JP2013002777A - Movable hearth furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary hearth furnace which includes a discharger for discharging granular treated material uniformly without applying an excessive load on a furnace body even when a size of the rotary hearth furnace is increased.SOLUTION: The movable hearth furnace is so structured that raw material containing a reducing agent and oxidized iron is supplied on a moving hearth 1a and is heated, and the obtained treated material is discharged outside the furnace by a discharge device 6 arranged on the hearth. The discharge device 6 includes at least first and second screw conveyers 6a, 6b each having a screw shaft and screw blades formed on the screw shaft. A formation length of each screw blade is smaller than a hearth width. A part of the treated material is discharged from one side in a width direction of the hearth by the first screw conveyer 6a. A part of the other, or the entire treated material is discharged from the other side in the width direction of the hearth by the second screw conveyer 6b.

Description

  The present invention relates to a moving hearth furnace for producing a reduced metal from an agglomerated product containing a carbonaceous reducing agent and iron oxide and formed into a lump shape.

  As shown in FIG. 8, a rotary hearth furnace as one of the moving hearth furnaces usually has an annular hearth 51 rotating at a constant speed around a vertical axis in a circular furnace body 50 (in the direction of arrow A). The agglomerated material is charged into the furnace from the charging port 52 and spread on the hearth 51.

  The agglomerated material on the hearth 51 is heated and reduced by the burner 53 when passing through the heating region downstream of the charging port 52.

  The metal produced | generated by reduction | restoration is discharged | emitted out of the furnace from the discharge port 55 by the feeding (arrow B direction) operation | movement of the screw feeder 54 (for example, refer patent document 1).

  In this type of rotary hearth furnace, granular metal iron can be produced up to about 500,000 to 600,000 tons per year, but in order to increase the production of granular metal iron beyond that, a plurality of rotary hearth furnaces are required. It becomes necessary, and if the number of rotary hearth furnaces is increased, construction costs and running costs increase.

  As a rotary hearth furnace for the purpose of reducing construction costs, the furnace body is made compact (reduction in furnace height) to reduce the amount of heat dissipated in the furnace body and to improve the fuel consumption rate. Is known (see, for example, Patent Document 2).

  The rotary hearth furnace described in Patent Document 2 reduces the distance (clearance) from the flame to the furnace ceiling by keeping the flame diameter of the burner small and maintaining a constant size regardless of the amount of combustion. It is configured to minimize the furnace height. According to this configuration, there is an effect that the fuel consumption rate can be improved by suppressing the construction cost.

  However, since the rotary hearth furnace described in Patent Document 2 does not propose a configuration of a rotary hearth furnace for significantly increasing the production amount of granular metallic iron, it is intended to increase the size of the rotary hearth furnace. This configuration is not realized at present.

JP 2001-152223 A JP 2003-279255 A

  In order to increase the size of the rotary hearth furnace, there are various problems to be solved, such as the structure of the furnace body, the arrangement of the burner, the structure of the agglomerate supply device, the structure of the discharger that discharges granular metallic iron to the outside of the furnace, etc. There's a problem. Above all, how the discharger is structured is important.

  The discharger is composed of a rotating shaft, screw blades spirally formed on the body of the rotating shaft, and a refractory material covering them. The discharger is for a plant with an annual output of 200,000 tons. Even if there is, total weight is 35t-40t.

  When the rotary shaft is made longer with the increase in the size of the rotary hearth furnace, the rotary shaft is deflected, and the granular metal iron remains in the hearth inner and outer peripheral parts without being discharged. Cannot be discharged uniformly. If the diameter of the rotating shaft is increased so as not to cause deflection, it will be difficult to store the rotating shaft in a furnace body that is restricted in the height of the ceiling surface of the furnace body, and the furnace body that supports the rotating shaft will also be reinforced. It becomes necessary and becomes large-scale.

  Under such circumstances, when a rotary hearth furnace is increased in size, the priority issue is the realization of a discharger capable of uniformly discharging processed objects such as metallic iron without excessive load on the furnace body. Become.

