JP7632343B2 - Apparatus for producing raw materials for blast furnaces and method for producing raw materials for blast furnaces - Google Patents

Description

The present invention relates to an apparatus and method for producing raw materials for blast furnaces.

In recent years, in order to prevent global warming, the steel industry is also required to reduce the amount of _CO2 gas generated, and it is urgent to reduce the amount of fossil fuel used. In the steel industry, molten iron is produced in a blast furnace by reducing iron ore with carbon (coke produced by carbonizing coal in a coke oven). In order to reduce the coke consumption, technology is being developed to use molded coke, especially ferrocoke, as a raw material for the blast furnace. Ferrocoke is produced by mixing a certain amount of iron ore with coal, agglomerating it, and then carbonizing it to disperse fine metallic iron particles in the coke. The catalytic action of the dispersed metallic iron increases the reactivity of the coke.

A method for carbonizing ferro-coke using a vertical carbonization furnace has been proposed. For example, Patent Document 1 discloses a method for producing ferro-coke using a vertical carbonization furnace having a carbonization zone at the top and a cooling zone at the bottom. This method includes a charging process in which molded materials made of carbon-containing materials and iron-containing materials are charged into the carbonization furnace using a molded material charging device (hereinafter referred to as a charging chute), a carbonization process in which heated gas is blown into the carbonization zone to carbonize the molded materials and produce ferro-coke, a cooling process in which cooling gas is blown in to cool the ferro-coke, an in-furnace gas discharge process in which furnace gas is discharged from an outlet at the top of the carbonization furnace, and a ferro-coke discharge process in which ferro-coke is discharged from the bottom of the cooling zone. In the carbonization process, the molded materials are heated by blowing low-temperature gas into the furnace through a low-temperature gas blowing tuyere in the middle of the carbonization zone and high-temperature gas into the furnace through a high-temperature gas blowing tuyere in the bottom of the carbonization zone. In the cooling process, the ferro-coke is cooled by blowing in cooling gas from the cooling gas blowing tuyeres at the bottom of the cooling zone. Here, in order to increase the amount of ferro-coke produced, it is necessary to increase the volume of the carbonization furnace, but in order to allow the heating gas and cooling gas to penetrate to the center of the carbonization furnace, the internal dimensions of the furnace in the depth direction (parallel to the horizontal component of the molded material charging direction) must be kept below a certain level. Therefore, the carbonization furnace has a shape that is longer in the furnace width direction (perpendicular to the depth direction in the cross section of the furnace) than in the depth direction.

JP 2011-57970 A JP 2011-162271 A

In a vertical carbonization furnace with a structure in which the furnace width direction is longer than the furnace depth direction as described above, it is difficult to obtain a uniform charging distribution even if multiple rows of molded material charging inlets are arranged in the furnace width direction. In particular, powder generated by the collision of molded materials with the charging chute wall or between molded materials tends to segregate inside the furnace body of the carbonization furnace and tend to concentrate near the charging inlet. This is because most of the powder in the charging material slips through the molded materials and settles, and the charging material separates into two layers, a molded material layer (upper layer) and a powder layer (lower layer), before reaching the furnace body of the carbonization furnace. If 1 ton of molded materials is supplied to the charging chute, the thickness of the charging material when it enters the carbonization furnace will be a maximum of about 150 mm, and the molded material particles in the upper layer will tend to fly to a position away from the charging inlet, while the powder in the lower layer will tend to fall near the charging inlet. The compacts form mountains according to their angle of repose, resulting in a relatively uniform distribution, but the powder is fixed in position by sinking between the compacts, so if the powder falls concentrated at one point, significant segregation will occur. One problem caused by powder segregation is that it causes uneven gas flow in the furnace, which affects the dry distillation of the compacts.

As a method for uniformly charging materials, Patent Document 2 discloses a method for dispersing materials radially by providing a dispersion guide section with an inclined surface that slopes radially downward from the widthwise center of the conveying path toward the outlet side, but this technology is specialized for improving dispersion in the furnace width direction. The presence or absence of a dispersion guide section does not affect the flying distance of the powder, and installing a dispersion guide section cannot eliminate powder segregation at the charging inlet side.

