JP2010223516A - Raw material molding device of rotary hearth furnace for manufacturing reduced iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raw material molding device of a rotary hearth furnace capable of efficiently transmitting heat to a raw material pellet by densifying and unifying air holes and moisture in the raw material pellet to efficiently reduce the raw material pellet in the rotary hearth furnace. <P>SOLUTION: In this molding device for molding the raw material, of the rotary hearth furnace in which a pair of screws 2 respectively having a raw material feeding screw 5 of various pitches of spiral blades 4, and an extruding screw 6 continued from the raw material feeding screw 5 are disposed in parallel with each other in a casing 1, a kneading section 9 is disposed in a state that a plurality of elliptical paddles 9a-9d for kneading the raw material pellet are disposed between the raw material feeding screw 5 and the extruding screw 6 in a state of being overlapped while staggered at equal angles on the whole periphery of a screw shaft 3, and clearances 10 through which the raw material passes, are respectively formed between top sections of the paddles adjacent to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a raw material molding apparatus for a rotary hearth furnace capable of improving the reduction efficiency of raw material pellets supplied to a rotary hearth furnace for producing reduced iron.

  In the production of reduced iron in a rotary hearth furnace, after mixing several types of sludge containing iron oxide, wet dust such as slurry, iron-making waste such as iron-making dust, carbon-based reducing agent and binder, molding into raw pellets To do. Reduced iron is manufactured by charging the obtained raw material pellets on a rotary hearth rotating on a horizontal plane and heating and reducing the pellets. When reducing steelmaking waste having high moisture content in a rotary hearth furnace, it is usually mixed with a carbonaceous material, dehydrated and formed into a raw material pellet (see Patent Document 1).

  FIG. 5 is a schematic view showing a conventional rotary hearth raw material molding apparatus.

  A pair of screws 2 are arranged in parallel in the casing 1 of the molding apparatus. The screw 2 is provided with blades 4 spirally continuous in the axial direction around the screw shaft 3. The screw 2 is integrally provided with a raw material feed screw 5 and an extrusion screw 6 having a different pitch following this.

  The raw material charged from the raw material charging port 7 is fed forward by a pair of raw material feed screws 5 rotating in the same direction, and subsequently extruded from the perforated plate 8 by the extrusion screw 6 to produce raw material pellets.

JP 2005-163140 A

  However, in the conventional raw material molding apparatus, the strength and quality of the pellets after reduction in the rotary hearth furnace are not sufficient depending on the properties of the raw materials. FIG. 6 is a schematic diagram showing the pore distribution in the raw material pellet, where (a) is a raw material pellet obtained by the conventional raw material molding apparatus of FIG. 5, and (b) is a view showing the raw material pellet according to the present invention.

  In the raw material pellet according to the conventional method shown in FIG. 6A, the distribution of the pores 11 and the moisture 11 in the raw material pellet is not precise and uniform, so the heat transfer efficiency in the pellet is low in the rotary hearth furnace. As a result, drying, heating, and reduction are not performed effectively in the rotary hearth furnace, and the reduced iron pellets after reduction have a low compressive strength and low iron metallization rate (ratio of metallic iron in the total iron). The product quality was not enough.

  Therefore, the present invention increases the heat transfer efficiency in the pellets by making the pores and moisture in the raw material pellets dense and uniform in order to achieve efficient reduction of the raw material pellets in the rotary hearth furnace that produces reduced iron. Thus, a raw material molding apparatus for a rotary hearth furnace capable of efficiently transferring heat to raw material pellets is provided.

  The present invention relates to a pellet molding apparatus for molding a raw material for a rotary hearth furnace, in which a raw material feed screw and a pair of screws formed continuously with an extrusion screw are arranged in parallel in a casing. A plurality of elliptical paddles are stacked at equal angles around the entire circumference of the screw shaft, and a gap through which the raw material passes is formed between adjacent paddles. The kneading part which knead | mixes the raw material pellet is arrange | positioned.

  In the kneading part, the ratio of the projected passage area of the paddle part (the area of the gap through which the raw material passes between the tops of adjacent paddles) to the cross-sectional area of the molding machine is 2% to 25%.

  Further, an elliptical paddle can be provided with a thickness of 30 to 200 mm. Further, the degree of kneading can be changed by changing the paddle angle.

  Since the molding apparatus of the present invention is kneaded into the raw material pellets at the kneading part, as shown in FIG. 6 (b), the pores in the raw material pellets and the pores containing moisture can be made small and dense and evenly dispersed. The heat transfer efficiency of the raw material pellets in the rotary hearth furnace is improved, and heat can be transferred efficiently. As a result, since drying, heating, and reduction are effectively performed, the compression strength and iron metallization rate of the pellet after reduction are increased, and the strength and quality of the reduced product are improved.

