of the disk member, and the screw cover 8 is rotatably supported by the rotating rollers 83. The screw cover 8 is connected to a side wall member 82 and a driving device (not shown) via a gear mechanism such as a gear, and is rotated by the driving mechanism. The rotating roller 83 can be supported by a base supported from the foundation or a side column of the furnace (both not shown).

  In FIG. 3, as a preferred example, when the upper end of the side wall member 82 is set to 0 °, the side wall member 82 is disposed in a phase of 22.5 °, 157.5 °, 202.5 °, and 337.5 °, respectively. A total of eight rotating rollers 83 are shown. However, the number and arrangement positions of the rotating rollers 83 are not limited.

  The material of the cover main body 81 and the side wall member 82 is not particularly limited as long as it can withstand the furnace temperature. However, about the part exposed to the high temperature atmosphere in a furnace, it is preferable to perform construction, such as sticking a refractory. Furthermore, if the temperature of the screw cover 8 is high, the workability and safety when the screw conveyor 5 is inspected / replaced deteriorates, so a flow path for passing cooling water into the cover body 81 and / or the side wall member 82. It is preferable that the screw cover 8 and the surrounding temperature be lowered by circulating cooling water, for example. Of course, a cooling structure other than water cooling may be used.

  A hole 84 is formed on the surface of the side wall member 82 so that the rotary shaft 53 of the screw conveyor 5 extending outside the furnace can rotate. The through-hole 84 has, for example, a range from a height that is positioned when the screw cover 8 is rotated and the screw conveyor 5 is carried out of the furnace to a height that is positioned when the heat treatment is performed. It is in the shape of a long hole so that it can move (see FIG. 5). That is, the shape corresponds to the trajectory along which the rotary shaft 53 moves. Accordingly, the through hole 84 is not limited to the elongated hole shape extending in the vertical direction as shown in FIG. 3. For example, when the screw conveyor 5 is configured to move up and down in an oblique direction, the through hole 84 may have an elongated hole shape extending in the oblique direction. . Furthermore, it does not necessarily have to be a long hole shape.

  The side wall member 82 is formed with a door 85 that forms a passage through which the rotary shaft 53 separates from the through hole 84 when the screw conveyor 5 that rotates the screw cover 8 and carries it out of the furnace is replaced. The door 85 is formed by making a disk member forming the side wall member 82 into a divided structure and making a part extending from the through hole 84 to the outer peripheral edge freely removable. For example, the door 85 may be formed in a portion that turns upward when the screw cover 8 is rotated 180 ° from the posture of FIG. 3, and the position and shape of the door 85 are not limited.

  Returning to FIG. 2, a seal cover 86 for closing the through hole 84 is disposed on the outer surface of the side wall member 82. The seal cover 86 is, for example, a flat plate having a rectangular outer shape, and a round hole through which the rotation shaft 53 passes is formed in the surface. The through hole 84 of the side wall member 82 has a gap with respect to the outer peripheral surface of the rotary shaft 53, but the through hole 87 of the seal cover 86 does not have a gap with the outer peripheral surface of the rotary shaft 53 using the seal member. Is sealed. Furthermore, the through hole 84 of the side wall member 82 is closed by disposing a sealing material between the surface of the seal cover 86 and the surface of the side wall member 82. The seal cover 86 is disposed so as to be in contact with or biased to the side wall member 82, and the seal cover 86 can be moved up and down in synchronization with the screw conveyor 5.

  In the rotary hearth furnace 1 having the above-described configuration, a procedure for inspecting and replacing the screw conveyor 5 will be described with reference to FIGS. 4 shows an AA cross section of FIG. 3, and FIG. 4 shows a BB cross section of FIG.

  First, when the heat treatment is performed, the position of the screw conveyor 5 in the height direction is set by the lifting device 55 so that the screw blades 52 are in contact with the hearth material on the upper surface of the hearth. On the other hand, the screw cover 8 is set in the posture of FIG. 3 and closes the opening 7 so as to cover the upper side of the screw conveyor 5. When performing the inspection / replacement operation, the screw conveyor 5 is stopped, but the heating device 32 such as a burner is operated as it is. Of course, the furnace temperature can be set low during the inspection / replacement operation. Further, it is preferable that the supply of the object to be processed is stopped during the rotation of the screw conveyor 5 so that the object to be processed does not remain on the hearth before the inspection / replacement operation is started.

