WO2025115294A1 - Method for producing coal cake and method for producing metallurgical coke - Google Patents

Abstract

Provided is a method for producing a coal cake capable of achieving both improvement of strength of a coal cake and improvement of productivity. This method is for producing a coal cake in a stamp charge coke oven, the method being characterized in that the coal cake is obtained by stamping mixed coal C that is obtained by blending and mixing a carbon material A and a carbon material B so that the mass ratio of the carbon material B to 100 mass% of the carbon material A is 0.5-15 mass%, wherein the ratio of the carbon material A having a particle diameter of 0.5 mm or less is 50 mass% or less, the ratio of the carbon material A having a particle diameter of 0.1 mm or less is 20 mass% or less, the ratio of the carbon material B having a particle diameter of 0.5 mm or less is 80 mass% or more, and the ratio of the carbon material B having a particle diameter of 0.1 mm or less is 50 mass% or more.

Description

Method for producing coal cake and method for producing metallurgical coke

The present invention relates to a method for producing coal cake and a method for producing metallurgical coke, and in particular to a method for producing coal cake and a method for producing metallurgical coke in a stamp charge coke oven.

Currently, in the production of pig iron using blast furnaces, coke produced by carbonizing coal in a coke oven is used as a reducing agent for iron ore and to ensure good ventilation inside the blast furnace. It is known that high-strength coke is suitable for efficient blast furnace operation. This is because when coke breaks down inside the blast furnace, the resulting powder reduces the ventilation of the blast furnace, preventing efficient blast furnace operation.

It is known that in order to produce high-strength coke, it is effective to increase the bulk density of the coal charged into the coke oven, and for this purpose, stamp-charge coke ovens are used. In typical coke ovens currently used in Japan (hereinafter referred to as "top-charge coke ovens"), the coal, which is the raw material for coke, is charged by gravity from the top of the coke oven's carbonization chamber, and the bulk density of the gravity-charged coal is 700 to 800 kg-dry/ ^m3 .

On the other hand, in a stamp-charge coke oven, before being charged into the coke oven, the coal is tamped by a stamping device arranged on the side of the coke oven carbonization chamber, and processed into a coal cake with a bulk density of 1000 kg-dry/m3 or ^more . The resulting coal cake is then mechanically pushed from the side into the coke oven carbonization chamber and charged. By using a stamp-charge coke oven, the density of the coke raw material can be increased before carbonization, and higher strength coke can be produced compared to a top-charge coke oven. In addition, by increasing the amount of charge per oven, productivity can be increased.

As described above, stamp-charge coke ovens are superior to top-charge coke ovens in terms of coke strength and productivity. However, if the strength of the coal cake produced by stamping is low, it may cause operational troubles such as the coal cake collapsing during charging into the coke oven carbonization chamber. Therefore, a technology for producing high-strength coal cakes is required for stable operation of stamp-charge coke ovens. In addition, in order to reduce _CO2 emissions, which is a social requirement in recent years, a technology is required to improve the density of the coal cake and further improve productivity.

Regarding the relationship between coal particle size and coal cake strength, Non-Patent Document 1 reports that a test was conducted in which the degree of crushing of the coal cake raw material was changed, and that the strength of the coal cake was improved by increasing the proportion of fine particles with a particle size of 3.15 mm or less in the raw material, i.e., by crushing the coal cake raw material more finely.

Furthermore, the use of caking binders has been investigated to improve the strength of coal cake. For example, Patent Document 1 reports a method in which caking coal is heated to 300-500°C and the coal in a softened, molten state is used as the binder for the coal cake. Furthermore, Non-Patent Document 2 reports that the strength of coal cake can be increased by adding pitch with a softening point of 80°C to the raw materials as a binder.

Japanese Unexamined Patent Publication No. 7-109467

M. Rejdak, et al., Physicochem. Probl. Miner. Process. 51(1), 2015, 151. S. H. Krishnan, et al., "Application of Binder in Stamp Charge Coke Making", ISIJ International, 44(2004), 1150.

Non-Patent Document 1 reports that by crushing the raw materials for the coal cake more finely, the strength of the coal cake is improved, but the density of the coal cake is reduced. In other words, a method of strengthening the crushing of the raw materials for the coal cake and reducing the particle size of the raw materials improves the strength of the coal cake and contributes to stable operation of the stamp charge furnace, but the decrease in the density of the coal cake results in a relative decrease in productivity.

In addition, in the method using a caking binder described in Patent Document 1 and Non-Patent Document 2, the caking raw material adheres to the belt conveyor and stamping device during the process of transporting the coke raw material containing the caking binder and during the process of compacting the raw material with the stamping device. This necessitates frequent cleaning of the equipment, resulting in a problem of reduced productivity.

