Method for producing coal cake and method for producing metallurgical coke

Abstract

To provide a method for producing a coal cake that can achieve both improvement in strength of the coal cake and improvement in productivity.SOLUTION: A method for producing a coal cake in a stamp-charging coke oven comprises obtaining the coal cake by stamping a blended coal C obtained by blending and mixing a carbonaceous material A, in which the proportion of particles having a particle size of 0.5 mm or less is 50 mass% or less and the proportion of particles having a particle size of 0.1 mm or less is 20 mass% or less, and a carbonaceous material B, in which 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, such that the 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.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Currently, in the production of pig iron using a blast furnace, coke produced by carbonizing coal in a coke oven is used as a reducing agent for iron ore and for ensuring the air permeability in the blast furnace. In order to efficiently operate the blast furnace, it is known that high-strength coke is suitable. This is because when coke pulverizes in the blast furnace, the air permeability of the blast furnace deteriorates due to the generated powder, and efficient blast furnace operation becomes impossible.

[0003] To produce high-strength coke, it is known that it is effective to improve the bulk density of the coal charged into the coke oven, and for this purpose, a stamp-charge coke oven is used. In a general coke oven currently used in Japan (hereinafter referred to as a "top-charge coke oven"), coal, which is the raw material for coke, is charged from the upper part of the coke oven carbonization chamber by gravity, and the bulk density of the coal charged by gravity is 700 - 800 kg-dry / m 3 is.

[0004] On the other hand, in a stamp-charge coke oven, before the coal is charged into the coke oven, it is compacted by a stamping device arranged on the side of the coke oven carbonization chamber, and after being processed into a coal cake with a bulk density of 1000 kg-dry / m 3 or more, it is mechanically pushed and charged into the coke oven carbonization chamber from the side. By using a stamp-charge coke oven, the density of the coke raw material can be increased before carbonization, and high-strength coke can be produced compared to a top-charge coke oven. Also, by increasing the charging amount per kiln, productivity can be increased.

[0005] The stamp-charging coke oven is superior to the top-charging coke oven in terms of coke strength and productivity as described above. However, if the strength of the coal cake produced by stamping is low, operational troubles such as the collapse of the coal cake may occur during the charging of the coal cake into the coke oven carbonization chamber. Therefore, in order to stably operate the stamp-charging coke oven, a technology for producing high-strength coal cakes is required. In addition, due to recent social requirements for reducing CO 2 emissions, technologies are demanded to improve the density of coal cakes and further enhance productivity.

[0006] Regarding the relationship between the particle size of coal and the strength of coal cakes, Non-Patent Document 1 reports that by conducting tests with varying degrees of pulverization of coal cake raw materials and increasing the proportion of fine particles with a particle size of 3.15 mm or less in the raw materials, that is, by pulverizing the coal cake raw materials more finely, the strength of the coal cakes is improved.

[0007] In addition, studies have been conducted on the use of a binding binder to improve the strength of coal cakes. For example, Patent Document 1 reports a method of heating a caking coal to 300 to 500 °C and using the coal in a softened and molten state as a binder for the coal cake. Non-Patent Document 2 also reports that by adding pitch with a softening point of 80 °C as a binder to the raw materials, the coal cake becomes higher in strength.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Non-Patent Documents

[0009]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] Non-Patent Document 1 reports that by pulverizing the coal cake raw material more finely, while the strength of the coal cake is improved, the density of the coal cake decreases. That is, the method of enhancing the pulverization of the coal cake raw material and reducing the particle size of the raw material contributes to improving the strength of the coal cake and the stable operation of the stamp charge furnace, but the productivity is relatively reduced due to the decrease in the coal cake density.

[0011] Also, in the method of using the cohesive binder described in Patent Document 1 and Non-Patent Document 2, in the process of transporting the coke raw material containing the cohesive binder and the process of compacting the raw material with a stamping device, the cohesive raw material adheres to the belt conveyor or the stamping device. Therefore, it is necessary to frequently clean the device, and as a result, there is a problem that the productivity decreases.