The present invention has been made to solve the above problems, and aims to propose a method and apparatus for producing high-quality, highly productive molded coke by reducing the amount of powder flowing into the furnace body of the carbonization furnace, thereby eliminating uneven distribution of powder inside the carbonization furnace when producing molded coke such as ferro coke.

The means for solving the above problems are as follows.
[1] A blast furnace raw material manufacturing apparatus comprising a carbonization furnace for producing molded coke by carbonizing a carbon-containing material, and a charging chute for supplying the carbon-containing material from an outside,
The charging chute has a sloped portion,
A sieve is provided on at least a portion of the lower surface side of the inclined portion of the charging chute,
4. The apparatus for producing raw material for a blast furnace, comprising: a means for separating or recovering small-sized particles of the carbon-containing material that have passed through the sieve.
[2] The blast furnace raw material manufacturing apparatus described in [1], characterized in that the charging chute has a branched portion, and a part of the branched portion is one of the inclined portions having a sieve.
[3] A raw material manufacturing apparatus for a blast furnace as described in [1] or [2], characterized in that a portion of the charging chute near the connection with the carbonization furnace is one of the inclined portions having a sieve.
[4] A blast furnace raw material manufacturing apparatus as described in any one of [1] to [3], characterized in that the sieve installed in the charging chute is a grizzly sieve.
[5] The apparatus for manufacturing raw materials for a blast furnace described in [2], characterized in that the sieve provided at the branching portion of the charging chute is a grizzly, and the rods constituting the grizzly are arranged so as to be parallel to the direction in which the carbon-containing material moves within the charging chute.
[6] A raw material manufacturing apparatus for a blast furnace as described in [3], characterized in that it has a gate for temporarily retaining carbon-containing materials near the connection portion of the charging chute with the carbonization furnace, a sieve provided near the connection portion of the charging chute with the carbonization furnace is a grizzly, and the rods constituting the grizzly are arranged so as to be perpendicular to the direction in which the carbon-containing materials move within the charging chute.
[7] A method for producing raw materials for a blast furnace, comprising producing raw materials for a blast furnace using an apparatus for producing raw materials for a blast furnace according to any one of [1] to [6].

The present invention improves the quality of molded coke for blast furnace charging and increases productivity.

1A and 1B are a front view and a side view, respectively, of a facility according to an embodiment of the present invention.

One embodiment of the present invention will be described below using as an example the manufacturing process of ferrocoke, a type of molded coke that is a raw material for blast furnaces. Note that the drawings are schematic and may differ from the actual product. In addition, the following embodiment is an example of a raw material manufacturing apparatus for blast furnaces and a raw material manufacturing method for blast furnaces that embodies the technical idea of the present invention, and is not intended to specify the configuration as described below. In other words, the technical idea of the present invention can be modified in various ways within the technical scope described in the claims.

1 is a front view and a side view of a carbonization furnace and a charging chute, which are ferro-coke manufacturing equipment in the present invention. The carbonization furnace is longer in the furnace width direction (perpendicular to the depth direction in the cross section of the carbonization furnace) than in the depth direction, which is the charging direction of the raw materials, and in the following, the side viewed from the side in the furnace width direction is the front. First, molded materials consisting of carbon-containing materials (coal, etc.) and iron-containing materials (iron ore, etc.), which are raw materials for ferro-coke, are supplied from the outside to the charging chute 1. When the molded materials are supplied, the gate 5 installed near the connection part of the charging chute with the carbonization furnace is closed, and one batch of molded materials is piled up upstream of the gate 5. Next, the gate 5 is opened, and the molded materials are charged into the inside of the furnace body 6 of the carbonization furnace installed at a lower position than the charging chute. At this time, the molded materials pass through the diffusion section 4, which promotes dispersion in the furnace width direction, and fall into the carbonization furnace. The diffusion section has a structure in which the length in the furnace width direction is longer than the charging chute.

