Method for producing metallurgical coke

Abstract

To provide a high-strength metallurgical coke with an appropriate particle size that can contribute to ensuring gas permeability in a blast furnace while using a larger amount of coal with poor caking properties than conventional methods.SOLUTION: When producing coke by dry distillation of a coal blend composed of molded coal manufactured by mechanically compacting and molding raw material A and the remaining powdery raw material B (fine coal), the raw material A is set to have a common logarithm value of maximum fluidity (logMF) of 1.50 or less as measured by the fluidity test method (Gieseler plastometer method) specified in JIS M 8801, and a maximum particle diameter of 300 μm or less, while the raw material B is set to have the common logarithm value of maximum fluidity (logMF) of 2.30 or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing metallurgical coke that enables a significant increase in the amount of raw materials with poor caking properties used in a molded coal blending method, in which the amount of raw materials with poor caking properties can be increased by mechanically compacting a portion of the raw materials. [Background technology]

[0002] Currently, in the production of pig iron using a blast furnace, coke produced by carbonizing coal in a chamber 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 the fluidity of coal during carbonization is important for producing high-strength metallurgical coke that can ensure gas permeability in such a blast furnace. For example, Non-Patent Document 1 reports that, in a fluidity measurement method using a Gieseler Plastometer, the coal must exhibit a fluidity of at least 200 ddpm (common logarithm 2.30), and preferably 400 ddpm (common logarithm 2.60) or more.

[0003] However, coking coal, which has sufficient fluidity to produce high-strength coke as described above, tends to be more expensive than steam coal used for fuel. In addition, resource reserves are limited, and there are concerns that they will be depleted in the future. Therefore, in order to reduce raw material costs and continue operating blast furnaces using a variety of raw materials, there is a strong demand for the development of coke production technology that allows the use of a large amount of raw materials with poor fluidity during carbonization.

[0004] To meet such demands, efforts have been made to increase the use of coal with poor fluidity by using techniques that utilize briquetted coal. For example, Patent Document 1 describes a method in which the thermoplasticity and melting properties of a coal blend used in briquettes are calculated as a weighted average of the total expansion coefficients of the constituent coals. If this value is below a certain level, the method performs a crushing operation to increase the proportion of coal particles with a particle size of 3 mm or less, thereby enabling the production of coke with sufficient coke strength even when the briquettes contain a large amount of inferior coal.

[0005] Furthermore, Patent Document 2 describes a method for obtaining coke with sufficient coke strength by adding a caking filler when the blended coal used for molding contains a large amount of inferior coal with a small total expansion coefficient.

[0006] Recent research has shown that a method for producing high-strength agglomerates that can withstand blast furnace use from coal with poor fluidity involves first pulverizing the coal to 106 μm or less (approximately 3 mm or less in the normal coke manufacturing process), then compacting and molding the coal in a mold 15 mm in diameter and 20 mm deep, followed by carbonization, which has been reported to produce high-strength agglomerates with an indirect tensile strength exceeding 10 MPa (compared to 5 MPa for normal coke) (Non-Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-117279 [Patent Document 2] JP 2016-65111 A [Non-patent literature]

[0008] [Non-Patent Document 1] Miyazu et al., Japan Steel Pipe Engineering Report, 67 (1975), 1 [Non-patent document 2] M. Matoba, et Al., ISIJ international, 59(2019), 1440. [Non-patent document 3] K. Uchida, et Al., ISIJ international, 59(2019), 1449. Summary of the Invention [Problem to be solved by the invention]

[0009] However, when producing coke by carbonizing molded coal blended with inferior-quality coal together with powdered coal, even if the particle size of the coal is adjusted by the method described in Patent Document 1 or a caking filler is added by the method described in Patent Document 2, if the proportion of inferior-quality coal, i.e., coal with low fluidity, is high, the coke strength still decreases and sufficient strength may not be obtained.

[0010] Furthermore, Non-Patent Documents 2 and 3 report that high-strength agglomerates can be produced using only coal with poor melting property, without using any caking filler. However, the molding methods using molds reported in the literature are insufficient in terms of production speed to be applied to coke production, which uses several thousand to several tens of thousands of tons of coal per day.

