Method for producing coke

Abstract

To provide a method for producing coke capable of effectively improving a bulk density of coal.SOLUTION: A method for producing coke comprises a raw material preparation step (#5), an agent preparation step (#10), and an addition step (#15). In the raw material preparation step (#5), coal serving as a raw material for coke is prepared. In the agent preparation step (#10), a plurality of bulk density improvers having different specific gravities are prepared. In the addition step (#15), a bulk density improver having a specific gravity corresponding to a particle size of the coal is selected from among the plurality of bulk density improvers, and the selected bulk density improver is added to the coal.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing coke. [Background technology]

[0002] The raw material for coke is coal. Coke is produced by charging coal into a coke oven and carbonizing the coal inside the oven at high temperatures. In coke production, the bulk density of the coal has a significant impact on the quality (strength) and productivity of the coke. Therefore, there is a need to improve the bulk density of the coal used as the raw material for coke.

[0003] Known methods for increasing the bulk density of coal include those described in Patent Documents 1 to 3. In the method described in Patent Document 1, a bulk density improver (surfactant) is added to coal after it has been crushed by a crusher in a transfer line that transports the coal to a coke oven. Patent Document 1 describes that this method provides a superior bulk density improvement effect compared to adding a bulk density improver to coal before crushing. In the method described in Patent Document 1, an aqueous solution of polyoxyethylene alkyl ether sulfate is used as the bulk density improver.

[0004] In the method described in Patent Document 2, a treating agent containing polyether-modified silicone oil is added to coal in a coal transport line. Patent Document 2 describes that the bulk density-improving effect is further enhanced by using this treating agent in combination with a surfactant. In the method described in Patent Document 3, a bulk density-improving agent (chemical) with a viscosity adjusted to 10 to 45 mPa·s is added to coal. Patent Document 3 describes that by using a bulk density-improving agent with such a viscosity, the coal and bulk density-improving agent can be uniformly mixed without using a mixer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-773687 [Patent Document 2] Japanese Patent Application Publication No. 2-59410 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-63420 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, when producing coke, a bulk density improver such as a surfactant is usually added to coal. However, when coal with a large proportion of small particles, i.e., finely pulverized coal, is used as a raw material, the bulk density is difficult to improve due to factors such as an increase in the specific surface area of ​​the coal. In this case, in order to improve the bulk density, it is necessary to add a larger amount of bulk density improver to the coal. From the viewpoint of improving the quality of the coke, it is preferable that the proportion of small particles in the coal is as large as possible. Therefore, there is a need to effectively improve the bulk density of coal.

[0007] An object of the present disclosure is to provide a method for producing coke that can effectively improve the bulk density of coal. [Means for solving the problem]

[0008] The coke manufacturing method according to the present disclosure includes a raw material preparation step, an agent preparation step, and an addition step. In the raw material preparation step, coal as a raw material for the coke is prepared. In the agent preparation step, multiple bulk density improvers with different specific gravities are prepared. In the addition step, a bulk density improver with a specific gravity corresponding to the particle size of the coal is selected from the multiple bulk density improvers, and the selected bulk density improver is added to the coal. [Effects of the Invention]

[0009] According to the coke manufacturing method according to the present disclosure, the bulk density of coal can be effectively improved. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a diagram showing the bulk density of coals to which samples A to J have been added. [Figure 2] FIG. 2 is a flow diagram showing a method for producing coke according to an embodiment. [Figure 3] FIG. 3 is a diagram showing the relationship between the −3 mm particle size and the −0.3 mm particle size of coal. DETAILED DESCRIPTION OF THE INVENTION

[0011] The inventors conducted extensive research to solve the above-mentioned problems. They prepared two types of coal: Coal X, which had 80% -3mm particle size, and Coal Y, which had 95% -3mm particle size. The "-3mm particle size" refers to the mass percentage (%) of coal that passed through a 2.8mm mesh sieve. The -3mm particle size was measured according to JIS M8801 (2004), section 5, "Particle Size Test Method." Coal Y has a larger -3mm particle size than Coal X, meaning that it has a higher proportion of small particles and is finer in size. Then, a bulk density enhancer was added to each coal, and the bulk density was measured. The bulk density was calculated by placing the coal in a cylindrical container of known volume without compacting it and measuring the mass of the coal when the surface was scraped off. The moisture content of Coal X and Coal Y was 10%.

