Method for producing coal cake and method for producing metallurgical coke

Abstract

Provided is a method of producing a coal cake that can improve both the strength of the coal cake and productivity. A method of producing a coal cake according to the present disclosure is a method of producing a coal cake in a stamp charging coke oven and includes stamping a blended coal C to obtain a coal cake, the blended coal C being obtained by mixing a carbonaceous material A and a carbonaceous material B so that a 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. The carbonaceous material A has a ratio of particles with a particle size of 0.5 mm or less of 50 mass% or less, and a ratio of particles with a particle size of 0.1 mm or less of 20 mass% or less, and the carbonaceous material B has a ratio of particles with a particle size of 0.5 mm or less of 80 mass% or more, and a ratio of particles with a particle size of 0.1 mm or less of 50 mass% or more.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method of producing a coal cake and a method of producing metallurgical coke, and more particularly to a method of producing a coal cake and a method of producing metallurgical coke in a stamp charging coke oven.BACKGROUND

[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 to ensure good gas permeability inside the blast furnace. It is known that high-strength coke is suitable for efficient operation of a blast furnace. This is because when coke is pulverized in a blast furnace, the resulting powder reduces the permeability of the blast furnace, making it impossible to operate the blast furnace efficiently.

[0003] It is known that increasing the bulk density of coal charged into a coke oven is effective for producing high-strength coke, and stamp charging coke ovens are used for this purpose. In the typical coke ovens currently used in Japan (hereinafter referred to as "top charging coke ovens"), coal, which is the raw material for coke, is charged by gravity from the top of the coke oven's carbonization chamber, and the bulk density of the gravity-charged coal is 700 kg-dry / m 3< to 800 kg-dry / m 3< .

[0004] On the other hand, in a stamp charging coke oven, the coal is compacted by a stamping device located on the side of the coke oven carbonization chamber before being charged into the coke oven to be processed into a coal cake with a bulk density of 1,000 kg-dry / m 3< or more. The resulting coal cake is then mechanically pushed from the side into the coke oven carbonization chamber. By using a stamp charging coke oven, the density of the coke raw material can be increased before carbonization, and higher-strength coke can be produced compared to a top charging coke oven. Also, productivity can be increased by increasing the charge per kiln.

[0005] As described above, stamp charging coke ovens are superior to top charging coke ovens in terms of coke strength and productivity. However, if the strength of the coal cake produced by stamping is low, the coal cake may collapse during charging into the carbonization chamber of the coke oven, causing operational problems. Therefore, for stable operation of stamp charging coke ovens, a technique to produce a high-strength coal cake is required. Furthermore, in response to the recent social demand for reducing CO 2 emissions, demand exists for techniques that can improve the density of coal cakes and achieve further improvements in productivity.

[0006] Regarding the relationship between coal particle size and coal cake strength, Non-patent Literature (NPL) 1 reports on a test conducted by changing the degree of grinding of the coal cake raw material. NPL 1 reports that the strength of the coal cake was improved by increasing the ratio of fine particles with a particle size of 3.15 mm or less in the raw material, i.e., by grinding the coal cake raw material more finely.

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

[0008] PTL 1: JP H7-109467 ANon-patent Literature

[0009] NPL 1: M. Rejdak, et al., Physicochem. Probl. Miner. Process. 51(1), 2015, 151. NPL 2: SH Krishnan, et al., "Application of Binder in Stamp Charge Coke Making", ISIJ International, 44(2004), 1150. SUMMARY(Technical Problem)

[0010] NPL 1 reports that by grinding the raw materials of the coal cake more finely, the strength of the coal cake is improved, but the density of the coal cake is reduced. That is, the method of intensifying the grinding of the coal cake raw materials and reducing the particle size of the raw materials improves the strength of the coal cake and contributes to stable operation of the stamp charge furnace, but the density of the coal cake decreases, resulting in a relative decrease in productivity.

[0011] Furthermore, in the methods using a caking binder described in PTL 1 and NPL 2, the caking raw material adheres to the belt conveyor and the stamping device during the process of transporting the coke raw material containing the caking binder and during the process of compacting the raw material with a stamping device. This necessitates frequent cleaning of the device, resulting in a problem of reduced productivity.

[0012] An aim of the present disclosure is to provide a method of producing a coal cake that can improve both the strength of the coal cake and productivity.(Solution to Problem)

[0013] We have conducted extensive studies to solve the aforementioned technical problem and have made the following discovery. The density and strength of the coal cake can be improved by stamping blended coal prepared by blending a small amount of a pulverized coal material with blended coal having a ground particle size ordinarily used in a stamp charging oven.

[0014] The primary features of the present disclosure are as follows. [1] A method of producing a coal cake in a stamp charging coke oven, the method comprising: stamping a blended coal C to obtain a coal cake, the blended coal C being obtained by mixing a carbonaceous material A and a carbonaceous material B so that a 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, wherein the carbonaceous material A has a ratio of particles with a particle size of 0.5 mm or less of 50 mass% or less, and a ratio of particles with a particle size of 0.1 mm or less of 20 mass% or less, and the carbonaceous material B has a ratio of particles with a particle size of 0.5 mm or less of 80 mass% or more, and a ratio of particles with a particle size of 0. 1 mm or less of 50 mass% or more. [2] A method of producing metallurgical coke, the method comprising carbonizing a coal cake produced by the method according to [1] in a coke oven to obtain coke. (Advantageous Effect)

[0015] According to the present disclosure, a method of producing a coal cake that can improve both the strength of the coal cake and productivity in a stamp charging oven can be provided. Furthermore, according to the present disclosure, by improving the strength of the coal cake, problems such as collapse of the coal cake can be reduced, enabling stable operation of the stamp charging oven. In addition, by increasing the density of the coal cake, the productivity of the stamp charging oven can be improved.DETAILED DESCRIPTION

[0016] Embodiments of the present disclosure are described below. A method of producing a coal cake according to the present disclosure is a method of producing a coal cake in a stamp charging coke oven and includes preparing a carbonaceous material A that has a ratio of particles with a particle size of 0.5 mm or less of 50 mass% or less, and a ratio of particles with a particle size of 0.1 mm or less of 20 mass% or less, and a carbonaceous material B that has a ratio of particles with a particle size of 0.5 mm or less of 80 mass% or more, and a ratio of particles with a particle size of 0.1 mm or less of 50 mass% or more, and stamping a blended coal C to obtain a coal cake, the blended coal C being obtained by mixing the carbonaceous material A and the pulverized carbonaceous material B so that the mass ratio of the pulverized carbonaceous material B to 100 mass% of the carbonaceous material A is 0.5 mass% or more and 15 mass% or less.[Carbonaceous material A]

[0017] The carbonaceous material A in the present disclosure is a typical raw material that has been conventionally used as a coke raw material in top charging coke ovens and stamp charging coke ovens and may be produced by grinding the raw material using a hammer crusher or the like so that the proportion of particles having a particle size of 3 mm or less is 70 mass% or more, as is done in conventional coke oven operations. The "ratio of particles with a particle size of 3 mm or less" refers to the ratio of the mass of a raw material passing through a sieve to the total mass of the raw material when the raw material is sieved using a 3 mm sieve. The same definition applies in this specification when the particle size differs.

