Method for producing coal cake and method for producing metallurgical coke

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

[0001] The present invention relates to a method for producing a coal cake and a method for producing metallurgical coke, and more particularly to a method for producing a coal cake and a method for producing metallurgical coke in a stamp charge coke oven.

[0002] 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 gas permeability 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 gas permeability of the blast furnace, preventing efficient blast furnace operation.

[0003] It is known that increasing the bulk density of the coal charged into a coke oven is effective for producing high-strength coke, and for this purpose, stamp-charge coke ovens are used. In the 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 / m ３ is.

[0004] On the other hand, in a stamp-charge coke oven, coal is compacted by a stamping device located on the side of the coke oven carbonization chamber before being charged into the coke oven, and the bulk density is 1000 kg-dry / m ３ The resulting coal cake is then mechanically pushed from the side and charged into the coke oven chamber. The use of a stamp-charge coke oven increases the density of the coke raw material before carbonization, allowing for the production of higher-strength coke than top-charge coke ovens. Furthermore, productivity can be increased by increasing the amount of material charged per oven.

[0005] As mentioned 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, the coal cake may collapse during charging into the coke oven carbonization chamber, causing operational problems. Therefore, technology to produce high-strength coal cakes is required for stable operation of stamp-charge coke ovens. In addition, in response to recent social demands for high-strength coal cakes, ２ To reduce emissions, technology is needed to improve coal cake density and further increase productivity.

[0006] 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.

[0007] Furthermore, the use of a caking binder has been investigated with the aim of improving the strength of the coal cake. For example, Patent Document 1 reports a method in which caking coal is heated to 300 to 500°C and the coal in a softened, molten state is used as a binder for the coal cake. Furthermore, Non-Patent Document 2 reports that the strength of the coal cake can be increased by adding pitch with a softening point of 80°C to the raw material as a binder.

[0008] Japanese Unexamined Patent Publication No. 7-109467

[0009] M. Rejdak, et al., Physicochem. Probl. Miner. Process. 51(1), 2015, 151.SH Krishnan, et al., "Application of Binder in Stamp Charge Coke Making", ISIJ International, 44(2004), 1150.

[0010] 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.

[0011] Furthermore, in the methods 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 a stamping device, which requires frequent cleaning of the device and results in a problem of reduced productivity.

[0012] An object of the present invention is to provide a method for producing a coal cake that can improve both the strength of the coal cake and productivity.

[0013] The inventors have conducted extensive research to solve the above problems and have discovered the following: By preparing a coal blend by blending a small amount of fine carbonaceous materials with a coal blend of a pulverized particle size normally used in a stamp charge furnace and stamping the blended coal, the density and strength of the coal cake can be improved.

[0014] That is, the gist of the present invention is as follows: [1] A method for producing a coal cake in a stamp charge coke oven, comprising: mixing a carbonaceous material A having a proportion of particles having a particle size of 0.5 mm or less of 50 mass% or less and a proportion of particles having a particle size of 0.1 mm or less of 20 mass% or less with a carbonaceous material B having a proportion of particles having a particle size of 0.5 mm or less of 80 mass% or more and a proportion of particles having a particle size of 0.1 mm or less of 50 mass% so that the mass ratio of the carbonaceous material B to 100 mass% of the carbonaceous material A is 0.5 mass% to 15 mass%, to obtain a coal blend C, and stamping the resulting coal cake.

[0015] [2] A method for producing metallurgical coke, characterized by carbonizing the coal cake produced by the method described in [1] above in a coke oven to obtain coke.

[0016] 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 a stamp charge furnace. Furthermore, according to the present invention, the improved strength of the coal cake reduces problems such as collapse of the coal cake, enabling stable operation of the stamp charge furnace. In addition, the increased density of the coal cake can improve the productivity of the stamp charge furnace.

[0017] The present invention provides a method for producing a coal cake in a stamp charge coke oven, comprising the steps of: preparing a carbonaceous material A having a proportion of particles of 0.5 mm or less in particle size of 50% by mass or less and a proportion of particles of 0.1 mm or less in particle size of 20% by mass or less; and preparing a carbonaceous material B having a proportion of particles of 0.5 mm or less in particle size of 80% by mass or more and a proportion of particles of 0.1 ...50% by mass or more; blending and mixing the carbonaceous material A and the fine carbonaceous materials B so that the mass proportion of the fine carbonaceous materials B relative to 100% by mass of the carbonaceous material A is 0.5% to 15% by mass; and stamping the resulting coal blend C to obtain a coal cake.

