WO2008078916A1

WO2008078916A1 - Apparatus for manufacturing compacted irons

Info

Publication number: WO2008078916A1
Application number: PCT/KR2007/006727
Authority: WO
Inventors: Myung-Chan Shin; Il-Hyun Cho
Original assignee: Posco
Priority date: 2006-12-22
Filing date: 2007-12-21
Publication date: 2008-07-03
Also published as: KR100797866B1; CN101589160B; CN101589160A

Abstract

The present invention relates to an apparatus for manufacturing compacted iron. An apparatus for manufacturing compacted iron includes i) a pair of rolls that compact direct reduced iron and manufacture compacted iron; and ii) a screw feeder that rotates to transfer the direct reduced iron toward a gap formed between the pair of rolls. The screw feeder includes i) a shaft that extends toward the gap; and ii) a screw that is formed on an outer surface of the shaft. A distance from a center axis passing through a center of the shaft to at least one edge of the screw is maintained to be the same or become less as the at least one edge is close to the pair of rolls.

Description

APPARATUS FOR MANUFACTURING COMPACTED IRONS

Technical Field

The present invention relates to an apparatus for manufacturing compacted iron by compacting direct reduced iron DRI, and more specifically to an apparatus for manufacturing compacted iron that improves transferring efficiency of the direct reduced iron. Background Art

Since a blast furnace method for producing molten iron has many problems such as environment pollution, a smelting reduction process, which can replace the blast furnace method, has been researched. In the smelting reduction process, raw coal is are directly used as a fuel and a reducing agent and iron ore is directly used as an iron source, and thereby molten iron is manufactured. After the iron ore is converted into reduced iron in a reduction reactor, the reduced iron is charged into a melter-gasifier.

Then, the reduced iron is melted therein, and thereby molten iron is manufactured.

Here, direct reduced iron DRI is compacted into the compacted iron by using an apparatus for manufacturing compacted iron, and then the compacted iron is charged into the melter-gasifier to secure permeability of gas in the melter-gasifier. The apparatus for manufacturing compacted iron includes a screw feeder and a pair of rolls. The direct reduced iron is charged into a gap formed between the pair of rolls by force of the screw feeder, and is then manufactured into compacted iron. DISCLOSURE

Technical Problem

An apparatus for manufacturing compacted iron that is capable of manufacturing compacted iron with a high compressive strength by efficiently transferring the direct reduced iron to a pair of rolls is provided. Technical Solution

An apparatus for manufacturing compacted iron according to an embodiment of the present invention includes i) a pair of rolls that compact direct reduced iron and manufacture compacted iron; and ii) a screw feeder that rotates to transfer the direct reduced iron toward a gap formed between the pair of rolls. The screw feeder includes i) a shaft that extends toward the gap; and ii) a screw that is formed on an outer surface of the shaft. A distance from a center axis passing through a center of the shaft to at least one edge of the screw is maintained to be the same or become less as the at least one edge is close to the pair of rolls.

At least one edge may include a plurality of edges. The plurality of edges may include i) a first edge; and ii) a second edge that is closer to the pair of rolls than the first edge. A first distance from the center axis of the shaft to the first edge may be the same or greater than a second distance from the center axis of the shaft to the second edge. A ratio of an area that is obtained by subtracting a cross-sectional area of the shaft located at the same plane with the first distance from an imaginary circle provided with the radius of the first distance with respect to an area that is obtained by subtracting a cross-sectional area of the shaft located at the same plane with the second distance from an imaginary circle provided with the radius of the second distance may be in a range from 1 to 1.4. The ratio may be substantially 1.2. The screw may further include a third edge that is closer to the pair of rolls than the second edge. A third distance from the center axis of the shaft to the third edge may be the same as the second edge. The first edge may be located to correspond to the second edge, and an imaginary line connecting the first and second edges may be substantially parallel to the outer surface of the shaft. A first radius of the shaft corresponding to the first edge may be greater than a second radius of the shaft corresponding to the second edge.

