EP4775646A1

EP4775646A1 - Coke production method

Info

Publication number: EP4775646A1
Application number: EP24897052.7A
Authority: EP
Inventors: Yuya Kawai; Yusuke Dohi; Daisuke Igawa
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-11-29
Filing date: 2024-09-24
Publication date: 2026-07-15
Also published as: JPWO2025115362A1; WO2025115362A1

Abstract

Provided is a method of producing coke that does not require any operations posing a risk of ignition and that is capable of producing high-strength coke using ordinary raw materials for coke production. A method of producing coke by charging blended coal into a coke oven and carbonizing the blended coal includes preparing the blended coal by blending 1 mass% or more and 10 mass% or less of a carbonaceous material B, which has a ratio of particles with a particle size of 125 µm or less of 50 mass% or more, with a carbonaceous material A, which has a ratio of particles with a particle size of 3 mm or more of 10 mass% or more and 30 mass% or less, and a ratio of particles with a particle size of 0.5 mm or more of 60 mass% or more, the carbonaceous material B being one, or a mixture of two or more, selected from the group consisting of coal, pitches, oil coke, and dry distillation products thereof.

Description

TECHNICAL FIELD

The present disclosure relates to a method of producing coke, and more particularly to a method of producing coke that can increase the bulk density of blended coal charged into a coke oven, using ordinary raw materials for coke production.

BACKGROUND

Blast furnace coke is used in blast furnaces as a reducing agent, a heat source, and a support material to maintain gas permeability and liquid permeability. To ensure stable operation of a blast furnace, it is necessary to ensure good gas permeability and liquid permeability within the blast furnace, which requires coke with excellent properties such as strength and particle size. Among these, coke strength such as drum strength is particularly important.
When coke is produced by charging blended coal into a coke oven and carbonizing, it is generally known that the coke strength improves as the bulk density of the charged blended coal increases (see, for example, Non-patent Literature (NPL) 1). Therefore, various methods for improving the bulk density of the blended coal charged into the coke oven have been investigated.
As a method of improving the bulk density of coal charged by gravity, for example, NPL 2 describes a method of 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 before being charged.
Furthermore, PTL 1 and 2 describe methods of improving the bulk density of coal by adding a bulk density enhancing agent to blended coal.

CITATION LIST

Patent Literature

PTL 1: JP 2010-77332 A
PTL 2: JP 2013-107930 A

Non-patent Literature

NPL 1: Handbook of Iron and Steel, 3rd Edition, Vol. II, p. 170
NPL 2: Handbook of Iron and Steel, 5th Edition, Vol. 1, p. 107

SUMMARY

(Technical Problem)

All of the above-mentioned conventional methods of improving the bulk density of blended coal to be charged into a coke oven are problematic. For example, in the method based on the preheated coal charging method described in NPL 2, coal is preheated and dried at a high temperature of about 200 °C before being charged, and a nitrogen atmosphere is thus required to prevent ignition and oxidation of the coal. Therefore, additional equipment is required to maintain the nitrogen atmosphere. Moreover, if the nitrogen atmosphere is not maintained, there is a risk of explosion or ignition due to the high temperature and low moisture content of the coal.
Furthermore, in the methods described in PTL 1 and 2, an additive that is generally known to be effective in improving flowability is used to achieve an improvement in bulk density. However, use of additives other than the raw materials used in ordinary coke production may result in a decrease in coke quality such as coke strength.
The present disclosure has been made in view of the aforementioned problems, and an aim thereof is to provide a method of producing coke that does not require any operations posing a risk of ignition and that is capable of producing high-strength coke using ordinary raw materials for coke production.

(Solution to Problem)

We have conducted extensive studies to solve the aforementioned technical problem and have made the following discovery. We discovered that it is possible to increase the bulk density of the coal blend charged into a coke oven through preparation of a coal blend by pulverizing a portion of the carbonaceous material used in ordinary coke production and then blending a small amount of the pulverized carbonaceous material with carbonaceous material having the ground particle size used in ordinary coke production.
The present disclosure is made based on these discoveries, and primary features are as described below.