The object of the present invention is to provide a method for producing coal cake that can improve both the strength of the coal cake and productivity.

The inventors conducted extensive research to solve the above problems and discovered the following: By preparing a coal blend containing a small amount of fine coal material and stamping it, the density and strength of the coal cake can be improved.

That is, the gist and configuration of the present invention are as follows.
[1] A method for producing a coal cake in a stamp charge coke oven, comprising the steps of:
A carbonaceous material A having a ratio of grains having a particle size of 0.5 mm or less being 50% by mass or less and a ratio of grains having a particle size of 0.1 mm or less being 20% by mass or less;
A carbonaceous material B having a ratio of grains having a particle size of 0.5 mm or less of 80 mass% or more and a ratio of grains having a particle size of 0.1 mm or less of 50 mass% or more;
A method for producing a coal cake, comprising: mixing the carbonaceous material A and the carbonaceous material B so that a mass ratio of the carbonaceous material B to 100 mass% of the carbonaceous material A is 0.5 mass% or more and 15 mass% or less; and stamping the resulting blended coal C to obtain a coal cake.

[2] A method for producing metallurgical coke, comprising carbonizing the coal cake produced by the method described in [1] above in a coke oven to obtain coke.

According to the present invention, a method for manufacturing a coal cake can be provided that can improve both the strength of the coal cake and the productivity of the stamp charge furnace. Furthermore, according to the present invention, by improving the strength of the coal cake, problems such as the collapse of the coal cake can be reduced, and the stamp charge furnace can be operated stably. In addition, by increasing the density of the coal cake, the productivity of the stamp charge furnace can be improved.

The following describes an embodiment of the present invention. The method for producing a coal cake according to the present invention is a method for producing a coal cake in a stamp-charge coke oven, and is characterized in that carbonaceous material A having a ratio of particle sizes of 0.5 mm or less to 50 mass % or less and a ratio of particle sizes of 0.1 mm or less to 20 mass % or less and carbonaceous material B having a ratio of particle sizes of 0.5 mm or less to 80 mass % or more and a ratio of particle sizes of 0.1 mm or less to 50 mass % or more are prepared, and the carbonaceous material A and the fine carbonaceous material B are blended and mixed so that the mass ratio of the fine carbonaceous material B to 100 mass % of the carbonaceous material A is 0.5 mass % to 15 mass % to obtain blended coal C, which is then stamped to obtain a coal cake.

[Charcoal material A]
The carbonaceous material A in the present invention is a typical raw material used as a coke raw material in conventional top-charged coke ovens and stamp-charged coke ovens, and may be produced by crushing the raw material using a hammer crusher or the like so that the ratio of particles having a particle size of 3 mm or less is 70 mass% or more, as is done in conventional coke oven operations. Note that the "ratio of particles having a particle size of 3 mm or less" refers to the ratio of the mass of the particles under the sieve to the mass of the entire raw material when the raw material is sieved through a 3 mm sieve, and this also applies when the particle size is different in this specification.

In order to obtain the effects of the present invention, the particle size of carbonaceous material A must be significantly different from that of carbonaceous material B, and therefore must be higher than a certain level. Specifically, the proportion of particles with a particle size of 0.5 mm or less must be 50% by mass or less, and the proportion of particles with a particle size of 0.1 mm or less must be 20% by mass or less. However, since the effects of the present invention can be increased by making the difference in particle size with carbonaceous material B more pronounced, it is preferable that the particle size of carbonaceous material A is larger. Specifically, it is preferable that the proportion of particles with a particle size of 0.5 mm or less must be 40% by mass or less, and the proportion of particles with a particle size of 0.1 mm or less must be 15% by mass or less, and it is even more preferable that the proportion of particles with a particle size of 0.5 mm or less must be 35% by mass or less, and the proportion of particles with a particle size of 0.1 mm or less must be 12% by mass or less.

The raw materials for the carbonaceous material A that constitutes the coal cake are mainly raw coals that are generally used in coke production, but in addition to raw coals, non- or slightly caking coals, oil cokes, pitches, biomass, other raw materials mainly composed of carbon, and charcoals obtained by heating the above raw materials may also be used, so long as the quality of the coke after carbonization is not an issue. In addition, when multiple raw materials are used as the carbonaceous material A, each raw material may be individually crushed and then blended to be used as the carbonaceous material A, or multiple raw materials may be blended and then crushed together.