  The present invention has been made in consideration of the problems in increasing the size of the rotary hearth furnace as described above, and even if the moving hearth furnace is increased in size, it does not give an excessive load to the furnace body and is uniformly processed. It is intended to provide a moving hearth furnace equipped with a discharger that can discharge the waste gas.

The present invention is configured to supply and heat a raw material containing a reducing agent and iron oxide onto a moving hearth, and discharge the processed product to the outside of the furnace by a discharge device disposed on the hearth. In the moving hearth furnace,
The discharge device has at least first and second screw conveyors having a screw shaft and screw blades formed on the screw shaft,
The formation length of each screw blade is shorter than the hearth width,
A part of the processed material is discharged from the one side in the width direction of the hearth by the first screw conveyor, and another part or all of the processed material is the second side from the other side in the width direction of the hearth. It is a moving hearth furnace discharged by a screw conveyor.

  The moving hearth furnace of the present invention includes a hearth furnace in which the hearth moves linearly and a rotary hearth furnace in which an annular hearth rotates around a vertical axis.

  The form of the raw material in the present invention includes agglomerates and powders.

  The increase in the size of the rotary hearth furnace is to determine the outer diameter, inner diameter, and width of the furnace so that the hearth area increases in proportion to the production amount of the furnace. However, the outer diameter of the furnace, the inner diameter, and the furnace width are not increased at the same ratio as the existing rotary hearth furnace, but the increase in the outer diameter of the furnace is suppressed by increasing the furnace width by reducing the inner diameter of the furnace. However, it is preferable to expand the hearth area. Thereby, it can enlarge more effectively, suppressing construction cost.

  In the present invention, for example, when the screw conveyor is constituted by two stations, a part of the processed product is discharged by the first screw conveyor, and the remaining processed product is discharged by the second screw conveyor. Further, when the screw conveyor is constituted by three or more stations, the first and second screw conveyors are included, and the processed products are discharged by being shared by a plurality of screw conveyors.

In the first aspect of the present invention, as the first screw conveyor, a screw shaft provided so as to straddle the hearth, and a range from one end portion in the width direction of the hearth or the vicinity thereof to a predetermined portion in the width direction The screw blades formed on the screw shaft corresponding to
The screw shaft provided so as to straddle the hearth as the second screw conveyor, and the screw shaft corresponding to the range from the predetermined part in the width direction of the hearth to the other end in the width direction or the vicinity thereof. And the formed screw blade.

In the second embodiment of the present invention, as the first screw conveyor, a frame provided so as to straddle the hearth, and a width direction predetermined from one end portion in the width direction of the hearth or the vicinity thereof supported by the frame. A screw shaft extending to the site, and a screw blade formed on the screw shaft,
A frame provided to straddle the hearth as the second screw conveyor, and a screw shaft supported by the frame and extending from a predetermined position in the width direction of the hearth to the other end in the width direction or the vicinity thereof And screw blades formed on the screw shaft.

  When the screw conveyor is constituted by two stations, the predetermined portion can be the center in the width direction of the hearth or the vicinity thereof.

  The predetermined portion is not limited to the case where the processed material is discharged evenly from both sides in the width direction of the hearth with the center in the width direction of the hearth, but the predetermined portion is biased in the hearth width direction, It is also possible to change the discharge rate of the processed material discharged from the tank, for example, 4: 6, 3: 7, or the like.

  According to the present invention, the screw conveyor is arranged side by side on the hearth, and because the deflection range of the screw shaft is suppressed by limiting the formation range of each heavy screw blade to a range shorter than the hearth width, When the hearth furnace is increased in size, the load on the furnace body is not excessive, and the processed product can be discharged uniformly.

1 is a schematic plan view of a rotary hearth furnace according to the present invention. It is CC longitudinal cross-sectional view of FIG. It is explanatory drawing which expand | deployed and showed the rotary hearth furnace of FIG. 1 in the rotational movement direction. It is an enlarged plan view which shows the 1st form of the discharge device which concerns on this invention. It is a side surface longitudinal cross-sectional view of FIG. It is an enlarged plan view which shows the 2nd form of the discharge device which concerns on this invention. It is a JJ arrow longitudinal cross-sectional view of FIG. It is a top view which shows the structure of the conventional rotary hearth furnace.

