JP7520799B2 - Raw material hopper discharge chute - Google Patents

Description

The present invention relates to technology for a discharge chute installed in a raw material hopper that stores powdered raw materials.

In general, in the sintering process, various brands of iron ore (e.g., from Australia or South America) and auxiliary materials (limestone, dolomite, etc.) are mixed in a granulator at a predetermined ratio and granulated. The granulated material is then loaded into a sintering machine and fired to produce sintered ore.
Raw materials such as iron ore and auxiliary materials are temporarily stored in a raw material hopper (also called a raw material tank) in the sinter plant. A belt conveyor is installed below the raw material hopper. When the raw materials are discharged from the raw material hopper through a discharge chute onto the belt conveyor, the belt conveyor transports the raw materials horizontally while weighing them. The belt conveyor supplies the raw materials to the granulator.

Techniques for transporting and supplying raw materials are disclosed in, for example, Patent Documents 1 to 3.
The purpose of Patent Document 1 is to improve the air permeability by controlling the charging density of the pseudo-particle packed bed in the pallet, even when using normal granulated raw materials, without subjecting the raw materials to special pre-treatment or granulating them with a binder, in a charging method of sintering raw materials.

Specifically, when the sintering raw materials are loaded onto the sintering pallet, a loading hopper is placed on the sintering pallet, and the bottom end of the loading hopper on the pallet entry side is located near the grate, and the bottom end on the pallet exit side is located on the surface of the sintered layer. The raw materials are fed into the hopper to form a packed layer, and this loaded raw material is continuously moved down in accordance with the movement of the sintering pallet. If the loading hopper is shaped to be divergent so that it is wider at the bottom, the interparticle distance of the loaded raw materials becomes larger, and it is said that the loading density can be made smaller than with a vertical type.

In order to solve the problems of Patent Document 1, Patent Document 2 aims to control the charging density of the pseudo-particle packed bed charged onto a pallet when charging the sintering raw material, and at the same time, to blend a large amount of coarse raw material into the lower layer of the sintering layer.
Specifically, a filling hopper is placed on the sintering pallet, raw material is supplied into the filling hopper to form a filling layer, and the filling raw material is continuously lowered by the movement of the sintering pallet to load the sintering raw material. The filling hopper is positioned so that the lower end on the pallet exit side is located at the surface layer of the sintering material, and the height of the lower end of the filling hopper on the pallet entry side is adjusted so that a large amount of coarse raw material is mixed into the lower layer of the sintering layer.

The aim of the document 3 is to achieve uniform cooling of a bulk material in a cooling device for cooling the bulk material. The bulk material can be, for example, sintered iron ore, also called sinter, i.e. the cooling device can be a so-called sinter cooler.
Specifically, a cooling device for cooling a bulk material includes a feed chute for introducing the bulk material into a cooling shaft, the feed chute having a first wall at least partially disposed at a different inclination angle with respect to the vertical than the second wall, the first wall being disposed at an inclination angle with respect to the vertical between 27° and 47° and the second wall being disposed at an inclination angle with respect to the vertical between 7° and 27°.

Japanese Unexamined Patent Publication No. 61-195928 Japanese Patent Application Publication No. 61-217533 Special table 2018-520329 publication

By the way, in order to recycle generated materials (non-products) in steelworks, yard-blended raw materials, which are obtained by mixing multiple brands of iron ore and generated products in the yard, are sometimes used as raw materials for sintering. These yard-blended raw materials have a high moisture content due to the influence of moisture from rainfall during storage in the yard and the fact that they are mixed with generated products with high moisture content (such as steelmaking slag).

As shown in FIG. 1, when the moisture content of the raw material is low, the fluidity of the raw material increases, and the raw material is easily discharged from the raw material hopper.
However, when the moisture content of the raw material increases, the flowability of the raw material decreases, so the movement of the raw material decreases. In particular, the area where the raw material is stationary near the inner wall of the raw material hopper (non-moving layer) increases. In other words, the flow range of the raw material in the hopper becomes narrower, and the dischargeability from the raw material hopper (raw material tank) becomes worse.

In addition, if the discharge of raw materials from the raw material hopper becomes unstable due to the occurrence of hanging (when the raw materials stop flowing and the raw material hopper becomes clogged), the amount of raw materials supplied to the downstream granulator (e.g., drum mixer, etc.) will fluctuate, causing the granulation state to fluctuate. As a result, the strength of the granulated material will decrease, and the air permeability will decrease when the raw material packed bed is formed, making it necessary to reduce the production of sintered ore.

To address these issues, the current practice is to periodically use high-pressure cleaning or other methods to remove materials adhering to the inner walls of the raw material hopper.
The technology in Patent Document 1 relates to a filling hopper. The filling hopper is disposed on a sintering pallet and is a part of a feeding device that supplies raw materials (after granulation) to a sintering machine. On the other hand, the present invention is directed to a raw material hopper that stores raw materials (before granulation), which is different from the technology in Patent Document 1.

