JP7701945B2 - Apparatus and method for preventing powdering of raw materials in a chute - Google Patents

Description

The present invention relates to a device and method for preventing powdering of raw materials in a chute, which is used to prevent powdering of raw materials during transport in a transport chute with refractory materials, liners, etc. installed on the walls.

In the steelmaking process, multiple belt conveyors are used to transport lump-shaped raw materials for steelmaking, such as coal, iron ore, briquettes, and pellets, to blast furnaces, carbonization furnaces, etc. At the transfer points between the belt conveyors, there is a drop, and a transport chute (hereafter simply referred to as a chute) is installed.

However, when the lump raw materials for ironmaking thrown from the upper belt conveyor collide with the chute wall surface, which is the wall surface at the bottom where the raw materials slide down, or with the lower belt conveyor, some of the raw materials are broken and fine powder is generated. If there is a lot of fine powder in the raw materials for ironmaking, the porosity decreases and uneven heating occurs due to non-uniformity in the downstream process of blast furnaces, carbonization furnaces, etc. (hereinafter sometimes abbreviated as furnaces, etc.), which deteriorates the operating yield and product quality. There are also environmental problems such as scattering and falling of fine powder from the belt conveyor and dust generation. Currently, after transportation by the belt conveyor, a sieving device is installed before feeding the raw materials into the furnace, etc. to remove the fine powder. Also, if the proportion of fine powder in the raw materials for ironmaking is high, the amount of material that falls through the sieve increases, the yield decreases, the amount of material fed into the furnace, etc. decreases, and the production volume also decreases. Therefore, it is desirable to prevent the falling and powdering of raw materials in the chute. Various methods have been proposed to prevent such powdering of raw materials in the chute.

For example, one method proposed for preventing powdering of raw materials inside a chute is to install shelves on the wall of the chute to intentionally form a dead stock of raw materials, and then drop the raw materials onto the dead stock to buffer and slow down the raw materials and prevent powdering (Patent Document 1). This dead stock acts as a buffer for the falling raw materials onto it, and also as a means of slowing down the falling raw materials that go over it. However, this method is difficult to install additional shelves after the chute is installed if the wall of the chute is covered with refractory material or a liner (ceramic, etc.). This is because the shelves cannot be fixed in place with welding or bolts unless the refractory material or liner is removed.

In addition, if the raw material is a combustible material such as coal, there is a risk of fire caused by the deadstock drying out after a long period of time and spontaneously combusting. In particular, if the chute is directly connected to a furnace or the like below, there is a higher risk of fire caused by heat from the furnace or the like.

Another method proposed is to install stepped irregularities on the wall of the chute to intentionally form a dead stock of the raw materials, and then drop the raw materials onto the dead stock to buffer, slow down, and prevent the raw materials from pulverizing (Patent Document 2). However, as in the case of Patent Document 1, it is difficult to install additional irregularities after the chute has been installed. Also, as in the case of Patent Document 1, if the raw materials are combustible materials such as coal, there is a disaster prevention risk that the dead stock that has been left there for a long period of time will dry out and spontaneously ignite.

Another method has been proposed in which a part of the chute shape is made into a recess in advance to intentionally form a dead stock of the raw material, and the raw material is dropped onto the dead stock to cushion, slow down, and prevent the raw material from pulverizing (Patent Document 3). However, with this method, as with Patent Document 1, it is difficult to modify the recess after the chute is installed. Also, as with Patent Document 1, if the raw material is a combustible material such as coal, there is a disaster prevention risk that the dead stock that has been left there for a long period of time will dry out and spontaneously ignite.

Patent No. 6464790 JP 2014-118294 A Japanese Utility Model Application Publication No. 6-76227

In view of the above, the present invention aims to provide a device and method for preventing powdering of raw materials in a chute that can be easily attached to the chute regardless of the presence or absence of refractories or liners, and that can easily prevent the long-term retention of dead stock of raw materials.