[0011] Furthermore, one of the important roles of coke in a blast furnace is to ensure gas permeability as a spacer inside the furnace, and a particle size of at least a certain level is required. Although the methods described in Non-Patent Documents 2 and 3 can produce high-strength agglomerates, it is extremely difficult to produce coke with a particle size sufficient to ensure gas permeability in the blast furnace.

[0012] The present invention has been made in consideration of the above circumstances, and aims to provide a metallurgical coke with high strength and an appropriate particle size that can contribute to ensuring gas permeability in a blast furnace while using a larger amount of raw materials such as coal or biomass, which have poor caking properties, than conventionally. [Means for solving the problem]

[0013] That is, the gist of the present invention is as follows. 1. A method for producing metallurgical coke, in which raw material A' is formed by molding raw material A through mechanical compaction into molded coal, and raw material A' is blended with powdered raw material B (powdered coal) to produce a blended coal, which is then carbonized to produce coke, wherein raw material A has a common logarithm of the maximum fluidity (logMF) of 1.50 or less in the fluidity test method (Gieseler Plastometer method) specified in JIS M 8801, raw material A has a maximum particle size of 300 μm or less, and raw material B has a common logarithm of the maximum fluidity (logMF) of 2.30 or more.

[0014] 2. The method for producing metallurgical coke described in 1 above, wherein a double-roll molding machine is used for the mechanical compaction.

[0015] 3. The density of the raw material A' is 1.00 g / cm 3 3. The method for producing metallurgical coke according to 1 or 2 above.

[0016] 4. The method for producing metallurgical coke according to any one of the above items 1 to 3, wherein the mass ratio of raw material A' to the total mass of raw material A' and raw material B is 0.30 or less. [Effects of the Invention]

[0017] According to the present invention, even when a larger amount of raw material with poor caking properties is used than in the past, by compacting the finely pulverized raw material, it is possible to prevent a significant decrease in the drum strength of the coke, which is a problem when the above raw material is used as a coke raw material. In addition, by using a raw material with a certain level of fluidity for the powdered coal, a good bond can be formed at the interface between the molded coal and the powdered coal, which can advantageously solve issues related to productivity and coke particle size. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing the state of filling into an 'alumina crucible' used in the examples. [Figure 2] This is a photograph of the interface between raw coal 1 (right) and molded coal 6 (left). [Figure 3] This is a photograph of the interface between raw coal 2 (left) and molded coal 6 (right). DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention relates to a method for producing metallurgical coke by carbonizing a coal blend obtained by blending powdered raw material B (also referred to as powdered coal in the present invention) with molded coal (also referred to as raw material A' in the present invention), which is produced by molding a part of the raw material (referred to as raw material A in the present invention) by mechanical compaction, to produce coke. In particular, raw material A has a common logarithm of maximum fluidity (logMF) of 1.50 or less in the fluidity test method (Gieseler Plastometer method) specified in JIS M 8801 (hereinafter referred to as "JIS8801"), and a maximum particle size of 300 μm or less. In addition, raw material B has a common logarithm of maximum fluidity (logMF) of 2.30 or more in the fluidity test method. In the following, the maximum fluidity (MF) in the fluidity test method (Gieseler Plastometer method) specified in JIS8801 may be simply referred to as maximum fluidity or fluidity.

[0020] [The raw material A is subjected to a fluidity test using the Gieseler Plastometer method specified in JIS 8801, in which the common logarithm of the maximum fluidity (logMF) is 1.50 or less] The raw material A (raw material for molded coal) in the present invention has a common logarithm of the maximum fluidity (logMF) of 1.50 or less in the fluidity test method (Gieseler Plastometer method) specified in JIS8801. The purpose of the present invention is to enable the use of a low-fluidity raw material as a coke raw material while suppressing a decrease in coke strength, when the raw material has low fluidity and would otherwise be subject to a significant decrease in coke strength in a conventional manufacturing method. In other words, pulverizing and using highly fluid raw materials that can be used in normal coke production in accordance with the present invention is not economically desirable because the pulverization is costly and the improvement in coke strength is limited. Therefore, it is essential to use raw material A whose common logarithm of the maximum fluidity is 1.50 or less, and preferably 1.30 or less.