In addition, the granulated material (pseudo particles) supplied to the ore feeder is manufactured by mixing and granulating multiple raw materials in a granulator, and the moisture content is averaged during this process. Therefore, the moisture content of the granulated material is at most about 8%.
On the other hand, the raw material before being fed to the granulator is a low-fluidity raw material with a moisture content exceeding 10%. Raw materials with a high moisture content have low fluidity in the raw material hopper and may cause clogging. For this reason, the present invention is directed to raw materials with low fluidity, which is different from the target of Patent Document 1.

Therefore, although Patent Document 1 describes the shape of the filling hopper, its purpose is to reduce the charging density of the raw materials when the raw materials (after granulation) are moved by lowering them from the filling hopper to the sintering machine, but it does not suppress the adhesion of the raw materials to the inner wall surface of the raw material hopper, which is the purpose of the present invention. In other words, the present invention and Patent Document 1 target different technologies.

Like Patent Document 1, Patent Document 2 is a technology related to a filling hopper arranged on a sintering pallet. The filling hopper is a part of a feeding device that supplies raw materials (after granulation) to a sintering machine. On the other hand, the present invention is directed to a raw material hopper that stores raw materials (before granulation), which is different from Patent Document 2.
In addition, the moisture content of the granulated material supplied to the ore feeder is averaged during granulation in the granulator. The moisture content of the granulated material is at most about 8%. However, the present invention is directed to low-fluidity raw materials with a moisture content of more than 10% before entering the granulator, which is different from the subject matter of Patent Document 2.

Therefore, although the object of Patent Document 2 is to reduce the charging density when the raw material (after granulation) is charged from the filling hopper to the sintering machine, it does not suppress the raw material from adhering to the inner wall surface of the raw material hopper (the raw material has low fluidity in the raw material hopper, causing clogging), which is the object of the present invention. In other words, the present invention and Patent Document 2 target different technologies.
Patent Document 3 is a technology that targets a chute that supplies bulk material to a cooling device. On the other hand, the present invention targets a discharge chute when a raw material (before granulation) is discharged horizontally by a belt conveyor in a raw material hopper that stores the raw material, and is therefore different from Patent Document 3 in target area.

Patent Document 3 also describes the shape of the supply chute, but its purpose is to obtain an even cooling effect by evenly distributing the bulk material to the cooling shaft, but it does not prevent the raw material from adhering to the inner wall surface of the raw material hopper (reduced fluidity of the raw material in the raw material hopper, causing clogging), which is the purpose of the present invention. In other words, the present invention and Patent Document 3 target different technologies.

In view of the above problems, the present invention aims to provide a discharge chute for a raw material hopper that stores raw materials and has a shape (lower outlet portion) that makes it easy to discharge the raw materials, thereby preventing discharge problems such as clogging caused by the raw materials adhering to the inner wall surface of the raw material hopper, i.e., hanging, even when raw materials with a high moisture content are used, and enabling stable discharge of the raw materials.

In order to achieve the above object, the present invention provides the following technical solutions.
The discharge chute of a raw material hopper according to the present invention is a discharge chute that contains iron ore and is provided below a raw material hopper that stores raw material before it is granulated in a granulator , and discharges the raw material onto a belt conveyor that transports the raw material horizontally, the discharge chute having a first guide wall downstream in the transport direction of the raw material, and a second guide wall that faces the first guide wall and is upstream in the transport direction, the second guide wall being arranged at an incline so that its lower edge faces the downstream side in the transport direction when viewed from the side of the discharge chute, and the first guide wall being arranged at an angle inclined toward the downstream side in the transport direction from the vertical.

Preferably, the first guide wall is disposed in a direction parallel to the second guide wall. The moisture content of the raw material is more than 10 mass %.

According to the discharge chute of the raw material hopper of the present invention, by making the shape of the discharge chute of the raw material hopper that stores the raw materials easy to discharge, even if raw materials with a high moisture content are used, clogging caused by the raw materials adhering to the inner wall surface of the raw material hopper, i.e., discharge problems such as hanging, can be suppressed, and the raw materials can be discharged stably.

FIG. 2 is a diagram showing a schematic diagram of the fluidity of the raw material in a hopper. FIG. 2 is a schematic diagram illustrating an outline of a discharge chute of a raw material hopper (comparative example). FIG. 2 is a schematic diagram showing an outline of a discharge chute of a raw material hopper according to the present invention. FIG. 2 is a schematic diagram showing an example of a flow of a sintering process. FIG. 1 is a diagram illustrating an outline of a flow test. FIG. 1 is a diagram showing the relationship between the moisture content of yard blended raw materials and the flowability of the raw materials. FIG. 2 is a schematic diagram showing an example of the structure of a raw material hopper. FIG. 1 is a diagram showing the configuration of an apparatus used in a hopper model experiment. This figure shows the results of a hopper model experiment in which the moisture content of the raw material was changed (moisture content of raw material: 8 mass%, 10 mass%, 12 mass%). FIG. 13 is a diagram showing the flow of raw material in a discharge chute provided at the bottom of a raw material hopper (comparative example, inclination angle: 69°). FIG. 13 shows experimental results when the shape of the discharge chute was changed (inclination angle: 69° (comparative example), inclination angle: 90°, 111° (present embodiment)). FIG. 1 shows the flow of raw material in a discharge chute provided at the bottom of a raw material hopper (in this embodiment, inclination angle: 111°). FIG. 4 is a diagram showing a change in the amount of raw material adhering to the inside of a raw material hopper.