[0012] The inventors prepared a number of samples A to J with different specific gravities as bulk density-increasing agents. The specific gravities of samples A to J are shown in Table 1. The specific gravities are the ratios of the densities of samples A to J to the density of water. The surface tensions of samples A to J were 10 or more and less than 40.

[0013] [Table 1]

[0014] FIG. 1 is a diagram showing the bulk density of coals to which samples A to J were added. In FIG. 1, the vertical axis represents the bulk density improvement rate, and the horizontal axis represents the specific gravity of samples A to J to which an additive was added. In FIG. 1, the relationship between the bulk density improvement rate and the specific gravity of samples A to J to which an additive was added is plotted for each of coal X and coal Y. Here, the bulk density improvement rate of coal X is the value (%) obtained by dividing the difference between the bulk density of coal X to which no bulk density improver was added and the bulk density of coal X to which each of samples A to J was added and the reference value by the reference value. Similarly, the bulk density improvement rate of coal Y is the value (%) obtained by dividing the difference between the bulk density of coal Y to which no bulk density improver was added and the bulk density of coal Y to which each of samples A to J was added and the reference value by the reference value.

[0015] Furthermore, approximate lines S1 and S2 were determined for the plots of coal X and coal Y shown in Figure 1. The determined approximate lines S1 and S2 are also shown in Figure 1.

[0016] For coal X, the slope of the approximate line S1 is positive, meaning that the larger the specific gravity of the added bulk density improver, the higher the bulk density improvement rate of the coal. On the other hand, for coal Y, the slope of the approximate line S2 is negative, meaning that the smaller the specific gravity of the added bulk density improver, the higher the bulk density improvement rate of the coal. This shows that the specific gravity of the bulk density improver suitable for improving bulk density varies depending on the particle size of the coal used (for example, -3 mm particle size).

[0017] From the viewpoint of improving bulk density, when coal with a relatively small proportion of small particles, such as coal X with a small -3 mm particle size, is used, it is preferable to add a bulk density improver with a high specific gravity to the coal. From the same viewpoint, when coal with a relatively large proportion of small particles, such as coal Y with a large -3 mm particle size, is used, it is preferable to add a bulk density improver with a low specific gravity to the coal.

[0018] When using coal with a high proportion of small particles, such as coal Y with a large -3mm particle size, the reason why the bulk density increases as the specific gravity of the bulk density improver added is thought to be as follows. Generally, adding a bulk density improver with a low specific gravity to coal reduces the coal's angle of repose. The angle of repose of coal is the angle of the coal surface relative to the horizontal when the coal is allowed to fall freely from above onto a flat surface (e.g., the bottom of a container). A small angle of repose of coal means that the coal has good fluidity and the particles can move relatively freely. In coal Y, which has a high proportion of small particles, good fluidity means that the particles can move easily to fill the gaps between particles. Therefore, adding a bulk density improver with a low specific gravity to coal Y increases the bulk density.

[0019] As described above, conventionally, when coal containing a large proportion of small particles is used, it has been difficult to improve the bulk density. Even when such coal is used, the bulk density can be effectively improved by adding a bulk density improver with a low specific gravity.

[0020] The coke manufacturing method according to an embodiment of the present disclosure was completed based on the above findings.

[0021] The coke manufacturing method according to this embodiment includes a raw material preparation step, an agent preparation step, and an addition step. In the raw material preparation step, coal, which is the raw material for the coke, is prepared. In the agent preparation step, multiple bulk density improvers with different specific gravities are prepared. In the addition step, a bulk density improver with a specific gravity corresponding to the particle size of the coal is selected from the multiple bulk density improvers, and the selected bulk density improver is added to the coal (first configuration).

[0022] As described above, the specific gravity of a bulk density improver suitable for improving bulk density varies depending on the particle size of the coal used as a coke raw material. Therefore, in the first manufacturing method, in the addition step, a bulk density improver having a specific gravity corresponding to the particle size of the coal is selected from among a plurality of bulk density improvers. A bulk density improver having a specific gravity corresponding to the particle size of the coal is a bulk density improver having a specific gravity suitable for improving the bulk density of the coal. Adding the bulk density improver selected in this manner can effectively improve the bulk density of the coal.