[0021] In coke production, raw materials with different fluidities are generally blended to form raw material A. In such a case, in the present invention, the raw materials are blended so that the weighted average value calculated from the common logarithm of the maximum fluidity of each raw material that is the raw material of raw material A and the mass proportion of each raw material is 1.50 or less, and the blended raw material can be used as raw material A used in the present invention.

[0022] Here, for raw materials that do not exhibit any fluidity at all, i.e., raw materials whose maximum fluidity (MF) is 0 ddpm in the fluidity test method (Gieseler Plastometer method) specified in JIS8801, the common logarithm of the maximum fluidity (logMF) is set to 0 in the calculation.

[0023] Because bonds are formed between particles inside the molded coal by a solid-phase sintering-like phenomenon rather than by the conventional liquid-phase sintering-like phenomenon, there is no particular lower limit on the maximum fluidity of raw material A. Therefore, even raw materials that exhibit no fluidity at all can be used as coke raw materials in the present invention. Therefore, the lower limit of the logMF is not particularly limited and may be 0.00.

[0024] Furthermore, in the present invention, the carbonaceous material serving as raw material A is not particularly limited as long as it has low fluidity and is primarily carbon. However, in addition to coal, biomass, precipitated carbon, and the like can also be used. The carbides obtained by heat-treating these materials, as well as mixtures thereof, are also suitable. When using a large amount of raw materials with a high volatile content, such as low-quality coal or biomass, it is preferable to heat-treat the raw material in advance to reduce the volatile content to 30 mass% or less. This increases the yield of coke and prevents the expansion of gas from inhibiting solid-phase sintering-like phenomena. On the other hand, if the volatile content is too low, aromatization and polycyclization, which are the driving forces behind solid-phase sintering-like phenomena, become difficult to occur. Therefore, the volatile content is preferably 1 mass% or more, and more preferably 6 mass% or more. The volatile content can be adjusted by heat treatment in an atmosphere where oxygen supply is blocked, for example, by storing the raw materials in a container that blocks air inflow and forms a space through which an inert gas flows. The container containing the raw materials can be heated and heat transferred from the container. The heat treatment temperature can be, for example, 400°C or higher.

[0025] [Raw material A, maximum particle size 300 μm or less] In the present invention, raw material A is pulverized so that the maximum particle size is 300 μm or less. If raw material A contains more than 5% coarse particles with a particle size of over 300 μm, these coarse particles will remain in the molded coal after carbonization, reducing its strength. This is because the smaller the particle size, the more accelerated the solid-phase sintering phenomenon that bonds particles together, so the remaining coarse particles will inhibit the bonding between particles and cause a decrease in strength.

[0026] The maximum particle size of the raw material A is preferably 100 μm or less. A moderately small particle size of the carbonaceous material makes the physical structure in the molded coal dense and uniform, contributing to an increase in coke strength. The finer the particle size of the carbonaceous material, the better the bonding strength in the molded coal, which is preferable. Therefore, there is no lower limit for the maximum particle size of the raw material A. However, considering productivity, even when the particle size of the raw material A is reduced, setting the maximum particle size of the raw material A to less than 20 μm increases the cost of pulverization while limiting the improvement in coke strength. Therefore, it is preferable that the maximum particle size is about 20 μm or more.

[0027] In the present invention, the particle size refers to the maximum particle size unless otherwise specified. When measuring with a particle size distribution analyzer, the maximum particle diameter can be measured as follows. That is, in the present invention, the particle size and particle size distribution may be values ​​measured using a commercially available particle size distribution measuring device. Specifically, the particle size and particle size distribution (volume basis) measured using a laser diffraction / scattering particle size distribution measuring device "Laser Micronsizer LMS-3000" manufactured by Malvern Panalytical (hereinafter simply referred to as particle size distribution measuring device) are used.

[0028] In the present invention, the maximum particle size (maximum value) is defined as the particle size that is 95% of the particle size distribution of the particles contained in the mixed powder measured using a particle size distribution measuring device, calculated from the smallest particle size (the particle size at the lower limit of detection). Hereinafter, when simply referring to particle size or particle size distribution, it means the value measured using the particle size distribution measuring device.