Hereinafter, an embodiment of a discharge chute for a raw material hopper according to the present invention will be described with reference to the drawings. Note that the embodiment described below is an example of the present invention, and the configuration of the present invention is not limited to this specific example.
An outline of the discharge chute 2 (lower outlet portion) of the raw material hopper 1 according to the present invention will be described.

FIG. 2A is a schematic diagram showing a discharge chute 2 (comparative example) of a raw material hopper 1.
FIG. 2B is a schematic diagram showing the discharge chute 2 of the raw material hopper 1 of the present invention.
The raw material hopper 1 stores the raw material 6. The raw material hopper 1 has a tapered shape with a diameter that decreases toward the bottom. The raw material hopper 1 has an insertion opening at the top for inserting the raw material 6, and a discharge chute 2 at the bottom. The bottom of the discharge chute 2 has a discharge opening 2a that discharges the raw material 6 by lowering it.

A belt conveyor 3 (primary belt conveyor 3a) is disposed below the discharge chute 2. The belt conveyor 3 carries the raw material 6 discharged from the discharge chute 2, moves it in the horizontal direction, and transports it to the granulator 4.
2A and 2B, the direction toward the left side of the paper is the direction in which the raw material 6 is transported. This transport direction is sometimes called the raw material extrusion direction. In other words, when the raw material 6 drops from the discharge chute 2 onto the belt conveyor 3, it is transported by the belt conveyor 3 toward the left side of the paper. In addition, in the discharge chute 2, the first guide walls 2b and 2d on the raw material extrusion direction side are labeled (A), and the opposing second guide walls 2c and 2e are labeled (B).

When a new raw material loading surface of the belt conveyor 3 advances from the upstream side in the conveying direction, the raw material 6 located at the upper part of the second guide wall 2c (B) side of the discharge chute 2 descends preferentially and is discharged from the discharge outlet 2a of the discharge chute 2, and is placed on the belt conveyor 3 flowing in the raw material discharging direction and transported. As a result, the raw material 6 located on the first guide wall 2b (A) on the raw material discharging direction side becomes more difficult to discharge.

Therefore, the shape of the discharge chute 2 provided below the raw material hopper 1 is as follows.
First, as shown in Fig. 2A, the discharge chute 2 of the conventional raw material hopper 1 is shaped so that the size decreases toward the discharge outlet 2a at the bottom in side view. In other words, the first guide wall 2b and the second guide wall 2c approach each other as they proceed downward, and the shape is an upside-down V shape in side view (comparative example).

As shown in FIG. 2B, in the present invention, the inclination angle α (chute angle α) of the first guide wall 2d (A) on the raw material discharging direction side is set to an angle that widens outward (downstream in the raw material 6 conveying direction) from the vertical direction (90°) compared to the inverted V shape of the conventional (comparative example) in side view. In other words, the outer angle of the first guide wall 2d on the raw material discharging direction side of the discharge chute 2 is set to an obtuse angle. It is preferable that the first guide wall 2d and the second guide wall 2e are arranged so that they are in the same direction (parallel) in side view.

By adopting the above-mentioned shape, the descent of the raw material 6 at the upper part of the first guide wall 2d (A) on the raw material extrusion direction side in the discharge chute 2 is promoted, thereby preventing the formation of a non-moving layer of the raw material 6 on the inner wall surface, expanding the flow range of the raw material 6 in the raw material hopper 1, and preventing the raw material 6 from adhering to the inner wall surface.
The discharge chute 2 of the raw material hopper 1 according to the present invention will be described in detail below.

FIG. 3 shows a schematic diagram of an example of the flow of the sintering process.
As shown in Fig. 3, in the sintered ore production process, iron ore (e.g., many brands from Australia, South America, etc.) and auxiliary raw materials (limestone, dolomite, etc.) are charged as raw materials 6 in a predetermined mixing ratio, together with carbonaceous material as a heat source, into a granulator 4 (e.g., a drum mixer, etc.). The raw materials 6 charged into the granulator 4 are mixed by rolling while adding moisture (granulation water), to granulate granules 7 (sintered raw material). After granulation, the granules 7 (sintered ore raw material) are filled into a sintering machine 5 and fired to produce sintered ore.