[Charcoal material B]
In the present invention, the density and strength of the coal cake can be improved by blending a portion of the carbonaceous material B having a sufficiently low particle size with the carbonaceous material A. The particle size of the carbonaceous material B for obtaining the effects of the present invention needs to be such that the proportion of particles having a particle size of 0.5 mm or less is 80 mass% or more and the proportion of particles having a particle size of 0.1 mm or less is 50 mass% or more. In order to obtain a greater effect of improving the density and strength of the coal cake, it is preferable that the proportion of particles having a particle size of 0.5 mm or less is 82 mass% or more and the proportion of particles having a particle size of 0.1 mm or less is 56 mass% or more, and it is more preferable that the proportion of particles having a particle size of 0.5 mm or less is 85 mass% or more and the proportion of particles having a particle size of 0.1 mm or less is 70 mass% or more.

The raw materials for carbonaceous material B are mainly raw coals generally used in coke production, but in addition to raw coals, non- or slightly caking coals, oil cokes, pitches, biomass, other raw materials mainly composed of carbon, and charcoals obtained by heating the above raw materials may also be used, so long as the quality of the coke after carbonization is not an issue. In addition, carbonaceous material B may be obtained by extracting a portion of carbonaceous material A and pulverizing it.

The method for adjusting the particle size of carbonaceous material B is not particularly specified as long as the specified particle size is obtained, but for example, equipment such as a ball mill, roller mill, tower mill, bead mill, or jet mill can be used. In addition, carbonaceous material generated within the steelworks that meets the above particle size conditions may be used as carbonaceous material B without particle size adjustment. Examples of raw materials generated within the steelworks include dust powder collected from powder generated by a coke dry quenching (CDQ) device or by transporting coke. In addition, when multiple raw materials are used as carbonaceous material B, each raw material may be individually crushed and then blended to be used as carbonaceous material B, or multiple raw materials may be blended and then crushed together.

[Blend coal C]
The blended coal C is obtained by mixing the carbonaceous material A and the fine carbonaceous material B. In order to obtain the effect of improving the density and strength of the coal cake according to the present invention, the mass ratio of the carbonaceous material B to 100% by mass of the carbonaceous material A must be 0.5% by mass or more. In order to obtain a greater effect, the mass ratio of the carbonaceous material B is more preferably 1% by mass or more, and more preferably 2% by mass or more. On the other hand, the purpose of the present invention is not to pulverize the entire coal cake raw material, but to add a part of the carbonaceous material B having a smaller particle size than the carbonaceous material A to the carbonaceous material A pulverized to a normal pulverized particle size. As a result, as shown in the examples described later, a unique effect of improving both the density and strength of the coal cake can be obtained. Therefore, the mass ratio of the carbonaceous material B to 100% by mass of the carbonaceous material A must be 15% by mass or less. Considering that the production of the fine carbonaceous material requires an increase in the pulverization capacity, from the viewpoint of economy, the mass ratio of the carbonaceous material B is preferably 12% by mass or less, more preferably 10% by mass or less.

The method for mixing carbonaceous material A and carbonaceous material B is not particularly limited and may be a mixer that is generally used to mix coal in coke plants. Another example is a method in which carbonaceous material A and carbonaceous material B are placed on the same belt conveyor and mixed by the flow of the materials when they are transferred from one conveyor to another.

The moisture content of the coal blend C is preferably 9 to 12% by mass in order to maximize the strength of the coal cake. Moisture adjustment can be performed by drying using a coal moisture control system, spraying water from a nozzle, or other processes. The moisture adjustment is preferably performed after mixing of the carbonaceous materials A and B, but depending on the layout of the plant, it may be performed before or after the crushing process of the carbonaceous materials A and B. However, as will be explained using data in Example 2 below, the effect of the present invention can be obtained as long as the moisture content of the coal blend C is between 7 and 13% by mass. The moisture content of coal stored in the yard varies depending on the season and weather, but the range of variation is approximately within the range of 7 to 13% by mass, so the moisture range for obtaining the effect of the present invention is not particularly limited within the range of normal coke production conditions.

<Production of coal cake>
In the present invention, the blended coal C is stamped and compacted to produce a high-strength coal cake.

When producing coal cake from the coal blend C prepared as described above, a stamping device that compacts the raw material by the impact of a falling weight may be used. In this case, by using coal blend C, which is a blend of carbonaceous material B and carbonaceous material A, as the raw material, it is possible to produce a coal cake that is denser and stronger than when using only carbonaceous material A. As a result, the coal cake is less likely to collapse, allowing for stable operation of the coke oven. In addition, productivity is improved by increasing the amount of coal charged per oven.