[0029] In the present invention, the pulverization method and pulverization device are not particularly limited. Conventional pulverization methods may be used, and media mills such as cutter mills, hammer mills, pin mills, jet mills, and ball mills may be used as pulverization devices. In addition, the pulverization device is not limited to devices that only perform pulverization, and for example, a pulverizer with a built-in classifier may also be used.

[0030] [Raw material B has a common logarithm of the maximum fluidity (logMF) of 2.30 or more] In the present invention, by using a raw material B (powdered raw material or powdered coal) that has a certain level of fluidity when heated, a strong bond is formed at the interface between the molded coal and the powdered coal during carbonization, and the entire raw material is agglomerated, making it possible to produce high-strength coke with a particle size suitable for use in a blast furnace. Therefore, the fluidity of the powdered coal must be at least as high as that of the raw coal normally used in coke production. Specifically, raw material B must have a common logarithm of the maximum fluidity of 2.30 or more in the fluidity test method (Gieseler Plastometer method) specified in the aforementioned JIS 8801. From the viewpoint of producing stronger coke, the common logarithm is preferably 2.40 or more, and more preferably 2.60 or more. If the fluidity of Raw Material B is too high, the bond between the molded coal and the powder coal at the interface will be strong, but Raw Material B will expand excessively, reducing the density of the coke and possibly reducing the strength of the coke. Therefore, it is desirable that the common logarithm of the maximum fluidity of Raw Material B (logMF) be 3.00 or less.

[0031] In coke production, raw materials with different fluidities are generally blended and used as raw material B. In this case, the raw materials are blended so that the weighted average value calculated from the common logarithm of the maximum fluidity of each raw material that serves as the raw material of raw material B and the mass proportion of each raw material is 2.30 or more, and the blended raw materials can be used as raw material B used in the present invention.

[0032] [Manufacturing method of molded coal (raw material A')] From the viewpoint of ensuring coke strength, the method for producing molded coal is not particularly limited, but the use of a double-roll molder is preferred in order to increase the production rate of molded coal and achieve productivity appropriate for the amount of coke produced.

[0033] Generally, when producing molded coal, a binder may be used to improve the handleability of the molded coal. In the present invention, a binder can be added as needed to raw material A that satisfies the above-mentioned fluidity and particle size requirements. Examples of such binders that may be used include coal-based binders (coal tar pitch, solvent-refined coal, tar, tar slag, etc.), petroleum-based binders (asphalt, asphalt pitch, propane-deasphalted asphalt, etc.), and organic binders (starch, molasses, resin, etc.).

[0034] Furthermore, as a method for improving the handleability of molded coal without using a binder, a method of molding while forcing raw material A between double rolls with a screw can also be used. The closer the distance between particles in raw material A, the more the solid-phase sintering phenomenon is promoted and the stronger the bond between particles is formed during carbonization. Therefore, the density of molded coal (raw material A') is 1.00 g / cm 3 The above is preferable, and from the viewpoint of producing stronger coke, 1.05 g / cm 3 More preferably, it is 1.10 g / cm or more. 3 Although there is no particular upper limit to the density of the molded coal (raw material A'), if the molding pressure is too high in order to increase the density, rebound cracks will occur in the molded coal, and the yield will decrease, resulting in a decrease in productivity. Therefore, the target value for the density of the molded coal is 1.30 g / cm 3 The following is preferred:

[0035] In the present invention, there is no need to impose any restrictions on the size of the briquettes, and for example, briquettes having a volume of 6 to 120 cc may be used. In consideration of the strength of the briquettes, the size of the briquettes is preferably in the range of 6 to 80 cc, and more preferably in the range of 6 to 50 cc.

[0036] In the present invention, the production rate is preferably 45 tons / day or more in terms of processing capacity, since the process is applied to coke production using several thousand to several tens of thousands of tons of coal per day. On the other hand, the upper limit is not particularly limited, but industrially it is about 4,500 tons / day.