[1] A method of producing coke by charging blended coal into a coke oven and carbonizing the blended coal, the method comprising:
preparing the blended coal by blending 1 mass% or more and 10 mass% or less of a carbonaceous material B, which has a ratio of particles with a particle size of 125 µm or less of 50 mass% or more, with a carbonaceous material A, which has a ratio of particles with a particle size of 3 mm or more of 10 mass% or more and 30 mass% or less, and a ratio of particles with a particle size of 0.5 mm or more of 60 mass% or more, the carbonaceous material B being one, or a mixture of two or more, selected from the group consisting of coal, pitches, oil coke, and dry distillation products thereof.

(Advantageous Effect)

According to the present disclosure, a method of producing coke that does not require any operations posing a risk of ignition and that is capable of producing high-strength coke using ordinary raw materials for coke production can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional view schematically illustrating a bulk density measuring device used in a bulk density measurement test; and
FIG. 2 is a graph illustrating the relationship, in the Examples, between the blending ratio of carbonaceous material B and the strength difference ΔDI relative to a Conventional Example (No. 1) obtained by carbonizing only carbonaceous material A.

DETAILED DESCRIPTION

An embodiment of the present disclosure is described below with reference to the drawings. A method of producing coke according to the present disclosure is a method of producing coke by charging blended coal into a coke oven and carbonizing the blended coal, the method including preparing the blended coal by blending 1 mass% or more and 10 mass% or less of a carbonaceous material B, which has a ratio of particles with a particle size of 125 µm or less of 50 mass% or more, with a carbonaceous material A, which has a ratio of particles with a particle size of 3 mm or more of 10 mass% or more and 30 mass% or less, and a ratio of particles with a particle size of 0.5 mm or more of 60 mass% or more, the carbonaceous material B being one, or a mixture of two or more, selected from the group consisting of coal, pitches, oil coke, and dry distillation products thereof.
Typically, to increase the bulk density of blended coal 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 flowability of the coal. It is generally known that reducing the ground particle size of blended coal reduces the bulk density of the blended coal charged into a coke oven. Hence, to increase bulk density, it is desirable to increase the ground particle size of the blended coal.
We considered that, if an increase in bulk density could be achieved solely by the raw materials ordinarily used in coke production through controlling the particle size distribution of the blended coal charged into a coke oven, it would be possible to increase the bulk density of the charged blended coal without adverse effects on coke quality caused by additives and without cost increases resulting from the use of expensive chemicals. As a result of extensive research based on this idea, we discovered that by pulverizing a portion of the raw material used in ordinary coke production and then blending the pulverized raw material, the pulverized raw material acts as a bulk density enhancer, thereby increasing the bulk density of the blended coal at the time of charging.
The method of producing coke of the present disclosure will be described in detail below.
The method of producing coke of the present disclosure is a technique for improving the bulk density of blended coal at the time of charging by pulverizing a portion of blended coal used in ordinary coke production and then blending the pulverized coal. Here, the blended coal used in ordinary coke production is mainly composed of carbonaceous materials such as coal, pitches, oil coke, and dry distillation products thereof.
In the method of producing coke of the present disclosure, a blended coal is prepared by blending 1 mass% or more and 10 mass% or less of a pulverized carbonaceous material B, which has a ratio of particles with a particle size of 125 µm or less of 50 mass% or more, with a carbonaceous material A, which has a ratio of particles with a particle size of 3 mm or more of 10 mass% or more and 30 mass% or less, and a ratio of particles with a particle size of 0.5 mm or more of 60 mass% or more.
The carbonaceous material A has a ratio of particles with a particle size of 3 mm or more of 10 mass% or more and 30 mass% or less, and a ratio of particles with a particle size of 0.5 mm or more of 60 mass% or more, and is a carbonaceous material with a particle size used in ordinary coke production. It is known that reducing the particle size of blended coal reduces the bulk density of the blended coal charged into a coke oven. Therefore, in the present disclosure, the ground particle size of the carbonaceous material A, which accounts for the majority of the blended coal, is controlled so that the ratio of particles of 3 mm or more is 10 mass% or more and 30 mass% or less.
