AU2011296874B2

AU2011296874B2 - Method for producing metallurgical coke and caking additive for producing metallurgical coke

Info

Publication number: AU2011296874B2
Application number: AU2011296874A
Authority: AU
Inventors: Yusuke Dohi; Kiyoshi Fukada; Izumi Shimoyama; Hiroyuki Sumi; Tetsuya Yamamoto
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2010-09-01
Filing date: 2011-08-31
Publication date: 2014-07-31
Anticipated expiration: 2031-08-31
Also published as: AU2011296874A1; CN103189474B; KR20130079514A; WO2012029978A1; TW201217509A; JP5201250B2; KR101484866B1; JP2012072390A; CN103189474A; TWI450954B

Abstract

Provided is a method for producing metallurgical coke excellent in terms of the quality of strength and the like compared to that produced through a conventional method. This method for producing metallurgical coke uses a caking additive that exhibits a significant effect in improvement of the strength of metallurgical coke and that is selected by accurately assessing the plastic properties of the caking additive added to mixed coal, by measuring the plastic properties in a state that simulates the surrounding environment of the plasticized coal and caking additive in a coke oven. The method for producing metallurgical coke is characterized in that when carbonizing coal and producing coke, the penetration distance of the caking additive is measured, and caking additive having a penetration distance of a prescribed value or lower is added to coal and followed by carbonization thereof. In addition, the coking additive for use in the production of metallurgical coke: heat treats organic material that contains ash in the amount of 1 mass% or less and that plasticizes in a temperature range between 300°C and 550°C, or treats the organic material in an oxygen-containing atmosphere that is room temperature or warmer; and has a penetration distance reduced to a prescribed value or lower.