The shaft may include a diameter-reducing portion with a diameter that is gradually reduced close to the gap. The screw may include a surface contacting the direct reduced iron along a direction toward the gap, and an area of the surface may be maintained or is reduced as the surface is closer to the gap. The area of the surface may be reduced and then may be identically maintained as the surface is close to the gap.

A diameter of the shaft corresponding to the surface may be reduced close to the gap when the area of the surface is identically maintained. A transferring amount of the direct reduced iron may be linearly increased by the screw feeder as a rotating speed of the screw feeder increases. The rotating speed of the screw feeder may be in a range from 50 rpm to 100 rpm. Advantageous Effects

Since the direct reduced iron is compacted with an improved transferring efficiency of the screw feeder, a large amount of compacted iron with good compressive strength can be manufactured.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of the apparatus for manufacturing compacted iron according to a first embodiment of the present invention. FIG. 2 is a schematic enlarged view of a portion II of FIG. 1.

FIGs. 3 and 4 are graphs showing transferring amount of the direct reduced iron according to Exemplary Examples 1 and 2 of a present invention, respectively.

FIG. 5 is a partial schematic enlarged view of the screw feeder according to a Comparative Example of a prior art.

FIG. 6 is a graph showing a transferring amount of the direct reduced iron according to a Comparative Example of a prior art.

FIG. 7 is a graph comparing a ratio of a transferring amount of the direct reduced iron according to the Exemplary Examples 1 and 2, and the Comparative Example, with each other.

BEST MODE

Exemplary embodiments of the present invention will be explained in detail below with reference to the attached drawings in order for those skilled in the art in the field of the present invention to easily perform the present invention. However, the present invention can be realized in various forms and is not limited to the embodiments explained below. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and/ or sections, these elements, components, regions, layers, and/ or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The direct reduced iron mean materials containing iron that are reduced. The materials containing iron can be not only iron itself but also all materials containing iron. For example, materials containing iron can further contain additives. The materials containing iron contain iron ore. In addition, iron can be true iron, oxidized iron, or reduced iron. A reducing ratio of the reduced iron is not limited. Therefore, the reduced iron can be partially reduced or completely reduced. FIG. 1 is schematic perspective view of an apparatus for manufacturing compacted iron 100 according to an embodiment of the present invention. A structure of the apparatus for manufacturing compacted iron shown in FIG. 1 is merely to illustrate the present invention and the present invention is not limited thereto. Therefore, the structure of the apparatus for manufacturing compacted iron 100 can be modified in other forms. For example, the direct reduced iron can enter into a gap formed between the pair of rolls 20 without using a charging hopper 10. As shown in FIG. 1, the apparatus for manufacturing compacted iron 100 includes screw feeders 10, the pair of rolls 20, and the charging hopper 30. The direct reduced iron is charged into the charging hopper 30 through an opening 301 located at a center of the charging hopper 30. Ventilation openings 303 are located at an upper side of the charging hopper 30. A gas generated from the direct reduced iron that enters into the charging hopper 30 is ventilated to the outside of the charging hopper 30 through the ventilation openings 303.

As shown in FIG. 1, the screw feeders 10 are installed in the charging hopper 30 to be slanted at an acute angle. The screw feeders 10 rotate by transferring motors (not shown). The screw feeders 10 rotate to transfer the direct reduced iron to the gap (not shown) formed between the pair of rolls 20 in force. Therefore, a compressive density of the direct reduced iron entered into the gap by the screw feeders 10 can be increased. As illustrated by the dotted lined in FIG. 1, the screw feeder 10 includes a shaft 101 and a screw 103. The shaft 101 extends toward the gap. The screw 103 is formed on a lower portion of the shaft 101. The screw 103 is formed along an outer surface of the shaft 101. Therefore, after the direct reduced iron falls to a lower side of the charging hopper 30, it is caught by the screw 103, thereby entering into the gap. The screw 103 rotates to charge the direct reduced iron toward the gap in force. Therefore, the direct reduced iron can be manufactured into compacted iron with a high density.