[0037] Furthermore, in the present invention, the type of raw material for the powdered coal is not particularly limited, and raw materials mainly consisting of raw coal generally used in coke production may be used. As raw materials for the powdered coal, in addition to coal, charcoal obtained by heat treatment of coal or biomass, and mixtures thereof may be used. Furthermore, pitches such as coal tar pitch and asphalt pitch may be used in part as raw materials for the powdered coal in order to improve the strength of the coke. In addition, even if a material does not fall under Raw Material A' (molded coal) or Raw Material B (powdered coal) (for example, lumps of plastics added for the purpose of gas recovery from waste), it is acceptable without any problems as long as it has the components and amounts used in conventionally known blended coal for coke production.

[0038] The particle size of the powdered coal is not particularly limited, and the powdered coal may be pulverized in accordance with a general coke manufacturing process so that the proportion of particles having a diameter of 3 mm or less is 70 to 100 mass %. Regarding the blending ratio of briquettes and powdered coal, it is desirable that the mass ratio of briquettes to the total raw material, including briquettes and powdered coal, is 30 mass% or less. In the present invention, bonds are formed within the briquettes by a solid-phase sintering-like phenomenon. Meanwhile, bonds are formed at the interface between the powdered coal and the briquettes by a liquid-phase sintering-like phenomenon that utilizes the fluidity of coal during carbonization. As a result, the entire raw material is agglomerated, and coke with a large particle size suitable for use in a blast furnace can be produced.

[0039] Therefore, if the proportion of powdered coal is too low, the adhesive strength between the molded coal and the powdered coal will be insufficient, making it impossible to produce coke with a large particle size. Therefore, the mass proportion of molded coal in the total raw material is desirably 30 mass% or less, and more preferably 25 mass% or less. Furthermore, from the viewpoint of the above-mentioned adhesion, there is no particular lower limit for the mass proportion of molded coal. However, in light of the purpose of using a large amount of low-fluidity raw material that has been difficult to use in the past, the mass proportion of molded coal is preferably 3 mass% or more, and more preferably 5 mass% or more.

[0040] The raw material pretreatment process in the present invention may include some or all of the steps of crushing, classifying, mixing, kneading, drying, adding water, and preheating. Carbonization may be carried out in a general chamber-type coke oven at a temperature of about 900°C or higher.

[0041] In the method for producing metallurgical coke according to the present invention, any item not described in this specification can be produced by a conventional method. [Example]

[0042] The present invention will be described below based on examples, but the present invention is not limited to the following examples. Example 1 The coals listed in Table 1 were used as raw material A. Coals 2 and 4 had a maximum fluidity of 0 ddpm, and since the common logarithm of the maximum fluidity could not be calculated, they were described as "not meltable." Furthermore, the briquette produced by briquetting raw material A was designated as raw material A'.

[0043] The molded coals (raw material A') 1 to 6 shown in Table 2 were produced by the following procedure. The coals listed in Table 1 were used as raw material A. First, each raw material was crushed to particle sizes of 3 mm or less, 106 μm or less, and 74 μm or less (hereinafter and in the tables, "less than" is indicated by a minus sign (-)). An ultracentrifugal crusher (manufacturer: Verder Scientific, model: ZM200) was used to crush the raw materials to -106 μm and -74 μm. Molded coals (raw material A') 1 to 4 were prepared by adding 6 mass% of tar and 6 mass% of tar pitch (both outer frames) as binders to 100 mass% of the pulverized coal 1 or 2 (raw material A), and thoroughly kneading them in a kneader to obtain a kneaded product. The kneaded product was then molded in a small double-roll molding machine equipped with a mold. In addition, molded coal (raw material A') 5-6 was molded using a small double-roll molding machine equipped with a screw in front of the rolls and a mold, by compressing the crushed coal 3 or 4 with the double rolls while pushing it with the screw.

[0044] In the following conventional examples, comparative examples, and invention examples, the raw coals shown in Table 3 were used as powdered coal (raw material B). In the present invention, the fluidity of the briquettes is extremely low compared to conventional methods, and since the briquettes are produced by grinding the briquettes to a finer particle size, they are carbonized together with the powdered coal. This leads to a decrease in the adhesion between the powdered coal and the briquettes, which is expected to be a factor in reducing the strength of the coke. The following experiment was conducted to investigate the effect of the fluidity of the powdered coal on the adhesion at the interface. Raw coals 1 and 2 listed in Table 3 were crushed to 1 mm (100%) and used as powdered coal. Each raw coal listed in Table 3 and molded coal 6 listed in Table 2 were packed into an alumina crucible as shown in Figure 1. At this time, the density of the powdered coal was 750 kg-dry / m 3 The alumina crucible filled with powdered coal and other materials was then covered with a lid and heated in an electric furnace from room temperature to 1000°C at a heating rate of 3°C / min. After cooling, the obtained coke sample was embedded in resin and cut, and the interface between the powdered coal and the molded coal was observed under a microscope.