[0012] An object of the present invention is to provide a method for manufacturing a coal cake that can achieve both an improvement in the strength of the coal cake and an improvement in productivity.

Means for Solving the Problems

[0013] The inventors conducted intensive research to solve the above problems and obtained the following findings. That is, by preparing a blended coal in which a small amount of fine coal material is blended with the pulverized particle size blended coal usually used in a stamp charge furnace and stamping it, the density and strength of the coal cake can be improved.

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

[0015] [2] A method for manufacturing metallurgical coke, characterized in that the coal cake manufactured by the method described in [1] is carbonized in a coke oven to obtain coke.

Effects of the Invention

[0016] According to the present invention, it is possible to provide a method for manufacturing a coal cake that can achieve both an improvement in the strength of the coal cake and an improvement in productivity in a stamp-charge furnace. Further, according to the present invention, due to the improvement in the strength of the coal cake, troubles such as the collapse of the coal cake can be reduced, and in addition to enabling the stable operation of the stamp-charge furnace, the productivity of the stamp-charge furnace can be improved by increasing the density of the coal cake.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described. 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, which comprises a carbon material A having a proportion of particles with a particle size of 0.5 mm or less of 50% by mass or less and a proportion of particles with a particle size of 0.1 mm or less of 20% by mass or less, and a carbon material B having a proportion of particles with a particle size of 0.5 mm or less of 80% by mass or more and a proportion of particles with a particle size of 0.1 mm or less of 50% by mass or more. The blended coal C obtained by blending and mixing the carbon material A and the fine powder carbon material B so that the mass ratio of the fine powder carbon material B to 100% by mass of the carbon material A is 0.5% by mass or more and 15% by mass or less is stamped to obtain a coal cake.

[0018] [Carbon material A] The carbon material A in the present invention is a general raw material conventionally used as a coke raw material in a top-charge coke oven or a stamp-charge coke oven. As is conventionally done in the operation of a coke oven, the raw material may be pulverized using a hammer crusher or the like so that the proportion of particles with a particle size of 3 mm or less is 70% by mass or more. The "proportion of particles with a particle size of 3 mm or less" refers to the ratio of the mass of the material passing through a 3-mm sieve to the total mass of the raw material when the raw material is sieved through a 3-mm sieve, and the same applies when the particle sizes are different in this specification.

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

[0020] As the raw material of carbon material A that constitutes the coal cake, generally centered on the raw coal used in coke production, within the range where the coke quality after carbonization is not a problem, in addition to the raw coal, non-caking coal, oil coke, pitches, biomass, other carbon-based raw materials, and carbides obtained by heating the above raw materials may be used. Also, when using a plurality of raw materials as carbon material A, each raw material may be individually pulverized and then blended for use as carbon material A, or a plurality of raw materials may be blended and then pulverized together.

[0021] [Carbon material B] In the present invention, by partially blending and mixing carbon material B with a sufficiently low particle size with respect to the above carbon material A, the density and strength of the coal cake can be improved. As the particle size of carbon material B for obtaining the effect of the present invention, it is necessary that the proportion of particles with a particle size of 0.5 mm or less is 80% by mass or more, and the proportion of particles with a particle size of 0.1 mm or less is 50% by mass or more. In order to obtain a greater improvement effect on the density and strength of the coal cake, it is preferable that the proportion of particles with a particle size of 0.5 mm or less is 82% by mass or more, and the proportion of particles with a particle size of 0.1 mm or less is 56% by mass or more, and it is more preferable that the proportion of particles with a particle size of 0.5 mm or less is 85% by mass or more, and the proportion of particles with a particle size of 0.1 mm or less is 70% by mass or more.

[0022] As the raw material of carbon material B, generally centered on the raw coal used in coke production, within the range where the coke quality after carbonization is not a problem, in addition to the raw coal, non-caking coal, oil coke, pitches, biomass, other carbon-based raw materials, and carbides obtained by heating the above raw materials may be used. Also, carbon material B may be obtained by taking out a part of carbon material A and finely pulverizing it.

