Coke production method

Abstract

Provided is a method for producing coke by which high-strength coke can be produced by using a raw material for ordinary coke production, without requiring an operation that poses a fire risk. Provided is a method for producing coke by charging blended coal into a coke oven and carbonizing the same, the method being characterized in that: the blended coal is prepared by blending 1–10 mass %, inclusive, of a carbonaceous material B, in which the percentage thereof having a particle diameter of 125μm or less is 50 mass % or more, with a carbonaceous material A, in which the percentage thereof having a particle diameter of 3 mm or more is 10–30 mass %, inclusive, and the percentage thereof having a particle diameter of 0.5 mm or more is 60 mass %; and the carbonaceous material B is a mixture composed of one or more kinds selected from coal, pitch, oil coke, and dry distillation products of the foregoing.

Description

Coke manufacturing method

[0001] The present invention relates to a coke manufacturing method, and more particularly to a coke manufacturing method that can improve the bulk density of a coal blend charged into a coke oven using ordinary raw materials for coke manufacturing.

[0002] Blast furnace coke is used in the blast furnace as a reducing agent, a heat source, and a support material to maintain gas permeability and liquid permeability. Stable operation of the blast furnace requires ensuring gas permeability and liquid permeability within the furnace, which requires coke with excellent properties such as strength and particle size. Among these, coke strength, such as rotational strength, is particularly important.

[0003] When a coal blend is charged into a coke oven and carbonized to produce coke, it is generally known that the coke strength improves as the bulk density of the charged coal blend increases (see, for example, Non-Patent Document 1). Therefore, various methods for improving the bulk density of the coal blend charged into a coke oven have been investigated.

[0004] As a method for improving the bulk density of coal that is gravity-charged, for example, Non-Patent Document 2 describes a method for improving the bulk density of coal based on a preheated coal charging method in which coal is preheated and dried at a high temperature of about 200°C and then charged.

[0005] Furthermore, Patent Documents 1 and 2 describe methods for improving the bulk density of coal by adding a bulk density improver to a coal blend.

[0006] JP 2010-77332 A JP 2013-107930 A

[0007] 3rd Edition Steel Handbook Vol. II p. 170 5th Edition Steel Handbook Vol. 1 p. 107

[0008] All of the above-mentioned conventional methods for improving the bulk density of a coal blend charged into a coke oven have had problems. For example, in the method based on the preheated coal charging method described in Non-Patent Document 2, coal is preheated and dried at a high temperature of about 200°C before being charged, so a nitrogen atmosphere is required to prevent ignition and coal oxidation. Therefore, additional equipment is required to maintain the nitrogen atmosphere, and if the nitrogen atmosphere is not maintained, there is a risk of explosion or ignition due to high-temperature, low-moisture coal.

[0009] Furthermore, in the methods described in Patent Documents 1 and 2, an additive that is generally known to be effective in improving lubricity is used to improve bulk density. However, adding raw materials other than those used in normal coke production may result in a decrease in coke quality, such as coke strength.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a coke production method that does not require any operation that poses a risk of fire and that is capable of producing high-strength coke using raw materials for ordinary coke production.

[0011] The present inventors have conducted extensive research to solve the above-mentioned problems and have discovered the following: It has been found that the bulk density of a coal blend to be charged into a coke oven can be improved by preparing a coal blend by finely pulverizing a portion of the carbonaceous material used in normal coke production and blending the finely pulverized carbonaceous material with a small amount of carbonaceous material having a pulverized particle size used in normal coke production.

[0012] The gist and configuration of the present invention, which has been completed based on the above findings, is as follows.

[0013] [1] A method for producing coke by charging a coal blend into a coke oven and carbonizing it, wherein the coal blend is prepared by blending carbonaceous material A having a ratio of 10% by mass to 30% by mass and a ratio of 0.5 mm or larger to 60% by mass or larger of carbonaceous material B having a ratio of 125 μm or smaller to 50% by mass or larger, in a ratio of 1% by mass to 10% by mass, and the carbonaceous material B is one or a mixture of multiple types selected from coal, pitches, oil coke, and carbonized products thereof.

[0014] According to the present invention, a coke production method can be provided that does not require any operations that pose a risk of fire and that can produce high-strength coke using raw materials for ordinary coke production.

[0015] 1 is a graph showing the relationship between the blending ratio of carbonaceous material B in an example and a conventional example (No. 1) obtained by dry distilling only carbonaceous material A, and the strength difference ΔDI between the blending ratio of carbonaceous material B in an example and a conventional example (No. 1) obtained by dry distilling only carbonaceous material A.