[0018] [Carbon material A] The carbon material A in the present invention is a typical raw material conventionally used as a coke raw material in top-charge coke ovens and stamp-charge coke ovens, and may be produced by crushing the raw material using a hammer crusher or the like so that the proportion 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 "proportion of particles having a particle size of 3 mm or less" refers to the proportion of the mass of particles under the sieve to the total mass of the raw material when the raw material is sieved through a 3 mm sieve, and this also applies in the present specification even when the particle size is different.

[0019] In order to obtain the effects of the present invention, the particle size of carbonaceous material A needs to be significantly different from that of carbonaceous material B, and therefore needs to be higher than a certain level. Specifically, the proportion of particles with particle sizes of 0.5 mm or less needs to be 50 mass% or less, and the proportion of particles with particle sizes of 0.1 mm or less needs to be 20 mass% or less. However, since the effects of the present invention can be enhanced by making the difference in particle size from carbonaceous material B more significant, it is preferable that the particle size of carbonaceous material A be larger. Specifically, it is preferable that the proportion of particles with particle sizes of 0.5 mm or less is 40 mass% or less, and the proportion of particles with particle sizes of 0.1 mm or less is 15 mass% or less, and more preferably the proportion of particles with particle sizes of 0.5 mm or less is 35 mass% or less, and the proportion of particles with particle sizes of 0.1 mm or less is 12 mass% or less.

[0020] The raw materials for the carbonaceous material A that constitutes the coal cake mainly include raw material coals generally used in coke production, but may also include 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, as long as the quality of the coke after carbonization is not an issue. When multiple raw materials are used as the carbonaceous material A, the raw materials may be individually crushed and then blended to form the carbonaceous material A, or the multiple raw materials may be blended and then crushed together.

[0021] [Carbonaceous Material B] In the present invention, the density and strength of the coal cake can be improved by blending a portion of carbonaceous material B with the carbonaceous material A, the carbonaceous material B having a sufficiently low particle size. To obtain the effects of the present invention, the particle size of carbonaceous material B needs to be such that the proportion of particles having a particle size of 0.5 mm or less is 80% by mass or more and the proportion of particles having a particle size of 0.1 mm or less is 50% by mass or more. To obtain a greater effect of improving the density and strength of the coal cake, the proportion of particles having a particle size of 0.5 mm or less is preferably 82% by mass or more and the proportion of particles having a particle size of 0.1 mm or less is 56% by mass or more, and more preferably the proportion of particles having a particle size of 0.5 mm or less is 85% by mass or more and the proportion of particles having a particle size of 0.1 mm or less is 70% by mass or more.

[0022] As the raw material for carbonaceous material B, mainly raw material coal generally used for coke production may be used, but other than raw material coal, non- or slightly caking coal, oil coke, 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 does not become an issue. Also, carbonaceous material B may be obtained by extracting a portion of carbonaceous material A and pulverizing it.

[0023] The method for adjusting the particle size of the carbonaceous material B is not particularly specified as long as a predetermined particle size is obtained, and for example, equipment such as a ball mill, roller mill, tower mill, bead mill, or jet mill can be used. Furthermore, carbonaceous material generated in a steelworks and satisfying the above particle size conditions may be used as the carbonaceous material B without particle size adjustment. Examples of raw materials generated in the steelworks include dust powder collected from a coke dry quenching (CDQ) system or powder generated by transporting coke. Furthermore, when multiple raw materials are used as the carbonaceous material B, each raw material may be individually pulverized and then blended to be used as the carbonaceous material B, or multiple raw materials may be blended and then pulverized together.