Before being inserted into the granulator 4, the raw materials 6 are temporarily stored in a raw material hopper 1 (also called raw material tank 1) in the sintering plant. The raw materials 6 are discharged from the raw material hopper 1 through a discharge chute 2 onto a belt conveyor 3. The raw materials 6 are transported in the raw material cut-out direction (horizontal direction) while being weighed by the belt conveyor 3 according to the operational blending conditions. The raw materials 6 are then supplied to the granulator 4.

By the way, in order to recycle materials (not products) generated within the steelworks, yard blended raw materials, which are made by mixing multiple brands of iron ore and generated products in the yard, are sometimes used as raw material 6 for sintering. This yard blended raw material has a moisture content of 10 to 12 mass%, which is very high among sintering raw materials 6, due to the influence of moisture from rainfall when it was stored in the yard and the fact that it contains generated products with high moisture content (steelmaking slag, etc.).

Here, the fluidity of Raw Material 6 was investigated. The fluidity was investigated using a method simulating a flow test, which is a method for evaluating concrete.
FIG. 4 shows a schematic diagram of the flow test carried out.
The flow test procedure is exemplified as follows (1) to (4) (for details, see Table 1).
(1) The raw material (raw material 6) adjusted to a predetermined moisture content was filled into the cylindrical member 8a up to the level of the surface. The cylindrical member 8a had an inner diameter of 100 mm and a height of 200 mm.

(2) The cylindrical member 8a is quickly (for about 1 to 2 seconds) pulled out vertically from the flat plate member 8b.
(3) The "longest diameter" and the "diameter perpendicular to the longest diameter" of the ridge formed by the raw material 6 inside the cylindrical member 8a are measured.
(4) The average of the "longest diameter" and the "diameter perpendicular to the longest diameter" is the flow value [mm].
Table 1 shows the conditions for the flow test.

The parameters in this embodiment are defined as follows.
Table 2 shows the definitions of the parameters in this embodiment.

FIG. 5 shows, as an example, the relationship between the moisture content and the fluidity of a yard blend material (material 6).
As shown in FIG. 5, when the moisture content of the raw material 6 is low, the adhesive force between the particles is weak, so that the raw material 6 flows to the foot of the mountain, and the flow value becomes high.
On the other hand, when the moisture content of the raw material 6 exceeds 10 mass%, the fluidity of the raw material 6 is significantly reduced. Furthermore, when the moisture content of the raw material 6 is 14 mass%, the raw material 6 hardly flows at all.

However, since the inner diameter of the cylindrical member 8a is 100 mm, when the flow value is close to 100 mm, even if the cylindrical member 8a is removed, the raw material 6 remains solidified like "jelly paste."
That is, the moisture that reduces the fluidity varies depending on the water absorption and surface properties of the powder, but has similar properties regardless of the brand of raw material 6.
In this way, when the fluidity of the raw material 6 decreases due to an increase in the moisture content, only the powder (raw material 6) present directly above the discharge port 2a of the discharge chute 2 is preferentially discharged when the raw material 6 is discharged, and the surrounding area remains stationary (funnel flow).

If the stationary portion (also called the non-moving layer) of the raw material 6 in the discharge chute 2 expands, the flow range of the raw material 6 becomes narrower, causing the discharge chute 2 to become clogged, resulting in frequent discharge failures (also called hanging).
FIG. 6 shows a schematic diagram of an example of the structure of a raw material hopper 1 provided in the raw material conveying equipment.
The raw material conveying equipment includes a raw material hopper 1 for storing raw material 6, a discharge chute 2 provided below the raw material hopper 1 and for discharging the raw material, and a belt conveyor 3 provided below the discharge chute 2 and for conveying the raw material 6 horizontally.

As shown in Fig. 6, the raw material hopper 1 of this embodiment is fixed to a building and has a lower hopper 1a and an upper hopper 1b. When the raw materials 6 stored in the raw material hopper 1 are discharged and transported horizontally by the belt conveyor 3, a discharge chute 2 is provided at the lower part of the raw material hopper 1 (lower hopper 1a).
In this embodiment, the upper hopper 1b has a rectangular cross section in plan view. The lower hopper 1a has a tapered shape with a diameter decreasing downward and a circular cross section in plan view. The discharge chute 2 has a tapered shape with a diameter decreasing downward and a rectangular cross section in plan view.

The discharge chute 2 receives the raw materials 6 flowing in from the raw material hopper 1 and places them on the belt conveyor 3 (primary belt conveyor 3a) from the discharge port 2a. A secondary belt conveyor 3b is provided downstream of the primary belt conveyor 3a. A weighing device 9 is provided on the secondary belt conveyor 3b.
Regarding the direction in which the raw material 6 is transported, the direction toward the left side of the paper in FIG. 6 is the primary transport direction, and the direction toward the right side of the paper is the secondary transport direction.

However, the present invention also covers a small-scale raw material hopper having a lower structure in which the lower hopper 1a and the discharge chute 2 are integrated together, without providing a separate discharge chute 2.
Incidentally, in order to prevent the above-mentioned improper discharge (hanging), it is considered desirable for the raw material hopper 1 to have the following structure.
The ideal characteristics of the raw material hopper 1 are shown below in (1) to (6).