Description

Our.Ref.,2011S01226 DESCRIPTION METHOD FOR PRODUCING METALLURGICAL COKE AND CAKING ADDITIVE FOR PRODUCING METALLURGICAL COKE Technical Field [0001] The present invention relates to a method for producing a metallurgical coke and a caking additive for use in this production method. In particular, it relates to a caking additive prepared or selected according to a standard set by a new method for evaluating thermal plasticity exhibited during thermal carbonization and to a method for producing a high-strength metallurgical coke by using the caking additive. Background Art [0002] Coke used in a blast furnace process, which is the most prevalent iron making process, has many roles including a reducing agent for reducing iron ore, a heat source, and a spacer. In order to efficiently and stably operate a blast furnace, maintaining the gas permeability in the blast furnace is critical and thus production of coke having high strength is desirable. Coke is produced by carbonizing, in Our.Ref.,2011S01226 -2 a coke oven, a coal blend in which various coke-making coals of size adjusted by pulverization are blended. Coke-making coal becomes plastic in a temperature range of about 300'C to 550 0 C during carbonization and at the same time foams and swells as it releases volatile matter, thereby bonding particles to each other and giving lump semicoke. In the subsequent process of elevating the temperature to about 1000 0 C, the semicoke contracts and solidifies, thereby giving hard coke. Accordingly, the bonding property of coal in a plastic phase greatly affects the properties after carbonization, such as coke strength and particle size. [0003] For the purpose of enhancing the bonding in the coke making coal (coal blend), a method for producing a coke in which a caking additive that exhibits high fluidity in a plastic temperature range of the coal is added to a coal blend has been widely practiced. Concrete examples of the caking additive include tar pitch, petroleum pitch, solvent refined coal, and solvent-extracted coal. As with the case of coal, the bonding property of the caking additive in a plastic phase significantly affects the properties of the coke after carbonization. [0004] As discussed above, the thermal plasticity of the coal and the caking additive is extremely important since it Our.Ref.,2011S01226 -3 greatly affects the coke properties and coke cake structures after carbonization and studies have been actively conducted for a long time on the method for measuring the thermal plasticity. In particular, the coke strength, which is an important quality of the coke, is greatly affected by the properties of the raw material coal, especially the coal rank and the thermal plasticity. Thermal plasticity is a property of coal to soften and melt when heated and is usually measured and evaluated through the fluidity, viscosity, adhesive property, swelling property, or the like of plastic matter. [0005] An example of a typical method for measuring a thermal plasticity of coal, namely, a fluidity of the coal in a plastic state is a coal fluidity test method by Gieseler plastometry provided in Japanese Industrial Standards (JIS) M 8801. According to this Gieseler plastometry, coal pulverized to 425 pm or smaller is placed in a predetermined crucible and heated at a predetermined heating rate, and the speed of rotation of a stirring rod on which a known torque is applied is observed through a dial plate and indicated as dial divisions per minute (ddpm). [0006] Whereas the Gieseler plastometry measures the speed of rotation of the stirring rod under a constant torque, there Our.Ref.,2011S01226 -4 has also been suggested a method in which the torque is measured while the speed of rotation is fixed. For example, Patent Literature 1 describes a method in which the torque is measured while turning a rotator at a constant speed of rotation. [0007] Also available is a method for measuring viscosity with a dynamic viscoelastometer aimed to measure the viscosity that is physically significant as the thermal plasticity (for example, refer to Patent Literature 2). Dynamic viscoelasticity measurement is measurement of a viscoelastic behavior exhibited when force is periodically applied to a viscoelastic material. According to the method described in Patent Literature 2, the viscosity of the plastic coal is evaluated in terms of complex viscosity among parameters obtained by measurement, and the feature of the method is that the viscosity of the plastic coal can be measured at a desired shear rate. [0008] A case in which the bonding property of the coal to activated coal or glass beads is measured as the thermal plasticity of the coal has also been reported. According to this report, a small quantity of a coal sample is sandwiched between activated coal and glass beads in the vertical direction, heated, and cooled after softening and melting, Our.Ref.,2011S01226 -5 and the bonding properties between the coal and the activated coal and between the coal and the glass beads are observed from the appearance. [0009] An example of the typical method for measuring the swelling property of coal in a plastic phase is a dilatometer method provided in JIS M 8801. A dilatometer method is a method that includes molding coal, which has been pulverized to 250 ptm or smaller, by a prescribed method, placing the molded coal into a predetermined crucible, heating the coal at a specified heating rate, and measuring the changes in displacement of coal over time with a detector rod placed on the coal. [0010] For the purposes of simulating the thermoplastic behavior of the coal in the coke oven, a coal dilatation test method in which the permeation behavior of gas generated during softening and melting of the coal is improved is also known (e.g., refer to Patent Literature 3). In this method, a permeable material is placed between a coal layer and a piston or under the coal layer in addition to between the coal layer and the piston to increase the number of the paths through which volatile matter and liquid substances generated from coal permeate so that the measurement environment resembles the swelling behavior in Our.Ref.,2011S01226 -6 the coke oven. Similarly, a method for measuring the swelling property of coal by placing a material having penetrating paths on a coal layer and heating the coal with microwaves while applying load is also known (refer to Patent Literature 4). Citation List Patent Literature [0011] [PTL 1] Japanese Unexamined Patent Application Publication No. 6-347392 [PTL 2] Japanese Unexamined Patent Application Publication No. 2000-304674 [PTL 31 Japanese Patent No. 2855728 [PTL 4] Japanese Unexamined Patent Application Publication No. 2009-204609 Non Patent Literature [0012] [NPL 1] MOROTOMI et al., Journal of the Fuel Society of Japan, Vol. 53, 1974, pp 779-790 [NPL 2] MIYATU et al., Nippon Kokan Technical report vol. 67, 1975, pp 125-137 Disclosure of Invention Technical Problem [0013] Generally, a coal blend in which two or more brands of Our.Ref.,2011S01226 -7 coals are blended at a designated ratio is used for producing a metallurgical coke. However, the required coke strength cannot be achieved unless the thermal plasticity is accurately evaluated. If low-strength coke not satisfying a required strength is used in shaft furnaces such as blast furnaces, the amount of dust generated in the shaft furnaces may increase, the pressure