JP7425302B2 - How to transport pellets - Google Patents

Description

The present invention relates to a method for conveying pellets obtained by rolling granulation of powder containing iron oxide upward on a belt conveyor.

The raw fuel to be charged into the blast furnace is normally conveyed to the top of the blast furnace, for example, about 50 meters above the ground using a belt conveyor. At this time, the inclination angle of the belt conveyor is often set to a gentle inclination of 8° to 15° with respect to the horizontal plane so that the raw fuel does not fall from the belt conveyor used. However, even with a gentle slope, it may not be possible to prevent pellets used as raw materials from falling.

Pellets are formed by rolling granulation of iron-containing powder such as iron oxide, and may also be fired, but since they are roughly spherical with a diameter of about 10 mm, they are transported upwards on a belt conveyor. It may roll off the conveyance surface when being conveyed. Hereinafter, in this specification, rolling down of the pellet from the conveyance surface will be referred to as "falling down."

Usually, pellets are conveyed along with other raw materials (sintered ore, lump ore, etc.) on a belt conveyor. If the proportion of pellets in the raw material is about 2 to 3% by mass, falling of the pellets is often not considered a problem, but if the proportion of pellets increases to, for example, about 5% by mass, the falling of pellets becomes a problem that cannot be ignored. increase

Therefore, in Patent Document 1, a sheet of rubber or the like is arranged on the tail side of the belt conveyor (in the opposite direction to the conveyance direction), the sheet is bent and brought into contact with the conveyance surface of the belt conveyor, and the sheet is transported from the tail side of the belt conveyor. A technique for preventing objects from spilling is disclosed.
Further, Patent Document 2 discloses a technique in which a brush material tail skirt is arranged at the tail portion of an inclined belt conveyor to prevent sandy debris from falling from the tail portion.

Utility Model Publication No. 51-153986 Japanese Patent Application Publication No. 2016-84217

However, when the techniques described in Patent Document 1 and Patent Document 2 are applied to conveying pellets, it has been found that the following problems occur.
In the case of the technique described in Patent Document 1, a large amount of fallen pellets accumulates on the leading edge of a sheet placed on a belt conveyor, causing the leading edge of the sheet to wear out. As a result, the sheet does not come into contact with the conveying surface, causing the pellets to fall to the tail side of the belt conveyor.
On the other hand, according to the technique described in Patent Document 2, although the brush material tail skirt can suppress falling of pellets to some extent, it is not sufficient because some pellets pass through the brush material tail skirt and fall. Further, when the pellets that have passed through the brush tail skirt are conveyed again by the belt conveyor, the brush tail skirt becomes an obstacle and cannot be conveyed upward.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method that can prevent pellets from falling toward the tail side, compared to conventional methods, when pellets are conveyed upward on a belt conveyor. shall be.

In order to achieve the above object, the present invention provides a method for conveying pellets obtained by rolling granulation of powder containing iron oxide using a belt conveyor tilting upward in the conveyance direction, comprising:
A skirt is disposed in the width direction of the conveyance surface with a clearance provided between the conveyance surface and the conveyance surface at a location below the conveyance surface of the belt conveyor from a location where the pellets are supplied to the belt conveyor; A sheet whose tail side is curved to be convex and whose bent tip contacts the conveyance surface is arranged in the width direction of the conveyance surface at a location further down along the conveyance surface from the location where the skirt is arranged. and
The clearance is characterized in that the diameter of the pellet is 1.0×d to 3.5×d.

Conventionally, when conveying raw materials upwards on a belt conveyor, a skirt or sheet was placed alone, but when conveying raw materials that easily roll, such as pellets, it was not possible to sufficiently prevent the pellets from falling. Ta.
However, the present inventors have discovered that by devising a combination of a skirt and a sheet, remarkable effects that could not be predicted from conventional methods can be obtained.
In the present invention, wear of the skirt is prevented by arranging a skirt that has enough clearance between the conveyor surface and the conveyor surface to allow the pellets to pass through, at a location below the conveyor surface from the point where the pellets are fed to the belt conveyor. At the same time, most of the falling pellets are caught by the skirt and the direction of pellet travel is reversed to the conveying direction. The pellets that have passed through the clearance of the skirt roll upward on a sheet placed further down along the conveyance surface, then roll downward and return to the conveyance surface. The pellets returned to the conveying surface are conveyed again by the belt conveyor, pass through the clearance of the skirt, and are conveyed upward.