If the particle size of the carbonaceous material A is large, a distribution of properties occurs in coke production that uses 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 ratio 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, the bulk density of the blended coal decreases when it is charged, as conventionally known. Therefore, the particle size of the carbonaceous material A is controlled so that the ratio of particles with a particle size of 3 mm or more is 10 mass% or more. The ratio of particles of the carbonaceous material A having a particle size of 3 mm or more is preferably 15 mass% or more. This ratio is preferably 25 mass% or less. No particular upper limit is placed on the particle size of the carbonaceous material A as long as the ratio of particles having a particle size of 3 mm or more is 30 mass% or less, but from the perspective of preventing imbalance of components, the upper limit is preferably 25 mm or less.
Furthermore, even for the carbonaceous material A having a particle size of less than 3 mm, if the particle size were to become excessively small, then the bulk density of the blended coal would decrease and the difference in particle size with the carbonaceous material B would become small. In this case, the bulk density improving effect of the present disclosure could not be obtained. Therefore, in the present disclosure, the ratio of particles of the carbonaceous material A having a particle size of 0.5 mm or more is set to 60 mass% or more. That is, the ratio of particles having a particle size of 0.5 mm or more and less than 3 mm is set to 30 mass% or more and 90 mass% or less. In addition, the ratio of particles of the carbonaceous material A having a particle size of 0.5 mm or more is preferably 80 mass% or less. Furthermore, the ratio of fine particles with a particle size of less than 0.5 mm is less than 40 mass% and is preferably less than 20 mass%. If a large amount of fine particles of less than 0.5 mm are produced during grinding, the fine particles may be removed by sieving or the like.
On the other hand, the carbonaceous material B, which has a ratio of particles having a particle size of 125 µm or less of 50 mass% or more, is a portion of the carbonaceous material used in coke production and is blended in a ratio of 1 mass% to 10 mass% with respect to the entire blended coal. In the present disclosure, the effect of improving the bulk density can be obtained by blending the carbonaceous material B having an extremely small particle size with the carbonaceous material A. Specifically, when the blended coal is charged into a coke oven, the pulverized carbonaceous material B is mixed among the coarse carbonaceous material A, thereby functioning as a lubricant to improve the flowability of the blended coal and increasing the bulk density. Furthermore, the pulverized carbonaceous material B enters between coarse particles of the carbonaceous material A, thereby disrupting water-mediated interparticle bridging among carbonaceous particles in the blended coal, which also improves the flowability of the carbonaceous material. The blending ratio of the carbonaceous material B is preferably 1 mass% or more. The blending ratio is preferably 9 mass% or less. The blending ratio is more preferably 2 mass% or more. The blending ratio is more preferably 5 mass% or less.
The carbonaceous material B is a raw material used in ordinary coke production, and is one, or a mixture of two or more, selected from the group consisting of coal, pitches, oil coke, and dry distillation products thereof. The method of adjusting the particle size of the carbonaceous material B is not particularly specified as long as a predetermined particle size is obtained, but in order to pulverize a large amount of carbonaceous material for use in coke production, equipment such as a roller mill or a tower mill can be used. Furthermore, the production cost of the carbonaceous material B can be reduced by reusing pulverized carbonaceous material generated within a steelworks. Examples of pulverized carbonaceous materials generated in steelworks include pulverized coal pulverized for injection into the blast furnace, coke powder generated in a coke dry quenching (CDQ) system, and collected dust produced in dust collectors installed in the coal and coke conveyance process.
As long as the carbonaceous material B can be blended with the carbonaceous material A in a ratio of 1% by mass to 10% by mass, the flow for grinding and blending the carbonaceous materials A and B is not particularly specified, but these materials can be blended by the following methods, for example.