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

1. Rotary hearth furnace The rotary hearth furnace of the present invention includes a rotating donut-shaped hearth, FIG. 1 shows a plan view of the rotary hearth furnace 1, and FIG. The figure is shown.

  In the rotary hearth furnace of the present invention, (a) the agglomerate charged on the rotary hearth is heated while making a round in the furnace, the iron oxide contained in the agglomerate is reduced by the carbonaceous material, and the reduced iron The "FASTMET method" that discharges to the outside of the furnace, and (b) either the "ITmk3 method" that produces granular metallic iron by melting the reduced iron once after heating and reducing in the furnace, and then cooling In the following embodiment, a rotary hearth furnace used for the “ITmk3 method” will be described as an example.

  In both figures, the hearth la of the rotary hearth furnace 1 is configured to rotate around a vertical axis at a constant speed by a driving device (not shown).

  The rotary hearth furnace 1 of the present invention is intended to increase the size of the rotary hearth furnace 1 by expanding the area of the hearth 1a by bringing the inner peripheral edge 1b of the hearth 1a closer to the center O. In addition, the circle D shown with the dashed-two dotted line in the figure has shown the position of the conventional inner periphery of a hearth.

  A plurality of combustion burners 3 are disposed at appropriate positions on the inner peripheral wall surface and the outer peripheral side wall surface of the furnace body 2, and the raw material charged on the hearth 1 a with the combustion heat and the radiant heat of these combustion burners 3. In this embodiment, the pellet is heated and reduced and melted by transferring it to, for example, a pellet as an agglomerated product. In addition, illustration is abbreviate | omitted about the combustion burner arrange | positioned by the inner peripheral side wall surface. The agglomerated material includes various forms such as pellets and briquettes.

  FIG. 3 is an explanatory view showing the rotary hearth furnace 1 shown in FIG. 1 expanded in the rotational movement direction in order to explain the heat reduction melting process.

In the figure, the internal structure of the furnace body 2 is partitioned from the reduction zone Z ₁ to the cooling zone Z ₄ by partition walls K _{1 to} K ₃ , and the furnace floor 1 a faces the upstream side in the rotational direction of the furnace body 2. The hearth material charging device 4 and the raw material supply device 5 are arranged at the most downstream side in the rotation direction (because of the rotating structure, it is actually also directly upstream of the hearth material charging device 4). A discharge device 6 is arranged.

  When the rotary hearth furnace 1 is operated, the hearth la is rotated at a constant speed, and pellets are supplied from the raw material supply device 5 onto the hearth la.

Pellets supplied onto the hearth 1a receives combustion heat and radiation heat by the combustion burners 3 during the course of moving the reduction and melting zone Z ₁ to Z _3, iron oxide pellets are reduced by the carbonaceous reducing agent .

The reduced iron, which has been almost completely reduced, is melted by further heating and agglomerates into granular molten metal iron while being separated from by-product slag, and is cooled by the cooling device 7 in the cooling zone Z ₄ . It solidifies and is sequentially scraped out of the rotary hearth furnace 1 by the discharge device 6 provided on the downstream side thereof.

  At this time, slag produced as a by-product is also discharged at the same time, but after passing through the discharge unit 8, the separation of the granular metal iron and slag is performed by a separation device (such as a sieve or a magnetic separator), and finally, Granular metallic iron with a very low slag component content can be obtained.

  In FIG. 3, the inside of the furnace body 2 is divided into four zones, but the number of zones to be divided can be changed as appropriate.

2. 2. Discharge device 2.1 First embodiment of discharge device FIG. 4 is an enlarged plan view showing a first embodiment of the discharge device 6 according to the present invention, and FIG. 5 is a side longitudinal sectional view thereof.

  First, in FIG. 4, the discharge device 6 includes a dual discharger (first screw conveyor) 6 a and a discharger (second screw conveyor) 6 b arranged on the upstream side and the downstream side in the hearth rotation direction. It is configured.