[0024] [Coal Blend C] Coal Blend C is obtained by mixing the above-mentioned carbonaceous material A and fine carbonaceous material B. To achieve the effect of improving the coal cake density and strength according to the present invention, the mass ratio of carbonaceous material B relative to 100 mass% of carbonaceous material A needs to be 0.5 mass% or more. To achieve a greater effect, the mass ratio of carbonaceous material B is preferably 1 mass% or more, and more preferably 2 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 portion of carbonaceous material B having a particle size smaller than that of carbonaceous material A to carbonaceous material A pulverized to a normal pulverized particle size. This achieves a unique effect of improving both the density and strength of the coal cake, as shown in the examples described later. Therefore, the mass ratio of carbonaceous material B relative to 100 mass% of carbonaceous material A needs to be 15 mass% or less. Considering that the production of fine carbonaceous materials requires an increased pulverization capacity, from an economical standpoint, the mass ratio of carbonaceous material B is preferably 12 mass% or less, and more preferably 10 mass% or less.

[0025] The method for mixing the carbonaceous material A and the carbonaceous material B is not particularly limited, and a mixer generally used for mixing coals in a coke plant may be used. Another example is a method in which the carbonaceous material A and the carbonaceous material B are placed on the same belt conveyor and mixed by the flow of the materials when they are transferred between conveyors.

[0026] The moisture content of the coal blend C is desirably 9 to 12% by mass in order to maximize the strength of the coal cake. Moisture adjustment can be performed by processes such as drying using coal moisture control equipment and spraying water from a nozzle. The moisture adjustment is preferably performed after mixing of the carbonaceous materials A and B, but may be performed before or after the crushing process of the carbonaceous materials A and B depending on the layout of the plant. However, as will be explained using data in Example 2 described later, the effects 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 a yard varies depending on the season and weather, but the range of variation is generally within the range of 7 to 13% by mass. Therefore, the moisture range for obtaining the effects of the present invention is not particularly limited within the range of normal coke production conditions.

[0027] <Production of Coal Cake> In the present invention, a high-strength coal cake can be produced by stamping and compacting the above-mentioned coal blend C.

[0028] When producing a coal cake from the coal blend C prepared as described above, it can be produced using a stamping device that compacts the raw material by impact with a falling weight. In this case, by using coal blend C, in which carbonaceous material B is blended with carbonaceous material A, as the raw material, it is possible to produce a coal cake with higher density and strength 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.

[0029] Although the factors that improve the density and strength of the coal cake are not fully understood, it is speculated that this is due to the fact that carbonaceous material B penetrates between the particles of carbonaceous material A, functions as a lubricant, and improves the fluidity of the carbonaceous material as a whole. By improving the fluidity of the carbonaceous material as a whole, it is thought that rearrangement of particles is more likely to occur when stamping with the same energy, making it possible to produce a coal cake with higher density and strength.

[0030] (Method for Producing 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.

[0031] The coal cake produced by the above-described coal cake manufacturing method according to the present invention is mechanically charged into the side of the coke oven carbonization chamber. During this process, the coal cake is subjected to impacts from its own weight and the vibrations of the charging machine. If the coal cake has low strength, an operational problem may occur in which the coal cake collapses during charging. However, by using a coal blend C, which is a mixture of carbonaceous material A and carbonaceous material B with a smaller particle size than carbonaceous 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. Furthermore, the coal cake produced from the coal blend C, which is a mixture of carbonaceous material A and carbonaceous material B with a smaller particle size than carbonaceous material A, has a higher density than coal cakes produced by conventional methods. This increases the amount of coal charged per kiln, thereby improving productivity.

[0032] There are no particular restrictions on the conditions for carbonizing the coal cake. The coal cake may be carbonized at a temperature of approximately 900° C. or higher using a general stamp charge coke oven.

[0033] Hereinafter, examples of the present invention will be described, 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.

[0034] (Example 1) In Example 1, different carbonaceous materials A and B were blended and mixed to produce a coal cake, and the strength of the coal cake was evaluated. Table 1 shows the production conditions and the evaluation results.

[0035] Specifically, a coal blend containing a plurality of coals was used as the carbonaceous material A, and was pulverized to the particle size shown in Table 1. Coke powder, slightly non-caking coal, and carbonized biomass were pulverized to the particle size shown in Table 1 and used as the carbonaceous material B. Then, the carbonaceous materials A and B were blended and mixed at the blending ratios shown in Table 1 to prepare the coal blend C, and the moisture content of the coal blend C was adjusted to 10% by mass.