The factors that improve the density and strength of the coal cake are not fully understood, but it is speculated that this is due to carbon material B penetrating between the particles of carbon material A and acting as a lubricant, improving the fluidity of the carbon material as a whole. By improving the fluidity of the carbon material as a whole, it becomes easier for particles to rearrange when stamped with the same energy, and it is believed that a coal cake with higher density and strength can be produced.

(Method of manufacturing metallurgical coke)
Next, a method for producing metallurgical coke according to the present invention will be described. The method for producing metallurgical coke according to the present invention is characterized in that the coal cake produced by the above-mentioned method for producing coal cake according to the present invention is carbonized in a coke oven.

The coal cake produced by the above-mentioned method for producing coal cake according to the present invention is mechanically charged into the side of the coke oven carbonization chamber. At this time, the coal cake is subjected to the impact of its own weight and the vibration of the charging machine. If the strength of the coal cake is low, an operational problem may occur in which the coal cake collapses during charging. However, by using blended coal C, which is a mixture of carbon material A and carbon material B having a smaller particle size than carbon material A, as the raw material for the coal cake, the strength of the coal cake is improved and the collapse of the coal cake can be prevented. In addition, the coal cake produced from blended coal C, which is a mixture of carbon material A and carbon material B having a smaller particle size than carbon material A, has a higher density than the coal cake produced by the conventional method, and therefore the amount of coal charged per kiln is increased, thereby improving productivity.

There are no particular restrictions on the conditions for carbonizing the coal cake. The coal cake can be carbonized at a temperature of approximately 900°C or higher using a typical stamp charge coke oven.

The following describes examples of the present invention, but the present invention is not limited to the following examples and can be modified as desired without departing from the gist of the present invention.

Example 1
As Example 1, different carbonaceous materials A and B were blended and mixed to produce a coal cake, and the strength of the cake was evaluated. The production conditions and evaluation results are shown in Table 1.

Specifically, a coal blend containing multiple coals was used as the carbonaceous material A, and was crushed to the particle size shown in Table 1. Coke powder, non- or slightly caking coal, and carbonized biomass were crushed to the particle size shown in Table 1 and used as the carbonaceous material B. Carbonaceous material A and carbonaceous material B were then mixed in the blending ratio shown in Table 1 to prepare coal blend C, and the moisture content of coal blend C was then adjusted to 10% by mass.

A coal cake was produced using the coal blend C prepared by the above procedure, as follows: First, approximately 200 g of coal blend C was charged into a metal mold with an inner diameter of 10 cm and a height of 20 cm, and a rammer weighing 9 kg was dropped 10 times from a height of 30 cm above the sample surface, compacting the charged coal blend C with the impact. The above procedure from charging the coal blend C to dropping the rammer was repeated 10 times to produce a coal cake with a diameter of 10 cm, a height of 20 cm, and a mass of approximately 2 kg. The mold was then gently removed from the coal cake, and the dry density and strength of the coal cake were measured.

The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio shown in Table 1 are the density ratio and strength ratio of the coal cake produced from blended coal C mixed with carbonaceous material B, when the dry density and strength of the coal cake produced by the above procedure using only carbonaceous material A without mixing carbonaceous material B are taken as 1. Therefore, when the density ratio and strength ratio are each greater than 1, it can be determined that the properties of the coal cake have been improved by the present invention, that is, by mixing carbonaceous material A with carbonaceous material B, which has a smaller particle size than carbonaceous material A.

In Comparative Examples 1 and 4, carbonaceous material A is mixed with carbonaceous material B of approximately the same particle size. The density and strength of the coal cake are hardly changed by the addition of carbonaceous material B. In Comparative Examples 2, 3, 5, and 6, carbonaceous material A is mixed with carbonaceous material B of a relatively small particle size. The strength ratio becomes greater than 1 by the addition of carbonaceous material B, while the density ratio becomes less than 1. It has been reported in Non-Patent Document 1 and elsewhere that the strength improves while the density decreases as the particle size of the raw material decreases, and this result can be said to be in line with prior art findings.

In contrast, in Examples 1 to 7, carbonaceous material A is mixed with carbonaceous material B, which is sufficiently finely pulverized to achieve the effects of the present invention. By mixing carbonaceous material B, both the density ratio and strength ratio become greater than 1, and it can be seen that the properties of the coal cake are improved. In addition, comparing Comparative Examples 5 and 6 with Examples 3 and 4, the strength improvement effect of the Examples is clearly greater than that of the Comparative Examples. Therefore, it is believed that the strength of the coal cake is improved by mixing carbonaceous material A with carbonaceous material B, which has a smaller particle size than carbonaceous material A. Note that Examples 1 to 7 only describe examples in which the proportion of particles with a particle size of 3 mm or less is 78 to 100 mass%, but the same effect can be obtained even when carbonaceous material A has a larger particle size (the proportion of particles with a particle size of 3 mm or less is 70 mass%) because carbonaceous material B is mixed.