As illustrated by arrows, the pair of rolls 20 rotate in opposite directions to each other while compacting the direct reduced iron to manufacture compacted iron. The pair of rolls 20 rotate while being combined to each other by a gear 201. The pair of rolls 20 are received in a casing 40. Since a lower side of the casing 40 is opened, the pair of rolls 20 compact the direct reduced iron to manufacture compacted iron, and discharge it them through the lower side of the casing 40. The screw 103 will be explained in detail hereinafter with reference to FIG. 2.

FIG. 2 schematically illustrates an enlarged portion II of FIG. 1. That is, FIG. 2 shows an enlarged view of the screw 103 formed in the lower portion of the shaft 101 of FIG. 1.

As shown in FIG. 2, the shaft 101 has an imaginary center axis C passing through a center thereof. Here, the center axis C passes through a center of a circle formed by cutting the shaft 101 along a direction perpendicularly crossing a longitudinal direction of the shaft 101.

As shown in FIG. 2, the shaft 101 includes a diameter-reducing portion 1015 with a diameter that gradually reduces as the shaft 101 gets closer to the gap. For example, a first radius ri of the shaft 101 is greater than a second radius r₂ thereof due to the diameter-reducing portion 1015. Since the direct reduced iron can secure a larger space toward a lower direction due to the diameter-reducing portion 1015, a large amount of the direct reduced iron smoothly enters into the gap. Therefore, production amount of the compacted iron can be largely increased.

As shown in FIG. 2, the screw 103 of the shaft 101 includes first, second, third and fourth edges 1031, 1033, 1035 and 1037, respectively. The second edge 1033 is located below the first edge 1031, and the third edge 1035 is located below the second edge 1033. In addition, the fourth edge 1037 is located below the third edge 1035. Therefore, from the first edge 1031 to the fourth edge 1037 while passing through the second and third edges 1033 and 1035, the gap becomes closer. Here, the first edge 1031 corresponds to the first radius T₁ of the shaft 101 and the second edge 1033 corresponds to the second radius r₂ of the shaft 101. That is, the first and second radiuses n and r₂ are located at the same line with the first and second edges 1031 and 1033, respectively. As shown in FIG.2, a second distance d₂ from the center axis C to the second edge 1033 is less than a first distance di from the center axis C to the first edge 1031. In addition, a third distance d₃ from the center axis C to the third edge 1035 is the same as a fourth distance d₄ from the center axis C to the fourth edge 1037. Therefore, distances from the center axis C to the edges 1031, 1033, 1035, and 1037 of the screw 103 are identically maintained or becomes less as the edges 1031, 1033, 1035, and 1037 are closer to the gap. Therefore, since a large space in a lower portion of the screw feeder 10 can be secured to fill the direct reduced iron, transferring efficiency of the direct reduced iron can be improved.

Meanwhile, on the contrary to FIG. 2, first, second, third, and fourth distances di, d₂, d₃, and άi can be set up by selecting any edge of the screw from the center axis C. Therefore, the first distance di can be the third distance d₃ while the second distance d₂ can be the third distance d₃. In this case, the first distance di is the same as the second distance d₂. In addition, since the second distance d₂ can be the fourth distance d₄, the second distance d₂ can also be the same as the third distance d₃. A first area πdi² of an imaginary circle provided with a first distance di as a radius is greater than a second area πd₂ ² of an imaginary circle provided with a second distance d₂ as a radius. Here, a ratio of an area that is obtained by subtracting a cross-sectional area of the shaft 101 located at the same plane with the first distance di from an imaginary circle provided with the radius of the first distance di with respect to an area that is obtained by subtracting a cross-sectional area of the shaft 101 located at the same plane with the second distance d₂ from an imaginary circle provided with the radius of the second distance d₂ can be in a range from 1 to 1.4. The above- described area can be referred to as a projection cross-sectional area of the screw 103.

In this case, as a rotating speed of the screw feeder 10 increases, transferring amount of the direct reduced iron linearly increases by the screw feeder 10. If the above-described ratio is over 1.4, transferring efficiency of the direct reduced iron does not increase when the screw feeder rotates with a certain rotating speed. More specifically, the above-described ratio can be substantially 1.2. In this case, transferring amount of the direct reduced iron can be optimally increased as a rotating speed of the screw feeder 10 increases. On the contrary, if the above-described ratio is less than 1, the transferring amount of the direct reduced iron does not linearly increase even if the rotating speed of the screw feeder 10 increases.