[0036] A coal cake was produced using the coal blend C prepared by the above procedure, as follows. First, approximately 200 g of the coal blend C was charged into a metal mold having an inner diameter of 10 cm and a height of 20 cm, and a rammer with a mass of 9 kg was dropped 10 times from a height of 30 cm above the sample surface, thereby 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.

[0037] The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio listed in Table 1 are the density ratio and strength ratio of the coal cake produced from the 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 set to 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.

[0038]

[0039] In Comparative Examples 1 and 4, carbonaceous material A is mixed with carbonaceous material B having a similar particle size. In this case, 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 having a relatively small particle size. In this case, the addition of carbonaceous material B makes the strength ratio greater than 1, while the density ratio becomes smaller than 1. It has been reported in Non-Patent Document 1 and elsewhere that when the particle size of the raw material is reduced, the strength improves while the density decreases, and this result can be said to be in line with the findings of the prior art.

[0040] On the other hand, 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 adding carbonaceous material B, both the density ratio and strength ratio become greater than 1, improving the properties of the coal cake. Furthermore, 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 B, which has a smaller particle size than carbonaceous material A, with 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% by mass. However, the same effect can be obtained even when carbonaceous material A has a larger particle size (70% by mass of particles with a particle size of 3 mm or less) because carbonaceous material B is added.

[0041] 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 smaller particle size than carbonaceous material A, is too high, the carbonaceous material B, which has a smaller particle size than carbonaceous material A, will be excessively present in the gaps between the carbonaceous material A, which has a larger particle size, as described above, and it is thought that the effect of the invention will not be fully obtained.

[0042] As described above, the present invention not only stabilizes the operation of a coke oven by improving the strength of the coal cake, but also improves productivity by increasing the density of the coal cake.

[0043] As is clear from the present example, 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. Furthermore, if a carbon-neutral raw material such as carbonized biomass is used as the carbonaceous material B, the CO ２ This will contribute to reducing emissions and meet current social demands.

[0044] Example 2 In Example 2, coal cakes were produced by varying the moisture content of coal blend C, and the strength of the produced coal cakes was evaluated. Table 2 shows the production conditions and the evaluation results.

[0045]

[0046] Specifically, a coal blend containing a plurality of coals was used as the carbonaceous material A, and was pulverized to the particle size shown in Table 2. Furthermore, coke powder was pulverized to the particle size shown in Table 2 and was used as the carbonaceous material B. Then, the carbonaceous materials A and B were blended and mixed at the blending ratios shown in Table 2 to prepare the coal blend C, and the moisture content of the coal blend C was adjusted to 7% by mass or 13% by mass.

[0047] A coal cake was produced using the coal blend C prepared by the above procedure, as follows. First, approximately 200 g of the coal blend C was charged into a metal mold having an inner diameter of 10 cm and a height of 20 cm, and a rammer with a mass of 9 kg was dropped 10 times from a height of 30 cm above the sample surface, thereby 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.

[0048] The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio listed in Table 2 are the density ratio and strength ratio of the coal cake produced from the 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 set to 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 adding carbonaceous material B.

[0049] As shown in Table 2, regardless of whether the moisture content of coal blend C was 7% by mass or 13% by mass, by mixing carbonaceous material A with carbonaceous material B, which has a smaller particle size than carbonaceous material A, the density ratio and strength ratio became 1 or more, and the properties of the coal cake were improved. The moisture content of coal stored in a 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 within the range of 7 to 13% by mass.

[0050] 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 productivity.

Claims

1. A method for producing a coal cake in a stamp charge type coke oven, comprising: mixing carbonaceous material A having a ratio of particle sizes of 0.5 mm or less to 50 mass% and a ratio of particle sizes of 0.1 mm or less to 20 mass%; and carbonaceous material B having a ratio of particle sizes of 0.5 mm or less to 80 mass% and a ratio of particle sizes of 0.1 mm or less to 50 mass%; such that the mass ratio of carbonaceous material B to 100 mass% of carbonaceous material A is 0.5 mass% to 15 mass% to obtain a blended coal C, and stamping the resulting coal cake.

2. 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.

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