JP7252451B2 - Multi-layered coke and method for producing multi-layered coke - Google Patents

Description

TECHNICAL FIELD The present invention relates to coke having excellent coke reactivity and a method for producing coke.

In a blast furnace, ore raw materials and coke are charged in layers from the top of the furnace to form a packed bed, and the ore raw materials are reduced in the blast furnace to produce molten pig iron. When coke is charged into the blast furnace, a coke gasification reaction represented by C + CO ₂ = 2CO (hereinafter sometimes simply referred to as coke gasification reaction) occurs, and the ore raw material is reduced by CO gas. be done. In the following description, this coke gasification reaction may be referred to as coke reactivity.

Here, in the upper stage of the packed bed, the reducing power of the reducing gas blowing up from the bottom of the furnace toward the top of the furnace is reduced, so the gasification reaction of coke is promoted (that is, the reactivity of coke is increased). It is necessary to generate a reducing gas and efficiently reduce the ore raw material. On the other hand, since the ore raw material is easily reduced by the reducing gas blowing up toward the top of the furnace in the middle to lower stages of the packed bed, there is no need to increase the coke reactivity. Rather, if the reactivity of coke increases in the middle to lower stages of the packed bed, the coke whose strength has decreased due to excessive gasification reaction will be crushed and pulverized, which may hinder the air permeability inside the blast furnace. Therefore, coke with high coke reactivity in the upper part of the packed bed and low coke reactivity in the middle to lower part of the packed bed is required.

In Patent Document 1, a liquid obtained by dissolving and/or dispersing in a solvent a catalyst substance that activates the reaction that produces carbon monoxide from carbon and carbon dioxide is mixed with a single brand of coal or multiple brands of coal. A method for producing highly reactive coke for blast furnaces with different catalyst concentration distributions is described, which is characterized by penetrating from the surface of coke produced by dry distillation of charcoal and imparting a concentration distribution of catalyst substances from the surface to the inside of the coke. ing.

Referring to FIG. 6, according to the production method described in Patent Document 1, the concentration distribution of the catalyst substance is controlled from the surface to the inside of the coke, and the concentration distribution is changed in a curve (curve (a), See curve (a')) highly reactive coke can be produced.

JP 2004-315664 A

In the method of Patent Literature 1, coke with higher coke reactivity in the outside than in the inside of the coke can be obtained. That is, coke with high coke reactivity is obtained in the upper stage of the packed bed, and coke with low coke reactivity is obtained in the middle to lower stages of the packed bed. However, in the method of Patent Document 1, since the coke contains a certain amount of water, the blast furnace requires a heat amount to evaporate the water, and the reducing agent ratio increases, so it is desirable that the water content in the coke is low. .

In order to solve the above problems, the multi-layered coke according to the present invention is provided by: (1) The coke charged into the blast furnace has a multi-layered structure, and the outer layer coke is more likely to react with coke than the inner layer coke. It is characterized by a high sexual CRI.

(2) The multi-layered coke according to (1) above, wherein the coke reactivity CRI of the outer layer coke is greater than 35.

(3) The multi-layered coke according to (1) or (2) above, wherein the mass ratio of the outer layer coke is 10% by mass or more and 50% by mass or less when the total coke is 100% by mass.

The method for producing multi-layered coke according to the present invention is (4) a method for producing multi-layered coke, wherein raw coal for inner layer coke is placed in the center and coke reaction occurs when coking Coal having a higher reactive CRI than the coke-reactive CRI when the raw coal for the inner layer coke is coked is placed in the outer layer as the raw coal for the outer layer coke. It is characterized by producing coke by carbonizing charcoal.

(5) The method for producing multi-layered coke according to (4) above, wherein the raw coal for the inner layer coke and the raw coal for the outer layer coke are of different coal types.

According to the present invention, it is possible to provide coke having a higher coke reactivity and a lower water content in the outer coke layer than in the inner coke layer.