  The discharger 6a disposed on the upstream side includes a shaft (screw shaft) 10c having a shaft end portion 10a at one end and a shaft end portion 10b at the other end, and the shaft 10c straddles the hearth la. It is provided on the hearth 1a.

  A screw blade 10d for discharging granular metal iron as a processed product to the inner peripheral side of the hearth (in the direction of arrow E) is spirally formed on the outer peripheral surface of the shaft 10c. However, the range in which the screw blade 10d is formed is from the end of the shaft 10c on the shaft end 10a side (corresponding to one end in the width direction of the hearth) to the substantially central portion of the shaft 10c (the width of the hearth). It is limited to a range F up to (corresponding to a predetermined direction part).

  One shaft end portion 10a is rotatably supported by a bearing 10e disposed inside the hearth 1a, and the other shaft end portion 10b is rotatably supported by a bearing 10f disposed outside the hearth 1a.

  A sprocket 10g is fixed to the tip of the shaft end portion 10a, and the sprocket 10g is connected to a driving device via a roller chain described later.

  The discharger 6b arranged on the downstream side is basically composed of the same one as the above-described discharger 6a, but is arranged symmetrically with respect to the discharger 6a in the shaft axial direction. In the discharger 6b, the same components as those of the discharger 6a are denoted by the same reference numerals, and the description thereof is omitted. In the figure, G indicates the rotation direction of the hearth 1a.

  A screw blade 10d for discharging granular metal iron to the inner peripheral side of the hearth (opposite to the direction of arrow E) is formed in a spiral shape on the outer peripheral surface of the shaft 10c of the discharger 6b arranged on the downstream side. Has been. However, the range in which the screw blades 10d are formed ranges from a substantially central portion of the shaft 10c (corresponding to a predetermined portion in the width direction of the hearth) to a shaft end portion (corresponding to the other end in the width direction of the hearth) 10a. The range is limited to F ′.

  It is preferable that the discharge ranges of the granular metallic iron by the screw blades 10d are partially overlapped in the adjacent two dischargers 6a and 6b.

  Note that the arrangement of the dischargers 6a and 6b may be the reverse of the above arrangement.

  In the above embodiment, the discharger is constituted by two stations, and the case where the screw blades are formed by dividing into two ranges from the widthwise end of the hearth to the substantially central part of the width of the hearth is described as an example. However, the widthwise end of the hearth may be in the vicinity thereof, and the predetermined widthwise portion of the hearth may be in the center of the hearth or in the vicinity thereof.

  Further, in the above embodiment, the case where the processed material is discharged uniformly from both sides in the width direction of the hearth has been described as an example, but not limited to this, the width direction of the hearth that specifies the range in which the screw blades are formed The predetermined part can be set at a position deviated from the center in the width direction of the hearth, and the discharge sharing by each discharger can be changed.

  In FIG. 5, two series of dischargers 6 a and 6 b are supported by the elevating frame 11 and housed in the water cooling cover 12.

  When the driving device 10h provided on the lifting frame 11 transmits the rotational force to the sprocket 10g of the shaft end portion 10a via the roller chain 10i, the screw blade 10d formed on the shaft 10c of the upstream discharger 6a is Rotate and transfer the granular metal iron (including the hearth material) on the hearth to the inner peripheral side (direction of arrow E), which is one side in the width direction of the hearth 1a, and is arranged below the tip of the screw blade 10d. Through the chute 13a, the granular metallic iron is dropped onto the inner peripheral discharge hopper 8a constituting the discharge portion 8.

  Similarly, if the shaft end portion 10a of the downstream discharger 6b is rotated via a drive device, a roller chain, and a sprocket 10g (not shown), the screw blade 10d formed on the shaft 10c rotates, The granular metal iron (including the hearth material) is transferred to the hearth outer peripheral side (the direction opposite to the arrow E direction), which is the other side in the width direction of the hearth la, and the chute 13b disposed below the tip of the screw blade 10d. The granular metallic iron is dropped on the outer peripheral side discharge hopper 8b constituting the discharge portion 8 through.