loss may increase, and the operation of the shaft furnaces may become instable. Moreover, a problem of local concentration of gas flow also known as channeling may arise. [0014] Existing thermal plasticity indices frequently fail to accurately predict the strength. Accordingly, the coke strength has been empirically managed to a particular level or higher by considering variation in coke strength owing to inaccuracy of the thermal plasticity evaluation and setting the target coke strength on the high side. However, according to this method, the average grade of the coal blend needs to be set high by using relatively expensive coal generally known to exhibit good thermal plasticity and thus the cost is high. [0015] In the coke oven, coal softens and melts while being restricted by adjacent layers. Since the thermal conductivity of the coal is low, the coal in the coke oven Our.Ref.,2011S01226 -8 is not homogeneously heated and thus forms a coke layer, a plastic layer, and a coal layer that respectively exhibit different states in that order from the oven wall side, which is the heating surface. Since the coke oven itself rarely deforms during carbonization although it swells slightly, the plastic coal is restricted by the coke layer and the coal layer. [0016] Moreover, there are a large number of defective structures around the plastic coal, such as gaps in the coal layer between coal particles, gaps between particles of the plastic coal, coarse pores formed by evaporation of pyrolysis gas, and cracks in the adjacent coke layer. In particular, cracks in the coke layer are believed to have a width of about several hundred micrometers to several millimeters and are large compared to pores and gaps between coal particles which are several tens to several hundred micrometers in size. Accordingly, it is believed that not only the pyrolysis gas or liquid substances, which are by products of coal, but also the plastic coal permeates into such coarse defects generated in the coke layer. Moreover, it is anticipated that the shear rate acting on the plastic coal during penetration differs from one brand to another. [0017] The inventors of the present invention thought it Our.Ref.,2011S01226 -9 necessary to use as an indicator the coal thermal plasticity measured under conditions that simulate the environment in the coke oven in which the coal is placed in order to more accurately control the coke strength. They considered it particularly important to conduct measurement under conditions in which plastic coal is restricted and movements and penetration of the plastic matter into surrounding defective structures are simulated. However, existing measurement methods have following drawbacks. [0018] According to the Gieseler plastometry, measurement is conducted while coal is packed in a vessel and thus there is a problem in that the restricting and penetration conditions are left out of consideration. Moreover, this method is not suitable for measuring coal that exhibits high fluidity. The reason for this is that when coal having high fluidity is measured, a phenomenon in which hollow spaces are generated on the side wall side of the vessel (Weissenberg effect) occurs and the fluidity may not always be evaluated accurately since the stirring rod may turn idle (for example, refer to Non-Patent Literature 1). [0019] The method in which the torque is measured while maintaining the constant speed of rotation also has a drawback in that the restricting conditions and the Our.Ref.,2011S01226 - 10 penetration conditions are unconsidered. Moreover, since measurement is conducted at an any shear rate, the thermal plasticity of the coal cannot be accurately compared and evaluated as described above. [0020] A dynamic viscoelastometer measures the viscosity as the thermal plasticity and is an instrument that measures the viscosity under any desired strain rate. Accordingly, the viscosity of the plastic coal in the coke oven can be measured by setting the shear rate used in the measurement to a value of the shear rate applied to the coal in the coke oven. However, it is usually difficult to preliminarily measure in or forecast the shear rate applied to each brand of coal in the coke oven. [0021] The method in which the bonding property of the coal to the activated carbon or the glass beads is measured as the thermal plasticity of the coal attempts to reproduce the penetration conditions that simulate the presence of the coal layer but has a problem in that the coke layer and the coarse defects are not simulated. Moreover, the method is deficient in that the measurement is not conducted under restriction. [0022] According to the coal swelling test method using the Our.Ref.,2011S01226 - 11 permeable material described in Patent Literature 3, movements of the gas and liquid substances generated from the coal are considered but the movement of the plastic coal itself is not considered, which is a problem. This is because the permeability of the permeable material used in Patent Literature 3 is not high enough to allow the plastic coal to move. The inventors have actually conducted the test described in Patent Literature 3 but penetration of the coal into the permeable material did not occur. Accordingly, new conditions must be taken into account in order to induce penetration of the plastic coal into the permeable material. [0023] Patent Literature 4 also discloses a coal dilatation measurement method in which a material having penetrating paths is placed on the coal layer so as to consider the movements of the gas and liquid substance generated from the coal but there is a problem in that the heating method is limited and that the conditions for evaluating the penetration phenomena in the coke oven are not clearly established. Moreover, according to Patent Literature 4, the relationship between the softening and melting coal penetration phenomenon and the thermoplastic behavior is not clarified, no suggestion is made regarding the relationship between the softening and melting coal penetration phenomenon and the quality of the produced coke, and the - 12 production of high quality coke is not described. [0024) In sum, according to existing techniques, measurement of the thermal plasticity of the coal and caking additive, such as fluidity, viscosity, adhesive property, penetration property, dilatation during penetration, and pressure during penetration, has not been conducted while satisfactorily simulating the environment surrounding the caking additive and the coal in a plastic phase in the coke oven. [0025] It would be advantageous if at least preferred embodiments of the present invention were to provide a method for producing a metallurgical coke of high quality such as a higher strength than that achieved by conventional technologies, the method including measuring thermal plasticity of a caking additive to be added to a coal blend while simulating the environment surrounding the coals and caking additive in a plastic phase in a coke oven to accurately evaluate the thermal plasticity of the caking additive and preparing and selecting a caking additive for use in production of a metallurgical coke and having a higher effect of improving the strength of a metallurgical coke. It would also be advantageous to provide a caking additive for use in production of a metallurgical coke and having a higher effect of improving the strength of a metallurgical coke.