[0018] To obtain the effects of the present disclosure, the particle size of the carbonaceous material A must be significantly different from that of the carbonaceous material B and therefore must be at least a certain level. Specifically, the ratio of particles with a particle size of 0.5 mm or less must be 50 mass% or less, and the ratio of particles with a particle size of 0.1 mm or less must be 20 mass% or less. However, since the effects of the present disclosure can be enhanced by making the difference in particle size between carbonaceous material A and carbonaceous material B more significant, the particle size of the carbonaceous material A is preferably larger. Specifically, the ratio of particles having a particle size of 0.5 mm or less is preferably 40 mass% or less. The ratio of particles having a particle size of 0.1 mm or less is preferably 15 mass% or less. The ratio of particles having a particle size of 0.5 mm or less is more preferably 35 mass% or less. The ratio of particles having a particle size of 0.1 mm or less is more preferably 12 mass% or less.

[0019] The raw material for the carbonaceous material A forming part of the coal cake mainly includes raw coal generally used for coke production, but other raw materials, such as non-caking or slightly-caking coal, oil coke, pitches, biomass, other raw materials mainly composed of carbon, and carbides obtained by heating the aforementioned raw materials may also be used, as long as the quality of the coke after carbonization is not problematic. Furthermore, when a plurality of raw materials is used as the carbonaceous material A, each raw material may be individually ground and then blended for use as the carbonaceous material A, or the plurality of raw materials may be blended and then ground together.[Charcoal material B]

[0020] In the present disclosure, by blending a portion of the carbonaceous material B having a sufficiently low particle size with the carbonaceous material A, the density and strength of the coal cake can be improved. To obtain the effects of the present disclosure, the particle size of the carbonaceous material B must be such that the ratio of particles with a particle size of 0.5 mm or less is 80 mass% or more and the ratio of particles with a particle size of 0.1 mm or less is 50 mass% or more. To obtain a greater effect of improving the density and strength of the coal cake, the ratio of particles with a particle size of 0.5 mm or less is preferably 82 mass% or more. The ratio of particles with a particle size of 0.1 mm or less is preferably 56 mass% or more. The ratio of particles with a particle size of 0.5 mm or less is more preferably 85 mass% or more. The ratio of particles with a particle size of 0.1 mm or less is more preferably 70 mass% or more.

[0021] The raw material for the carbonaceous material B mainly includes raw coal generally used for coke production, but other raw materials, such as non-caking or slightly-caking coal, oil coke, pitches, biomass, other raw materials mainly composed of carbon, and carbides obtained by heating the aforementioned raw materials may also be used, as long as the quality of the coke after carbonization is not problematic. A portion of the carbonaceous material A may be removed and pulverized to obtain the carbonaceous material B.

[0022] The method of adjusting the particle size of the carbonaceous material B is not particularly limited as long as a predetermined particle size is obtained, but equipment such as a ball mill, roller mill, tower mill, bead mill, or jet mill, for example, can be used. Furthermore, carbonaceous material generated in a steelworks and satisfying the aforementioned particle size conditions may be used as carbonaceous material B without adjusting the particle size. Examples of raw materials generated in the steelworks include collected dust obtained by recovering powder generated by a coke dry quenching (CDQ) system or by coke conveying. Furthermore, when a plurality of raw materials is used as the carbonaceous material B, each raw material may be individually ground and then blended for use as the carbonaceous material B, or the plurality of raw materials may be blended and then ground together.[Blended coal C]

[0023] The blended coal C is obtained by mixing the carbonaceous material A and the pulverized carbonaceous material B. To obtain the effect of improving the density and strength of the coal cake according to the present disclosure, the mass ratio of the carbonaceous material B relative to 100 mass% of the carbonaceous material A must be 0.5 mass% or more. To obtain a greater effect, the mass ratio of the carbonaceous material B is more preferably 1 mass% or more. The mass ratio of the carbonaceous material B is more preferably 2 mass% or more. On the other hand, the purpose of the present disclosure is not to pulverize the entire coal cake raw material, but to add a part of the carbonaceous material B having a particle size smaller than that of the carbonaceous material A to the carbonaceous material A, which has been ground to an ordinary ground particle size. This has the unique effect of improving both the density and strength of the coal cake, as will be illustrated in the examples below. Therefore, the mass ratio of the carbonaceous material B to 100 mass% of the carbonaceous material A must be 15 mass% or less. Considering that the production of pulverized carbonaceous material requires an increased grinding capacity, from the perspective of economic efficiency, the mass ratio of the carbonaceous material B is preferably 12 mass% or less. The mass ratio of the carbonaceous material B is more preferably 10 mass% or less.

[0024] The method of mixing the carbonaceous material A and the carbonaceous material B is not particularly limited, and a mixer generally used for mixing coal in a coke plant may be used. Another example is a method in which the carbonaceous material A and the carbonaceous material B are placed on the same belt conveyor and mixed by the flow that occurs during transfer between conveyors.

[0025] The moisture content of the blended coal C is preferably 9 mass% to 12 mass% in order to maximize the strength of the coal cake. The moisture content can be adjusted by treatment such as drying using coal moisture control equipment or spraying water from a nozzle. The moisture adjustment is preferably carried out after the carbonaceous material A and the carbonaceous material B are mixed but may be carried out before or after the carbonaceous material A and the carbonaceous material B are ground, depending on the layout of the factory. However, as will be explained with reference to data in Example 2 below, the effects of the present disclosure can be obtained as long as the moisture content of the blended coal C is between 7 mass% and 13 mass%. The moisture of coal stored in a yard varies depending on the season and weather, but the range of variation is within a range of approximately 7 mass% to 13 mass%. Therefore, the moisture content range for obtaining the effects of the present disclosure is not particularly limited within the range of ordinary coke production conditions.<Production of coal cake>

[0026] In the present disclosure, a high-strength coal cake can be produced by stamping and compacting the aforementioned blended coal C.