(1) The outlet 2a should be as large as possible and cylindrical.
(2) It is effective to place a vertical partition inside the raw material hopper 1.
(3) It is very effective to provide a smooth lining on the inner wall of the raw material hopper 1.
(4) The wall angle of the raw material hopper 1 should be as small as possible.
(5) A vibrator is attached to the raw material hopper 1 to vibrate the raw material hopper 1 itself.

(6) Air is blown into the wall of the raw material hopper 1 to fluidize the raw material 6.
For more details, please refer to "Ironmaking Raw Material Processing, Iron and Steel College, p.122."
However, while these structures of the raw material hopper 1 are effective for raw materials with a relatively low moisture content and high fluidity, they may not function adequately for raw materials 6 with a high moisture content and low fluidity, such as yard blend raw materials, and may not be installable due to equipment restrictions.

Here, in order to investigate the range of flow of the raw material 6 that changes due to an increase in the moisture content of the raw material 6 in the raw material hopper 1, a model experiment of the raw material hopper 10, the inside of which can be observed, was carried out.
FIG. 7 shows an outline of the device configuration used in the hopper model experiment.
The size of the model of the raw material hopper 10, the specifications of the belt conveyor 3, the specifications of the discharge chute 20, and the procedure for testing the model hopper are shown below (see Table 3 for details).

The size of the model of the raw material hopper 10 is as follows:
Height of upper hopper 10b: 600mm, height of lower hopper 10a: 650mm
Width: 650mm, Depth: 150mm
Capacity: 180kg
・Exhaust width: 150mm, depth: 150mm
The belt conveyor 3 that conveys the raw material 6 is as follows.

・Cutting speed of raw material 6: 10 kg/min
・Descent speed of raw material 6: 6.5m/h
However, the descending speed of the raw material 6 was calculated by the following formula (1).
Descending speed of raw material 6 [m/h]=Cutting speed of raw material 6 [t/h]÷Density [t/m ³ ]÷Cross-sectional area of raw material hopper 10 [m ² ] (1)
The discharge chute 20 is as follows.

Height: 85mm
・Cutting thickness of raw material 6: 20mm
The chute angle α of the discharge chute 20 on the raw material discharge direction side (the inclination angle α of the first guide walls 20b, 20d, and 20f)
(i) Existing type discharge chute 20: inclination angle α of the first guide wall 20b = 69° (comparative example, inverted V-shape, see FIG. 2A)
(ii) Improved discharge chute 20: the inclination angle α of the first guide wall 20d is 111° (parallel to the second guide wall 20e in this embodiment, see FIG. 2B)
The steps (1) to (3) of the model hopper test are as follows.

(1) The model hopper 10 (raw material hopper 10) is filled with raw material with adjusted moisture content.
At this time, in order to observe the flow of the raw material 6 inside the model hopper, a limestone layer having a thickness of 15 mm is formed in stripes on a raw material layer having a thickness of 150 mm.
(2) The belt conveyor 3 is operated to cut out the raw material 6 from the model hopper 10 (raw material hopper 10).

(3) Observe the stationary portion (non-moving layer) of the raw material 6 in the model hopper 10 (raw material hopper 10) during the process of discharging the raw material 6.
Table 3 shows the conditions for the model hopper experiment.

By making the descending speed of the raw material 6 approximately the same, the similarity between the hopper model experiment and the actual machine is ensured.
FIG. 8 shows the results of a hopper model experiment, illustrating the flow of raw material 6 in the raw material hopper 10 when the moisture content of the yard blend raw material (raw material 6) was changed (raw material moisture percentage: 8 mass%, 10 mass%, 12 mass%).

FIG. 8 shows the state inside the raw material hopper 10 when about 30% of the raw material 6 has been discharged.
The white dashed lines in the figure indicate the position after the limestone layer, which was originally at the same height, is discharged, and show the difference in the falling range of the raw material 6. The area where the raw material 6 is stationary (immobile layer) is hatched in white. The white solid arrows indicate the flow of the raw material 6 estimated from the position of the limestone layer.

As shown in the left diagram of Figure 8, when the moisture content of the raw material 6 is 8 mass%, the raw material 6 in the raw material hopper 10 drops almost uniformly throughout. In other words, since the moisture content is low, the raw material 6 tends to flow overall.
As shown in the center of Figure 8, when the moisture content of the raw material 6 is 10 mass%, the flow range of the raw material 6 in the raw material hopper 10 is narrowed, and the raw material 6 directly above the discharge port 20a is preferentially discharged. In other words, the raw material 6 in the center is significantly lowered, and the raw material 6 on the inner wall side of the raw material hopper 10 is difficult to discharge.