Meanwhile, a third area πd₃ ² of an imaginary circle provided with a third distance d₃ as a radius can be the same as a fourth area πd4² of an imaginary circle provided with a fourth distance dU as a radius. Therefore, a ratio of a third area πd₃ ² with respect to a fourth area πd₄ ² can be 1. In this case, a cross-sectional area of the shaft 101 located at the same plane with the third distance d₃ is the same as a cross-sectional area of the shaft 101 located at the same plane with the fourth distance d4.

A rotating speed of the screw feeder 10 can be in a range from 50 to 100 rpm. If the rotating speed of the screw feeder 10 is less than 50rpm, a large amount of the compacted iron cannot be produced since the transferring amount of the direct reduced iron is small. In addition, if the rotating speed of the screw feeder 10 is over lOOrpm, a severe load is applied to the pair of rolls 20 since a large amount of the direct reduced iron is charged thereinto. Furthermore, a large amount of dust can be scattered outside the apparatus for manufacturing compacted iron 100 when a large amount of the direct reduced iron is transferred. As shown in FIG. 2, an imaginary line L indicated by a dotted line connecting the first and second edges 1031 and 1033 is substantially parallel to an outer surface 101s of the shaft 101. That is, the imaginary line L is parallel to the outer surface 101s of the diameter-reducing portion 1015. Therefore, an area of a surface 1039 of the screw 103 is identically maintained even if the diameter of the shaft 101 is reduced. As a result, the amount of the direct reduced iron filled around the diameter-reducing portion 1015 is constantly maintained.

The above-described surface 1039 contacts the direct reduced iron along a direction toward the gap. An area of the surface 1039 is identically maintained or is reduced close to the gap. That is, as shown in FIG. 2, the area of the surface 1039 in the diameter-reducing portion 1015 is identically maintained. In addition, an area of the surface 1039 is also identically maintained in a portion of the shaft 101, with a constant radius r_3/ located below the diameter-reducing portion 1015. A diameter of the shaft 101 is reduced as toward a lower portion in the diameter-reducing portion 1015 corresponding to the surface 1039.

On the contrary, an area of the surface 1039 is reduced in a connected portion from the diameter-reducing portion 1015 to a portion of the shaft 101 with a constant radius r₃. Accordingly, an area of the surface 1039 is reduced and then identically maintained in the portion of the shaft 101 with a constant radius r₃. Therefore, transferring amount of the direct reduced iron can be significantly increased close to the gap.

The present invention will be explained in detail hereinafter with reference to Exemplary Examples. The Exemplary Examples are merely to illustrate the present invention, and the present invention is not limited thereto. Exemplary Example 1

The compacted iron was manufactured by using the apparatus for manufacturing compacted iron in which the screw feeder was installed. A first distance between the center axis of the shaft and the edge of the screw formed at a portion into which the direct reduced iron entered in a portion of the screw formed in the screw feeder was measured. In addition, a second distance between the center axis of the shaft and the edge of the screw formed where the direct reduced iron is discharged was measured. As a result of measuring, the first and second distances were found to be almost the same. The direct reduced iron was charged into the gap formed between the pair of rolls by using the screw feeder, and the compacted iron was continuously manufactured by compacting the direct reduced iron by rotating the pair of rolls in opposite directions. In this case, transferring amount of the direct reduced iron was measured according to a rotating speed of the respective screw feeder while a rotating speed of the screw feeder was increased.