[0027] A coal cake may be produced from the blended coal C prepared as described above by using a stamping device that compacts raw materials by impact with a falling weight. In this case, a coal cake having a higher density and higher strength than when only using the carbonaceous material A can be produced by using the blended coal C, in which the carbonaceous material B is blended with the carbonaceous material A as a raw material. As a result, the coal cake is less likely to collapse, and the coke oven can be operated stably. In addition, productivity is improved by increasing the amount of coal charged per kiln.

[0028] Although the factors that improve the density and strength of the coal cake are not completely clear, it is speculated that this is due to the carbonaceous material B penetrating between the particles of the carbonaceous material A, functioning as a lubricant, and improving the fluidity of the carbonaceous material as a whole. By improving the fluidity of the carbonaceous material as a whole, stamping with the same energy is more likely to provoke particle rearrangement, which is thought to result in the production of a coal cake with higher density and higher strength.(Method of producing metallurgical coke)

[0029] Next, a method of producing metallurgical coke according to the present disclosure will be described. The method of producing metallurgical coke according to the present disclosure includes carbonizing, in a coke oven, the coal cake produced by the above-described method of producing a coal cake according to the present disclosure.

[0030] The coal cake produced by the above-described method of producing a coal cake according to the present disclosure is mechanically charged into the coke oven carbonization chamber from the side. At this time, the coal cake is subjected to its own weight and to impact from vibration of the charging machine. If the strength of the coal cake is low, an operational problem may occur in which the coal cake collapses during charging. However, by use of the blended coal C, which is a mixture of the carbonaceous material A and the carbonaceous material B having a smaller particle size than the carbonaceous material A, as the raw material for the coal cake, the strength of the coal cake is improved, and the collapse of the coal cake can be prevented. Furthermore, the coal cake produced from the blended coal C, which is a mixture of the carbonaceous material A and the carbonaceous material B having a smaller particle size than the carbonaceous material A, has a higher density than the coal cake produced by conventional methods. The amount of coal charged per kiln is therefore increased, thereby improving productivity.

[0031] No particular restrictions are placed on the conditions for carbonizing the coal cake. The coal cake may be carbonized at a temperature of approximately 900 °C or higher in a typical stamp charging coke oven.EXAMPLES

[0032] Examples of the present disclosure will be described below, but 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.(Example 1)

[0033] In Example 1, different carbonaceous materials A and B were blended and mixed to produce a coal cake, and the strength of the coal cake was evaluated. The production conditions and evaluation results are listed in Table 1.

[0034] Specifically, a blended coal containing a plurality of coals was used as the carbonaceous material A and was ground to the particle sizes listed in Table 1 before use. As the carbonaceous material B, coke powder, non-caking or slightly-caking coal, and carbonized biomass were ground to the particle sizes listed in Table 1 before use. Then, the carbonaceous material A and the carbonaceous material B were blended and mixed at the blending ratios listed in Table 1 to prepare a blended coal C, and the moisture content of the blended coal C was then adjusted to 10 mass%.

[0035] A coal cake was produced in the following manner using the blended coal C prepared by the above-described procedure. First, approximately 200 g of the blended coal C was charged into a metal mold having an inner diameter of 10 cm and a height of 20 cm, and a rammer having a mass of 9 kg was dropped 10 times from a height of 30 cm from the surface of the sample, thereby compacting the charged blended coal C by the impact. This procedure, from charging the blended coal C to dropping the rammer, was repeated 10 times to produce a coal cake having a diameter of 10 cm, a height of 20 cm, and a mass of approximately 2 kg. Thereafter, the mold was gently removed from the coal cake, and the dry density and strength of the coal cake were measured.

[0036] The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio listed in Table 1 are the ratios of the coal cake produced from the blended coal C, into which the carbonaceous material B was mixed, relative to the dry density and strength of a coal cake produced by the above procedure using only the carbonaceous material A, without mixing in the carbonaceous material B, which are set to 1. Therefore, when the density ratio and the strength ratio are each greater than 1, it can be determined that the properties of the coal cake have been improved by the present disclosure, i.e., by mixing the carbonaceous material B, which has a smaller particle size than the carbonaceous material A, in with the carbonaceous material A.[Table 1]

[0037] Table 1Carbonaceous material ACarbonaceous material BBlended coal CRate of change in coal cake properties due to mixing in of carbonaceous material BRatio of particles with a particle size of 3 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.5 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbonaceous material A (mass%)Type of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material B (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbon material B (mass%)Mass ratio of carbonaceous material B to carbonaceous material A (mass%)Moisture content of blended coal C (mass%)Density ratioStrength ratioComparative Example 193287Coke powder8875101.000.99Comparative Example 293287Coke powder88205100.981.16Comparative Example 393287Coke powder882010100.971.10Example 11004015Coke powder1001001101.011.26Example 21004015Coke powder1001003101.021.40Comparative Example 493287Non-caking coal3175101.001.02Comparative Example 593287Non-caking coal70215100.991.10Comparative Example 693287Non-caking coal702110100.981.12Example 393287Non-caking coal98725101.021.46Example 493287Non-caking coal987210101.021.74Comparative Example 793287Non-caking coal987220100.991.33Example 578165Carbonized biomass82562101.011.23Example 678165Carbonized biomass82564101.011.33Example 778165Carbonized biomass82566101.011.36

[0038] In Comparative Examples 1 and 4, the carbonaceous material B that is mixed in has a particle size approximately the same as that of the carbonaceous material A. In this case, the density and strength of the coal cake hardly change as a result of mixing in the carbonaceous material B. In Comparative Examples 2, 3, 5, and 6, the carbonaceous material B mixed with the carbonaceous material A has a relatively small particle size. In this case, the strength ratio becomes greater than 1 due to the mixing in of the carbonaceous material B, whereas the density ratio becomes smaller than 1. It has been reported in NPL 1, for example, that a reduction in the particle size of the raw material improves strength but lowers density, and the present results are in line with such findings in the prior art.