[0023] The first configuration of the manufacturing method preferably has the following configuration: In the adding step, if the -3mm particle size of the coal is less than 85%, a bulk density improver with a specific gravity of more than 0.95 and not more than 1.00 is added to the coal, and if the -3mm particle size of the coal is 85% or more, a bulk density improver with a specific gravity of 0.80 or more and not more than 0.95 is added to the coal (second configuration). In the second configuration of the manufacturing method, in the adding step, a bulk density improver with a high specific gravity is added to coal with a -3mm particle size of less than 85%, and a bulk density improver with a low specific gravity is added to coal with a -3mm particle size of 85% or more. This makes it possible to more reliably improve the bulk density of the coal.

[0024] In the manufacturing method of the first or second aspect, the surface tension of each of the plurality of bulk density enhancers may be less than 40 mN / m (third aspect). Generally, the lower the surface tension of the bulk density enhancer added to coal, the higher the bulk density of the coal. According to the manufacturing method of the third aspect, a bulk density enhancer with a relatively low surface tension is used, thereby enabling the bulk density of coal to be improved more stably.

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0026] Fig. 2 is a flow diagram showing a coke production method according to this embodiment. As shown in Fig. 2, the production method according to this embodiment includes a raw material preparation step (#5), a chemical preparation step (#10), and an addition step (#15).

[0027] [Raw material preparation process (#5)] In the raw material preparation step (#5), coal that will be used as a raw material for coke is prepared. The coal prepared in the raw material preparation step (#5) is typically coal that has been crushed in a crusher on a conveyance line that transports coal to a coke oven.

[0028] The particle size of the coal is not particularly limited. In the raw material preparation step (#5), the particle size of the prepared coal is measured in accordance with JIS M8801 (2004) "5. Particle size test method."

[0029] The moisture content of the coal prepared in the raw material preparation step (#5) is not particularly limited. However, when the coal contains less moisture, the interparticle sliding is improved compared to when the coal contains more moisture, and the bulk density is more likely to be improved. Therefore, it is preferable that the moisture content of the prepared coal be as low as possible. On the other hand, the manufacturing method of this embodiment is effective even when the moisture content of the coal is relatively high (e.g., 7% or higher). In short, the manufacturing method of this embodiment can improve bulk density even when it is necessary to use coal with a high moisture content, for example, when it is not possible to dehydrate (dry) the coal in the raw material preparation step (#5). The moisture content of the coal prepared in the raw material preparation step (#5) is, for example, 15% or less, preferably 10% or less.

[0030] [Drug preparation process (#10)] In the agent preparation step (#10), multiple bulk density enhancers with different specific gravities are prepared. The bulk density enhancer may be mineral oil, animal or vegetable oil, or an engineered oil made from these oils. Alternatively, the bulk density enhancer may be a surfactant (surfactant) with surface activity. The surfactant may be, for example, dialkyl sulfosuccinic acid or a salt thereof (e.g., sodium salt, ammonium salt, potassium salt, triethanolamine salt). Alternatively, the surfactant may be an anionic surfactant (such as a polyoxyethylene alkyl ether sulfate) or a nonionic surfactant (such as a polyoxyethylene (POE) addition polymer or a salt thereof). The bulk density enhancer may be the oil or surfactant diluted with water.

[0031] The specific gravity of the bulk density increaser is, for example, 0.80 or more. The number of bulk density increasers prepared in the chemical preparation step (#10) is not particularly limited. In the chemical preparation step (#10), it is preferable to prepare at least a bulk density increaser having a specific gravity of more than 0.95 and not more than 1.00, and a bulk density increaser having a specific gravity of not less than 0.80 and not more than 0.95.

[0032] Generally, the lower the surface tension of the bulk density improver added to coal, the higher the bulk density of the coal. Therefore, the surface tension of each of the bulk density improvers is typically lower than the surface tension of water. Preferably, the surface tension of each of the bulk density improvers is less than 40 mN / m. In this case, the bulk density of the coal can be improved more stably.