The inventors conducted extensive research to solve the above-mentioned problems. As a result, they discovered that by installing a means for temporarily retaining the raw materials inside the chute in a suspended form from above, it would be easier to attach or modify the means after the chute is installed, and it would also be easier to control the retention period of the retained raw materials. After further research, they developed the present invention.

That is, the present invention is as follows.
[1] A device for preventing powdering of raw materials fed into a conveying chute due to the impact of the raw materials falling thereon,
A support portion;
a plurality of suspension members each having an upper end supported by the support portion and extending downward within the chute;
a lower end member fixed to the lower ends of the plurality of hanging members and having a means for retaining the raw material;
A device for preventing powdering of raw material in a conveying chute, characterized in that the multiple suspension members are arranged at intervals in the width direction of the chute.
[2] The device for preventing powdering of raw materials in a conveying chute described in [1], wherein the support section is provided with a means for adjusting the arrangement interval and/or the height direction position of the hanging members.
[3] The device for preventing powdering of raw materials in a conveying chute described in [1] or [2] above, characterized in that the suspension member and the means for retaining the raw materials are made of steel.
[4] The device for preventing powdering of raw materials in a conveying chute described in any one of [1] to [3], characterized in that the raw materials are raw materials for ironmaking.
[5] The device for preventing powdering of raw materials in a conveying chute according to any one of [1] to [4], characterized in that the raw materials are molded coals having an average particle size of 10 to 60 mm.
[6] The device for preventing powdering of raw materials in a conveying chute according to any one of [1] to [5], characterized in that the chute is covered with a refractory material or a liner.
[7] A method for preventing powdering of raw materials in a conveying chute using the device for preventing powdering of raw materials in a conveying chute according to any one of [1] to [5],
A method for preventing powdering of raw materials in a conveying chute, characterized in that the arrangement spacing and/or height position of the hanging members are set by the support part, and the raw materials are held back by a means for retaining the raw materials to form a raw material pool, thereby mitigating the impact of the fall.
[8] The method for preventing powdering of raw material in a conveying chute described in [7] above, further comprising raising a height direction position of the suspension member to open the raw material reservoir.
[9] The method for preventing powdering of raw materials in a conveying chute according to [7] or [8], characterized in that the raw materials are molded coals having an average particle size of 10 to 60 mm.

According to the present invention, the upper ends of multiple suspended members arranged in the width direction of the chute are supported, and the raw materials can be held by the lower end member, so that the newly added raw materials are cushioned and slowed down to prevent pulverization. The support part can be placed above the chute, which does not have a refractory material or liner, making it easy to install. In addition, by supporting the upper ends of the suspended members with the support part, it is possible to control the amount of raw materials accumulated by adjusting the arrangement interval of the suspended members and the gap below the lower end member, and spontaneous combustion due to flammable raw materials remaining for a long period of time can be avoided.

FIG. 1 is a perspective view showing a schematic configuration of an example of an apparatus according to the present invention. FIG. 2 is a side cross-sectional view of FIG. 3 is a view taken along the line AA in FIG. 2.

The device of the present invention is a device that prevents pulverization of raw materials fed into a transport chute due to the impact of the raw materials being dropped, and includes a support section and multiple suspension members whose upper ends are supported by the support section and extend downward within the chute. The device also includes a lower end member that is fixed to the lower ends of the multiple suspension members and has a means for retaining the raw materials, and the multiple suspension members are arranged at intervals in the width direction of the chute. The raw materials that are prevented from pulverizing include lump-shaped raw materials for ironmaking, and specific examples include coal, iron ore, molded coal, and pellets.

Below, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing the schematic configuration of one example of the device of the present invention, Fig. 2 is a side cross-sectional view of Fig. 1, and Fig. 3 is a view taken along the line A-A of Fig. 2. In the examples shown in Figs. 1 to 3, the raw material is molded coal 6, and preferably has an average particle size of 10 to 60 mm ([5] of the present invention). More preferably, it is 20 to 35 mm. Here, the average particle size is defined as the particle size at which the cumulative undersieve distribution value is 50%, i.e., D50 (median size).