1 is a cross-sectional view of coke; FIG. 1 is an elevational view of a coal briquetting apparatus; FIG. FIG. 2 is a cross-sectional view of the coal briquette manufacturing apparatus cut along the A plane; 1 is a perspective view of a forming roll included in a charcoal forming apparatus; FIG. 1 is a cross-sectional view of coal briquette; FIG. FIG. 2 is a conceptual schematic diagram showing the concentration distribution of catalyst in conventional high-reactivity coke.

(First embodiment)
FIG. 1 is a cross-sectional view of coke according to this embodiment. The coke 10 has a two-layer structure in which the outer layer coke has a higher coke reactivity CRI (hereinafter sometimes simply referred to as “CRI”) than the inner layer coke. Here, the inner coke layer is referred to as a low-reactive layer portion 11 having a low CRI, and the outer coke layer is referred to as a high-reactive layer portion 12 having a high CRI. The low reaction layer portion 11 is located in the center of the coke 10 and forms an inner layer. The highly reactive layer portion 12 forms an outer layer of the coke 10 so as to cover the entire low reactive layer portion 11 .

CRI is an evaluation value that evaluates the reactivity between coke and _CO2 gas. Measure the mass of the sample after reacting at a temperature of 1100 ° C. and a reaction time of 2 hours. is. The higher the CRI, the more reactive the coke, and the lower the CRI, the less reactive the coke.

CRI can be controlled by coal type. Specifically, a plurality of coals of different coal types are measured for their respective CRIs when coked, and a single coal with a low CRI is used as the coal for forming the low reaction layer portion 11. , plain coal having a high CRI is used as the coal forming the highly reactive layer 12 .

CRI may also be controlled by adding catalytic materials to the coal that increase coke reactivity. As this type of catalyst material, for example, alkali metals, alkali metal compounds, alkaline earth metals, alkaline earth metal compounds, transition metals, and mixtures of two or more of transition metal compounds are used. be able to. Preferably, the catalytic material is solid. However, when coal is carbonized in a coke oven, a liquid obtained by dissolving and/or dispersing a catalyst substance in a solvent may be used within the range of heat quantity allowed by the coke oven used.

In the present embodiment, since a solid catalyst substance can be added to the raw coal of the coke 10, the amount of heat required to evaporate the moisture in the coke oven can be minimized. can provide coke with a low coke to the blast furnace. As a result, useful coke 10 with controlled coke reactivity can be produced without increasing the moisture content. The moisture content of coke 10 is preferably less than 1% by weight. The details of the catalyst substance are disclosed in Patent Document 1, so the description is limited to the above.

The CRI of the low reaction layer portion 11 is preferably 35 or less. Although the lower limit of the CRI of the low-reaction layer 11 is not particularly limited, it is approximately 15 considering the minimum CRI of coke produced from general coke-making coking coal. The CRI of the highly reactive layer portion 12 is preferably greater than 35. Although the upper limit of the highly reactive layer 12 is not particularly limited, it is approximately 60 considering the maximum CRI of coke produced from general coke-producing coking coal.

In a blast furnace, approximately 20% by mass of coke is consumed by the coke gasification reaction. Therefore, when the entire coke 10 is 100% by mass, the mass ratio of the highly reactive layer 12 having excellent reactivity is preferably 10% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 30% by mass. % or less, more preferably 15 mass % or more and 25 mass % or less.

When the coke 10 is charged into the blast furnace, the highly reactive layer 12 with high coke reactivity is selectively gasified, so that reducing gas can be efficiently generated. On the other hand, the low reaction layer portion 11 with low coke reactivity falls in the packed bed while maintaining a high-strength lump state, so it is possible to suppress coke pulverization and obstruction of air permeability.

Next, a method for producing coke 10 will be described in detail. FIG. 2 is an elevational view of the coal briquetting apparatus. FIG. 3 is a cross-sectional view of the coal briquetting apparatus cut along the A plane. FIG. 4 is a perspective view of a forming roll included in the charcoal forming apparatus. In these figures, the X-axis, Y-axis and Z-axis indicate different three axes orthogonal to each other.