[0016] A coke production method according to the present invention is a method for producing coke by charging a coal blend into a coke oven and carbonizing the coal blend, the method comprising blending a carbonaceous material A having a particle size of 3 mm or more in a proportion of 10% by mass to 30% by mass and a particle size of 0.5 mm or more in a proportion of 60% by mass or more, with a carbonaceous material B having a particle size of 125 μm or less in a proportion of 50% by mass or more, in a proportion of 1% by mass to 10% by mass, the carbonaceous material B being one or a mixture of a plurality of types selected from coal, pitches, oil coke, and carbonized products thereof.

[0017] Typically, in order to improve the bulk density of a coal blend to be charged into a coke oven, the moisture content of the coal is reduced by preheating or drying, or a chemical or lubricant is added to improve the lubricity of the coal. In addition, it is generally known that reducing the crushed particle size of the coal blend reduces the bulk density of the coal blend to be charged into a coke oven, and therefore, increasing the crushed particle size of the coal blend is aimed at in order to improve the bulk density.

[0018] The present inventors believed that if the bulk density of a coal blend charged into a coke oven could be improved using the raw materials used in ordinary coke production by controlling the particle size distribution of the coal blend, the bulk density of the charged coal blend could be improved without the adverse effects on coke quality caused by additives or the increase in costs caused by using expensive chemicals. As a result of extensive research based on this belief, they found that by pulverizing some of the raw materials used in ordinary coke production and then blending them, the fine raw materials could act as a bulk density improver, thereby improving the bulk density of the coal blend when it is charged.

[0019] The method for producing coke of the present invention will be described in detail below.

[0020] The cokemaking method of the present invention is a technology for improving the bulk density of a coal blend at the time of charging by pulverizing a portion of a coal blend used in ordinary cokemaking and then blending it. Here, the coal blend used in ordinary cokemaking is mainly composed of carbonaceous materials such as coal, pitches, oil coke, and carbonized products thereof.

[0021] In the coke production method of the present invention, a coal blend is prepared by blending carbonaceous material A having a particle size of 3 mm or more in a proportion of 10 mass % to 30 mass % and a particle size of 0.5 mm or more in a proportion of 60 mass % or more with fine carbonaceous material B having a particle size of 125 μm or less in a proportion of 50 mass % inclusive.

[0022] The carbonaceous material A, which has a proportion of particles with a particle size of 3 mm or more of 10% by mass to 30% by mass and a proportion of particles with a particle size of 0.5 mm or more of 60% by mass or more, has a particle size used in ordinary coke production. It is known from prior art that reducing the particle size of a coal blend reduces the bulk density of the coal blend charged into a coke oven. Therefore, in the present invention, the pulverized particle size of the carbonaceous material A, which accounts for the majority of the coal blend, is controlled so that the proportion of particles with a particle size of 3 mm or more is 10% by mass to 30% by mass.

[0023] If the particle size of the carbonaceous material A is high, a property distribution occurs in coke production using a mixture of various components with different properties, such as coal. Therefore, the particle size of the carbonaceous material A is controlled so that the proportion of particles of 3 mm or more is 30 mass% or less. On the other hand, if the particle size of the carbonaceous material A is low, as previously known, the bulk density of the blended coal during charging decreases, so the proportion of particles of 3 mm or more is controlled so that the proportion of particles of 3 mm or more is 10 mass% or more. Preferably, the proportion of particles of 3 mm or more in the carbonaceous material A is 15 mass% or more and 25 mass% or less. Note that the upper limit of the particle size of the carbonaceous material A is not particularly limited as long as the proportion of particles of 3 mm or more is 30 mass% or less, but it is preferably 25 mm or less from the viewpoint of preventing component imbalance.

[0024] Furthermore, if the particle size of carbonaceous material A is too small, the bulk density of the coal blend will decrease and the difference in particle size with carbonaceous material B will become small, and the bulk density improvement effect of the present invention will not be obtained. Therefore, in the present invention, the proportion of particles with particle sizes of 0.5 mm or more in carbonaceous material A is set to 60 mass% or more. That is, the proportion of particles with particle sizes of 0.5 mm or more and less than 3 mm is set to 30 mass% or more and 90 mass% or less. Furthermore, the proportion of particles with particle sizes of 0.5 mm or more in carbonaceous material A is preferably set to 80 mass% or less. Furthermore, the proportion of fine particles with particle sizes less than 0.5 mm is set to less than 40 mass%, and preferably less than 20 mass%. If a large amount of fine particles less than 0.5 mm are present during pulverization, they can be removed by sieving or the like.