In the present invention, in order to eliminate uneven distribution of powder in the carbonization furnace, a sieve is provided on a part of the inclined part of the charging chute, and a means is provided for separating only small-diameter particles (hereinafter also referred to as small-diameter powder and powder) from the charging material as it passes along the inclined part and recovering them at the bottom of the sieve. Here, small-diameter powder among the charging material refers to particles whose particle diameter is two-thirds or less of the average particle diameter of the molded product. As mentioned above, since the powder in the charging material settles through the gaps in the molded product while moving through the charging chute, and since the powder is generated not only at the inlet side of the charging chute but also near the outlet of the charging chute, in order to increase the powder recovery rate, it is desirable that the inclined part where the sieve is installed is a part near the connection part of the charging chute with the carbonization furnace. Specifically, the lower side 2b of the upstream part of the gate 5 near the connection part of the charging chute with the carbonization furnace is preferable, and the distance between the gate 5 and the sieve is preferably 0.5 m or less. In addition, when the charging chute branches into two or more branches on the way, the lower surface side 2a of the branching part is also preferable as a sieve installation location. As mentioned above, the powder in the charging material settles through the gaps in the molded products, but the degree of settling depends on the amount of charging material (thickness of the charging material layer). The larger the amount of charging material (thicker the layer), the longer the distance that the powder particles originally in the upper layer travel before reaching the bottom layer, making it more difficult to settle. Therefore, in efficiently separating and recovering powder with a sieve, it is important to suppress the supply speed of the charging material passing over the sieve and to allow as much powder as possible to settle to the bottom layer. The branching part is an inclined surface with a certain length, and is preferable because the charging material passes through it continuously or intermittently at a small flow rate without stagnation. In addition, it is preferable to adopt a grizzly type sieve because it is possible to efficiently recover the powder while suppressing clogging. Here, the grizzly type sieve refers to a sieve in which rods are arranged in one direction. The recovered powder 7 may be molded again and then fed back into the charging chute.

It is desirable to arrange the bars constituting the grizzly so that they are parallel to the direction in which the charge moves along the inclined portion on the underside 2a of the branching portion, and perpendicular to the direction in which the charge moves along the inclined portion on the underside 2b of the upstream portion of the charging chute exit gate. As mentioned above, the charge is temporarily retained on the grizzly on the underside of the upstream portion of the gate close to the charging chute exit, so that the powder in the charge that has settled through the gaps in the molded material while passing through the charging chute can be recovered. Next, after the gate 5 is opened, a large amount of charge particles pass over the grizzly in a short time. Immediately after the gate 5 is opened, the molded material is clogged between the bars (holes) of the grizzly, so the powder recovery rate is low, and the molded material that has been retained on the grizzly flows down into the furnace body 6 of the carbonization furnace, and as the number of particles present on the grizzly decreases, the powder recovery rate increases. Here, when the rods constituting the grizzly are arranged parallel to the flow direction of the charge material, the molded material that has been retained immediately after the gate is opened slides down along the hole while blocking the hole, so that the grizzly is almost entirely blocked, and the powder recovery rate temporarily drops to 0%. On the other hand, when the rods are arranged perpendicular to the flow direction of the charge material, the molded material that flows down on the grizzly cannot move along the hole of the grizzly, and proceeds by repeating a falling motion into the hole and a motion over a step formed by the rods. In other words, the molded material follows a trajectory that looks like it is vibrating, and a gap is created between the molded material and the grizzly. Therefore, it is possible to recover the powder immediately after the gate 5 is opened, and the final powder recovery rate is significantly increased. Note that when the rods are arranged perpendicular to the flow direction of the charge material, molded material remains on the grizzly even after the charging into the carbonization furnace is completed, but this residual portion does not adversely affect the powder recovery rate. As mentioned above, a large amount of charge particles pass through the grizzly near the outlet of the charging chute in a short period of time, causing strong interference between the charge particles, and most of the molded material remaining on the grizzly is washed away by newly supplied charge particles.

On the other hand, if a grizzly is installed at the branch of the charging chute, the charged molded material will be appropriately sorted by the sorting damper 3, and the charged material will slide down without stagnation. In this case, since the particles of the charged material do not interfere with each other very much, it is not easy to push away the molded material that has once stagnated on the grizzly. Even if the molded material slides down along the hole, it will not block the entire grizzly. In addition, if the bar is oriented perpendicular to the flow direction of the charged material, part of the charged material will collide with the side of the bar and fly up, which means that the contact time between the grizzly and the charged material will be shortened, and the powder recovery rate will decrease by a few percent, so there is no advantage to aligning the grizzly perpendicular to the flow direction of the charged material at the branch where the charged material does not stagnate.