[0045] [Table 1]

[0046] [Table 2]

[0047] [Table 3]

[0048] The observation results are shown in Figures 2 and 3. As shown in Figure 2, when raw coal 1 with low fluidity was used as the raw material for the powder coal, it was observed that the interior of the briquette and the powder coal were integrated, but there was no adhesion at all at the interface between the briquette and the powder coal, and uniform voids of about 200 μm were observed. It is thought that because the powder coal had low fluidity, good adhesion did not form at the interface between the briquette and the powder coal, and voids were generated at the interface due to the difference in the shrinkage rates of the two coals during carbonization.

[0049] On the other hand, when raw coal 2 with high fluidity was used as the powder coal raw material, a bond was formed at the interface between the briquettes and the powder coal, and it was observed that the briquettes and the powder coal were integrated, as shown in Figure 3. The results of this experiment confirmed that the fluidity of the powder coal is important for forming a bond at the interface between the briquettes and the powder coal and integrating the entire coke raw material, and that by using powder coal with a certain level of fluidity or higher, good adhesion can be formed at the interface between the briquettes and the powder coal.

[0050] Example 2 The effects of the present invention will be described below based on examples in which coke was produced and the coke strength was measured. First, a coal blend was prepared by blending powder coal (raw material B) and molded coal (raw material A') under the blending conditions shown in Table 4. In Conventional Examples 1 and 2, raw coals 3 and 4 shown in Table 3 were crushed to 100% -3 mm and used as powder coal, and only the powder coal was used as the blended coal. In Examples 1 and 2 of the present invention and Comparative Examples 1 to 6, raw coals 3 and 4 listed in Table 3 were crushed to 100% -3 mm and used as powder coal (80 mass% of the total), and coals 1 to 3 listed in Table 1 were either used as unbriquette (i.e., raw material A) or blended as briquette coal (raw material A') listed in Table 2 at 20 mass% of the total to form a blended coal. In Example 3 of the invention and Comparative Example 7, raw coal 4 listed in Table 3 was crushed to 100% -3 mm and used as powder coal (90 mass% of the total), and coal 4 listed in Table 1 was used either as unbriquette (i.e., raw material A) or as briquette coal (raw material A') listed in Table 2, making a blended coal at 10 mass% of the total.

[0051] When the blended coal was used without briquettes (Conventional Examples 1 and 2, Comparative Examples 2, 5, 6, and 7), the bulk density of the entire raw material was 750 (kg-dry / m 3 The mixture was charged into a stainless steel dry distillation vessel shown in Figure 1 so that the temperature was 100°C. In addition, when the blended coal contains briquettes (Comparative Examples 1, 3, and 4, and Invention Examples 1 to 3), the bulk density of the powder coal is 750 (kg-dry / m 3 The mixture was charged into a stainless steel dry distillation vessel shown in Figure 1 so that the temperature was 100°C. The SUS carbonization vessel containing the blended coal was heated for 6 hours in an electric furnace at an internal temperature of 1050°C to obtain coke. The obtained coke was cooled in a nitrogen atmosphere, and then its coke strength was evaluated by the 15 mm index (DI 150 / 15) at 150 revolutions in the drum test specified in JIS K2151:2004.

[0052] Table 4 shows the blending conditions of the coke raw materials and the drum strength of the coke, and explains the effects of the present invention.

[0053] [Table 4]

[0054] [Conventional Examples 1 and 2] This is the level of coke produced from coking coal 3, 4, which is generally used in coke production. Coke for blast furnaces requires strength, and under the above coke production conditions, a DI 150 / 15 of 73 or more (preferably 75 or more) is required.