Further, in the pellet conveying method according to the present invention, it is preferable that the ratio of the pellets to the raw material supplied to the belt conveyor is 30% or more.

Fallen pellets accumulate on the tail side of the belt conveyor, which requires cleaning.
When pellets and raw materials other than pellets are mixed and conveyed upward on a belt conveyor, if the blending ratio of pellets is less than 30%, the cleaning load will be reduced because the raw materials other than pellets will suppress the pellets from falling. Therefore, although falling pellets occur, it does not pose a problem that affects actual operations, but when the blending ratio of pellets exceeds 30%, the amount of falling pellets increases significantly, and the cleaning load increases significantly. Therefore, when the present invention is applied when the blending ratio of pellets is 30% or more, greater effects can be obtained.

Further, in the pellet conveying method according to the present invention, the sheet is wound into a roll and stored directly above the belt conveyor, and the leading end of the sheet is rolled up by stretching the sheet wound into a roll. It is preferable to contact the conveyance surface.

When a sheet breaks or wears out, it is necessary to replace it in the conventional technology, but in the present invention, since the sheet is wound into a roll, it is sufficient to stretch the sheet, and the work of replacing the sheet can be omitted, which is efficient. .
According to the findings of the present inventors, if natural rubber (hard) with a thickness of 5 mm is used as a sheet under the conditions according to the present invention, it will wear out in about 4 weeks, ensuring sufficient contact between the sheet tip and the conveying surface. become unable.

In the pellet conveying method according to the present invention, a skirt having a clearance between the conveying surface and the conveying surface that is large enough to allow the pellets to pass is disposed at a location below the conveying surface from the location where the pellets are fed to the belt conveyor, and By placing a sheet further down along the conveyance surface that reverses the rolling direction of pellets that have passed through the skirt clearance, the amount of pellets falling toward the tail side is significantly suppressed compared to conventional methods. be able to. As a result, the frequency of cleaning is reduced and the workload is reduced.

FIG. 2 is a schematic diagram for explaining a pellet conveying method according to an embodiment of the present invention. FIG. 3 is a schematic diagram for explaining the function of a skirt in the pellet conveying method according to the present embodiment. FIG. 3 is a schematic diagram for explaining a problem that occurs in a sheet when the clearance between the conveyance surface and the skirt is large. (A) is a schematic diagram of the sheet leading edge in the pellet conveying method according to the present embodiment, and (B) is a schematic diagram of the sheet leading edge in the conventional method.

Next, embodiments embodying the present invention will be described with reference to the attached drawings to provide an understanding of the present invention.

The raw materials charged to the blast furnace include lump ore, sintered ore, small coke lumps, and pellets, but there is almost no possibility that raw materials other than pellets will fall to the tail side of the belt conveyor, and The extent of this is that some people may fall.
The present invention relates to a method of transporting pellets while suppressing falling of the pellets using a belt conveyor that is inclined upward in the transport direction. An embodiment thereof will be described below.

The belt conveyor used in this embodiment has an inclination angle of 8° to 15° with respect to the horizontal plane, and pellets are supplied to the tail side conveyance surface of the belt conveyor. In this embodiment, as shown in FIGS. 1(A) and 1(B), the skirt 12 is disposed at a location lower along the conveying surface 11 than the location where pellets P are supplied to the belt conveyor 10. The sheet 13 is disposed in the width direction of the conveyance surface 11 at a location further down along the conveyance surface 11 from the location where the sheet 13 is placed.

The pellets P are made by rolling granulation of powder containing iron oxide and are approximately spherical. Pellets are usually traded in nominal diameter. For example, a pellet with a diameter of 10 mm means that the nominal diameter is 10 mm, but the actual diameter range is about 5 mm to 15 mm (0.5 to 1.5 times the nominal diameter), and pellets with a diameter of 10 mm are most common.

The skirt 12 is a plate-shaped body that stands vertically, and is arranged in the width direction of the conveyance surface 11 with a clearance C provided between the lower end surface of the skirt 12 and the conveyance surface 11. It is preferable to use a material for the skirt 12 that does not easily bend or flex.

The sheet 13 is curved so that the tail side is convex, and the bent tip 13a is brought into contact with the conveying surface 11. In the conventional sheet, as shown in FIG. 4(B), only the leading end 13b was in contact with the conveying surface 11, but in this embodiment, as shown in FIG. 4(A), the sheet 13 is made to have a bend, The entire tip portion 13a is brought into contact with the conveying surface 11. The sheet 13 can be made of flexible resin, rubber, or the like.
The distance L from the skirt 12 to the tip 13b of the sheet 13 is 1 m or less.