[0023] The method for adjusting the particle size of carbon material B is not particularly specified as long as a predetermined particle size is obtained. For example, equipment such as ball mills, roller mills, tower mills, bead mills, and jet mills can be used. Also, the carbon material that satisfies the above particle size conditions generated within the steelworks may be used as carbon material B without adjusting the particle size. Examples of the raw materials generated within the steelworks include, for example, the dust collected by recovering the powder generated by the coke dry quenching (CDQ) equipment or the conveyance of coke. Also, when using a plurality of raw materials as carbon material B, each raw material may be used as carbon material B by individually pulverizing and then blending them, or they may be pulverized together after blending a plurality of raw materials.

[0024] [Blended coal C] Blended coal C is obtained by mixing the above carbon material A and fine carbon material B. In order to obtain the effect of improving the density and strength of the coal cake according to the present invention, it is necessary that the mass ratio of carbon material B to 100% by mass of carbon material A is 0.5% by mass or more. In order to obtain a greater effect, the mass ratio of carbon material B is more preferably 1% by mass or more, and even more preferably 2% by mass or more. On the other hand, as the gist of the present invention, instead of granulating the entire coal cake raw material, by adding a part of carbon material B having a lower particle size than carbon material A to carbon material A pulverized to a normal pulverized particle size, as shown in the examples described later, a specific effect of improving both the density and strength of the coal cake can be obtained. Therefore, it is necessary that the mass ratio of carbon material B to 100% by mass of carbon material A is 15% by mass or less. Considering that enhancing the pulverization ability is required for the production of fine carbon material, from the perspective of economy, the mass ratio of carbon material B is preferably 12% by mass or less, and more preferably 10% by mass or less.

[0025] The method for mixing carbon material A and carbon material B may generally use a mixer used for mixing coal in a coke plant and is not particularly limited. Also, a method can be exemplified in which carbon material A and carbon material B are placed on the same belt conveyor and the two are mixed by the flow at the transfer of the conveyor.

[0026] For the purpose of maximizing the strength of the coal cake, the moisture content of the blended coal C is desirably 9 to 12% by mass. Moisture adjustment can be carried out by processes such as drying using coal moisture conditioning equipment and water spraying from nozzles. The timing of moisture adjustment is preferably after mixing of coal material A and coal material B, but depending on the factory layout, it may also be carried out before and after the pulverization treatment of coal material A and coal material B. However, as will be described with reference to Example 2 later, if the moisture content of the blended coal C is between 7 and 13% by mass, the effects of the present invention can be obtained. The moisture content of the coal stored in the yard varies depending on the season and weather, but the variation range is approximately within 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] <Manufacture of Coal Cake> In the present invention, a high-strength coal cake can be manufactured by stamping and compacting the above-mentioned blended coal C.

[0028] When manufacturing a coal cake from the blended coal C prepared as described above, it may be manufactured using a stamping device in a form that compacts the raw material by drop hammer impact. At this time, by using the blended coal C in which coal material B is blended with coal material A as the raw material, a coal cake with higher density and strength can be manufactured compared to the case of using only coal material A. As a result, the coal cake is less likely to collapse, and stable operation of the coke oven can be carried out. In addition, productivity is improved by increasing the amount of coal charged per kiln.

[0029] Although the factors contributing to the improvement of the density and strength of the coal cake have not been fully clarified, it is presumed that coal material B enters between the particles of coal material A and functions as a lubricant, improving the fluidity of the entire coal material. By improving the fluidity of the entire coal material, when stamping with the same energy, particle rearrangement is more likely to occur, so it is considered that a coal cake with higher density and strength can be manufactured.

[0030] (Method for Manufacturing Coke for Metallurgy) Next, a method for manufacturing metallurgical coke according to the present invention will be described. The method for manufacturing metallurgical coke according to the present invention is characterized by carbonizing the coal cake manufactured by the method for manufacturing a coal cake according to the present invention described above in a coke oven.