Our.Ref.,2011S01226 - 13 Solution to Problem [0026] The features of the present invention that solves the problem are as follows: [1] A method for producing a metallurgical coke by carbonizing coal, the method including measuring a permeation distance of a caking additive to be added to coal and conducting carbonization by adding a caking additive having a permeation distance equal to or lower than a predetermined value to the coal. [2] The method for producing a metallurgical coke according to [1], in which the coal is a coal blend that contains a plurality of types of coal and the predetermined value of the permeation distance is defined by formula (1) below: Permeation distance = 1.3 x a x log MFp (1) where a is a constant equal to 0.7 to 1.0 times a coefficient of a common logarithm, log MF, of a Gieseler maximum fluidity MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest Our.Ref.,2011S01226 - 14 detectable value. [3] The method for producing a metallurgical coke according [2], in which a is a constant equal to 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend. [4] The method for producing a metallurgical coke according to [1], in which the coal is a coal blend that contains a plurality of types of coal and the predetermined value of the permeation distance is defined by formula (2) below: Permeation distance = a' x log MFp + b (2) where a' is a constant equal to 0.7 to 1.0 times a coefficient of a common logarithm, log MF, of a Gieseler maximum fluidity MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend; b is a constant equal to or more than but not more than 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from Our.Ref.,2011S01226 - 15 brands used in obtaining the linear regression line; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value. [5] The method for producing a metallurgical coke according to [4], in which a' is a constant equal to 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend. [6] The method for producing a metallurgical coke according to [1], in which the coal is a coal blend that contains a plurality of types of coal and the predetermined value of the permeation distance is 2.0 times a weighted average permeation distance of the coal blend. [7] The method for producing a metallurgical coke according to [1], in which the predetermined value of the permeation distance is 15 mm according to a value observed when a sample of the caking additive prepared by pulverizing the caking additive so that particles having a diameter of 2 mm or less account for 100 mass% and packing a vessel with the pulverized caking additive at a packing density of 0.8 g/cm 3 to a layer thickness of 10 mm is heated in an inert gas Our.Ref.,2011S01226 - 16 atmosphere from room temperature to 550'C at a heating rate of 3 0 C/min while a load is applied from above glass beads having a diameter of 2 mm placed on the sample so that the pressure is 50 kPa. [8] The method for producing a metallurgical coke according to any one of [1] to [7], wherein a mean particle diameter of the caking additive to be added is 0.5 mm or more. [9] The method for producing a metallurgical coke according to any one of [1] to [8], in which the caking additive to be added is an organic substance that has an ash content of 1 mass% or less and becomes plastic in a temperature range within a range of 300 0 C to 550 0 C. [10] The method for producing a metallurgical coke according to any one of [1] to [9], in which the caking additive is heat-treated or treated at room temperature or higher in an atmosphere that contains at least one component selected from 02, C0 2 , and H 2 0 so that the caking additive added to the coal comes to have a permeation distance smaller than the permeation distance before the treatment. [11] The method for producing a metallurgical coke according to [10], in which the caking additive to be added has been subjected to a treatment in an oxygen-containing atmosphere at a treatment temperature of 100 0 C to 300 0 C for a treatment time of 1 to 120 minutes. [12] The method for producing a metallurgical coke according Our.Ref.,2011S01226 - 17 to [11], in which the caking additive to be added has been subjected to a treatment in an oxygen-containing atmosphere at a treatment temperature of 180 0 C to 220'C for a treatment time of 1 to 30 minutes. [13] The method for producing a metallurgical coke according to any one of Claims [10] to [12], in which log MF of the caking additive that has been heat-treated or treated at room temperature or higher in an atmosphere that contains at least one component selected from 02, C0 2 , and H 2 0 is 2.5 or more. [14] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF > 2.5, and a permeation distance equal to or less than a value defined by formula (1) below: Permeation distance = 1.3 x a x log MFp (1) where a is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among types of coal contained in a coal blend; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking Our.Ref.,2011S01226 - 18 additive exceeds a detection limit, MFp is the highest detectable value. [15] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to be equal to or lower than a predetermined value defined by formula (1) below, the caking additive being prepared by heat-treating or treating at room temperature or higher in an atmosphere containing at least one component selected from 02, C0 2 , and