[Shoot]
The molded coal 6 is fed into the chute by a belt conveyor (not shown) or a feeding device (not shown) installed above the chute. The conveying surface of the chute (the lower bottom of the chute wall surface 4) is inclined downward from the horizontal plane, and the inclination angle is preferably 35° or more (above the angle of repose) and 70° or less for proper conveyance. A carbonization furnace (not shown) is installed below the outlet side of the chute. The chute wall surface 4 is preferably covered with a refractory material 5 to protect the chute from the heat of the carbonization furnace. The thickness D of the refractory material 5 is appropriately selected, and is D = 120 mm in the example shown in Figures 1 to 3. In addition, a frame member 8 is installed above the inlet side of the chute to fix necessary parts by welding, bolt fasteners, etc.

[Suspension member]
The upper end of the hanging member 2 is supported by a support part 9 described later and extends downward inside the chute. A plurality of hanging members 2 are arranged at intervals in the width direction of the chute. This is to prevent the hanging members 2 from blocking the passage of the raw material. The arrangement interval Δ of the hanging members 2 (meaning the interval between adjacent hanging members 2, see FIG. 3) is preferably 3 to 10 times the average particle size of the raw material so that the raw material can pass through with ease. If the arrangement interval Δ is less than 3 times the average particle size of the raw material, the amount of raw material passing through may be small, resulting in a decrease in production efficiency. Also, if it exceeds 10 times, it is not preferable because the means for retaining the raw material of the lower end member 3 described later may be deformed due to an insufficient number of fixing points. In the example shown in FIGS. 1 to 3, the arrangement interval Δ is 120 mm.
From the viewpoint of ensuring strength, the material constituting the suspension member 2 is preferably a steel material ([3] of the present invention). Examples of steel materials include steel pipes, steel sections, and steel plates. In the example shown in Figures 1 to 3, the suspension member 2 is made of a square steel pipe.

[Lower end member]
The lower end member 3 is fixed to the lower end of the hanging member 2 and has the function of retaining the raw material. In the example shown in Figures 1 to 3, the lower end member 3 itself is used as a means for retaining the raw material. The means for retaining the raw material (lower end member 3) is to dam the raw material and promote the formation of the raw material pool 7 (corresponding to the above-mentioned dead stock). From the viewpoint of ensuring strength, the constituent material of the lower end member 3 is preferably steel (steel pipe, steel section, steel plate, etc.) ([3] of the present invention). In the example shown in Figures 1 to 3, the lower end member 3 is fixed by fastening multiple steel plates with bolt holes to fastening holes provided at the lower end of the hanging member 2 with bolts and nuts. Note that a single steel plate can be used instead of multiple steel plates. Whether a single steel plate or multiple steel plates are used, it is preferable to shield the entire width of the chute in order to stably form the raw material pool 7.

In addition, it is preferable that the downstream end height H (see Figures 2 and 3) of the raw material pool 7 is in the range of 3 to 10 times the average particle size of the raw material. If the downstream end height H is less than 3 times the average particle size of the raw material, the powdering prevention effect may be too small. If it exceeds 10 times, the force with which the raw material pool 7 presses the lower end member 3 and the hanging member 2 increases, and the load on the support member 1 described later may become excessive. Therefore, it is preferable that the height dimension h (see Figures 2 and 3) of the lower end member 3 is within the suitable range of the downstream end height H of the raw material pool 7 (a range of 3 to 15 times the average particle size of the raw material). However, since the downstream end height H of the raw material pool 7 includes the overflow of raw material from the upper part of the raw material pool 7, it is preferable that h<H.