In the present embodiment, a belt-shaped sheet 13 is wound into a roll and stored directly above the belt conveyor 10, and by stretching the rolled sheet 13, the leading end 13a of the sheet 13 is brought to the conveying surface 11. I'm trying to make contact.

Next, a method for conveying pellets P upward using the belt conveyor 10 having the above configuration will be described.

When pellets P are supplied to the belt conveyor 10 that is inclined upward in the conveyance direction, most of the pellets P are conveyed upward by the belt conveyor 10, but some of the pellets P fall to the tail side. As shown in FIG. 1(A), some of the pellets P that have fallen to the tail side bounce on the conveyance surface 11, collide with the skirt 12, and then return to the conveyance surface 11 and are conveyed upward.
On the other hand, as shown in FIG. 2, some of the fallen pellets P pass through the clearance C provided between the skirt 12 and the conveying surface 11 and fall to the tail side, while others bounce and collide with the skirt 12 and then fall to the tail side. , some objects pass through clearance C and fall to the tail side.

As shown in FIG. 1(A), pellets P that have fallen toward the tail side may accumulate in the clearance C between the conveyance surface 11 and the skirt 12. The accumulation state of the pellets P is cleared at a certain frequency, and after the accumulation state is cleared, a part of the pellets P moves in the conveying direction, and the remaining part passes through the clearance C and falls toward the tail side.

The pellets P that have passed through the clearance C between the conveyance surface 11 and the skirt 12 roll upward on the sheet 13 placed further down along the conveyance surface 11, and then roll downward to reach the conveyance surface. 11 (see FIG. 1(A)). The pellet P that has returned to the conveyance surface 11 is conveyed again by the belt conveyor 10, passes through the clearance C of the skirt 12, and is conveyed upward (see FIG. 1(B)).

The clearance C is 1.0×d to 3.5×d, where d is the diameter of the pellet P.
Since the conveyance surface 11 moves up and down when the belt conveyor 10 is in operation, the clearance C is defined as the distance between the conveyance surface 11 and the lower end surface of the skirt 12 when the belt conveyor 10 is stopped. In addition, when the conveying surface 11 is provided with unevenness, the distance is defined as the distance between the upper surface of the convex portion of the conveying surface 11 and the lower end surface of the skirt 12.

If the clearance C is less than 1.0 times the diameter of the pellets P, the pellets P rolling on the sheet 13 may not be able to pass through the skirt 12 and will accumulate between the skirt 12 and the sheet 13.
On the other hand, if the clearance C is more than 3.5 times the diameter of the pellet P, most of the pellet P falls to the tail side, and a large amount of the pellet P stays on the sheet 13 (see FIG. 3). As a result, the wear of the sheet 13 becomes noticeable, and the pellets P often fall further toward the tail side from the gap between the worn sheet 13 and the conveyance surface 11 and fall off the belt conveyor 10.

Therefore, if the clearance C is 1.0 times or more and 3.5 times or less than the diameter of the pellet P, the pellet P that has rolled on the sheet 13 can be prevented from falling to the tail side, and the pellet P that has rolled on the sheet 13 can be transferred to the skirt 12. It passes through the clearance C and is conveyed upward.

In addition, when the ratio of pellets P to the raw material supplied to the belt conveyor 10 is 30% or more, the effect of suppressing falling of pellets P becomes even greater.

Although one embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the above-described embodiment, and within the scope of the claims. It also includes other possible embodiments and modifications. For example, in the embodiment described above, the sheet is rolled up and stored directly above the belt conveyor, but a rectangular sheet may be hung from above the belt conveyor.

A verification test conducted to verify the effects of the present invention will be described.
For validation tests, pellets were used with a diameter of 5 mm to 15 mm (average diameter: 10 mm), with the most frequent particle size range being 9.5 mm to 10.5 mm.
The raw material conveyed by the belt conveyor is a mixture of sintered ore, lump ore, and pellets, and the total raw material is 100% by mass, and the blending ratio of pellets (mass%) is rounded to the nearest tenth. . The reason for using such a unit is that even if the pellet blending ratio is set to 30% by mass, it will fluctuate within the range of 26 to 33% by mass depending on the daily operation status of the blast furnace and the arrival status of pellets. This is because there is.