H

2 0 an organic substance that becomes plastic in a temperature range within the range of 300 0 C to 550OC: Permeation distance = 1.3 x a x log MFp (1) where a is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among types of coal contained in a coal blend; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value. [16] The caking additive for producing a metallurgical coke according to [14] or [15], in which a is a constant 1.0 Our.Ref.,2011S01226 - 19 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend. [17] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF 2.5, and a permeation distance equal to or less than a value defined by formula (2) below: Permeation distance = a' x log MFp + b (2) where a' is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in a coal blend; b is a constant equal to 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from brands used in obtaining the linear regression line; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, Our.Ref.,2011S01226 - 20 MFp is the highest detectable value. [18] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to be equal to or lower than a predetermined value defined by formula (2) below, the caking additive being prepared by heat-treating or treating at room temperature or higher in an atmosphere containing at least one component selected from 02, CO 2 , and

H

2 0 an organic substance that becomes plastic in a temperature range within the range of 300'C to 550'C: Permeation distance = a' x log MFp + b (2) where a' is a constant equal to 1.0 times a coefficient of log MF determined.from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among types of coal contained in a coal blend; b is a constant equal to 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from brands used in obtaining the linear regression line; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value.

Our.Ref.,2011S01226 - 21 [19] The caking additive for producing a metallurgical coke according to [17] or [18], in which a' is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend. [20] A caking additive for producing a metallurgical coke in which the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF > 2.5, and a permeation distance equal to or lower than a predetermined value defined by processes (a) and (b) below: (a) determining in advance types of coal that constitute a coal blend to which the caking additive is to be added and a blending ratio of each type of coal; and (b) setting the predetermined value to be 2.0 times a weighted average permeation distance of the coal blend. [21] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to be equal to or lower than a predetermined value defined by processes (a) and (b) below, the caking additive being prepared by heat treating or treating at room temperature or higher in an atmosphere that contains at least one component selected Our.Ref.,2011S01226 - 22 from 02, C0 2 , and H 2 0 an organic substance that becomes plastic in a temperature range within the range of 300'C to 550OC: (a) determining in advance types of coal that constitute a coal blend to which the caking additive is to be added and a blending ratio of each type of coal; and (b) setting the predetermined value to be 2.0 times a weighted average permeation distance of the coal blend. [22] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF > 2.5, and a permeation distance of 15 mm or less according to a value determined through processes (c) to (f) below: (c) pulverizing the caking additive or a coal so that particles having a diameter of 2 mm or less account for 100 mass% and packing a vessel with the pulverized caking additive or coal at a packing density of 0.8 g/cm 3 to a layer thickness of 10 mm to prepare a sample; (d) placing glass beads 2 mm in diameter on the sample to a layer thickness equal to or more than the permeation distance; (e) heating the sample from room temperature to 550'C at a heating rate of 3 0 C/min in an inert gas atmosphere while applying a load from above the glass beads so that a pressure is 50 kPa; and Our.Ref.,2011S01226 - 23 (f) measuring a permeation distance of the softening and melting sample that has permeated into the glass bead layer. [23] A caking additive for producing a metallurgical coke, in which the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to 15 mm or less according to a value determined by steps (c) to (f) below, the caking additive being prepared by heat-treating or a treating at a temperature equal to or more than room temperature in an atmosphere containing at least one component selected from 02, C0 2 , and H 2 0 an organic substance that becomes plastic in a temperature range within the range of 300 0 C to 550 C: (c) pulverizing the caking additive or a coal so that particles having a diameter of 2 mm or less account for 100 mass% and packing a vessel with the pulverized caking additive or coal at a packing density of 0.8 g/cm 3 to a layer thickness of 10 mm to prepare a sample; (d) placing glass beads 2 mm in diameter on the sample to a layer thickness equal to or more than the permeation distance; (e) heating the sample from room temperature to 550'C at a heating rate of 3 0 C/min in an inert gas atmosphere while applying a load from above the glass beads so that a pressure is 50 kPa; and (f) measuring a permeation distance of the softening and Our.Ref.,2011S01226 - 24 melting sample that has permeated into the glass bead layer. [24] The caking additive for producing a metallurgical coke according to [15], [18], [21], or [23], in which the treatment at room temperature or higher in the atmosphere containing at least one component selected from 02, C0 2 , and