[0039] On the other hand, in Examples 1 to 7, the carbonaceous material B mixed with the carbonaceous material A has been pulverized sufficiently to achieve the effects of the present disclosure. It can be seen that by mixing carbonaceous material B, both the density ratio and the strength ratio become larger than 1, and the properties of the coal cake are improved. Furthermore, when Comparative Examples 5 and 6 are compared with Examples 3 and 4, the strength improving effect of the Examples is clearly greater than that of the Comparative Examples. Therefore, it is thought that the strength of the coal cake was improved by mixing the carbonaceous material B, which has a smaller particle size than the carbonaceous material A, in with the carbonaceous material A. In addition, although Examples 1 to 7 of the present disclosure only describe examples in which the ratio of particles with a particle size of 3 mm or less is 78 mass% to 100 mass%, the same effect can be obtained as a result of mixing in the carbonaceous material B even when the carbonaceous material A has a larger particle size (a ratio of particles with a particle size of 3 mm or less of 70 mass%).

[0040] In Comparative Example 7, 20 mass% of sufficiently pulverized carbonaceous material B was mixed with the carbonaceous material A, but in this case, the density of the coal cake decreased. If the proportion of carbonaceous material B, which has a smaller particle size than carbonaceous material A, is too high, there will be an excess of the carbonaceous material B in the gaps between the carbonaceous material A, which has a larger particle size, as described above. This is thought to impede the full achievement of the effects of the disclosure.

[0041] As described above, the present disclosure not only stabilizes the operation of a coke oven by improving the strength of the coal cake but also improves productivity by increasing the density of the coal cake.

[0042] As is clear from the present example, the raw material of the carbonaceous material B for obtaining the effects of the present disclosure is not particularly limited. If coke powder or non-caking coal generated in a steelworks is used as the carbonaceous material B, the effects of the present disclosure can be obtained at a relatively low cost. Furthermore, using a carbon-neutral raw material such as carbonized biomass as the carbonaceous material B can contribute to reducing CO 2 emissions, which meets current social demands.(Example 2)

[0043] In Example 2, coal cakes were produced by varying the moisture content of the blended coal C, and their strength was evaluated. The production conditions and evaluation results are listed in Table 2.[Table 2]

[0044] Table 2Carbonaceous material ACarbonaceous material BBlended coal CRate of change in coal cake properties due to mixing in of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbonaceous material A (mass%)Type of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material B (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbon material B (mass%)Mass ratio of carbonaceous material B to carbonaceous material A (mass%)Moisture content of blended coal C (mass%)Density ratioStrength ratioExample 82612Coke powder100100171.011.15Example 92612Coke powder100100371.011.33Example 102612Coke powder1001001131.011.06Example 112612Coke powder1001003131.021.15

[0045] Specifically, a blended coal containing a plurality of coals was used as the carbonaceous material A and was ground to the particle sizes listed in Table 2 before use. As the carbonaceous material B, coke powder was ground to the particle sizes listed in Table 2 before use. Then, the carbonaceous material A and the carbonaceous material B were blended and mixed at the blending ratios listed in Table 2 to prepare a blended coal C, and the moisture content of the blended coal C was then adjusted to 7 mass% or 13 mass%.

[0046] A coal cake was produced in the following manner using the blended coal C prepared by the above-described procedure. First, approximately 200 g of the blended coal C was charged into a metal mold having an inner diameter of 10 cm and a height of 20 cm, and a rammer having a mass of 9 kg was dropped 10 times from a height of 30 cm from the surface of the sample, thereby compacting the charged blended coal C by the impact. This procedure, from charging the blended coal C to dropping the rammer, was repeated 10 times to produce a coal cake having a diameter of 10 cm, a height of 20 cm, and a mass of approximately 2 kg. Thereafter, the mold was gently removed from the coal cake, and the dry density and strength of the coal cake were measured.

[0047] The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio listed in Table 2 are the ratios of the coal cake produced from the blended coal C, into which the carbonaceous material B was mixed, relative to the dry density and strength of a coal cake produced by the above procedure using only the carbonaceous material A, without mixing in the carbonaceous material B, which are set to 1. Therefore, when the density ratio and the strength ratio are each greater than 1, it can be determined that the properties of the coal cake have been improved by mixing in the carbonaceous material B.

[0048] As illustrated in Table 2, regardless of whether the moisture content of the blended coal C was 7 mass% or 13 mass%, by mixing the carbonaceous material B, which had a smaller particle size than the carbonaceous material A, in with the carbonaceous material A, the density ratio and strength ratio became 1 or more, and the properties of the coal cake improved. The moisture content of coal stored in a yard varies depending on the season and weather, but the range of variation is approximately 7 mass% to 13 mass%. Therefore, as is clear from Tables 1 and 2, the present disclosure can be widely used when the moisture content of the blended coal C varies within the range of 7 mass% to 13 mass%.INDUSTRIAL APPLICABILITY

[0049] According to the present disclosure, a method of producing a coal cake that can improve both the strength of the coal cake and productivity can be provided.

Examples

example 1

(Example 1)

[0033]In Example 1, different carbonaceous materials A and B were blended and mixed to produce a coal cake, and the strength of the coal cake was evaluated. The production conditions and evaluation results are listed in Table 1.

[0034]Specifically, a blended coal containing a plurality of coals was used as the carbonaceous material A and was ground to the particle sizes listed in Table 1 before use. As the carbonaceous material B, coke powder, non-caking or slightly-caking coal, and carbonized biomass were ground to the particle sizes listed in Table 1 before use. Then, the carbonaceous material A and the carbonaceous material B were blended and mixed at the blending ratios listed in Table 1 to prepare a blended coal C, and the moisture content of the blended coal C was then adjusted to 10 mass%.

[0035]A coal cake was produced in the following manner using the blended coal C prepared by the above-described procedure. First, approximately 200 g of the blended coal C was char...

example 2

(Example 2)

[0043]In Example 2, coal cakes were produced by varying the moisture content of the blended coal C, and their strength was evaluated. The production conditions and evaluation results are listed in Table 2.

[Table 2]

[0044]

Table 2

Carbonaceous material ACarbonaceous material BBlended coal CRate of change in coal cake properties due to mixing in of carbonaceous material B

Ratio of particles with a particle size of 0.5 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbonaceous material A (mass%)Type of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material B (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbon material B (mass%)Mass ratio of carbonaceous material B to carbonaceous material A (mass%)Moisture content of blended coal C (mass%)Density ratioStrength ratio

Example 82612Coke powder100100171.011.15

Example 92612Coke powder100100371.011.33

Ex...