The lower end member 3 can be in contact with the lower bottom of the chute wall surface 4 (not shown), but as in the example shown in Figures 1 to 3, a gap δ (see Figures 2 and 3) can be provided between the lower end member 3 and the lower bottom of the chute wall surface 4. By providing the gap δ, as described below, it is possible to prevent flammable raw materials from being retained for long periods of time and eliminate the risk of spontaneous combustion. In the case of flame-retardant raw materials (iron ore, pellets), the risk of spontaneous combustion is small even if there is no gap δ.

One method for adjusting the gap δ is to use a bottom adjustment means in which the fastening hole at the bottom end of the suspension member 2 is an elongated hole (not shown), the bottom end member 3 is fixed to this elongated hole with a bolt, and the gap δ is adjusted by changing the fixing position within the elongated hole.

[Support part]
The support part 9 supports the suspension member 2 at its upper end. In this embodiment, a frame member 8 installed above the chute and a support member 1 attached to the frame member 8 function as the support part 9 of the present invention. An example of a mechanism for supporting the suspension member 2 is a mechanism for fixing the upper end of the suspension member 2 with a bolt to a fastening hole provided in the support member 1. The support member 1 provided in the support part 9 can be fixed to the frame member 8 above the chute by welding or the like, rather than to the chute itself. Therefore, the device of the present invention can be easily installed regardless of the presence or absence of refractory material 5 on the chute wall surface 4, and regardless of before or after the chute is installed.

The support unit 9 is preferably provided with a means for adjusting the arrangement interval Δ and/or the height position of the suspension members 2. The support unit 9 is preferably provided with an arrangement adjustment means for adjusting the arrangement interval Δ of the suspension members 2. This makes it easy to change the arrangement interval Δ to one that is appropriate for the average particle size of the raw material after the change, in response to a change to a raw material with a different average particle size. An example of the arrangement adjustment means is one in which the fastening holes provided in the support member 1 are elongated holes, and the upper ends of the suspension members 2 are fixed to the elongated holes with bolts. This makes it possible to adjust the arrangement interval Δ by changing the fixing position within the elongated hole.

Furthermore, it is preferable that the support portion 9 is provided with an upper end adjustment means for adjusting the height direction position of the suspension member 2. This upper end adjustment means is also another means for providing the gap δ between the lower end member 3 and the lower bottom of the chute wall surface 4, as mentioned above.

By providing the lower end adjustment means and/or the upper end placement adjustment means, the following two operations are possible during operation.

(i) The gap δ is maintained at a predetermined value by the bottom end adjustment means and/or the top end adjustment means. By setting this predetermined value to 3 to 10 times the average particle size of the raw material, the raw material at the bottom of the raw material pool 7 flows out steadily through the gap δ. This makes it possible to prevent flammable raw materials from being retained for a long period of time, and eliminates the risk of spontaneous combustion.
Also, the supply of the raw material can be stopped, and the raw material in the raw material pool 7 can be made to flow out through the gap δ, thereby eliminating the raw material pool 7.
(ii) Furthermore, the upper end adjustment means enlarges the gap δ as needed to at least partially open the raw material reservoir 7. This makes it possible to quickly resolve the blockage even if the gap δ is accidentally blocked by raw material.

In the case of (i) above, it is preferable that the sum of the height dimension h of the lower end member 3 and the gap δ is within the preferred range of the downstream end height H of the raw material reservoir 7. However, since the downstream end height H of the raw material reservoir 7 includes the raw material overflowing from the top of the raw material reservoir 7, it is preferable that h + δ < H.

The upper end position adjustment means may be a lifting mechanism (not shown) that raises and lowers the support member 1 within a predetermined height range. Such a lifting mechanism may be constructed using a hydraulic cylinder or the like.