  Next, as shown to each (a) of FIG. 4A, FIG.5, and FIG.6, the screw conveyor 5 is raised by the raising / lowering apparatus 55. FIG. Then, when the cover main body 81 formed of a semicircular cylindrical member is rotated, the screw conveyor 5 is positioned at a position where the screw conveyor 5 is accommodated in the inner region of the rotation track of the cover main body 81. Preferably, positioning is performed so that the rotation shaft 53 of the screw conveyor 5 is positioned on the rotation shaft 81 a of the cover body 81.

  Next, as shown in FIG. 4A, FIG. 5 and FIG. 6B, the cover body 81 is rotated 180 ° to close the opening 7 with the cover body 81 and the screw conveyor 5 is exposed outside the furnace. Let Although the rotational speed of the cover main body 81 is not specifically limited, it can suppress that gas etc. leak outside a furnace by rotating rapidly. Thus, the cover main body 81 can block the furnace space 31 and the outside of the furnace and expose the screw conveyor 5 to the outside of the furnace, so that the inspection work can be performed without removing the screw conveyor 5. As a result, when it is determined that it is not necessary to replace the cover body 81, the cover body 81 can be returned to the original position, and the apparatus can be restarted.

  As a result of the inspection, if it is determined that the screw conveyor 5 needs to be replaced, as shown in FIGS. 4A, 5 and 6C, after removing the door 85, the bearing box 54 and the lifting device After releasing the fixed state of 55 and the urging state of the side wall member 82 and the seal cover 86, the screw conveyor 5 is picked up using a transport device (not shown) such as a crane. Accordingly, the screw conveyor 5, the seal cover 86, and the bearing box 54 are integrally removed from the furnace.

  The screw conveyor 5 thus removed from the furnace may be repaired and re-installed in the furnace. Alternatively, another screw conveyor 5 may be prepared and replaced with the removed screw conveyor 5. Furthermore, if the set of the screw conveyor 5, the bearing box 54, and the seal cover 86, which are separately prepared, is assembled in advance as one replacement unit, the time required for replacement can be shortened. The procedure for incorporating the screw conveyor 5 into the furnace may be the reverse of the procedure for removing it from the furnace.

  As described above, the rotary hearth furnace 1 of the present embodiment forms the opening 7 for carrying the screw conveyor 5 out of the furnace on the upper surface of the furnace body 3 forming the in-furnace space 31, and has a cross-sectional shape. The opening 7 can be opened and closed by rotating the screw cover 5 having a semicircular cylindrical member (cover body) 81. Therefore, the screw conveyor 5 can be quickly carried out of the furnace simply by positioning the screw conveyor 5 in the inner region of the rotation track of the cover body 81 and rotating the cover body 81 by 180 °. Since the furnace space 31 and the outside of the furnace are shut off, the screw conveyor 5 can be exchanged safely and easily.

  Therefore, it is not necessary to cool the inside of the furnace to near room temperature before performing the inspection / replacement work, and it is possible to replace the screw conveyor 5 without stopping the heating device 32 such as a burner. As described above, since it takes several days for the temperature increase to be completed again after the inside of the furnace is safely cooled to near normal temperature, this embodiment in which the time required for this cooling and temperature increase can be omitted. The time required for the replacement work of the screw conveyor 5 can be remarkably shortened. As a result, it is possible to minimize a decrease in equipment operation rate associated with inspection and replacement of the screw conveyor 5.

  Furthermore, since the gas in the furnace and the temperature are blocked by the screw cover 8 below the screw conveyor 5 carried out of the furnace, the inspection work can be performed without removing the screw conveyor 5. Moreover, since the furnace temperature is maintained, if it is determined that replacement is not necessary, the screw cover 8 can be returned to its original state and restarted quickly. At this time, if the screw conveyor 5 and / or the screw cover 8 has a water cooling structure, the workability and safety of the inspection work can be ensured more reliably.

  As described above, according to the present embodiment, since the inspection of the screw conveyor 5 can be easily performed in a short time, it is permitted to perform the inspection work more frequently than in the past. Therefore, since the remaining amount of the screw blades 52 can be measured frequently, the replacement time of the screw conveyor 5 can be optimized as compared with the conventional case.