[0033] [Addition step (#15)] In the adding step (#15), a bulk density improver with a specific gravity corresponding to the particle size of the coal prepared in the raw material preparing step (#5) is selected from the multiple bulk density improvers prepared in the chemical preparing step (#10). The bulk density improver with a specific gravity corresponding to the particle size of the coal is a bulk density improver with a specific gravity suitable for improving the bulk density of the coal.

[0034] For example, if the proportion of small coal particles is relatively small, a bulk density improver with a high specific gravity is selected, whereas if the proportion of small coal particles is relatively large, a bulk density improver with a low specific gravity is selected.

[0035] Whether or not the proportion of small particles in coal is high may be determined based on whether or not the -3mm particle size of the coal is 85% or more. Figure 3 is a diagram showing the relationship between the -3mm particle size and the -0.3mm particle size of coal. Figure 3 is a plot of the -0.3mm particle size obtained by investigating multiple coals with different -3mm particle sizes. In Figure 3, the vertical axis represents the -0.3mm particle size (%), and the horizontal axis represents the -3mm particle size (%). The "-0.3mm particle size" represents the mass fraction (%) of coal that passed through a sieve with 0.3mm openings. The -0.3mm particle size was measured in the same way as the -3mm particle size.

[0036] 3, it can be seen that when the -3mm particle size of the coal is 85% or more, the -0.3mm particle size increases sharply compared to when the -3mm particle size is less than 85%. Therefore, when the -3mm particle size of the coal is less than 85%, it can be determined that the proportion of small coal particles is relatively small, and when the -3mm particle size of the coal is 85% or more, it can be determined that the proportion of small coal particles is relatively large.

[0037] Referring to Figure 1, the specific gravity value at the intersection of the approximated lines S1 and S2 is 0.95. Whether a bulk density improver has a high specific gravity may be determined based on whether the specific gravity is greater than 0.95. The results shown in Figure 1 indicate that adding a bulk density improver with a specific gravity greater than 0.95 to coal (coal X) with a relatively small proportion of small particles can effectively increase the bulk density. Similarly, adding a bulk density improver with a specific gravity of 0.95 or less to coal (coal Y) with a relatively large proportion of small particles can effectively increase the bulk density.

[0038] In the adding step (#15), the selected bulk density improver is added to the coal. The bulk density improver is added, for example, to a conveying line that conveys the coal to a coke oven. In this case, the coal to which the bulk density improver has been added is charged into the coke oven. Coke is produced by carbonizing the coal in the coke oven.

[0039] In the adding step (#15), if the -3 mm particle size of the coal is less than 85%, a bulk density improver with a specific gravity of more than 0.95 and not more than 1.00 may be added to the coal, and if the -3 mm particle size of the coal is 85% or more, a bulk density improver with a specific gravity of 0.80 or more and not more than 0.95 may be added to the coal. In this way, adding a bulk density improver with an appropriate specific gravity depending on the -3 mm particle size of the coal can more reliably improve the bulk density of the coal.

[0040] [effect] The specific gravity of bulk density improvers suitable for improving bulk density varies depending on the particle size of the coal used as coke raw material. Therefore, in the coke manufacturing method according to this embodiment, in the addition step (#15), a bulk density improver with a specific gravity corresponding to the particle size of the coal is selected from among multiple bulk density improvers. In other words, depending on the particle size of the coal prepared in the raw material preparation step (#5), a bulk density improver to be added to the coal is selected from among multiple bulk density improvers prepared in the agent preparation step (#10). This allows the bulk density of the coal to be effectively improved.

[0041] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

Claims

1. A method for producing coke, comprising: a raw material preparation step of preparing coal as a raw material for the coke; A chemical preparation step of preparing a plurality of bulk density enhancers having different specific gravities; an adding step of selecting a bulk density improver having a specific gravity corresponding to the particle size of the coal from the plurality of bulk density improvers, and adding the selected bulk density improver to the coal.

2. The method of claim 1, In the adding step, when the −3 mm particle size of the coal is less than 85%, the bulk density improver having a specific gravity of more than 0.95 and not more than 1.00 is added to the coal, and when the −3 mm particle size of the coal is 85% or more, the bulk density improver having a specific gravity of 0.80 or more and 0.95 or less is added to the coal.

3. The manufacturing method according to claim 1 or 2, The manufacturing method, wherein the surface tension of each of the plurality of bulk density enhancers is less than 40 mN / m.

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