TECHNICAL FIELD

[0001] The present disclosure relates to a method of producing a coal cake and a method of producing metallurgical coke, and more particularly to a method of producing a coal cake and a method of producing metallurgical coke in a stamp charging coke oven.BACKGROUND

[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 to ensure good gas permeability inside the blast furnace. It is known that high-strength coke is suitable for efficient operation of a blast furnace. This is because when coke is pulverized in a blast furnace, the resulting powder reduces the permeability of the blast furnace, making it impossible to operate the blast furnace efficiently.

[0003] It is known that increasing the bulk density of coal charged into a coke oven is effective for producing high-strength coke, and stamp charging coke ovens are used for this purpose. In the typical coke ovens currently used in Japan (hereinafter referred to as "top charging coke ovens"), coal, which is the raw material for coke, is charged by gravity from the top of the coke oven's carbonization chamber, and the bulk density of the gravity-charged coal is 700 kg-dry / m 3< to 800 kg-dry / m 3< .

[0004] On the other hand, in a stamp charging coke oven, the coal is compacted by a stamping device located on the side of the coke oven carbonization chamber before being charged into the coke oven to be processed into a coal cake with a bulk density of 1,000 kg-dry / m 3< or more. The resulting coal cake is then mechanically pushed from the side into the coke oven carbonization chamber. By using a stamp charging coke oven, the density of the coke raw material can be increased before carbonization, and higher-strength coke can be produced compared to a top charging coke oven. Also, productivity can be increased by increasing the charge per kiln.

[0005] As described above, stamp charging coke ovens are superior to top charging coke ovens in terms of coke strength and productivity. However, if the strength of the coal cake produced by stamping is low, the coal cake may collapse during charging into the carbonization chamber of the coke oven, causing operational problems. Therefore, for stable operation of stamp charging coke ovens, a technique to produce a high-strength coal cake is required. Furthermore, in response to the recent social demand for reducing CO 2 emissions, demand exists for techniques that can improve the density of coal cakes and achieve further improvements in productivity.

[0006] Regarding the relationship between coal particle size and coal cake strength, Non-patent Literature (NPL) 1 reports on a test conducted by changing the degree of grinding of the coal cake raw material. NPL 1 reports that the strength of the coal cake was improved by increasing the ratio of fine particles with a particle size of 3.15 mm or less in the raw material, i.e., by grinding the coal cake raw material more finely.

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

[0008] PTL 1: JP H7-109467 ANon-patent Literature

[0009] NPL 1: M. Rejdak, et al., Physicochem. Probl. Miner. Process. 51(1), 2015, 151. NPL 2: SH Krishnan, et al., "Application of Binder in Stamp Charge Coke Making", ISIJ International, 44(2004), 1150. SUMMARY(Technical Problem)

[0010] NPL 1 reports that by grinding the raw materials of the coal cake more finely, the strength of the coal cake is improved, but the density of the coal cake is reduced. That is, the method of intensifying the grinding of the coal cake raw materials and reducing the particle size of the raw materials improves the strength of the coal cake and contributes to stable operation of the stamp charge furnace, but the density of the coal cake decreases, resulting in a relative decrease in productivity.

[0011] Furthermore, in the methods using a caking binder described in PTL 1 and NPL 2, the caking raw material adheres to the belt conveyor and the stamping device during the process of transporting the coke raw material containing the caking binder and during the process of compacting the raw material with a stamping device. This necessitates frequent cleaning of the device, resulting in a problem of reduced productivity.

[0012] An aim of the present disclosure is to provide a method of producing a coal cake that can improve both the strength of the coal cake and productivity.(Solution to Problem)

[0013] We have conducted extensive studies to solve the aforementioned technical problem and have made the following discovery. The density and strength of the coal cake can be improved by stamping blended coal prepared by blending a small amount of a pulverized coal material with blended coal having a ground particle size ordinarily used in a stamp charging oven.

[0014] The primary features of the present disclosure are as follows. [1] A method of producing a coal cake in a stamp charging coke oven, the method comprising: stamping a blended coal C to obtain a coal cake, the blended coal C being obtained by mixing a carbonaceous material A and a carbonaceous material B so that a 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, wherein the carbonaceous material A has a ratio of particles with a particle size of 0.5 mm or less of 50 mass% or less, and a ratio of particles with a particle size of 0.1 mm or less of 20 mass% or less, and the carbonaceous material B has a ratio of particles with a particle size of 0.5 mm or less of 80 mass% or more, and a ratio of particles with a particle size of 0. 1 mm or less of 50 mass% or more. [2] A method of producing metallurgical coke, the method comprising carbonizing a coal cake produced by the method according to [1] in a coke oven to obtain coke. (Advantageous Effect)

[0015] According to the present disclosure, a method of producing a coal cake that can improve both the strength of the coal cake and productivity in a stamp charging oven can be provided. Furthermore, according to the present disclosure, by improving the strength of the coal cake, problems such as collapse of the coal cake can be reduced, enabling stable operation of the stamp charging oven. In addition, by increasing the density of the coal cake, the productivity of the stamp charging oven can be improved.DETAILED DESCRIPTION

[0016] Embodiments of the present disclosure are described below. A method of producing a coal cake according to the present disclosure is a method of producing a coal cake in a stamp charging coke oven and includes preparing a carbonaceous material A that has a ratio of particles with a particle size of 0.5 mm or less of 50 mass% or less, and a ratio of particles with a particle size of 0.1 mm or less of 20 mass% or less, and a carbonaceous material B that has a ratio of particles with a particle size of 0.5 mm or less of 80 mass% or more, and a ratio of particles with a particle size of 0.1 mm or less of 50 mass% or more, and stamping a blended coal C to obtain a coal cake, the blended coal C being obtained by mixing the carbonaceous material A and the pulverized carbonaceous material B so that the mass ratio of the pulverized carbonaceous material B to 100 mass% of the carbonaceous material A is 0.5 mass% or more and 15 mass% or less.[Carbonaceous material A]

[0017] The carbonaceous material A in the present disclosure is a typical raw material that has been conventionally used as a coke raw material in top charging coke ovens and stamp charging coke ovens and may be produced by grinding the raw material using a hammer crusher or the like so that the proportion of particles having a particle size of 3 mm or less is 70 mass% or more, as is done in conventional coke oven operations. The "ratio of particles with a particle size of 3 mm or less" refers to the ratio of the mass of a raw material passing through a sieve to the total mass of the raw material when the raw material is sieved using a 3 mm sieve. The same definition applies in this specification when the particle size differs.