[0025] On the other hand, carbonaceous material B, whose particle size is 125 μm or less, accounts for 50% by mass or more of the carbonaceous material used in coke production, and is blended in a proportion of 1% by mass to 10% by mass of the entire coal blend. In the present invention, blending carbonaceous material B, whose particle size is extremely small compared to carbonaceous material A, provides an improvement in bulk density. Specifically, when the coal blend is charged into a coke oven, fine carbonaceous material B enters between the coarse carbonaceous material A particles, functioning as a lubricant and improving the slipperiness of the coal blend and the bulk density. Furthermore, the fine carbonaceous material B enters between the coarse carbonaceous material A particles, disrupting the water bridges between the carbonaceous material particles in the coal blend, thereby improving the slipperiness of the carbonaceous material. The blending ratio of carbonaceous material B is preferably 1% by mass to 9% by mass, and more preferably 2% by mass to 5% by mass.

[0026] The carbonaceous material B is a raw material used in ordinary coke production, and is a mixture of one or more materials selected from coal, pitches, oil coke, and their dry distillates. The particle size adjustment method for the carbonaceous material B is not particularly specified as long as a predetermined particle size is obtained. However, in order to finely pulverize a large amount of carbonaceous material used in coke production, equipment such as a roller mill or tower mill can be used. Furthermore, the production cost of the carbonaceous material B can be reduced by utilizing finely powdered carbonaceous material generated in a steelworks. Examples of finely powdered carbonaceous material generated in a steelworks include pulverized coal pulverized for injection into a blast furnace, coke powder generated in a coke dry quenching system (CDQ), and dust powder generated in a dust collector installed in a coal or coke transport process.

[0027] As long as carbonaceous material B can be blended with carbonaceous material A in a ratio of 1% by mass to 10% by mass, the flow for crushing and blending carbonaceous materials A and B is not particularly specified, but they can be blended, for example, in the following manner.

[0028] (1) Of the carbonaceous materials used in the blended coal, part or all of a specific brand is finely pulverized to form carbonaceous material B, and the other carbonaceous materials are pulverized in a conventional coke-making pulverizer to form carbonaceous material A, which is then blended.

[0029] (2) Of the carbonaceous materials used in the blended coal, some or all of the multiple brands are finely crushed and blended to form carbonaceous material B, and the other carbonaceous materials are crushed in a crusher used in ordinary coke production to form carbonaceous material A, which is then blended.

[0030] (3) Of the carbonaceous materials used in the blended coal, some or all of the multiple brands are blended and then finely pulverized to form carbonaceous material B, and the other carbonaceous materials are pulverized in a conventional coke manufacturing pulverizer to form carbonaceous material A, which is then blended.

[0031] (4) After blending the carbonaceous materials to be used in the blended coal, a portion of the mixture is taken out and finely pulverized to form carbonaceous material B, and the remaining carbonaceous materials are pulverized in a conventional coke-producing pulverizer to form carbonaceous material A, which is then blended.

[0032] (5) The carbonaceous material to be used in the blended coal is crushed in a crusher for ordinary coke production, and after blending, a portion of the mixture is taken out and finely crushed to form carbonaceous material B, which is then blended with other carbonaceous materials (carbonaceous material A).

[0033] The moisture content of the coal blend in the present invention is preferably 6% by mass or more and 9% by mass or less. If the moisture content of the coal blend is less than 6% by mass, the drying of the coal blend may increase the risk of ignition and may also increase dust generation. On the other hand, if the moisture content of the coal blend is higher than 9% by mass, the increase in water may reduce the effect of improving bulk density by blending the fine carbonaceous material B, and a large amount of heat is required to evaporate the water during carbonization in coke production, which is undesirable.

[0034] Examples of the present invention will be described below. Note that 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.

[0035] Table 1 shows the particle size of carbonaceous material A, the particle size and blending ratio of carbonaceous material B, and the moisture content of the coal blend used in the bulk density measurement test. In this example, coal blend C is a coal blend with a vitrinite average maximum reflectance (Ro(-)) of 1.00 (%) and a common logarithm of the maximum fluidity (MF) measured by a Gieseler plastometer (logMF) of 2.50. Coal D is a raw coal with an Ro(-) of 0.98 (%) and a common logarithm of MF of 2.67, and coal E is a steam coal.

[0036] FIG. 1 is a cross-sectional view schematically illustrating a bulk density measurement device used in the bulk density measurement test. As shown in FIG. 1, the bulk density measurement device 1 includes a sample hopper 2, a guide 3 installed below the sample hopper, and a box-shaped container 4. The guide 3 has an inlet diameter of 300 mm and an outlet diameter of 150 mm. The container 4 is a rectangular box-shaped container measuring 250 mm wide, 250 mm long (depth direction in FIG. 1), and 200 mm high, with only the top surface being open. A slide gate 5 is installed below the sample hopper 2. When the slide gate 5 is opened, the blended coal in the hopper 2 falls into the container 4 via the guide 3. The height from the slide gate 5 installed below the hopper 2 to the bottom of the container 4 is 2 m.