[0055] [Comparative Examples 1 to 3] Coal 1 was blended with raw coal 3 in different shapes and carbonized to produce coke. In comparative example 2, coal 1 (-3mm 100%) was mixed with powdered coal in an unbriquette form, but the decrease in coke strength was small compared to conventional example 1. In comparative examples 1 and 3, coal 1 was crushed to different particle sizes to produce briquette coal, and the powdered coal was mixed, but the change in coke strength was small. In other words, if the coal has fluidity where the common logarithm of the maximum fluidity is about 2.08, there is no need to pulverize it before use, and it can be used as a coke raw material by conventional methods, so there is little need to pulverize it according to the present invention.

[0056] [Comparative Examples 4 and 5] Coal 2 is mixed with raw coal 3 in a different shape and carbonized to produce coke. In Comparative Example 5, coal 2 (-3mm 100%) is mixed with powdered coal in an unbriquette state, but the coke strength is significantly lower than that of Conventional Example 1. In Comparative Example 4, coal 2 is crushed to -3mm 100% to produce molded coal, and the powdered coal is mixed with the molded coal. However, the coke strength is similar to that of Comparative Example 5, and is significantly lower than that of Conventional Example 1.

[0057] [Example 1] In Example 1, coal 2 was crushed to 100% -74mm to produce molded coal (raw material A'), which was mixed with powdered coal. Although the coke strength was lower than that of Conventional Example 1, it was clearly higher than that of Comparative Examples 4 and 5, achieving a desirable strength (DI 150 / 15) of 75. These results confirm that when a raw material with low melting property is used as raw material A, the decrease in coke strength can be significantly reduced by following the method of the present invention.

[0058] [Comparative Examples 6 and 7] Coals 3 and 4 were mixed with raw coal 4 in different shapes and carbonized to produce coke. In Comparative Examples 6 and 7, coals 3 and 4, which were pulverized to 106 μm (100%), were mixed with powdered coal in an unbriquette state, but the coke strength was significantly reduced compared to Conventional Example 2. The strength reduction was particularly significant in Comparative Example 7, which used coal 4, which exhibited no fluidity whatsoever.

[0059] [Examples 2 and 3] In Examples 2 and 3, briquettes (raw material A') made from coals 3 and 4 pulverized to 100% -106 μm were mixed with powdered coal, and the coke strength was significantly improved compared to Comparative Examples 6 and 7, in which the same raw material A was used in an unbriquette state. As a result, in Example 2, the coke strength was comparable to that of Conventional Example 2, achieving a desirable strength (DI 150 / 15) of 75. In addition, in Example 3, the target strength (DI 150 / 15) of 73 was achieved. These results confirm that when using a raw material with low melting properties as a coke raw material, the adverse effects on coke strength can be reduced by following the method of the present invention, which involves finely pulverizing and compacting the raw material.

[0060] The particle size of the coke produced in Examples 1 to 3 was similar to that of the coke produced in Conventional Examples 1 and 2. It was confirmed that the coke derived from the molded coal (raw material A') was integrated with the coke derived from the surrounding powdered coal, and that coke with a particle size similar to that produced by conventional coke production methods could be produced.

Claims

1. In a method for producing metallurgical coke, raw material A' is formed into molded coal by mechanical compaction, raw material A' is blended with powdered raw material B (powdered coal), and the blended coal is carbonized to produce coke, The raw material A is made to have a common logarithm of the maximum fluidity (logMF) of 1.50 or less in the fluidity test method (Gieseler Plastometer method) specified in JIS M 8801, Furthermore, the raw material A has a maximum particle size of 300 μm or less, Furthermore, the common logarithm of the maximum fluidity (logMF) of the raw material B is set to 2.30 or more. Method for producing metallurgical coke.

2. 2. The method for producing metallurgical coke according to claim 1, wherein the mechanical consolidation is performed using a double-roll molding machine.

3. The density of the raw material A' is 1.00 g / cm ３ The method for producing metallurgical coke according to claim 1 or 2.

4. 3. The method for producing metallurgical coke according to claim 1, wherein the mass ratio of raw material A' to the total mass of raw material A' and raw material B is 0.30 or less.

5. 4. The method for producing metallurgical coke according to claim 3, wherein the mass ratio of raw material A' to the total mass of raw material A' and raw material B is 0.30 or less.

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