The inclination angle of the belt conveyor was 15° with respect to the horizontal plane, and the distance from the skirt to the tip of the sheet was 1 m.
The skirt is made of hard natural rubber with a thickness of 10 mm, which does not easily bend or flex, and the clearance between the skirt and the transport surface was adjusted when the skirt was attached.
A flexible natural rubber sheet with a thickness of 5 mm was used as the sheet. Note that the sheet is commercially available in the form of a roll.
Table 1 shows a list of test results.

Since the problem of the present invention is to suppress falling pellets, each case was evaluated based on the time (Hr) required to clean the fallen pellets.
The cleaning time for fallen pellets includes the time to clean the pellets that have passed through the skirt and the sheet and the time to remove the pellets that are constantly staying between the skirt and the sheet. Pellets that constantly remain between the skirt and the seat have a strong tendency to remain on the seat, accelerating wear of the seat. Therefore, in order to reduce falling pellets, it is also necessary to reduce the amount of stuck pellets.

In this test, when the blending ratio of pellets was 10%, cases where the cleaning time was improved by 30% or more compared to the conventional example were marked as ○, and other cases were marked as ×. In addition, when the blending ratio of pellets is 30%, based on Comparative Example 4, which had the shortest cleaning time among the comparative examples, if the cleaning time is improved by 30% or more compared to Comparative Example 4, it is marked as ○, and in other cases was marked as ×.

The findings from this test are listed below.
- The cleaning time of Examples 1 and 2 was less than half of the cleaning time of Comparative Example 4, and the cleaning time was shorter than that of the conventional example.
- When the blending ratio of pellets becomes 30% or more, the problems of the present invention become apparent (comparison between the conventional example and Example 1).
- By arranging a sheet with flexure at the tip, the amount of falling pellets is significantly reduced, and the cleaning time is significantly reduced (comparison between Comparative Example 1 and Example 1).

- The upper limit of the clearance between the skirt and the conveyance surface is known (comparison between Example 1 and Comparative Example 2).
In Comparative Example 2, since the clearance was too large, the number of pellets passing through the clearance and falling toward the seat increased. As a result, too many pellets remained at the leading end of the sheet (see FIG. 3), resulting in a longer cleaning time.

- The lower limit of the clearance between the skirt and the conveyance surface is known (comparison between Example 2 and Comparative Example 3).
The clearance in Comparative Example 3 is 0.8×d (d is the nominal diameter of the pellet), but since the diameter of the pellet has a wide range, some pellets pass through the clearance. When the pellets that have passed through the clearance are conveyed by a belt conveyor and try to pass through the skirt again, if the clearance is small, the number of pellets that cannot pass through the clearance increases. As a result, cleaning time becomes longer.

- By bending the tip of the sheet, it becomes possible to convey the pellets that have passed through the clearance of the skirt again on the belt conveyor (comparison between Example 1 and Comparative Example 4).
Comparative Example 4 is an example in which the sheet is short and sufficient deflection cannot be imparted to the tip of the sheet, but the pellets that have passed through the clearance of the skirt either stay near the contact area between the sheet and the conveyance surface, or stay in the contact area. It passed through and fell further to the tail side. In addition, the wear of the sheet was accelerated, and a further increase in the number of pellets falling to the tail side occurred. As a result, cleaning time became longer.

10: belt conveyor, 11: conveyance surface, 12: skirt, 13: sheet, 13a: tip, 13b: tip, C: clearance, L: distance, P: pellet

Claims (3)

A method of transporting pellets obtained by rolling granulation of powder containing iron oxide on a belt conveyor that slopes upward in the transport direction, the method comprising:
A skirt is disposed in the width direction of the conveyance surface with a clearance provided between the conveyance surface and the conveyance surface at a location below the conveyance surface of the belt conveyor from a location where the pellets are supplied to the belt conveyor; A sheet whose tail side is curved to be convex and whose bent tip contacts the conveyance surface is arranged in the width direction of the conveyance surface at a location further down along the conveyance surface from the location where the skirt is arranged. and
A method for conveying pellets, characterized in that the clearance is 1.0×d to 3.5×d, where d is the diameter of the pellet. 2. The method for transporting pellets according to claim 1, wherein the ratio of the pellets to the raw material supplied to the belt conveyor is 30% or more. In the pellet conveying method according to claim 1 or 2, the sheet is wound into a roll and stored directly above the belt conveyor, and the leading end of the sheet is stretched by stretching the rolled sheet. A method for conveying pellets, comprising bringing the pellets into contact with the conveying surface.

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