[0037] In this example, the bulk density measuring device described above was used to measure the bulk density of various coal blends listed in Table 1. The procedure for measuring the bulk density is described below.

[0038]

[0039] First, carbonaceous material A and carbonaceous material B, each adjusted to the particle size shown in Table 1, were blended, and water was added and mixed to obtain a coal blend. Next, 32 kg of the coal blend was loaded into hopper 2, and then slide gate 5 was opened to drop the coal blend into container 4. Subsequently, the coal blend protruding from the top of container 4 after the drop was removed, and the mass of the coal blend loaded in the container was measured. Thereafter, the weighed coal blend was divided into smaller pieces to measure its moisture content, and the bulk density (dry basis, d.b.) of the coal blend was calculated using the following formula (1). Note that the bulk density measurement was performed twice for each level, and the average of the two measurements was used as the bulk density for each level.

[0040] (1)

[0041] Table 1 shows the results of measuring the bulk density of each coal blend. In Levels 1 to 4, which are conventional examples that do not contain fine carbonaceous material B, the bulk density decreased as the mass ratio of particles less than 3 mm increased. As is conventional knowledge, the lower the crushed particle size, the lower the bulk density. On the other hand, in Levels 5 to 20, which are inventive examples in which fine carbonaceous material B was blended with carbonaceous material A, the bulk density was improved compared to the conventional example in which no carbonaceous material B was blended. Furthermore, in Level 21, a comparative example in which the blending ratio of carbonaceous material B exceeded 10 mass%, the bulk density was lower compared to the conventional example (Level 2) in which no carbonaceous material B was blended. These results confirm that blending fine carbonaceous material B in a ratio of 1 mass% to 10 mass% with a coal blend of particle sizes used in normal coke production allows the carbonaceous material B to act as a bulk density improver, thereby improving the bulk density of the coal blend when charged.

[0042] Next, in order to examine the influence of the bulk density-improving effect by blending the fine carbonaceous material B on the coke strength, coke was produced by the following method and the coke strength was evaluated.

[0043] Coal blend A and carbonaceous material B, prepared to have particle sizes shown in Table 2, were blended at the blending ratios shown in Table 2, and then water was added and mixed to make the moisture content 7%, to prepare a coal blend for carbonization. 16.5 kg of this coal blend was loaded into a carbonization can at the bulk density shown in Table 2 and carbonized in an electric furnace. After carbonization for 6 hours at a furnace wall temperature of 1,050°C, the coke was cooled under a nitrogen atmosphere, and the resulting coke was used to measure drum strength. The drum strength DI_150 / 15 index was measured in accordance with the rotational strength test method of JIS K2151. The strength difference from a conventional example (No. 1) obtained by carbonizing only carbonaceous material A was defined as ΔDI (ΔDI = [DI_150 / 15 index of target level] - [DI_150 / 15 index of No. 1]), and is shown in Table 2.

[0044]

[0045] In Table 2, level 1 is a conventional example in which carbonaceous material B is not blended, levels 2 to 13 are invention examples in which carbonaceous material B is blended, and level 14 is a comparative example in which the blending ratio of carbonaceous material B is outside the range of the present invention. The bulk density at the time of carbonization for each level reflects the bulk density measurement results in Table 1. In levels 2 to 13, which are invention examples in which carbonaceous material B is blended with carbonaceous material A and an improvement in bulk density is achieved, ΔDI exceeds 0, indicating that the blending of carbonaceous material B has the effect of improving coke strength. On the other hand, in level 14, in which the blending ratio of carbonaceous material B is outside the range of the present invention, ΔDI is less than 0, and strength is reduced.

[0046] Fig. 2 shows the relationship between the blending ratio of carbonaceous material B and ΔDI for the examples listed in Table 2. As shown in Fig. 2, when the blending ratio of carbonaceous material B is in the range of 1 mass % or more and 10 mass % or less, the bulk density is improved and ΔDI exceeds 0.

[0047] According to the present invention, a coke production method can be provided that does not require any operations that pose a risk of fire and that can produce high-strength coke using raw materials for ordinary coke production.

[0048] 1 Bulk density measuring device 2 Hopper 3 Guide 4 Container 5 Slide gate

Claims

1. A method for producing coke by charging a coal blend into a coke oven and carbonizing it, comprising the steps of: preparing the coal blend by blending carbon material A having a ratio of 10% by mass to 30% by mass of particles with a particle size of 3 mm or more and a ratio of 0.5 mm or more to 60% by mass of particles with a particle size of 0.5 mm or more with carbon material B having a ratio of 50% by mass or more of particle size of 125 μm or less in a ratio of 1% by mass to 10% by mass, and wherein carbon material B is one or a mixture of multiple types selected from coal, pitches, oil coke, and carbonized products thereof.

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