In Comparative Example 7, 20% by mass of sufficiently finely pulverized carbonaceous material B was mixed with carbonaceous material A, but in this case the density of the coal cake decreased. If the proportion of carbonaceous material B, which has a lower particle size than carbonaceous material A, is too high, there will be an excess of carbonaceous material B with a lower particle size than carbonaceous material A in the gaps between the carbonaceous material A with a higher particle size as described above, and it is believed that the effect of the invention will not be fully obtained.

As described above, the present invention not only stabilizes coke oven operation by improving the strength of the coal cake, but also improves productivity by increasing the density of the coal cake.

As is clear from this embodiment, the raw material of the carbonaceous material B for obtaining the effects of the present invention is not particularly limited. If coke powder or non-caking coal generated in a steelworks is used as the carbonaceous material B, the effects of the present invention can be obtained relatively inexpensively. In addition, if a carbon-neutral raw material such as carbonized biomass is used as the carbonaceous material B, it can contribute to reducing _CO2 emissions, and meets recent social demands.

Example 2
As Example 2, coal cakes were produced by varying the moisture content of the coal blend C, and the strength of the coal cakes was evaluated. The production conditions and evaluation results are shown in Table 2.

Specifically, a coal blend made of multiple coals was used as the carbonaceous material A, and was crushed to the particle size shown in Table 2. Coke powder was crushed to the particle size shown in Table 2 and used as the carbonaceous material B. Carbonaceous material A and carbonaceous material B were then mixed in the blending ratio shown in Table 2 to prepare coal blend C, and the moisture content of coal blend C was then adjusted to 7% by mass or 13% by mass.

A coal cake was produced using the coal blend C prepared by the above procedure, as follows: First, approximately 200 g of coal blend C was charged into a metal mold with an inner diameter of 10 cm and a height of 20 cm, and a rammer weighing 9 kg was dropped 10 times from a height of 30 cm above the sample surface, compacting the charged coal blend C with the impact. The above procedure from charging the coal blend C to dropping the rammer was repeated 10 times to produce a coal cake with a diameter of 10 cm, a height of 20 cm, and a mass of approximately 2 kg. The mold was then gently removed from the coal cake, and the dry density and strength of the coal cake were measured.

The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratios shown in Table 2 are the density ratio and strength ratio of the coal cake produced from blended coal C mixed with carbonaceous material B, when the dry density and strength of the coal cake produced by the above procedure using only carbonaceous material A without mixing carbonaceous material B are taken as 1. Therefore, when the density ratio and strength ratio are both greater than 1, it can be determined that the properties of the coal cake have been improved by adding carbonaceous material B.

As shown in Table 2, when the moisture content of coal blend C was either 7% by mass or 13% by mass, the density ratio and strength ratio became 1 or more by mixing carbonaceous material A with carbonaceous material B, which has a smaller particle size than carbonaceous material A, and the properties of the coal cake were improved. The moisture content of coal stored in the yard varies depending on the season and weather, but the range of variation is approximately 7 to 13% by mass. Therefore, as is clear from Tables 1 and 2, the present invention can be widely used when the moisture content of coal blend C varies in the range of 7 to 13% by mass.

According to the present invention, it is possible to provide a method for producing a coal cake that can improve both the strength of the coal cake and the productivity.

Claims (2)

A method for producing a coal cake in a stamp charge coke oven, comprising the steps of:
A carbonaceous material A having a ratio of grains having a particle size of 0.5 mm or less being 50% by mass or less and a ratio of grains having a particle size of 0.1 mm or less being 20% by mass or less;
A carbonaceous material B having a ratio of grains having a particle size of 0.5 mm or less of 80 mass% or more and a ratio of grains having a particle size of 0.1 mm or less of 50 mass% or more;
A method for producing a coal cake, comprising: mixing the carbonaceous material A and the carbonaceous material B so that a mass ratio of the carbonaceous material B to 100 mass% of the carbonaceous material A is 0.5 mass% or more and 15 mass% or less; and stamping the resulting blended coal C to obtain a coal cake. A method for producing metallurgical coke, comprising carbonizing the coal cake produced by the method according to claim 1 in a coke oven to obtain coke.