[0031] The coal cake manufactured by the above-described method for manufacturing a coal cake according to the present invention is mechanically charged from the side of the coke oven carbonization chamber. At this time, the coal cake is subjected to the impact of the self-weight of the coal cake and the vibration of the charging machine. When the strength of the coal cake is low, operational troubles such as the collapse of the coal cake may occur during the charging of the coal cake. However, by using a blended coal C in which a coal B having a lower particle size than the coal A is mixed with the coal A as a raw material of the coal cake, the strength of the coal cake is improved and the collapse of the coal cake can be avoided. Further, since the coal cake manufactured from the blended coal C in which the coal B having a lower particle size than the coal A is mixed with the coal A has a higher density than the coal cake manufactured by the conventional method, the productivity is improved by increasing the amount of coal charged per kiln.

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

Example

[0033] Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the following examples and can be arbitrarily changed without departing from the gist of the present invention.

[0034] (Example 1) As Example 1, different coal A and coal B were blended and mixed to manufacture a coal cake and evaluate its strength. The manufacturing conditions and evaluation results are shown in Table 1.

[0035] Specifically, as carbon material A, a blended carbon obtained by blending a plurality of coals was used, which was pulverized to the particle sizes described in Table 1 before use. Also, as carbon material B, coke powder, non-caking coal, and carbonized biomass were pulverized to the particle sizes described in Table 1 before use. Then, carbon material A and carbon material B were blended and mixed at the blending ratios shown in Table 1 to prepare blended carbon C, and after that, the moisture content of blended carbon C was adjusted to 10% by mass.

[0036] Using the blended carbon C adjusted by the above procedure, a coal cake was manufactured by the following procedure. First, about 200 g of blended carbon C was charged into a metal mold with 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, and the charged blended carbon C was compacted by the impact. By repeating the operation from the charging of the above blended carbon C to the dropping of the rammer 10 times, a coal cake with a diameter of 10 cm, a height of 20 cm, and a mass of about 2 kg was manufactured. Then, the mold was 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 defined in JIS A 1216. The density ratio and strength ratio described in Table 1 are the density ratio and strength ratio of the coal cake manufactured from the blended carbon C mixed with carbon material B when the dry density and strength of the coal cake manufactured by the above procedure using only carbon material A without mixing carbon material B are taken as 1. Therefore, when the density ratio and strength ratio are both greater than 1, it can be judged that the properties of the coal cake are improved in the present invention, that is, by mixing carbon material B with a lower particle size than carbon material A into carbon material A.

[0038]

Table 1

[0039] In Comparative Examples 1 and 4, Coal B with a similar particle size to Coal A is mixed. At this time, the density and strength of the coal cake hardly change due to the mixing of Coal B. Also, in Comparative Examples 2, 3, 5, and 6, Coal B with a relatively small particle size is mixed with Coal A. At this time, while the strength ratio becomes greater than 1 due to the mixing of Coal B, the density ratio becomes less than 1. It has been reported in Non-Patent Document 1 and the like that when the particle size of the raw material decreases, the strength improves while the density decreases, and it can be said that this result is in line with the findings of the prior art.

[0040] On the other hand, in Invention Examples 1 to 7, Coal B that has been sufficiently pulverized to exhibit the effects of the present invention is mixed with Coal A. By mixing Coal B, it can be seen that both the density ratio and the strength ratio become greater than 1, and the properties of the coal cake are improved. Also, when comparing Comparative Examples 5 and 6 with Invention Examples 3 and 4, the strength improvement effect of the invention examples is clearly greater than that of the comparative examples. Therefore, it is considered that the strength of the coal cake was improved by mixing Coal B with a lower particle size than Coal A into Coal A. Although Invention Examples 1 to 7 only describe examples where the proportion of particles with a size of 3 mm or less is 78 to 100% by mass, even when Coal A has a larger particle size (the proportion of particles with a size of 3 mm or less is 70% by mass), mixing Coal B will result in the same effects.