Experimental Result of the Exemplary Example 1 FIG. 3 is a graph showing transferring amounts of the direct reduced iron according to the Exemplary Example 1. In FIG. 3, transferring amounts of the direct reduced iron according to the rotating speed of the screw feeder are shown as a plurality of rectangles and lozenges. As shown in FIG. 3, the transferring amount of the direct reduced iron was gently increased as the rotating speed of the screw feeder was increased from about 75rpm to about 125rpm. That is, the transferring amount of the direct reduced iron was increased from 50t/h to 68t/h. Therefore, when the screw feeder with the above shape was used, it was confirmed that the transferring amount of the direct reduced iron linearly increased as the rotating speed of the screw feeder was increased. In this case, transferring efficiency of the direct reduced iron of the screw feeder was measured to be about 0.50. Exemplary Example 2 The compacted iron was manufactured by using the apparatus for manufacturing compacted iron in which the screw feeder was installed. A first distance between the center axis of the shaft and the edge of the screw formed at a portion into which the direct reduced iron entered in a portion of the screw formed in the screw feeder was measured. In addition, a second distance between the center axis of the shaft and the edge of the screw formed where the direct reduced iron is discharged was measured. As a result of measuring, a ratio of a projection cross-sectional area of a screw located at the same plane with the first distance with respect to that of a screw located at the same plane with the second distance was 1.4. The remaining exemplary procedures were the same as those of the above- described Exemplary Example 1.

Experimental Result of the Exemplary Example 2 FIG. 4 is a graph showing transferring amounts of the direct reduced iron according to the Exemplary Example 2. In FIG. 4, transferring amounts of the direct reduced iron according to the rotating speed of the screw feeder are shown as a plurality of lozenges. As shown in FIG. 4, the transferring amount of the direct reduced iron was somewhat rapidly increased as the rotating speed of the screw feeder was increased from about 75rpm to about 120rpm. That is, the transferring amount of the direct reduced iron was increased from 50t/h to 69t/h. Therefore, when the screw feeder with the above shape was used, it was confirmed that the transferring amount of the direct reduced iron linearly increased as the rotating speed of the screw feeder was increased. In this case, a transferring efficiency of the direct reduced iron of the screw feeder was measured to be about 0.52.

Comparative Example

FIG. 5 schematically shows an enlarged lower portion of the screw feeder 90 used in the Comparative Example of a prior art to be compared with the above-described Exemplary Examples 1 and 2. As shown in FIG. 5, a screw feeder 90 includes a shaft 901 and a screw 903. An area of a surface 9039 of the screw 903 is gradually increased toward a lower portion thereof to the contrary to the above-described Exemplary Examples 1 and 2.

The compacted iron was manufactured by using the apparatus for manufacturing compacted iron in which the screw feeder 90 of FIG. 5 was installed. A first distance between the center axis of the shaft and the edge of the screw formed at a portion into which the direct reduced iron entered a portion of the screw formed in the screw feeder was measured. In addition, a second distance between the center axis of the shaft and the edge of the screw formed where the direct reduced iron is discharged was measured.

As a result of measuring, a ratio of a projection cross-sectional area of a screw located at the same plane with the first distance with respect to that of a screw located at the same plane with the second distance was found to be 0.2.

The remaining exemplary procedures were the same as those of the above- described Exemplary Example 1.

Experimental Result of the Comparative Example

FIG. 6 is a graph showing transferring amounts of the direct reduced iron according to the Comparative Example. In FIG. 6, transferring amounts of the direct reduced iron according to the rotating speed of the screw feeder are shown as a plurality of lozenges. As shown in FIG. 6, the rotating speed of the screw feeder was in a range from about 60rpm to about 120rpm, and the transferring amount of the direct reduced iron was in a range from 5Ot/ h to 6Ot/ h. However, transferring amounts of most of the direct reduced iron were measured to be 58t/h or less. This was shown when the rotating speed of the screw feeder was 95rpm or more. Therefore, the rotating speed of the screw feeder was not increased to be proportionate to the transferring amount of the direct reduced iron. In this case, the transferring efficiency of the direct reduced iron of the screw feeder was measured to be about 0.2.

The above-described Exemplary Examples 1 and 2, and the Comparative Example, are explained to be compared with each other hereinafter. For comparing the above-described Exemplary Examples 1 and 2, and the Comparative Example with each other, the above-described Exemplary Examples 1 and 2, and the Comparative Example, are shown as a graph after a ratio of the transferring amount of the direct reduced iron is set as 100% when the rotating speed of the reduced iron is 50rpm. FIG. 7 is a graph comparing ratios of the transferring amount of the direct reduced iron according to the Exemplary Examples 1 and 2, and the Comparative Example, with each other.