[0018] To obtain the effects of the present disclosure, the particle size of the carbonaceous material A must be significantly different from that of the carbonaceous material B and therefore must be at least a certain level. Specifically, the ratio of particles with a particle size of 0.5 mm or less must be 50 mass% or less, and the ratio of particles with a particle size of 0.1 mm or less must be 20 mass% or less. However, since the effects of the present disclosure can be enhanced by making the difference in particle size between carbonaceous material A and carbonaceous material B more significant, the particle size of the carbonaceous material A is preferably larger. Specifically, the ratio of particles having a particle size of 0.5 mm or less is preferably 40 mass% or less. The ratio of particles having a particle size of 0.1 mm or less is preferably 15 mass% or less. The ratio of particles having a particle size of 0.5 mm or less is more preferably 35 mass% or less. The ratio of particles having a particle size of 0.1 mm or less is more preferably 12 mass% or less.

[0019] The raw material for the carbonaceous material A forming part of the coal cake mainly includes raw coal generally used for coke production, but other raw materials, such as non-caking or slightly-caking coal, oil coke, pitches, biomass, other raw materials mainly composed of carbon, and carbides obtained by heating the aforementioned raw materials may also be used, as long as the quality of the coke after carbonization is not problematic. Furthermore, when a plurality of raw materials is used as the carbonaceous material A, each raw material may be individually ground and then blended for use as the carbonaceous material A, or the plurality of raw materials may be blended and then ground together.[Charcoal material B]

[0020] In the present disclosure, by blending a portion of the carbonaceous material B having a sufficiently low particle size with the carbonaceous material A, the density and strength of the coal cake can be improved. To obtain the effects of the present disclosure, the particle size of the carbonaceous material B must be such that the ratio of particles with a particle size of 0.5 mm or less is 80 mass% or more and the ratio of particles with a particle size of 0.1 mm or less is 50 mass% or more. To obtain a greater effect of improving the density and strength of the coal cake, the ratio of particles with a particle size of 0.5 mm or less is preferably 82 mass% or more. The ratio of particles with a particle size of 0.1 mm or less is preferably 56 mass% or more. The ratio of particles with a particle size of 0.5 mm or less is more preferably 85 mass% or more. The ratio of particles with a particle size of 0.1 mm or less is more preferably 70 mass% or more.

[0021] The raw material for the carbonaceous material B mainly includes raw coal generally used for coke production, but other raw materials, such as non-caking or slightly-caking coal, oil coke, pitches, biomass, other raw materials mainly composed of carbon, and carbides obtained by heating the aforementioned raw materials may also be used, as long as the quality of the coke after carbonization is not problematic. A portion of the carbonaceous material A may be removed and pulverized to obtain the carbonaceous material B.

[0022] The method of adjusting the particle size of the carbonaceous material B is not particularly limited as long as a predetermined particle size is obtained, but equipment such as a ball mill, roller mill, tower mill, bead mill, or jet mill, for example, can be used. Furthermore, carbonaceous material generated in a steelworks and satisfying the aforementioned particle size conditions may be used as carbonaceous material B without adjusting the particle size. Examples of raw materials generated in the steelworks include collected dust obtained by recovering powder generated by a coke dry quenching (CDQ) system or by coke conveying. Furthermore, when a plurality of raw materials is used as the carbonaceous material B, each raw material may be individually ground and then blended for use as the carbonaceous material B, or the plurality of raw materials may be blended and then ground together.[Blended coal C]

[0023] The blended coal C is obtained by mixing the carbonaceous material A and the pulverized carbonaceous material B. To obtain the effect of improving the density and strength of the coal cake according to the present disclosure, the mass ratio of the carbonaceous material B relative to 100 mass% of the carbonaceous material A must be 0.5 mass% or more. To obtain a greater effect, the mass ratio of the carbonaceous material B is more preferably 1 mass% or more. The mass ratio of the carbonaceous material B is more preferably 2 mass% or more. On the other hand, the purpose of the present disclosure is not to pulverize the entire coal cake raw material, but to add a part of the carbonaceous material B having a particle size smaller than that of the carbonaceous material A to the carbonaceous material A, which has been ground to an ordinary ground particle size. This has the unique effect of improving both the density and strength of the coal cake, as will be illustrated in the examples below. Therefore, the mass ratio of the carbonaceous material B to 100 mass% of the carbonaceous material A must be 15 mass% or less. Considering that the production of pulverized carbonaceous material requires an increased grinding capacity, from the perspective of economic efficiency, the mass ratio of the carbonaceous material B is preferably 12 mass% or less. The mass ratio of the carbonaceous material B is more preferably 10 mass% or less.

[0024] The method of mixing the carbonaceous material A and the carbonaceous material B is not particularly limited, and a mixer generally used for mixing coal in a coke plant may be used. Another example is a method in which the carbonaceous material A and the carbonaceous material B are placed on the same belt conveyor and mixed by the flow that occurs during transfer between conveyors.

[0025] The moisture content of the blended coal C is preferably 9 mass% to 12 mass% in order to maximize the strength of the coal cake. The moisture content can be adjusted by treatment such as drying using coal moisture control equipment or spraying water from a nozzle. The moisture adjustment is preferably carried out after the carbonaceous material A and the carbonaceous material B are mixed but may be carried out before or after the carbonaceous material A and the carbonaceous material B are ground, depending on the layout of the factory. However, as will be explained with reference to data in Example 2 below, the effects of the present disclosure can be obtained as long as the moisture content of the blended coal C is between 7 mass% and 13 mass%. The moisture of coal stored in a yard varies depending on the season and weather, but the range of variation is within a range of approximately 7 mass% to 13 mass%. Therefore, the moisture content range for obtaining the effects of the present disclosure is not particularly limited within the range of ordinary coke production conditions.<Production of coal cake>

[0026] In the present disclosure, a high-strength coal cake can be produced by stamping and compacting the aforementioned blended coal C.

[0027] A coal cake may be produced from the blended coal C prepared as described above by using a stamping device that compacts raw materials by impact with a falling weight. In this case, a coal cake having a higher density and higher strength than when only using the carbonaceous material A can be produced by using the blended coal C, in which the carbonaceous material B is blended with the carbonaceous material A as a raw material. As a result, the coal cake is less likely to collapse, and the coke oven can be operated stably. In addition, productivity is improved by increasing the amount of coal charged per kiln.