Coal forming apparatus 30 includes an external coal feed hopper 31 , an internal coal feed nozzle 32 and a pair of forming rolls 33 , 34 . The forming roll 33 is cylindrical and rotates around an axis extending in the X-axis direction. An arrow K1 in FIG. 2 indicates the direction of rotation of the forming roll 33 . Forming cups 33 a are formed on the outer peripheral surface of the forming roll 33 . The molded cup 33a is formed in a shape (for example, a hemispherical shape) obtained by dividing the molded charcoal 20, which will be described later. The forming cups 33a are arranged at substantially equal intervals in the circumferential direction of the forming roll 33, and a group of forming cups 33a are arranged at predetermined intervals in the longitudinal direction (X-axis direction) of the forming roll 33. Queues are provided.

The forming roll 34 has the same shape as the forming roll 33, and a plurality of forming cups 34a are formed on the outer peripheral surface of the roll. The forming roll 34 is arranged at a position facing the forming roll 33 in the Y-axis direction. The arrow K2 in FIG. 2 is the opposite direction to the arrow K1 and indicates the rotation direction of the forming roll 34. As shown in FIG. That is, the forming roll 33 continuously rotates counterclockwise, and the forming roll 34 continuously rotates clockwise.

The external coal supply hoppers 31 are provided in the same number as the forming cups 33 a arranged in the longitudinal direction of the forming rolls 33 . In other words, one external coal supply hopper 31 is assigned to a group of forming cups 33a arranged in the circumferential direction. A hopper discharge port 31 a of the external coal supply hopper 31 is provided at a position close to the upper ends of the forming rolls 33 and 34 . The external coal supply hopper 31 stores raw material coal (hereinafter sometimes referred to as external coal) for forming the highly reactive layer 12 of the coke 10, and this external coal is supplied from the external coal supply hopper 31. discharged continuously.

The internal coal supply nozzle 32 extends toward the region where the pair of forming rolls 33 and 34 face each other, and the nozzle discharge port 32a of the internal supply nozzle 32 is located below the hopper discharge port 31a of the external coal supply hopper 31. positioned. A supply screw (not shown) is provided inside the internal coal supply nozzle 32, and the rotation of the supply screw causes the coal (raw material for forming the low reaction layer 11) toward the forming cups 33a and 34a. coal, hereinafter sometimes referred to as internal coal). The feed screw of internal coal feed nozzle 32 is driven intermittently.

The pair of forming rolls 33 and 34 rotate so that the forming cups 33a and 34a are in the same phase. That is, the pair of forming rolls 33 and 34 rotate so that the forming cups 33a and 34a face each other in the Y-axis direction intermittently.

Here, when the pair of forming cups 33a and 34a enter directly below the outlet of the external coal supply hopper 31, the external coal is dropped and supplied from the external coal supply hopper 31 to these forming cups 33a and 34a. Further rotation of the pair of forming rolls 33, 34 feeds the internal coal through the internal coal feeding nozzle 32 onto the external coal accumulated in the forming cups 33a, 34a. The supply amount of the internal coal is predetermined, and when the target supply amount is reached, the supply operation of the internal coal is immediately stopped. On the other hand, since the external coal is always continuously supplied, the external coal is further layered on the internal coal. As a result, coal having a two-layer structure is formed in which the inner coal is arranged in the central portion and the outer coal is arranged in the outer layer portion.

The two-layered coal is pressed against the forming cups 33a and 34a when the pair of forming cups 33a and 34a face each other in the Y-axis direction, forming the formed coal 20 serving as the base of the coke 10. FIG. 5 is a cross-sectional view of the coal briquette 20. As shown in FIG. The coal briquette 20 has a two-layer structure consisting of an inner coal bed 21 and an outer coal bed 22. When carbonized, the inner coal bed 21 becomes the low reaction layer 11 and the outer coal bed 22 becomes the high reaction layer 12. . In addition, the carbonization process of the coal briquette 20 can be performed, for example, in a vertical shaft carbonization furnace. The size of the coal briquette 20 is not particularly limited, but can be, for example, about 30 to 70 mm.