  In the above-described embodiment, the cover main body 81 is configured by a cylindrical member having a semicircular cross-sectional shape, but the cross-sectional shape may not necessarily be a semicircle. For example, an arc having a cross-sectional shape of a semicircle or more can be cited as an example. Further, the diameter of the cover main body 81 is not necessarily the same as the length of the opening 7 in the short direction. If the outer surface of the cover body 81 can block the opening 7 across the opposing longitudinal edges of the opening 7, the diameter of the cover body 81 can be arbitrarily changed.

  The above-mentioned embodiment cites the rotary hearth furnace 1 as a preferable example. However, the furnace applicable to the present invention is not limited to the rotary hearth furnace 1, and can be applied to all hearth furnaces having a mobile hearth. As a furnace other than the rotary hearth furnace 1, for example, a furnace in which the hearth moves linearly in a horizontal plane can be given as an example.

  Although the present invention has been described in detail with reference to specific embodiments, various substitutions, modifications, changes, etc. in form and detail are defined in the claims. It will be apparent to those skilled in the art that this can be done without departing from the spirit and scope. Therefore, the scope of the present invention should not be limited to the above-described embodiments and the accompanying drawings, but should be determined based on the description of the claims and equivalents thereof.

1 rotary hearth furnace 2 hearth 3 furnace body 4 supply device 5 screw conveyor 7 opening (upper surface)
71 Opening (side)
8 Screw cover 81 Cover body 82 Side wall member 83 Rotating roller 84 Through hole 86 Seal cover

Claims (9)

A movable hearth, a furnace body that forms a furnace space on the upper surface side of the hearth, a heating device that heats the furnace space, a screw conveyor disposed on the upper surface side of the hearth in the furnace body, In a mobile hearth furnace including
On the upper surface of the furnace body, an opening for carrying the screw conveyor out of the furnace formed wider than the diameter of the screw blades along the axial direction of the screw conveyor,
A cylindrical member having a semicircular or larger arc-shaped cross section larger than the diameter of the screw blade, the outer peripheral surface of the cylindrical member straddling the opposite longitudinal edge of the opening, and the opening A screw cover that is rotatable about the center of the semicircle or arc as a rotation axis;
A lifting device for moving the screw conveyor up and down relative to the upper surface of the rotary hearth so that the screw conveyor is located in a state away from the rotary hearth in the inner region of the rotation track of the screw cover; A mobile hearth furnace characterized by that.   The screw cover is rotatable to the position where the outer peripheral surface passes from the one longitudinal edge of the opening to the lower side of the screw conveyor and straddles the other longitudinal edge of the opening. The mobile hearth furnace according to claim 1, wherein:   The moving bed type hearth furnace according to claim 1 or 2, wherein a seal mechanism for sealing the longitudinal gap is disposed in a longitudinal gap between the screw cover and the furnace body.   The screw cover is disposed so that the center thereof is positioned on the rotating shaft, and further includes a disk-shaped side wall member connected to both ends of the cylindrical member, and the disk-shaped side wall is formed. The mobile hearth furnace according to any one of claims 1 to 3, wherein the mobile hearth furnace is rotatably supported by a plurality of rotating rollers arranged so as to be in contact with the outer peripheral surface of the member. The side wall member is
A hole through which the rotating shaft of the screw conveyor passes is formed at the center of the furnace body, and is disposed outside the side surface of the furnace body.
5. The mobile hearth furnace according to claim 4, wherein a part of the side wall member extending from the through hole to the outer peripheral edge is detachable in a split structure.   The shape of the through hole is such that when the screw conveyor is raised from the position positioned at the time of performing the heat treatment to the height positioned when being carried out of the furnace, the rotation axis of the screw conveyor moves. The mobile hearth furnace according to claim 5, wherein the shape is along the shape.   The mobile hearth furnace according to claim 6, further comprising a seal cover that is disposed on the outer surface of the side wall member and closes the through hole. In the mobile hearth furnace according to any one of claims 1 to 7,
The screw conveyor is removed / assembled by rotating the screw cover to a position where the screw conveyor is carried out of the furnace with the opening being closed without stopping the heating device. method of exchange.   The screw conveyor replacement method according to claim 8, wherein the screw conveyor, the bearing mechanism that pivotally supports the screw conveyor, and the seal cover are replaced as one unit.

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