[0041] In Comparative Example 7, 20% by mass of sufficiently pulverized Coal B was mixed with Coal A, but in this case, the density of the coal cake decreased. It is considered that when the proportion of Coal B with a lower particle size than Coal A is too high, Coal B with a lower particle size than Coal A will excessively exist in the gaps of Coal A with a higher particle size described above, so the effects of the invention could not be fully obtained.

[0042] As described above, according to the present invention, in addition to stabilizing the operation of the coke oven due to the improvement of the strength of the coal cake, it is possible to obtain the effect of improving productivity due to the increase in the density of the coal cake.

[0043] Also, as is clear from this embodiment, the raw material of carbon material B for obtaining the effects of the present invention is not particularly limited. If coke powder or non-bonded carbon generated in a steelworks is used as carbon material B, the effects of the present invention can be obtained at a relatively low cost. Further, if a carbon-neutral raw material such as carbonized biomass is used as carbon material B, it can contribute to the reduction of CO 2 emission and meets the current social requirements.

[0044] (Example 2) As Example 2, the water content of blended coal C was changed to produce a coal cake and its strength was evaluated. The production conditions and evaluation results are shown in Table 2.

[0045]

Table 2

[0046] Specifically, as carbon material A, a blended coal obtained by blending a plurality of coals was used, which was pulverized to the particle sizes described in Table 2 before use. Also, as carbon material B, coke powder was pulverized to the particle sizes described in Table 2 before use. Then, carbon material A and carbon material B were blended and mixed at the blending ratios shown in Table 2. After preparing blended coal C, the moisture of blended coal C was adjusted to 7% by mass or 13% by mass.

[0047] Using the blended coal C adjusted by the above procedure, a coal cake was produced by the following procedure. First, about 200 g of blended coal C was charged into a metal mold with 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 from the sample surface, and the charged blended coal C was compacted by the impact. By repeating the operation from the charging of the above blended coal C to the dropping of the rammer 10 times, a coal cake with a diameter of 10 cm, a height of 20 cm, and a mass of about 2 kg was produced. Then, the mold was 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 defined in JIS A 1216. The density ratio and strength ratio shown in Table 2 are the density ratio and strength ratio of the coal cake produced from the blended coal C mixed with coal B, when the dry density and strength of the coal cake produced by the above procedure using only coal A without mixing coal B are set to 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 are improved by mixing coal B.

[0049] As shown in Table 2, under the conditions where the moisture content of the blended coal C is either 7% by mass or 13% by mass, by mixing coal B with a lower particle size than coal A into coal A, the density ratio and strength ratio become 1 or more, and the properties of the coal cake are improved. The moisture content of the coal stored in the yard varies depending on the season and weather, but the fluctuation range 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 the blended coal C varies in the range of 7 to 13% by mass.

Industrial Applicability

[0050] According to the present invention, it is possible to provide a method for producing a coal cake that can achieve both an improvement in the strength of the coal cake and an improvement in productivity.

Claims

1. A method for producing a coal cake in a stamp-charged coke oven, comprising: coal material A having a proportion of particles with a particle size of 0.5 mm or less of 50% by mass or less and a proportion of particles with a particle size of 0.1 mm or less of 20% by mass or less; coal material B having a proportion of particles with a particle size of 0.5 mm or less of 80% by mass or more and a proportion of particles with a particle size of 0.1 mm or less of 50% by mass or more; compound coal C obtained by mixing the coal material A and the coal material B such that the mass ratio of the coal material B to 100% by mass of the coal material A is 0.5% by mass or more and 15% by mass or less, and stamping the compound coal C to obtain a coal cake. A method for producing a coal cake, characterized by the above.

2. A method for producing metallurgical coke, characterized by carbonizing the coal cake produced by the method according to Claim 1 in a coke oven to obtain coke.

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