  The granular metal iron dropped on the inner peripheral discharge hopper 8a and the outer peripheral discharge hopper 8b is separately or joined and sent to the above-described separator.

  In this way, if the discharge device 6 is constituted by the dual dischargers 6a and 6b, the metal is limited to the ranges F and F '(see FIG. 4) from the end of the shaft 10c to the substantially central portion of the shaft 10c. Since the screw blade 10d for scraping out iron is formed, the weight added to each shaft 10c is reduced. Therefore, the deflection of the shaft 10c can be suppressed even when the hearth width is expanded when the rotary hearth furnace is enlarged and the discharger is elongated accordingly.

  Further, the weight applied to the shaft 10c is reduced, so that the diameter of the shaft 10c can be reduced, whereby the discharge device 6 can be configured with a relatively small size.

2.2 Second Embodiment of Discharge Device FIG. 6 is an enlarged plan view showing the second embodiment of the discharge device according to the present invention, and FIG. 7 is a side view of the discharge device of FIG. It is a longitudinal cross-sectional view.

  The discharge device 6 shown in FIG. 6 includes a suspended discharger (second screw conveyor) 6c and a discharger (first screw conveyor) 6d, and each discharger 6c, 6d is in the direction of rotation of the hearth la ( In the G direction).

  The upstream discharger 6c includes a shaft (screw shaft) 14c having a shaft end 14a at one end and a shaft end 14b at the other end. The axial length of the shaft 14c has a length exceeding approximately half of the hearth width, and is arranged in the radial direction of the hearth 1a.

  A screw blade 14d for discharging the granular metal iron to the outer periphery of the hearth (in the direction of arrow H) is formed in a spiral shape on the outer peripheral surface of the shaft 14c.

  The shaft end portion 14a is rotatably supported by a bearing 14e, and the shaft end portion 14b is rotatably supported by a bearing 14f. The bearing 14e is supported at a lower portion of a support frame 15a suspended from the elevating frame 15, and the bearing 14f. Are fixed to the side wall 15b of the lifting frame 15 (see FIG. 7).

  The downstream discharger 6d is basically composed of the same one as the above-described discharger 6c, but is arranged symmetrically with respect to the discharger 6c in the shaft axial direction. In the discharger 6d, the same components as those of the discharger 6c are denoted by the same reference numerals, and the description thereof is omitted.

  The two dischargers 6 c and 6 d are supported by the elevating frame 15 and stored in the water cooling cover 16.

  The water cooling cover 16 includes partition outer walls 16a and 16b disposed on the outside thereof in parallel with the dischargers 6c and 6d, and a partition inner wall 16c disposed between the dischargers 6c and 6d. Partition walls 16d and 16e are provided on both sides of the discharger 6c in the axial direction, and partition walls 16f and 16g are provided on both sides of the discharger 6d in the axial direction.

  Further, as shown in FIG. 7, in order to prevent the bearings 14e and 14f from being exposed to high heat, the bearing 14e is disposed outside the water cooling walls 16d and 16f, and the bearing 14f is disposed outside the water cooling walls 16e and 16g. Is arranged (see FIG. 6).

  A sprocket 14g is provided at the shaft end 14b of the shaft 14c, and the sprocket 14g is connected to the driving device 14i via a roller chain 14h. Thereby, when the drive device 14i is driven, the shaft 14c rotates, and the granular metal iron (including the hearth material) on the hearth is moved to the outer periphery of the hearth by the feeding operation by the screw blade 14d formed on the shaft 14c. It is transferred in the direction of arrow H.

  The transferred granular metallic iron is dropped onto the outer discharge hopper 8b through a chute 13b disposed below the tip of the screw blade 14d.

  Similarly to the discharger 6c, the downstream discharger 6d is driven by a driving device (not shown), and the shaft 14c rotates. By the feed operation by the screw blades 14d formed on the shaft 14c, the granular metal on the hearth Iron (including the hearth material) is transferred to the inner peripheral side of the hearth (in the direction of arrow I), and the transferred granular metallic iron is passed through a chute (not shown) disposed below the tip of the screw blade 14d. It is dropped into the discharge hopper 8a (see FIG. 6).