As shown in the right diagram of FIG. 8, when the moisture content of the raw material 6 reaches 12 mass%, a huge immobile layer is formed on the first guide wall 20b on the raw material discharge direction side, and the immobile layer is formed on the first guide wall 20b on the raw material discharge direction side.
Only from the side (c) will the raw material 6 be preferentially discharged.
In other words, the angle of the first guide wall 20b is an acute angle that resists the raw material feeding direction (blocks the raw material 6), and a non-moving layer of the raw material 6 is formed at the top. The angle of the second guide wall 20c is an angle that makes it easier for the raw material 6 to flow in the raw material feeding direction, and the raw material 6 on the second guide wall 20c side is discharged by being pulled out in the raw material feeding direction by the operation of the belt conveyor 3.

FIG. 9 shows the flow of raw material 6 in discharge chute 20 provided at the bottom of raw material hopper 10 (comparative example, inclination angle α of first guide wall 20b = 69°).
As shown in FIG. 9, a detailed observation of the lower area inside the raw material hopper 10 reveals that the flow of the raw material 6 is biased toward the opposite side to the raw material discharge direction (the second guide wall 20c side).
The reason for this is that when the raw material 6 is cut horizontally from the raw material hopper 10 using the belt conveyor 3, the raw material 6 is discharged due to friction at the surface where the belt conveyor 3 and the raw material 6 come into contact, so the raw material 6 on the opposite side (the second guide wall 20c side) to the raw material cutting direction in which the new raw material loading surface of the belt conveyor 3 enters is preferentially discharged.

As a result, within the raw material hopper 10, an area (non-moving layer) where the raw material 6 is stationary is formed on the first guide wall 20b on the raw material discharging direction side (downstream side in the conveying direction of the raw material 6) where the raw material 6 is less likely to be discharged.
Therefore, in order to equalize the flow of the raw material 6 in the lower part of the raw material hopper 10 and reduce the immobile layer, the optimum shape of the discharge chute 20 was investigated.

FIG. 10 shows the results of an experiment in which the shape of the discharge chute 20 was changed.
As an example, when viewed from the side, the inclination angle α of the first guide wall 20b is 69° (comparison example), the inclination angle α of the first guide wall 20f is 90° (this embodiment), and the inclination angle α of the first guide wall 20d is 111° (this embodiment) are shown.
An experiment was conducted using the model hopper (raw material hopper 10) described above. The flow of raw material 6 in the raw material hopper 10 was observed when the inclination angle α of the first guide wall 20f provided on the raw material discharge direction side of the discharge chute 20 was set to "vertical."

In addition, the flow of raw material 6 in raw material hopper 10 was observed in a structure in which first guide wall 20d had an inclination angle α that was "parallel" to second guide wall 20e (rear wall).
However, for "vertical", the discharge chute 20 angle α = 90°, and for "parallel", the discharge chute 20 angle α = 111°.
In this embodiment, "parallel" does not mean mathematically parallel. In other words, "parallel" in this embodiment does not mean strictly parallel, but means roughly facing in the same direction (including a difference of several degrees).

In addition, the effect of the shape of the discharge chute 20 was compared under the condition that the discharge of the raw material 6 was extremely biased and a huge immobile layer was formed in the raw material hopper 10 with a moisture content of 12 mass%. That is, the present embodiment was compared with the comparative example.
As shown in Figure 10, by widening the inclination angle α of the first guide wall 20d that constitutes the discharge chute 20 outward (in the raw material extrusion direction) from vertical (perpendicular), the behavior of the raw material 6 discharged from the raw material hopper 10 is changed.

As shown in the center of Figure 10, by making the first guide wall 20f that constitutes the discharge chute 20 a "vertical" structure, the raw material 6 in the center starts to descend as shown by the white dashed line in the figure, followed by the raw material 6 on the first guide wall 20f and second guide wall 20g side, causing the raw material 6 to collapse into a roughly V-shape in side view, and the raw material 6 is discharged in order from the center. This shape can almost completely suppress the formation of a stationary layer in the raw material hopper 10. In other words, the desired effect can be expected even if the first guide wall 20f has a "vertical" structure.

As shown in the right diagram of FIG. 10, when the first guide wall 20d is "parallel" to the second guide wall 20e (rear wall), the raw material 6 starts to fall in the raw material hopper 10 as a whole (although the first guide wall 20d and the second guide wall 20e are slightly delayed) at the white dashed line shown in the diagram, and the fall of the raw material 6 becomes constant as it approaches the discharge chute 20, and the raw material 6 is discharged in sequence. With this shape, the flow range in the raw material hopper 10 is further expanded, the formation of a non-moving layer is suppressed, and the fall of the raw material 6 can be made uniform. In other words, by making the first guide wall 20d "parallel" to the second guide wall 20e (the first guide wall 20d opens outward (in the raw material cutting direction, downstream in the raw material 6 conveying direction)), the desired effect can be reliably expected.

FIG. 11 shows the flow of the raw material 6 in the discharge chute 20 provided at the bottom of the raw material hopper 10 (in this embodiment, the inclination angle α=111°).
As shown in FIG. 11, a detailed observation of the lower region inside the raw material hopper 10 revealed that the flow of the raw material 6 was uniform.
Now, in the case of the discharge chute 20 having an inverted U-shape structure as in the comparative example, as the raw materials 6 descend toward the bottom of the raw material hopper 10, the raw materials 6 concentrate in the center, creating resistance to the descent.