Next, a method for preventing powdering of raw material in a conveying chute using the above-mentioned device of the present invention will be described.
Its characteristic is that the arrangement interval Δ and/or height direction position (gap δ) of the suspended members 2 are set by the support part 9, and the lower end member 3 (means for retaining the raw material) blocks the raw material (e.g., molded coal 6) to form a raw material pool 7, which reduces the impact of the falling raw material ([7] of the present invention). The suspended member 2 and the lower end member 3 obstruct the flow of the raw material falling from above, and the raw material pool 7 is formed on the upstream side by contacting these members. By dropping new raw material onto this raw material pool 7, the mechanical impact acting on the raw material can be reduced and raw material powdering can be suppressed. In addition, by adjusting the arrangement interval Δ and the gap δ, it is possible to easily control the amount of raw material flowing out from the raw material pool 7 and the layer thickness of the raw material pool 7 (downstream end thickness H).

This corresponds to the operation of (i) above. This allows the raw material pool 7 to be formed stably, mitigating the impact of the falling raw material and preventing pulverization. At the same time, the raw material at the bottom of the raw material pool 7 is allowed to steadily flow out from the gap δ, preventing combustible raw materials (e.g., molded coal 6) from remaining for long periods of time and eliminating the risk of spontaneous combustion.

When the supply of raw materials is stopped, the raw materials in the raw material reservoir 7 flow out through the gap δ and the raw material reservoir 7 disappears, so by occasionally interrupting the supply of raw materials, it is possible to avoid the raw materials being stagnated for long periods of time.

In addition, in the method of the present invention, the height direction position of the suspension member 2 may be further increased (the gap δ may be enlarged) to open the raw material reservoir ([8] of the present invention). This corresponds to the operation of (ii) above. As a result, even if the gap δ is accidentally blocked by raw material, the blocked state can be quickly resolved.

In the method of the present invention, the raw material is preferably molded coal 6 with an average particle size of 10 to 60 mm ([9] of the present invention). More preferably, it is 20 to 35 mm. Molded coal 6 has small variation in shape and dimensions, small surface irregularities, and smooth flow, so the gap δ is less likely to be blocked. The average particle size is preferably 10 to 60 mm.

The present invention has been described above using an embodiment, but the present invention is not limited to this configuration. The scope of the present invention is determined based on the description of the appended claims, and within that scope, the present invention includes all configurations in which some of the components shown in the embodiment have been omitted or modified, as well as improvements thereon.

For example, in the above embodiment, the support portion includes a frame member installed above the chute and a support member fixed to the frame member, but the present invention is not limited to this configuration. For example, the support portion may be formed by fixing the support member by welding or the like to an installable portion of the chute wall that is not covered by a refractory material or liner. Also, a foundation member may be provided above the chute in addition to or instead of the frame member, and the support portion may be formed by fixing the support member to this foundation member.

In the carbonization process of molded coal, the embodiment illustrated in Figures 1 to 3 was carried out on the chute immediately before the carbonization furnace. The inclination angle of the transport surface of the chute was set to 45°. In addition, the state in which no suspension members were used (before the installation of the device of the present invention) was used as a comparative example.

As mentioned above, the chute wall 4 is covered with refractory material 5 having a thickness D of 120 mm, but the support member 1 provided in the support part 9 of the device of the present invention can be easily fixed by welding or the like to the upper frame member 8 that is not covered with refractory material. In this way, the device of the present invention can be easily installed even on an existing chute that has a refractory (or liner) coating layer.

In the present invention and comparative examples, it has been confirmed that the molded coal 6 has an average shape of an egg shape of 30 mm x 25.6 mm x 18.8 mm. Here, the molded coal 6 is intermittently charged, but the present invention can also be implemented in the case of continuous charging. In the present invention, a square steel pipe made of SS400 with an inner dimension of 77 mm square x 6 mm thickness x 1732 mm length was used for the hanging member 2. Note that a steel beam or a steel plate may be used instead of the steel pipe. In the present invention, the arrangement interval Δ was set to 120 mm by the arrangement adjustment means using the long holes described above. For the lower end member 3, an SS400 steel plate with a plate thickness of 6 mm was used. The height dimension h of the lower end member 3 was set to 200 mm. One lower end member 3 was fixed to each hanging member 2, and the entire width direction of the chute was shielded as a whole. Note that the number of lower end members 3 may be reduced and one may be fixed to each of the hanging members 2. In addition, in this example, the gap δ was set to 50 mm using the lower end adjustment means.