The above-mentioned device and method can reduce the amount of powder flowing into the furnace body of the carbonization furnace. This can eliminate uneven distribution of powder inside the carbonization furnace during the production of molded coke, improving ventilation inside the furnace body. In other words, poor carbonization caused by insufficient supply of carbonization gas to areas where powder is unevenly distributed is less likely to occur, stabilizing the quality of the carbonization product. In addition, it can prevent problems that could affect operation, such as the carbonization product being discharged at a high temperature due to insufficient supply of cooling gas at the bottom of the furnace, causing the carbonization product to catch fire, thereby realizing a manufacturing device and manufacturing method for molded coke with high quality and productivity.

The powder recovery rate when the molded material and the powder were charged was investigated using a test device simulating the ferro-coke manufacturing device in FIG. 1. The charging amount was 250 kg, and the initial powder rate was 8% by weight. Here, the oversieve (diameter 20 mm or more) with a sieve mesh of 20 mm was the molded material, and the undersieve (diameter less than 20 mm) was the powder. Recovery boxes were installed just below the grizzly and at the outlet side of the charging chute, and the powder weight in each recovery box was measured. The ratio of the powder weight in each recovery box just below the grizzly to the total powder weight in all recovery boxes was calculated and used as the "powder recovery rate". In addition, considering that the molded material diameter was about 30 mm, the bar spacing (distance between the end faces of the bar) of the grizzly was set to 25 mm. In addition, the bar was a rectangular parallelepiped, and the width of the face parallel to the flow direction of the charge was set to 10 mm.
[Example 1]
The effect of installing Grizzly at the branching section of the charging chute was investigated. The results are shown in Table 1. Grizzly was installed only at the branching section, and not near the outlet of the charging chute (upstream side of the gate). From Table 1, it can be seen that by arranging the bars that make up the Grizzly so that they are parallel to the direction in which the charging material moves along the inclined section (flow direction), it is possible to recover about half of the powder without causing clogging.

[Example 2]
The effect of installing a Grizzly near the outlet of the charging chute (upstream side of the gate) was investigated. The results are shown in Table 2. Grizzly was installed only near the outlet of the charging chute, and no Grizzly was installed at the branching section. From Table 2, it is possible to recover about 70% of the powder by arranging the rods that make up the Grizzly so that they are perpendicular to the direction in which the charging material moves along the inclined section (flow direction). In addition, although some molded material remains on the Grizzly, the powder recovery rate does not decrease even after repeated charging, which shows that the molded material remaining on the Grizzly does not have a negative effect on the powder recovery rate.

1: Charging chute 2a: Sieve on the lower side of the branch part (Grizzly)
2b: Sieve on the lower side near the outlet of the charging chute (Grizzly)
3: Distribution damper 4: Diffusion section 5: Gate 6: Furnace body of carbonization furnace 7: Recovered powder

Claims (5)

A blast furnace raw material manufacturing apparatus comprising a carbonization furnace for producing molded coke by carbonizing a carbon-containing material, and a charging chute for supplying the carbon-containing material from an outside,
The charging chute has a sloped portion,
A sieve is provided on at least a portion of the lower surface side of the inclined portion of the charging chute,
The charging chute has a branched portion, and a part of the branched portion is one of the inclined portions having a sieve,
4. The apparatus for producing raw material for a blast furnace, comprising: a means for separating or recovering small-sized particles of the carbon-containing material that have passed through the sieve. 2. The apparatus for producing raw materials for a blast furnace according to claim 1 , characterized in that a portion of the charging chute near the connection with the carbonization furnace is one of the inclined portions having a sieve. 3. The apparatus for producing raw material for a blast furnace according to claim 1, wherein a sieve provided in the charging chute is a grizzly sieve. The blast furnace raw material manufacturing apparatus according to claim 1, characterized in that the sieve provided at the branching portion of the charging chute is a grizzly, and the rods constituting the grizzly are arranged so as to be parallel to the direction in which the carbon-containing material moves within the charging chute. A method for producing raw material for a blast furnace, comprising the steps of: producing raw material for a blast furnace using an apparatus for producing raw material for a blast furnace according to any one of claims 1 to 4 .

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