However, in this embodiment, the first guide wall 20d provided on the raw material discharging direction side of the discharge chute 20 (downstream side in the conveying direction of the raw material 6) is wider than "vertical," i.e., the first guide wall 20d is configured to face the raw material discharging direction side, so that the resistance when the raw material 6 descends at the bottom of the raw material hopper 10 can be reduced. However, the effect of the present invention can be expected even if the first guide wall 20f is configured as "vertical."

In addition, even if the inclination angle α of the first guide wall 20d provided on the raw material discharging direction side of the discharge chute 20 (downstream side in the conveying direction of the raw material 6) is made wider than "parallel" to the second guide wall 20e, that is, even if the first guide wall 20d is made more inclined toward the raw material discharging direction side (discharge opening 20a is more open), it is believed that the formation of a non-moving layer can be suppressed and the effect of uniforming the lowering of the raw material 6 can be obtained.

In summary, the present invention relates to a discharge chute 2 that is provided below a raw material hopper 1 that stores raw material 6 and discharges the raw material 6 onto a belt conveyor 3 that transports the raw material 6 in a horizontal direction. In a side view, the discharge chute 2 has a first guide wall 2d on the downstream side in the transport direction of the raw material 6 (the raw material extrusion direction side), and a second guide wall 2e that faces the first guide wall 2d and is on the upstream side in the transport direction of the raw material 6.

The second guide wall 2e (rear wall) is inclined so that its lower edge faces downstream in the conveying direction of the raw material 6 (the raw material extrusion direction side) in a side view of the discharge chute 2.
In addition, the first guide wall 2d is positioned so that, when viewed from the side of the discharge chute 2, it is inclined at an angle α (chute angle α is an obtuse angle) downstream in the conveying direction of the raw material 6 (toward the raw material extrusion direction) from the vertical (perpendicular) direction.

Preferably, the first guide wall 2d is disposed in a direction parallel to the second guide wall 2e in a side view of the discharge chute 2.
That is, in the present invention, the inclination angle α (chute angle α) of the first guide wall 2d on the raw material discharge direction side is set to an angle that widens outward (toward the raw material discharge direction) from the vertical direction (90°).
In other words, when viewed from the side of the discharge chute 2, the angle α of the outer wall surface of the first guide wall 2d with respect to the raw material discharging direction is 90° or more (the outer angle is an obtuse angle (may be vertical)).

More preferably, the first guide wall 2d is disposed so as to be in the same direction (parallel) as the second guide wall 2e.
It should be noted that the present invention is not limited to the sintering process in the steel industry, since there are various processes in which the powder (raw material 6) as described above in detail is temporarily stored in the raw material hopper 1 and a certain amount is sent to the next process.

In other words, the present invention can be applied to any embodiment of the discharge chute 2 of a raw material hopper 1 that stores powder with low fluidity, such as powder that contains a lot of moisture.
[Example]
An embodiment carried out using the discharge chute 2 of the raw material hopper 1 of the present invention and a comparative example carried out for comparison with the present invention will be described below.

The conditions for carrying out this embodiment are as follows.
In this example, the shape of the discharge chute 2 provided in the raw material hopper 1 of the actual machine was changed, and a long-run test was carried out to compare the behavior of the discharge of raw materials 6 with that of an existing type chute 2 (comparative example). The actual machine is exemplified below (see Table 4 for details).
The raw material hopper 1 of the actual machine is as follows.

・Height of upper hopper 1b: 6.0m, height of lower hopper 1a: 6.5m
・Width: 6.5m, Depth: 6.5m
Capacity: 700t
・Discharge section size: φ1.5m
The belt conveyor 3 that transports the raw material 6 is as follows.

・Raw material 6 cutting speed: 70 to 130 t/h
・Average descent speed of raw material 6: 3.5 to 6.5 m/h
However, the descending speed of the raw material 6 was calculated by the following formula (1).
Descending speed of raw material 6 [m/h] = Cutting speed of raw material 6 [t/h] ÷ Density [t/m ³ ] ÷ Cross-sectional area of raw material hopper 1 [m ² ] ... (1)
For Feedstock 6, a yard blend feedstock was used.

The discharge chute 2 is as follows.
Height: 0.85m
The chute angle α on the raw material discharging direction side of the discharge chute 2 (the inclination angle α of the first guide walls 2b and 2d)
(i) Existing type discharge chute 2: inclination angle α of the first guide wall 2b = 69° (comparison example, inverted V-shape)
(ii) Improved discharge chute 2: the inclination angle α of the first guide wall 2d = 111° (parallel to the second guide wall 2e in this embodiment)
The evaluation period was five months.