It is the schematic which shows the shaping | molding apparatus of the raw material for rotary hearth furnaces of this invention. (A) is a perspective view of the screw provided with the kneading part, (b) is a figure which shows the example of arrangement | positioning of the paddle of a kneading part. It is a figure which shows the compressive strength of the reduced pellet of this invention and a prior art example. It is a figure which shows the metallization rate of this invention and a prior art example. It is the schematic which shows the conventional raw material shaping | molding apparatus for rotary hearth furnaces. It is a schematic diagram which shows distribution of the pore in a raw material pellet, (a) is the raw material pellet by a conventional method, (b) is a figure which shows the raw material pellet by this invention.

  Embodiments of the present invention will be described with reference to the drawings.

  1, in the molding apparatus of the present invention, a pair of screws 2 are arranged in parallel in a casing 1 of the molding apparatus, similarly to the molding apparatus shown in FIG. The screw 2 is provided with blades 4 spirally continuous in the axial direction around the screw shaft 3. In the screw 2, a raw material feed screw 5 that feeds out the raw material charged from the raw material inlet 7 and an extrusion screw 6 having a smaller pitch than the feed screw 5 are continuously provided.

  In the molding apparatus of the present invention, a kneading part 9 is further formed between the delivery screw 5 and the extrusion screw 6, in which a plurality of paddles 9 a to 9 d are arranged so as to be perpendicular to the screw shaft 3. Each paddle 9a-9d of the kneading part 9 is formed of an elliptical steel plate having a thickness of 30-200 mm. The elliptical paddles 9 a to 9 d are overlapped with the screw shaft 3 at the same height as the blades 4 and shifted at equal angles around the entire circumference of the screw shaft 3. In FIG. 2B, the paddles 9a to 9d (four in the figure) are shifted by a predetermined angle (45 degrees in the figure). A raw material passage gap (projected passage area) 10 through which the raw material passes is formed between the tops of the adjacent paddles 9a to 9d.

  Projected passage ratio = projected passage area / total cross-sectional area, where the raw material shortcuts the paddle part, that is, the ratio of the area of the gap through which the raw material passes between the tops of adjacent paddles to the cross-sectional area of the molding machine . The projection pass rate is preferably 2 to 25%. When the projected passage area of the paddle part is less than 2%, the raw material continuously fed from the raw material inlet is difficult to escape to the molding machine discharge side, so the load on the molding machine rises rapidly. In addition, when the projected passage area exceeds 25%, the raw material that shortcuts the paddle portion increases, and it is not possible to sufficiently knead, and the effect of subdividing pores and moisture existing in the raw material to make it dense and uniform descend.

  FIG. 3 shows the compressive strength of the reduced iron pellets of the present invention and the conventional example, and FIG. 4 is a diagram showing the metallization rates of the present invention and the conventional example.

  The dehydrated raw material having a moisture content of 17 to 27% fed from the raw material input side of the molding machine is sent toward the molding machine exit side by the raw material feed screw. The raw material tends to be returned to the raw material input side of the molding machine. On the other hand, since the raw material is continuously fed into the molding machine and sent to the molding machine exit side by the raw material feed screw, the raw material is kneaded and added to the paddle as a result. . By adding the kneading, the pores and moisture present in the raw material are subdivided to become dense and uniform.

 A part of the kneaded raw material passes through the gap of the paddle portion by being sent out by the raw material that is continuously fed, and is discharged from the molding machine by the raw material extrusion screw and molded into pellets.

1: casing 2: screw 3: screw shaft 4: blade 5: raw material feed screw 6: extrusion screw 7: raw material inlet 8: perforated plate 9: kneading part 10: raw material passage gap (projection passage area)
11: Pore and moisture

Claims (3)

  In a pellet molding apparatus for molding a raw material for a rotary hearth furnace in which a raw material feed screw and a pair of screws formed continuously with an extrusion screw are arranged in parallel in a casing of a molding machine, Between the raw material feed screw and the extrusion screw, a plurality of elliptical paddles are stacked at equal angles around the entire circumference of the screw shaft, and a gap through which the raw material passes is formed between the tops of adjacent paddles. An apparatus for forming a raw material for a rotary hearth furnace for producing reduced iron, wherein a kneading part for kneading raw material pellets is disposed.   The kneading part is a raw material molding apparatus for a rotary hearth furnace, wherein a ratio of a gap through which the raw material passes with respect to a cross-sectional area of the molding machine is 2% to 25%.   The raw material molding apparatus for a rotary hearth furnace according to claim 1 or 2, wherein the elliptical paddle has a thickness of 30 to 200 mm.

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