  The granular metal iron dropped on the inner peripheral discharge hopper 8a and the outer peripheral hopper 8b is sent separately or joined to the above-described separator.

  In addition, about the range of the code | symbol L (refer FIG. 7), the feed range by the screw blade 14d of each shaft 14c is overlapped so that the granular metal iron on the hearth 1a may be discharged | emitted completely.

  Thus, what comprised the discharge device 6 by the said dischargers 6c and 6d is arrange | positioned without increasing the length of the shaft 10c, so that the upstream and downstream sides in the hearth rotation direction Therefore, the granular metallic iron can be discharged uniformly without increasing the size of the dischargers 6c and 6d including the screw shaft.

  Moreover, although the structure which arrange | positions two dischargers in the said embodiment was shown, according to the hearth width | variety of the rotary hearth furnace which enlarges, it can also arrange | position two or more stations, such as three stations or four stations. In this case, regarding the discharge of the granular metallic iron on the hearth, it is preferable to set a plurality of discharge areas in the hearth radial direction and share the discharge of each discharge area with a plurality of dischargers.

DESCRIPTION OF SYMBOLS 1 Rotary hearth furnace 1a Hearth 2 Furnace body 3 Combustion burner 4 Hearth material charging device 5 Raw material supply device 6 Discharge device 6a Discharger (first screw conveyor)
6b Discharger (second screw conveyor)
DESCRIPTION OF SYMBOLS 7 Cooling device 8 Discharge part 8a Inner peripheral side discharge hopper 8b Outer peripheral side discharge hopper 10a, 10b Shaft end part 10c Shaft 10d Screw blade 10e, 10f Bearing 10g Sprocket 11 Lifting frame 12 Water cooling cover 13a, 13b Chute

Claims (7)

A moving hearth furnace configured to supply and heat a raw material containing a reducing agent and iron oxide to a moving hearth, and discharge the obtained processed product to the outside of the furnace by a discharge device disposed on the hearth. In
The discharge device has at least first and second screw conveyors having a screw shaft and screw blades formed on the screw shaft,
The formation length of each screw blade is shorter than the hearth width,
A part of the processed material is discharged from the one side in the width direction of the hearth by the first screw conveyor, and another part or all of the processed material is the second side from the other side in the width direction of the hearth. A moving hearth furnace which is discharged by a screw conveyor. The first screw conveyor includes a screw shaft provided so as to straddle the hearth, and the screw shaft corresponding to a range extending from one end portion in the width direction of the hearth or the vicinity thereof to a predetermined portion in the width direction. The screw blades formed,
The second screw conveyor includes a screw shaft provided so as to straddle the hearth, and the screw shaft corresponding to a range from a predetermined portion in the width direction of the hearth to the other end in the width direction or the vicinity thereof. The moving hearth furnace according to claim 1, comprising the screw blades formed. The first screw conveyor includes a frame provided so as to straddle the hearth, and a screw shaft supported by the frame and extending from one end portion in the width direction of the hearth or a vicinity thereof to a predetermined portion in the width direction. And a screw blade formed on the screw shaft,
The second screw conveyor includes a frame provided so as to straddle the hearth, and a screw shaft supported by the frame and extending from a predetermined position in the width direction of the hearth to the other end in the width direction or the vicinity thereof. The moving hearth furnace according to claim 1, further comprising: a screw blade formed on the screw shaft.   The moving hearth furnace according to claim 2 or 3, wherein the predetermined portion in the width direction is the center in the width direction of the hearth or in the vicinity thereof.   The moving hearth furnace according to any one of claims 1 to 4, wherein a discharge range of the processed product by each screw blade is configured to partially overlap in the adjacent screw conveyor.   The moving hearth furnace according to any one of claims 1 to 5, wherein the screw shaft on which the screw blades are formed is housed in a water-cooled cover provided on the hearth.   The moving hearth furnace according to any one of claims 1 to 6, wherein the moving hearth furnace is a rotary hearth furnace.

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