As shown in FIG. 7, transferring amounts of the direct reduced iron were linearly increased in the Exemplary Examples 1 and 2, and the Comparative Example, when the rotating speed of the screw feeder was in a range from Orpm to 50rpm. However, when the rotating speed of the screw feeder is 50rpm or more, the transferring amounts of the direct reduced iron were only linearly increased in the Exemplary Examples 1 and 2 while the transferring amount of the direct reduced iron was not increased and was identically maintained in the Comparative Example 1. Meanwhile, the transferring amount of the direct reduced iron did not increase any more as the rotating speed of the screw feeder exceeded lOOrpm in the Exemplary Examples 1 and 2. Since the Exemplary Examples 1 and 2 were merely to illustrate the present invention and the present invention is not limited thereto, a transferring amount of the direct reduced iron can be increased even though the rotating speed of the screw feeder exceeds lOOrpm in other conditions.

As shown in FIG. 7, in the Exemplary Examples 1 and 2 of the present invention, a large amount of the compacted iron could be manufactured since the transferring amount of the direct reduced iron linearly increased when the rotating speed of the screw feeder was in a range from 50rpm to lOOrpm. On the contrary, in the Comparative Example, it was not suitable to manufacture a large amount of compacted iron since the transferring amount of the direct reduced iron was not increased when the rotating speed of the screw feeder was over 50rpm.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

CLAIM

1. An apparatus for manufacturing compacted iron, comprising: a pair of rolls that compact direct reduced iron and manufacture compacted iron; and a screw feeder that rotates to transfer the direct reduced iron toward a gap formed between the pair of rolls, wherein the screw feeder comprises a shaft that extends toward the gap, and a screw that is formed on an outer surface of the shaft, and wherein a distance from a center axis passing through a center of the shaft to at least one edge of the screw is maintained to be the same or become less as the at least one edge is close to the pair of rolls.

2. The apparatus of Claim 1, wherein the at least one edge comprises a plurality of edges, and wherein the plurality of edges comprise: a first edge; and a second edge that is closer to the pair of rolls than the first edge, and wherein a first distance from the center axis of the shaft to the first edge is the same or greater than a second distance from the center axis of the shaft to the second edge.

3. The apparatus of Claim 2, wherein a ratio of an area that is obtained by subtracting a cross-sectional area of the shaft located at the same plane with the first distance from an imaginary circle provided with the radius of the first distance with respect to an area that is obtained by subtracting a cross-sectional area of the shaft located at the same plane with the second distance from an imaginary circle provided with the radius of the second distance is in a range from 1 to 1.4.

4. The apparatus of Claim 3, wherein the ratio is substantially 1.2.

5. The apparatus of Claim 2, wherein the screw further comprises a third edge that is closer to the pair of rolls than the second edge, and wherein a third distance from the center axis of the shaft to the third edge is the same as the second edge.

6. The apparatus of Claim 2, wherein the first edge is located to correspond to the second edge, and wherein an imaginary line connecting the first and second edges is substantially parallel to the outer surface of the shaft.

7. The apparatus of Claim 6, wherein a first radius of the shaft corresponding to the first edge is greater than a second radius of the shaft corresponding to the second edge.

8. The apparatus of Claim 1, wherein the shaft comprises a diameter-reducing portion whose diameter is gradually reduced close to the g^aP-

9. The apparatus of Claim 1, wherein the screw comprises a surface contacting the direct reduced iron along a direction toward the gap, and wherein an area of the surface is maintained or is reduced as the surface is closer to the gap.

10. The apparatus of Claim 9, wherein the area of the surface is reduced and is then identically maintained as the surface is close to the gap.

11. The apparatus of Claim 9, wherein a diameter of the shaft corresponding to the surface is reduced close to the gap when the area of the surface is identically maintained.

12. The apparatus of Claim 1, wherein a transferring amount of the direct reduced iron is linearly increased by the screw feeder as a rotating speed of the screw feeder increases.

13. An apparatus of Claim 12, wherein the rotating speed of the screw feeder is in a range from 50 rpm to 100 rpm.