(1) Among the carbonaceous materials used in the blended coal, part or all of a specific brand is pulverized to form the carbonaceous material B, and the other carbonaceous materials are ground in a grinder for ordinary coke production to produce the carbonaceous material A, which is then blended with the carbonaceous material B.
(2) Among the carbonaceous materials used in the blended coal, part or all of a plurality of brands is pulverized and blended to form the carbonaceous material B, and the other carbonaceous materials are ground in a grinder for ordinary coke production to produce the carbonaceous material A, which is then blended with the carbonaceous material B.
(3) Among the carbonaceous materials used in the blended coal, part or all of a plurality of brands is blended and then pulverized to form the carbonaceous material B, and the other carbonaceous materials are ground in a grinder for ordinary coke production to produce the carbonaceous material A, which is then blended with the carbonaceous material B.
(4) After blending the carbonaceous materials to be used in the blended coal, part of the mixture is removed and pulverized to form the carbonaceous material B, and the other carbonaceous materials are ground in a grinder for ordinary coke production to produce the carbonaceous material A, which is then blended with the carbonaceous material B.
(5) The carbonaceous materials to be used in the blended coal are ground in a grinder for ordinary coke production and blended, after which a portion of the mixture is removed and pulverized to form the carbonaceous material B, which is then blended with the other carbonaceous materials (carbonaceous material A).

The moisture content of the blended coal in the present disclosure is preferably 6 mass% or more. The moisture content is preferably 9 mass% or less. If the moisture content of the blended coal is less than 6 mass%, drying of the blended coal increases the risk of ignition and may also lead to an increased amount of dust generation. On the other hand, a moisture content of the blended coal exceeding 9 mass% is not desirable, since the increase in water may reduce the effect of improving bulk density by blending the pulverized carbonaceous material B, and a large amount of heat would be required to evaporate water during carbonization in coke production.

EXAMPLES

Examples of the present disclosure are described below. The present disclosure is not limited to the following examples and can be modified as desired without departing from the scope of the present disclosure.
For the blended coal used in the bulk density measurement test, Table 1 lists the particle size of the carbonaceous material A, the particle size and blending ratio of the carbonaceous material B, and the moisture content of the blended coal. In the present Examples, the blended coal C is a blended coal having an average maximum vitrinite reflectance (Ro(-)) of 1.00 (%) and a common logarithm (logMF) of the maximum fluidity (MF), measured by a Gieseler plastometer, of 2.50. The coal D is a raw material coal having an Ro(-) of 0.98 (%) and a common logarithm of MF of 2.67, and the coal E is a thermal coal.
FIG. 1 is a cross-sectional view schematically illustrating a bulk density measuring device used in a bulk density measurement test. As illustrated in FIG. 1, a bulk density measuring 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 having a width of 250 mm, a length of 250 mm (depth direction in FIG. 1), and a height of 200 mm, and having an opening only on the top surface. A slide gate 5 is installed at the bottom of the sample hopper 2, and by opening the slide gate 5, the blended coal in the hopper 2 falls into the container 4 via the guide 3. The height from the slide gate 5 installed at the bottom of the hopper 2 to the bottom of the container 4 is 2 m.
In these Examples, the bulk densities of the various blended coals listed in Table 1 were measured using the above-described bulk density measuring device. The procedure for measuring bulk density is described below.

[Table 1]