[0028] Although the factors that improve the density and strength of the coal cake are not completely clear, it is speculated that this is due to the carbonaceous material B penetrating between the particles of the carbonaceous material A, functioning as a lubricant, and improving the fluidity of the carbonaceous material as a whole. By improving the fluidity of the carbonaceous material as a whole, stamping with the same energy is more likely to provoke particle rearrangement, which is thought to result in the production of a coal cake with higher density and higher strength.(Method of producing metallurgical coke)

[0029] Next, a method of producing metallurgical coke according to the present disclosure will be described. The method of producing metallurgical coke according to the present disclosure includes carbonizing, in a coke oven, the coal cake produced by the above-described method of producing a coal cake according to the present disclosure.

[0030] The coal cake produced by the above-described method of producing a coal cake according to the present disclosure is mechanically charged into the coke oven carbonization chamber from the side. At this time, the coal cake is subjected to its own weight and to impact from vibration of the charging machine. If the strength of the coal cake is low, an operational problem may occur in which the coal cake collapses during charging. However, by use of the blended coal C, which is a mixture of the carbonaceous material A and the carbonaceous material B having a smaller particle size than the carbonaceous material A, as the raw material for the coal cake, the strength of the coal cake is improved, and the collapse of the coal cake can be prevented. Furthermore, the coal cake produced from the blended coal C, which is a mixture of the carbonaceous material A and the carbonaceous material B having a smaller particle size than the carbonaceous material A, has a higher density than the coal cake produced by conventional methods. The amount of coal charged per kiln is therefore increased, thereby improving productivity.

[0031] No particular restrictions are placed on the conditions for carbonizing the coal cake. The coal cake may be carbonized at a temperature of approximately 900 °C or higher in a typical stamp charging coke oven.EXAMPLES

[0032] Examples of the present disclosure will be described below, but 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.(Example 1)

[0033] In Example 1, different carbonaceous materials A and B were blended and mixed to produce a coal cake, and the strength of the coal cake was evaluated. The production conditions and evaluation results are listed in Table 1.

[0034] Specifically, a blended coal containing a plurality of coals was used as the carbonaceous material A and was ground to the particle sizes listed in Table 1 before use. As the carbonaceous material B, coke powder, non-caking or slightly-caking coal, and carbonized biomass were ground to the particle sizes listed in Table 1 before use. Then, the carbonaceous material A and the carbonaceous material B were blended and mixed at the blending ratios listed in Table 1 to prepare a blended coal C, and the moisture content of the blended coal C was then adjusted to 10 mass%.

[0035] A coal cake was produced in the following manner using the blended coal C prepared by the above-described procedure. First, approximately 200 g of the blended coal C was charged into a metal mold having an inner diameter of 10 cm and a height of 20 cm, and a rammer having a mass of 9 kg was dropped 10 times from a height of 30 cm from the surface of the sample, thereby compacting the charged blended coal C by the impact. This procedure, from charging the blended coal C to dropping the rammer, was repeated 10 times to produce a coal cake having a diameter of 10 cm, a height of 20 cm, and a mass of approximately 2 kg. Thereafter, the mold was gently removed from the coal cake, and the dry density and strength of the coal cake were measured.

[0036] The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio listed in Table 1 are the ratios of the coal cake produced from the blended coal C, into which the carbonaceous material B was mixed, relative to the dry density and strength of a coal cake produced by the above procedure using only the carbonaceous material A, without mixing in the carbonaceous material B, which are set to 1. Therefore, when the density ratio and the strength ratio are each greater than 1, it can be determined that the properties of the coal cake have been improved by the present disclosure, i.e., by mixing the carbonaceous material B, which has a smaller particle size than the carbonaceous material A, in with the carbonaceous material A.[Table 1]

[0037] Table 1Carbonaceous material ACarbonaceous material BBlended coal CRate of change in coal cake properties due to mixing in of carbonaceous material BRatio of particles with a particle size of 3 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.5 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbonaceous material A (mass%)Type of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material B (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbon material B (mass%)Mass ratio of carbonaceous material B to carbonaceous material A (mass%)Moisture content of blended coal C (mass%)Density ratioStrength ratioComparative Example 193287Coke powder8875101.000.99Comparative Example 293287Coke powder88205100.981.16Comparative Example 393287Coke powder882010100.971.10Example 11004015Coke powder1001001101.011.26Example 21004015Coke powder1001003101.021.40Comparative Example 493287Non-caking coal3175101.001.02Comparative Example 593287Non-caking coal70215100.991.10Comparative Example 693287Non-caking coal702110100.981.12Example 393287Non-caking coal98725101.021.46Example 493287Non-caking coal987210101.021.74Comparative Example 793287Non-caking coal987220100.991.33Example 578165Carbonized biomass82562101.011.23Example 678165Carbonized biomass82564101.011.33Example 778165Carbonized biomass82566101.011.36

[0038] In Comparative Examples 1 and 4, the carbonaceous material B that is mixed in has a particle size approximately the same as that of the carbonaceous material A. In this case, the density and strength of the coal cake hardly change as a result of mixing in the carbonaceous material B. In Comparative Examples 2, 3, 5, and 6, the carbonaceous material B mixed with the carbonaceous material A has a relatively small particle size. In this case, the strength ratio becomes greater than 1 due to the mixing in of the carbonaceous material B, whereas the density ratio becomes smaller than 1. It has been reported in NPL 1, for example, that a reduction in the particle size of the raw material improves strength but lowers density, and the present results are in line with such findings in the prior art.

[0039] On the other hand, in Examples 1 to 7, the carbonaceous material B mixed with the carbonaceous material A has been pulverized sufficiently to achieve the effects of the present disclosure. It can be seen that by mixing carbonaceous material B, both the density ratio and the strength ratio become larger than 1, and the properties of the coal cake are improved. Furthermore, when Comparative Examples 5 and 6 are compared with Examples 3 and 4, the strength improving effect of the Examples is clearly greater than that of the Comparative Examples. Therefore, it is thought that the strength of the coal cake was improved by mixing the carbonaceous material B, which has a smaller particle size than the carbonaceous material A, in with the carbonaceous material A. In addition, although Examples 1 to 7 of the present disclosure only describe examples in which the ratio of particles with a particle size of 3 mm or less is 78 mass% to 100 mass%, the same effect can be obtained as a result of mixing in the carbonaceous material B even when the carbonaceous material A has a larger particle size (a ratio of particles with a particle size of 3 mm or less of 70 mass%).