H

2 0 is conducted at a treatment temperature of 100 0 C to 300'C for a treatment time of 1 to 120 minutes. [25] The caking additive for producing a metallurgical coke according [24], in which the treatment at room temperature or higher in the atmosphere containing at least one component selected from 02, CO 2 , and H 2 0 is conducted at a treatment temperature of 180 0 C to 220 0 C for a treatment time of 1 to 30 minutes. [26] The caking additive for producing a metallurgical coke according to [15], [18], [21], [23], [24], or [25], in which the caking additive has a log MF of 2.5 or more after being heat-treated or treated at room temperature or higher in the atmosphere containing at least one component selected from 02, C0 2 , and H 2 0. Advantageous Effects of Invention [0027] According to the present invention, a caking additive having a high coke-strength-improving effect can be selected. Thus, the coke strength can be improved by producing coke by adding such a caking additive. Even in cases where high- Our.Ref.,2011S01226 - 25 strength coke is not needed, addition of a caking additive having a high coke-strength-improving effect enables production of coke having a required strength despite use of large quantities of inexpensive low-grade coals. Moreover, since the properties required for the caking additive are clarified, caking additives that have undesirable properties can be modified so that caking additives having desirable properties are obtained. Brief Description of Drawings [0028] [Fig. 1] Fig. 1 is a schematic diagram showing an example of an instrument for measuring thermal plasticity while applying a given load onto a caking additive sample and a material having through-holes extending from the upper to lower surface used in the present invention. [Fig. 2] Fig. 2 is a schematic diagram showing an example of the material having through-holes extending from the upper to lower surface used in the present invention, in which the material has circular through-holes. [Fig. 3] Fig. 3 is a schematic diagram showing an example of the material having through-holes extending from the upper to lower surface used in the present invention, in which the material is a spherical-particle-packed layer. [Fig. 41 Fig. 4 is a schematic diagram showing an Our.Ref.,2011S01226 - 26 example of the material having through-holes extending from the upper to lower surface used in the present invention, in which the material is a column-packed layer. [Fig. 5] Fig. 5 is a graph showing a positional relationship between the permeation distance and maximum fluidity of caking additives A and B used in Example 1 and the range of the permeation distance and maximum fluidity defined in (A). [Fig. 6] Fig. 6 is a graph showing a positional relationship between the permeation distance and maximum fluidity of the caking additives A and B used in Example 1 and the range of the permeation distance and maximum fluidity defined in (B). [Fig. 7] Fig. 7 is a graph showing a positional relationship between the permeation distance and maximum fluidity of a modified caking additive used in Example 3 and the range of the permeation distance and maximum fluidity defined in (A). [Fig. 8] Fig. 8 is a graph showing a positional relationship between the permeation distance and maximum fluidity of the modified caking additive used in Example 3 and the range of the permeation distance and maximum fluidity defined in (B) [Fig. 9] Fig. 9 is a schematic diagram showing an example of an instrument for measuring thermal plasticity - 27 while maintaining constant the volumes of a coal sample and a material having through-holes extending from the upper to lower surface used in the present invention. Description of Embodiments [0029] The inventors of the present invention have conducted extensive studies on the relationship between the coke strength and the thermal plasticity measured while simulating the environment surrounding the caking additive and the coal in a plastic phase in the coke oven and found that it is appropriate to evaluate the thermal plasticity of the coal and the caking additive by using the "permeation distance". The inventors have also found that coke strength is improved when a caking additive having a particular permeation distance is added to a coal blend and made the present invention. The permeation distance can be measured by the following method. [0030] Fig. 1 shows an example of an instrument for measuring the thermal plasticity (permeation distance) used in the present invention. The instrument shown in Fig. 1 is used for heating a coal sample while a given load is applied to the coal sample and a material having through-holes extending from the lower to upper surface. Coal is packed Our.Ref.,2011S01226 - 28 in the lower portion of a vessel 3 to prepare a sample 1, and a material 2 having through-holes extending from the lower to upper surface is placed on the sample 1. The sample 1 is heated to a temperature equal to or higher than the initial softening temperature and is allowed to permeate into the material 2 having through-holes extending