In this embodiment of the invention, during operation with intermittent feeding of molded coal 6, a raw material pool 7 is formed when feeding continues, and new raw material falling onto the raw material pool 7 is buffered and decelerated. In addition, an appropriate amount of raw material is sent from the raw material pool 7 through the gap δ to the carbonization furnace, maintaining the carbonization efficiency. In addition, when feeding is stopped, raw material flows out from the raw material pool 7 through the gap δ, eliminating the raw material pool 7 and preventing the raw material from being stagnated for long periods of time.

The powdering rate of raw materials was calculated and compared between the present invention and the comparative example. Here, the powdering rate of raw materials was evaluated as the ratio (%) of the powdered amount (tons) of raw materials that passed through the target chute to the amount (tons) of raw materials fed into the target chute. The powdered amount was calculated by collecting and weighing the raw materials that fell under a 15 mm mesh sieve installed at the outlet side of the target chute. In other words, a particle size of 15 mm or less is defined as powder.

The powdering rate of the raw material in the present invention example and the comparative example is shown in Table 1. As shown in Table 1, the powdering rate of the raw material in the present invention example is significantly lower than that in the comparative example, demonstrating the powdering suppression effect of the present invention.

In addition, in the present invention, it was confirmed that when the supply of raw materials was stopped, the raw materials in the raw material pool 7 flowed out from the gap δ, and the raw material pool 7 disappeared within about one minute.

1 Support member 2 Suspension member 3 Lower end member (means for retaining raw material)
4 Chute wall 5 Refractory material 6 Molded coal (raw material)
7 Raw material reservoir 8 Frame member 9 Support portion

Claims (7)

A device for preventing powdering of raw materials due to the impact of falling into a conveying chute whose lower bottom is inclined downward from a horizontal plane , comprising:
A support portion;
Three or more suspension members each having an upper end supported by the support portion and extending downward within the chute;
A lower end member is fixed to the lower end of the three or more suspension members and has a means for retaining the raw material,
The three or more suspension members are spaced apart in a width direction of the chute,
The device for preventing powdering of raw materials in a conveying chute is characterized in that the support section is provided with a means for adjusting the arrangement interval and height position of the hanging members. 2. The device for preventing powdering of raw materials in a conveying chute according to claim 1, wherein the suspension member and the means for retaining the raw materials are made of steel. 3. The device for preventing powdering of raw material in a conveying chute according to claim 1 or 2, characterized in that at least one of the following A, B and C is satisfied.
Note A: The raw material is a raw material for iron making. B: The raw material is molded coal with an average particle size of 10 to 60 mm. C: The chute is covered with a refractory material or a liner. A method for preventing powdering of raw materials in a conveying chute using the device for preventing powdering of raw materials in a conveying chute according to claim 1 or 2,
A method for preventing powdering of raw materials in a conveying chute, characterized in that the arrangement spacing and height position of the hanging members are set by the support part, and the raw materials are held back by a means for retaining the raw materials to form a raw material pool, thereby mitigating the impact of the fall. A method for preventing powdering of raw materials in a conveying chute using the device for preventing powdering of raw materials in a conveying chute according to claim 3,
A method for preventing powdering of raw materials in a conveying chute, characterized in that the arrangement spacing and height position of the hanging members are set by the support part, and the raw materials are held back by a means for retaining the raw materials to form a raw material pool, thereby mitigating the impact of the fall. The method for preventing powdering of raw material in a conveying chute as described in claim 4 , further characterized in that the vertical position of the suspension member is raised to open the raw material pool, and/or the raw material is molded coal and has an average particle size of 10 to 60 mm. The method for preventing powdering of raw material in a conveying chute as described in claim 5 , further comprising: raising the vertical position of the suspension member to open the raw material pool; and/or the raw material is molded coal having an average particle size of 10 to 60 mm.

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