[0040] In Comparative Example 7, 20 mass% of sufficiently pulverized carbonaceous material B was mixed with the carbonaceous material A, but in this case, the density of the coal cake decreased. If the proportion of carbonaceous material B, which has a smaller particle size than carbonaceous material A, is too high, there will be an excess of the carbonaceous material B in the gaps between the carbonaceous material A, which has a larger particle size, as described above. This is thought to impede the full achievement of the effects of the disclosure.

[0041] As described above, the present disclosure not only stabilizes the operation of a coke oven by improving the strength of the coal cake but also improves productivity by increasing the density of the coal cake.

[0042] As is clear from the present example, the raw material of the carbonaceous material B for obtaining the effects of the present disclosure is not particularly limited. If coke powder or non-caking coal generated in a steelworks is used as the carbonaceous material B, the effects of the present disclosure can be obtained at a relatively low cost. Furthermore, using a carbon-neutral raw material such as carbonized biomass as the carbonaceous material B can contribute to reducing CO 2 emissions, which meets current social demands.(Example 2)

[0043] In Example 2, coal cakes were produced by varying the moisture content of the blended coal C, and their strength was evaluated. The production conditions and evaluation results are listed in Table 2.[Table 2]

[0044] Table 2Carbonaceous material ACarbonaceous material BBlended coal CRate of change in coal cake properties due to mixing in of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbonaceous material A (mass%)Type of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material B (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbon material B (mass%)Mass ratio of carbonaceous material B to carbonaceous material A (mass%)Moisture content of blended coal C (mass%)Density ratioStrength ratioExample 82612Coke powder100100171.011.15Example 92612Coke powder100100371.011.33Example 102612Coke powder1001001131.011.06Example 112612Coke powder1001003131.021.15

[0045] Specifically, a blended coal containing a plurality of coals was used as the carbonaceous material A and was ground to the particle sizes listed in Table 2 before use. As the carbonaceous material B, coke powder was ground to the particle sizes listed in Table 2 before use. Then, the carbonaceous material A and the carbonaceous material B were blended and mixed at the blending ratios listed in Table 2 to prepare a blended coal C, and the moisture content of the blended coal C was then adjusted to 7 mass% or 13 mass%.

[0046] A coal cake was produced in the following manner using the blended coal C prepared by the above-described procedure. First, approximately 200 g of the blended coal C was charged into a metal mold having an inner diameter of 10 cm and a height of 20 cm, and a rammer having a mass of 9 kg was dropped 10 times from a height of 30 cm from the surface of the sample, thereby compacting the charged blended coal C by the impact. This procedure, from charging the blended coal C to dropping the rammer, was repeated 10 times to produce a coal cake having a diameter of 10 cm, a height of 20 cm, and a mass of approximately 2 kg. Thereafter, the mold was gently removed from the coal cake, and the dry density and strength of the coal cake were measured.

[0047] The strength of the coal cake was evaluated by the uniaxial compressive strength specified in JIS A 1216. The density ratio and strength ratio listed in Table 2 are the ratios of the coal cake produced from the blended coal C, into which the carbonaceous material B was mixed, relative to the dry density and strength of a coal cake produced by the above procedure using only the carbonaceous material A, without mixing in the carbonaceous material B, which are set to 1. Therefore, when the density ratio and the strength ratio are each greater than 1, it can be determined that the properties of the coal cake have been improved by mixing in the carbonaceous material B.

[0048] As illustrated in Table 2, regardless of whether the moisture content of the blended coal C was 7 mass% or 13 mass%, by mixing the carbonaceous material B, which had a smaller particle size than the carbonaceous material A, in with the carbonaceous material A, the density ratio and strength ratio became 1 or more, and the properties of the coal cake improved. The moisture content of coal stored in a yard varies depending on the season and weather, but the range of variation is approximately 7 mass% to 13 mass%. Therefore, as is clear from Tables 1 and 2, the present disclosure can be widely used when the moisture content of the blended coal C varies within the range of 7 mass% to 13 mass%.INDUSTRIAL APPLICABILITY

[0049] According to the present disclosure, a method of producing a coal cake that can improve both the strength of the coal cake and productivity can be provided.

Examples

example 1

(Example 1)

[0033]In Example 1, different carbonaceous materials A and B were blended and mixed to produce a coal cake, and the strength of the coal cake was evaluated. The production conditions and evaluation results are listed in Table 1.

[0034]Specifically, a blended coal containing a plurality of coals was used as the carbonaceous material A and was ground to the particle sizes listed in Table 1 before use. As the carbonaceous material B, coke powder, non-caking or slightly-caking coal, and carbonized biomass were ground to the particle sizes listed in Table 1 before use. Then, the carbonaceous material A and the carbonaceous material B were blended and mixed at the blending ratios listed in Table 1 to prepare a blended coal C, and the moisture content of the blended coal C was then adjusted to 10 mass%.

[0035]A coal cake was produced in the following manner using the blended coal C prepared by the above-described procedure. First, approximately 200 g of the blended coal C was char...

example 2

(Example 2)

[0043]In Example 2, coal cakes were produced by varying the moisture content of the blended coal C, and their strength was evaluated. The production conditions and evaluation results are listed in Table 2.

[Table 2]

[0044]

Table 2

Carbonaceous material ACarbonaceous material BBlended coal CRate of change in coal cake properties due to mixing in of carbonaceous material B

Ratio of particles with a particle size of 0.5 mm or less in carbonaceous material A (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbonaceous material A (mass%)Type of carbonaceous material BRatio of particles with a particle size of 0.5 mm or less in carbonaceous material B (mass%)Ratio of particles with a particle size of 0.1 mm or less in carbon material B (mass%)Mass ratio of carbonaceous material B to carbonaceous material A (mass%)Moisture content of blended coal C (mass%)Density ratioStrength ratio

Example 82612Coke powder100100171.011.15

Example 92612Coke powder100100371.011.33

Ex...

Claims

1. A method of producing a coal cake in a stamp charging coke oven, the method comprising: stamping a blended coal C to obtain a coal cake, the blended coal C being obtained by mixing a carbonaceous material A and a carbonaceous material B so that a 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, wherein the carbonaceous material A has a ratio of particles with a particle size of 0.5 mm or less of 50 mass% or less, and a ratio of particles with a particle size of 0.1 mm or less of 20 mass% or less, and the carbonaceous material B has a ratio of particles with a particle size of 0.5 mm or less of 80 mass% or more, and a ratio of particles with a particle size of 0.1 mm or less of 50 mass% or more.

2. A method of producing metallurgical coke, the method comprising carbonizing a coal cake produced by the method according to claim 1 in a coke oven to obtain coke.

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