from the lower to upper surface and the permeation distance is measured. Heating is conducted in an inert gas atmosphere. The inert gas refers to a gas that does not react with coal in the measurement temperature range. Typical examples of such a gas include argon gas, helium gas, and nitrogen gas. The permeation distance may be measured while heating the coal and material having through-holes while maintaining their volumes constant. An example of the instrument for measuring the thermal plasticity (permeation distance) used in such a case is shown in Fig. 9. [0031] As shown in Fig. 1, in the case where the sample 1 is heated while a given load is applied to the sample 1 and the material 2 having through-holes extending from the lower to upper surface, the sample 1 swells or contracts and the material 2 having through-holes extending from the lower to upper surface moves in a vertical direction. Accordingly, the dilatation during sample penetration can be measured by using the material 2 having through-holes extending from the Our.Ref.,2011S01226 - 29 lower to upper surface. As shown in Fig. 1, a dilatation detecting rod 13 is placed on top of the material 2 having through-holes extending from the lower to upper surface, a weight 14 for applying load is placed on the upper end of the dilatation detecting rod 13, and a displacement meter 15 is placed on the weight 14 to measure the dilatation. The displacement meter 15 may be one that can measure the range of dilatation of the sample (-100% to 300%). Since the inert gas atmosphere must be retained in the interior of the heating system, a non-contact-type displace meter is suitable and an optical displacement meter is desirably used. The inert gas atmosphere is preferably a nitrogen atmosphere. In the case where the material 2 having through-holes extending from the lower to upper surface is a particle packed layer, a plate is preferably interposed between the dilatation detecting rod 13 and the material 2 having through-holes extending from the lower to upper surface since the dilatation detecting rod 13 may sink into the particle-packed layer. The load is preferably applied evenly onto the upper surface of the material having through-holes extending from the lower to upper surface placed on top of the sample. Preferably, a pressure of 5 to 80 kPa, preferably 15 to 55 kPa, and most preferably 25 to 50 kPa is loaded with respect to the area of the upper surface of the material having through-holes extending from Our.Ref.,2011S01226 - 30 the lower to upper surface. The pressure is preferably set in accordance with the swelling pressure of the plastic layer in the coke oven. However, studies on the reproducibility of the measurement results and the power of detecting the difference in various coal brands have found that a pressure of about 25 to 50 kPa, which is slightly higher than the swelling pressure in the oven, is the most preferred measurement condition. [0032] The heating means is preferably of a type that can heat the sample at a designated heating rate while measuring the temperature of the sample. Concrete examples thereof include an electric furnace, an external heating system combining an electrically conductive vessel and high frequency induction, and an internal heating system such as by microwaves. When an internal heating system is employed, measures must be taken to make the temperature uniform within the sample. For example, the heat insulation property of the vessel is preferably enhanced. [0033] For the purposes of imulating the thermoplastic behaviors of the coal and the caking additive in the coke oven, the heating rate needs to be equal to the rate of heating coal in the coke oven. The rate of heating coal in the plastic temperature range in the coke oven differs Our.Ref.,2011S01226 - 31 depending on the position of the coal in the oven and the operation conditions but is generally 2 to 10'C/min, preferably 2 to 4 0 C/min on average, and most preferably about 3 0 C/min. However, in the case of heating a low fluidity coal such as slightly caking coal, the permeation distance or the dilatation is small at 3 0 C/min and thus may be difficult to detect. Generally, coal is known to exhibit improved fluidity measured with a Gieseler plastometer when rapidly heated. Accordingly, in the case where coal having a permeation distance of 1 mm or less is used, the measurement may be conducted by increasing the heating rate to 10 to 1000 C/min in order to improve the detection sensitivity. [0034] Since the object of the measurement is to evaluate the thermal plasticity of the coal and caking additive, it is sufficient if the heating can be conducted in the plastic temperature range of the coal and the caking additive and thus the temperature range of the heating may be such a temperature range. Considering the plastic temperature range of the coke-making coal and caking additive, heating may be conducted in a range of 0 0 C (room temperature) to 550'C and preferably in a range of 300 to 550 0 C, i.e., the plastic temperature range of the coal, at a designated heating rate.