The evaluation indicators are as follows (1) and (2).
(1) Adhesion rate in the raw material layer The raw material hopper 1 is periodically emptied until the discharge of the raw material 6 therein stops, and the amount of adhesion to the inner wall surface of the raw material hopper 1 at that time is investigated.
The adhesion rate was calculated using the following formula (2).

Adhesion rate [%] = Adhesion amount [t] ÷ Hopper capacity [t] × 100 ... (2)
The amount of adhesion was calculated by integrating the amount of raw material discharged from when raw material hopper 1 was filled with raw material 6 until the discharge of raw material 6 stopped, and calculating the difference between the capacity of raw material hopper 1 and the integrated discharge amount.
(2) Number of times discharge failure occurred The number of times the discharge of the raw material 6 was temporarily stopped due to hanging or the like during operation is counted.

If the discharge of the raw material 6 is stopped for one minute or more, it is determined that the discharge is defective.
Table 4 shows the implementation conditions in the actual machine demonstration experiment.

FIG. 12 shows the change in the amount of raw material 6 adhering to the raw material hopper 1 of the actual machine.
As shown in Fig. 12, in the comparative example (marked with ■), it is understood that the adhesion rate of the raw material 6 in the raw material hopper 1 increases in only about one month. In contrast, in the present embodiment (marked with ●), it is understood that the growth of the adhesion of the raw material 6 is suppressed to about 1/3.
Table 5 shows the number of times that raw material 6 failed to be discharged (hanging).

As shown in Table 5, in this embodiment, adhesion of the raw material 6 to the inner wall surface of the raw material hopper 1 (non-moving layer) is suppressed, and the number of discharge failures is reduced to 5 times/day/tank in this embodiment compared to 18 times/day/tank in the comparative example, which is less than one-third.
As described above, by changing the shape of the discharge chute 2 provided in the raw material hopper 1, i.e., by making the first guide wall 2d inclined toward the raw material dispensing direction (downstream in the conveying direction of the raw material 6), adhesion of the raw material 6 to the inner wall surface of the raw material hopper 1 (non-moving layer) is suppressed, thereby achieving the effect of stabilizing the discharge of the raw material 6.

Furthermore, if the raw material 6 adheres to the inner wall surface of the raw material hopper 1, the inside of the raw material hopper 1 must be cleaned using a high-pressure cleaner or the like, but the frequency of such cleaning can be reduced to one-third or less.
That is, according to the discharge chute 2 of the raw material hopper 1 of the present invention, by making the shape of the discharge chute 2 of the raw material hopper 1 in which the raw materials 6 are stored into a shape that makes discharge easy (the first guide wall 2d is inclined toward the raw material dispensing direction (downstream of the raw material 6 conveying direction)), even when raw materials 6 containing a high moisture content are used, clogging caused by the raw materials 6 adhering to the inner wall surface of the raw material hopper 1, i.e., discharge problems such as hanging, can be suppressed, and the raw materials can be discharged stably.

It should be noted that the embodiments disclosed herein should be considered as illustrative in all respects and not restrictive.
In particular, in the embodiments disclosed herein, matters not explicitly stated, such as operating conditions, operating conditions, various parameters, dimensions, weights, volumes of components, etc., do not deviate from the scope of ordinary practice of a person skilled in the art, and values that a person of ordinary skill in the art could easily assume are used.

1 Raw material hopper, raw material tank (actual machine)
1a Lower hopper 1b Upper hopper 2 Discharge chute 2a Discharge port 2b First guide wall (Comparative example, existing type)
2c Second guide wall 2d First guide wall (this embodiment, parallel type)
2e Second guide wall 3 Belt conveyor 3a Primary belt conveyor 3b Secondary belt conveyor 4 Granulator 5 Sintering machine 6 Raw material 7 Granulated material 8a Cylindrical member 8b Plate material 9 Weighing device 10 Raw material hopper (model experiment)
10a Lower hopper 10b Upper hopper 20 Discharge chute 20a Discharge port 20b First guide wall (Comparative example, existing type)
20c Second guide wall 20d First guide wall (this embodiment, parallel type)
20e: second guide wall 20f: first guide wall (vertical type in this embodiment)
20g Second guide wall

Claims (3)

A discharge chute is provided below a raw material hopper that stores raw material including iron ore before being granulated by a granulator , and discharges the raw material onto a belt conveyor that transports the raw material in a horizontal direction,
The discharge chute has a first guide wall on a downstream side in a conveying direction of the raw material, and a second guide wall facing the first guide wall and on an upstream side in the conveying direction,
The second guide wall is disposed at an incline such that a lower edge of the second guide wall faces a downstream side in a conveying direction in a side view of the discharge chute,
the first guide wall is disposed at an angle inclined toward a downstream side in a conveying direction from a vertical direction. The discharge chute of a raw material hopper according to claim 1, characterized in that the first guide wall is arranged in a direction parallel to the second guide wall. 3. The discharge chute of a raw material hopper according to claim 1, wherein the moisture content of the raw material is greater than 10 mass %.