Table 1

Level	Blended coal							Bulk density [kg/m³] (d.b.)	Classification
	Carbonaceous material A			Carbonaceous material B			Moisture (mass%)
	Type	Ratio of 3 mm or more (mass%)	Ratio of 0.5 mm or more (mass%)	Coal type	Ratio of 125 µm or less (mass%)	Blending ratio in blended coal (mass%)	Moisture (mass%)
1	Blended coal C	29	69	-	-	0	7	783	Conventional Example
2	Blended coal C	23	66	-	-	0	7	780	Conventional Example
3	Blended coal C	15	63	-	-	0	7	768	Conventional Example
4	Blended coal C	12	61	-	-	0	7	762	Conventional Example
5	Blended coal C	23	66	Coal D	95	1	7	797	Example
6	Blended coal C	23	66	Coal D	95	2	7	808	Example
7	Blended coal C	23	66	Coal D	95	3	7	816	Example
8	Blended coal C	23	66	Coal D	95	5	7	800	Example
9	Blended coal C	23	66	Coal D	95	9	7	792	Example
10	Blended coal C	23	66	Coke	55	1	7	799	Example
11	Blended coal C	23	66	Coke	55	3	7	819	Example
12	Blended coal C	23	66	Coke	55	5	7	810	Example
13	Blended coal C	23	66	Oil coke	100	3	7	803	Example
14	Blended coal C	23	66	Coal E	100	3	7	812	Example
15	Blended coal C	29	69	Blended coal C	100	3	7	818	Example
16	Blended coal C	23	66	Blended coal C	100	3	7	816	Example
17	Blended coal C	23	66	Blended coal C	100	5	7	804	Example
18	Blended coal C	23	66	Blended coal C	100	9	7	794	Example
19	Blended coal C	15	63	Blended coal C	100	3	7	803	Example
20	Blended coal C	12	61	Blended coal C	100	3	7	800	Example
21	Blended coal C	23	66	Blended coal C	100	12	7	769	Comparative Example

First, carbonaceous material A and carbonaceous material B, each adjusted to the particle sizes listed in Table 1, were blended, water was added to the mixture to obtain the moisture content listed in Table 1, and the result was mixed to yield blended coal. Next, 32 kg of the blended coal was filled into the hopper 2, and the slide gate 5 was subsequently opened to drop the blended coal into the container 4. Next, the blended coal protruding from the top of the container 4 after the blended coal had fallen was removed, and the mass of the blended coal filled in the container was measured. Subsequently, the weighed blended coal was divided into smaller samples to measure the moisture content, and the bulk density (dry basis, d.b.) of the blended coal was calculated using the following Equation (1). The measurement of the bulk density was carried out twice for each level, and the average value of the two measurements was used as the bulk density for each level.
[Math. 1] $\begin{array}{l} bulk density [kg / m^{3}] (d . b .) \\ = \frac{mass of blended coal in container [kg] \times \frac{100 - moisture content of blended coal [mass %]}{100}}{0.25 \times 0.25 \times 0.20} \end{array}$
Table 1 lists the bulk density measurement results for each blended coal. In Levels 1 to 4, which are Conventional Examples that do not contain the pulverized carbonaceous material B, the bulk density decreases as the mass ratio of particles less than 3 mm increases, and as is conventionally known, the bulk density decreases as the ground particle size decreases. On the other hand, in Levels 5 to 20, which are Examples in which the pulverized carbonaceous material B is blended with the carbonaceous material A, it is clear that the bulk density is improved compared to the Conventional Examples in which the carbonaceous material B is not blended. Furthermore, in Level 21, which is a Comparative Example in which the blending ratio of the carbonaceous material B exceeds 10 mass%, the bulk density is lower than that of the Conventional Example (Level 2) in which the Carbonaceous Material B is not blended. From the above results, it was confirmed that by blending pulverized carbonaceous material B in a ratio of 1 mass% or more and 10 mass% or less with blended coal of a particle size used in ordinary coke production, the carbonaceous material B acts as a bulk density enhancing agent, making it possible to increase the bulk density of the blended coal at the time of charging.
Next, to examine the impact, on coke strength, of the bulk density improvement effect of blending the pulverized carbonaceous material B, coke was produced by the following method, and the coke strength was evaluated.
Blended coal for carbonization was prepared by blending, at the blending ratios listed in Table 2, blended coal A and carbonaceous material B prepared to have the particle sizes listed in Table 2, and then adding water and mixing to obtain a moisture content of 7 %. This blended coal was charged into a carbonization container in an amount of 16.5 kg at the bulk density listed in Table 2 and carbonized in an electric furnace. After carbonization at a furnace wall temperature of 1050 °C for 6 hours, the result was cooled in a nitrogen atmosphere, and the drum strength of the obtained coke was measured. The drum strength index DI_150/15 was measured in accordance with the drum strength test method of JIS K2151. The difference in strength relative to a Conventional Example (No. 1) obtained by carbonizing only the carbonaceous material A is listed in Table 2 as ΔDI (ΔDI = [DI_150/15 index of the target level] - [DI_150/15 index of No. 1]).