The molded coal production apparatus 30 is driven based on a predetermined mass ratio of the low-reactive layer portion 11 and the high-reactive layer portion 12, and this mass ratio can be changed as appropriate. For example, when the supply speed of the internal coal is increased, the mass ratio of the internal coal bed 21 (low reaction layer portion 11) increases, and when the supply speed of the internal coal is decreased, the mass ratio of the internal coal bed 21 (low reaction layer portion 11) increases. The mass ratio is lowered. The feed rate of the internal coal can be changed by controlling the rotation speed of the feed screw or by changing the cross-sectional area of the feed nozzle.

(Modification)
In the above-described embodiment, two-layered coke with different CRIs has been described, but the present invention is not limited to this, and three or more layers of coke with different CRIs can also be used. In the case of three layers, an intermediate layer is formed between the inner layer and the outer layer, the CRI of the intermediate layer being higher than the CRI of the inner layer and lower than the CRI of the outer layer. Also, when a plurality of intermediate layers are formed, they are formed so that the CRI increases from the inner layer side to the outer layer side. As a result, it is possible to provide coke whose reactivity is more finely adjusted from the upper stage to the lower stage in the packed bed of the blast furnace. In this case, for example, coke having a multi-layer structure can be produced by forming the internal coal supply nozzle 32 into a multi-pipe structure.

(Example)
The present invention will be described in detail with reference to examples. First, molded coke was produced for each of single brand coals A to B, and coke reactivity was evaluated. After the coals A to B were pulverized to 100% by mass of 3 mm or less, 10% by mass of soft pitch liquefied by heating was added to the coal and kneaded. The kneaded coal was formed into a sphere equivalent diameter of 45 mm with a normal double roll, and after the formed coal was carbonized in a test coke oven, the CRI was measured. Table 1 shows the properties of coals A to B and the CRI of each formed coke. It was found that coal A resulted in highly reactive coke with a CRI greater than 35, and coal B resulted in less reactive coke with a CRI of 35 or less.

Based on the results in Table 1, coal B was selected as the internal coal and coal A was selected as the external coal. Coal A was pulverized to 100% by mass of 3 mm or less, then warmed and liquefied soft pitch was added to the pulverized coal in an external number of 10% by mass, kneaded, and introduced into an external coal supply hopper. Coal B, treated in the same manner as coal A, was fed to an internal coal feed nozzle. As a result of production under the conditions shown in Table 2, it was possible to produce coal briquette (coke briquette) with a mass ratio of the outer coal layer 22 (highly reactive layer 12) of 10% by mass to 40% by mass. When the moisture contained in the formed coke was measured, it was all less than 1% by mass. On the other hand, the coal formed into the same size as the above using only the coal B was carbonized in a test coke oven to prepare formed coke, and a 5% by mass aqueous solution of CaCl ₂ was added to the formed coke as a catalyst substance. The water content was examined by penetrating from the surface of the As conditions for liquid penetration, a method of spraying the aqueous solution for 10 seconds and a method of immersing the substrate in the aqueous solution for 10 seconds were used. As a result, the water content of the coke was 3.5% by mass for the spray method and 4.5% by mass for the immersion method, both of which were higher than the coke of the present invention. From the above, it was confirmed that according to the present invention, coke with a higher coke reactivity and a lower water content can be obtained in the outer layer of coke than in the inner layer of coke.

10 coke 11 low reaction layer 12 high reaction layer 20 coal briquette 21 internal coal 22 external coal

Claims (5)

The coke charged into the blast furnace has a multilayer structure,
A multi-layer structure coke characterized in that the outer layer coke has a higher coke reactivity CRI than the inner layer coke. 2. The multi-layered coke according to claim 1, wherein the coke reactivity CRI of said outer layer coke is greater than 35. 3. The multi-layered coke according to claim 1 or 2, wherein the outer layer coke has a mass ratio of 10% by mass or more and 50% by mass or less when the total coke is 100% by mass. A method for producing multi-layered coke, comprising:
The raw coal for the inner layer coke is placed in the center, and the coke reactivity CRI when coked is higher than the coke reactivity CRI when the raw coal for the inner layer coke is coked. As the raw material coal for the
A method for producing multi-layered coke, comprising producing coke by carbonizing the coal briquette. 5. The method for producing multi-layered coke according to claim 4, wherein the raw coal for the inner layer coke and the raw coal for the outer layer coke are of different coal types.

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