[Table 2]

Table 2

Level	Blended coal							Bulk density [kg/m³] (d.b.)	ΔDI	Classification	Notes
	Carbonaceous material A			Carbonaceous material B			Moisture (mass%)
	Type	Ratio of 3 mm or more (mass%)	Ratio of 0.5 mm or more (mass%)	Coal type	Ratio of 125 µm or less (mass%)	Blending ratio in blended coal (mass%)	Moisture (mass%)
1	Blended coal C	23	66	-	-	0	7	780	0.0	Conventional Example	Bulk density of Level 2 in Table 1
2	Blended coal C	23	66	Coal D	95	1	7	797	0.3	Example	Bulk density of Level 5 in Table 1
3	Blended coal C	23	66	Coal D	95	2	7	808	0.7	Example	Bulk density of Level 6 in Table 1
4	Blended coal C	23	66	Coal D	95	3	7	816	1.1	Example	Bulk density of Level 7 in Table 1
5	Blended coal C	23	66	Coal D	95	5	7	800	0.6	Example	Bulk density of Level 8 in Table 1
6	Blended coal C	23	66	Coal D	95	9	7	792	0.2	Example	Bulk density of Level 9 in Table 1
7	Blended coal C	23	66	Coke	55	1	7	799	0.3	Example	Bulk density of Level 10 in Table 1
8	Blended coal C	23	66	Coke	55	3	7	819	1.0	Example	Bulk density of Level 11 in Table 1
9	Blended coal C	23	66	Coke	55	5	7	810	0.5	Example	Bulk density of Level 12 in Table 1
10	Blended coal C	23	66	Oil coke	100	3	7	803	0.5	Example	Bulk density of Level 13 in Table 1
11	Blended coal C	23	66	Coal E	100	3	7	812	0.6	Example	Bulk density of Level 14 in Table 1
12	Blended coal C	23	66	Blended coal C	100	3	7	816	1.2	Example	Bulk density of Level 16 in Table 1
13	Blended coal C	23	66	Blended coal C	100	5	7	804	0.8	Example	Bulk density of Level 17 in Table 1
13	Blended coal C	23	66	Blended coal C	100	9	7	794	0.4	Example	Bulk density of Level 18 in Table 1
14	Blended coal C	23	66	Blended coal C	100	12	7	769	-0.6	Comparative Example	Bulk density of Level 21 in Table 1

In Table 2, Level 1 is a Conventional Example in which the carbonaceous material B is not blended, Levels 2 to 13 are Examples in which the 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 disclosure. The bulk density at each level during carbonization reflects the bulk density measurement results in Table 1. In Levels 2 to 13, which are Examples in which the carbonaceous material B was blended with the carbonaceous material A and the bulk density was improved, ΔDI exceeded 0, indicating that the blending of the carbonaceous material B had the effect of improving coke strength. On the other hand, at Level 14, for which the blending ratio of carbonaceous material B is outside the range of the present disclosure, ΔDI is less than 0, indicating reduced strength.
FIG. 2 illustrates the relationship between the blending ratio of carbonaceous material B and ΔDI for the Examples listed in Table 2. As illustrated in FIG. 2, when the blending ratio of the 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.

INDUSTRIAL APPLICABILITY

REFERENCE SIGNS LIST

1: Bulk density measuring device
2: Hopper
3: Guide
4: Container
5: Slide gate

Claims

A method of producing coke by charging blended coal into a coke oven and carbonizing the blended coal, the method comprising:
preparing the blended coal by blending 1 mass% or more and 10 mass% or less of a carbonaceous material B, which has a ratio of particles with a particle size of 125 µm or less of 50 mass% or more, with a carbonaceous material A, which has a ratio of particles with a particle size of 3 mm or more of 10 mass% or more and 30 mass% or less, and a ratio of particles with a particle size of 0.5 mm or more of 60 mass% or more, the carbonaceous material B being one, or a mixture of two or more, selected from the group consisting of coal, pitches, oil coke, and dry distillation products thereof.