Our.Ref.,2011S01226 - 32 [0035] The material having through-holes extending from the lower to upper surface is preferably one whose permeability coefficient can be measured or calculated in advance. Examples of the form of the material include an integral material having through-holes and a particle-packed layer. Examples of the integral material having through-holes include a material having circular through-holes 16 as shown in Fig. 2, a material having a rectangular through-holes, and a material having through-holes having irregular shapes. The type of particle-packed layers can be roughly divided into spherical-particle-packed layers and non-spherical particle-packed layers. Examples of the spherical-particle packed layers include one composed of bead-shaped packing particles 17 as shown in Fig. 3 and examples of the non spherical-particle-packed layers include one composed of irregularly shaped particles and one composed of packing columns 18 as shown in Fig. 4. In order to maintain the reproducibility of the measurement, the permeability coefficient within the material is preferably as homogeneous as possible and in order to facilitate measurement, the material preferably has a permeability coefficient that can be easily calculated. Accordingly, a spherical-particle packed layer is particularly preferable for use as a material having through-holes extending from the lower to Our.Ref.,2011S01226 - 33 upper surface used in the present invention. The raw material of the material having through-holes extending from the lower to upper surface may be any as long as the raw material undergoes substantially-no change in shape in and beyond the plastic temperature range of the coal, e.g., up to 600'C, and does not react with coal. The height thereof may be large enough to allow penetration of the softening and melting coal. In the case where a coal layer having a thickness of 5 to 20 mm is heated, the height may be about 20 to 100 mm. [0036] The permeability coefficient of the material having through-holes extending from the lower to upper surface needs to be set based on the prediction of the permeability coefficient of the coarse defects in the coke layer. The present inventors have carried out studies on the permeability coefficient particularly preferable for the present invention by investigating the factors that constitute the coarse defects and prediction of the size of the defects. As a result, they have found that a permeability coefficient in the range of 1 x 108 to 2 x 109 m2 is most suitable. The permeability coefficient is derived based on the Darcy's law represented by equation (3) below: AP/L = K-t-u ... (3) Our.Ref.,2011S01226 - 34 Here, AP represents a pressure loss [Pa] in the material having through-holes extending from the lower to upper surface, L represents the height [m] of the material having through-holes, K represents a permeability coefficient [m 2 ], jt represents the viscosity [Pa-s] of the fluid, and u represents the speed [m/s] of the fluid. For example, in the case where a layer of glass beads having uniform diameters is used as the material having through-holes extending from the lower to upper surface, glass beads preferably having a diameter of about 0.2 mm to 3.5 mm and most preferably 2 mm are selected in order for the permeability coefficient to be within the preferable range descried above. [0037] The coal and the caking additive to be formed into measurement samples are preliminarily pulverized and packed to a designated layer thickness at a designated packing density. The pulverization size may be equal to particle size of the coal charged in the coke oven (the ratio of particles having a diameter of 3 mm or less is about 70 to 80 mass%). Preferably, pulverization is conducted so that the ratio of the particles having a diameter of 3 mm or less is 70 mass% or more. Considering that the measurement is conducted in a small-size system, a pulverized product in which all of the particles are pulverized to 2 mm or less in Our.Ref.,2011S01226 - 35 diameter is particularly preferably used. The density of packing the pulverized product may be 0.7 to 0.9 g/cm 3 to match the packing density in the coke oven; however, studies on reproducibility and detection power have found that a preferable density of packing the pulverized product is 0.8 g/cm 3 . The thickness of the packed layer can be 5 to 20 mm based on the thickness of the plastic layer in the coke oven; however, studies on reproducibility and detection power have found that the thickness is preferably 10 mm. Representative measurement conditions in measuring the permeation distance described above are as follows: (1) Coal or a caking additive is pulverized so that particles with a diameter of 2 mm or less account for 100 mass% and a vessel is packed with the pulverized coal or caking additive at a packing density of 0.8 g/cm 3 such that the layer thickness is 10 mm to prepare a sample. (2) Glass beads having a diameter of 2 mm are placed on the sample so that the thickness of the layer of the glass beads is equal to or greater than the permeation distance. (3) Heating is performed in an inert gas atmosphere from room temperature to 550'C at a heating rate of 3 0 C/min while applying a load from above the glass beads so that the pressure is 50 kPa. (4) The permeation distance of the softening and melting sample that has permeated into the glass bead layer is Our.Ref.,2011S01226 - 36 measured. [0038] The permeation distances of the coal and caking additive in a plastic phase are preferably continuously and constantly measured during heating. However, constant measurement is difficult due to the influence of tar generated from the sample. The swelling and permeation phenomena of the coal induced by heating are irreversible and the sample that had undergone swelling and penetration once substantially retains its shape after cooling. Thus, after completion of the penetration of the softening and melting coal, the vessel as a whole may be cooled and the permeation distance after cooling may be measured so as to determine how much penetration occurred during heating. For example, it is possible to conduct measurement by taking out the material having through-holes extending from the lower to upper surface from the vessel after cooling and directly measuring the permeation distance with a caliper or a ruler. When particles are used as the material having through-holes extending from the lower to upper surface, the plastic matter penetrating the gaps between particles entirely consolidate a portion of the particle layer up to where the plastic matter had permeated. Accordingly, as long as the relationship between the mass and height of the particle packed layer is determined in advance, the mass of the Our.Ref.,2011S01226 - 37 particles that were not consolidated can be measured after completion of penetration and subtracted from the initial mass to determine the mass of the particles that had been consolidated, thereby enabling calculation of the permeation distance. [0039] The advantages of using the permeation distance are not only envisaged theoretically based on the fact that a measurement method simulating the conditions inside the coke oven is employed but are also clear from the results of studies investigating the influence of the permeation distance on the coke strength. Actually, the evaluation method of the present invention has clarified that even coals having about the same log MF (common logarithm of the maximum fluidity observed by Gieseler plastometry) have different permeation distances from one brand to another, and it was confirmed that the influence on the coke strength is also different, when coke is produced by blending coals having different permeation distances. [0040] According to evaluation of the thermal plasticity using a Gieseler plastometer in the related art, a coal or caking additive having higher fluidity has been considered to achieve a higher effect of bonding the coal particles to each other. Studies on the relationship between the Our.Ref.,2011S01226 - 38 permeation distance and the coke strength have found that when coals having extremely large permeation distances are blended, coarse defects remain during coking and a thin pore wall structure is formed, thereby decreasing the coke strength to a level lower than the value predicted by the average grade of the coal blend. This is presumably because coals having excessively large permeation distances significantly permeate the gaps between nearby particles of coals and the portions where those coal particles had existed form large cavities which form defects. In particular, coals that exhibit high fluidity in evaluation of the thermal plasticity with a Gieseler plastometer generate different amounts of coarse defects in the coke depending on the permeation distance. This relationship held true for the caking additives also. [0041] In general, caking additives have high fluidity and frequently added to coal blends having insufficient fluidity. In such a case, addition of caking additives will improve the fluidity of the coal blends as a whole and thus the coke strength is improved. However, it has been found that when the permeation distance of the caking additive is excessively large, defects are generated in the coke and the strength-improving effects achieved by improved fluidity are set-off. In other words, if the fluidity is about the same, Our.Ref.,2011S01226 - 39 caking additives with excessively large permeation distances have less coke-strength-improving effects compared to caking additives having appropriate permeation distances, and if the amount of the caking additives having large permeation distances is increased, the number of defects may be increased and the coke strength may be degraded in some cases. [0042] The inventors of the present invention have conducted extensive researches and found that it is effective to use the following four approaches (A) to (D) to define the permeation distance range of the coal or caking additive that causes a decrease in coke strength when blended into the coke-making raw materials: [0043] (A) The permeation distance range is defined by the following formula: Permeation distance > 1.3 x a x log MFp where a is a constant equal to 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend.

Our.Ref.,2011S01226 - 40 [0044] (B) The permeation distance range is defined by the following formula: Permeation distance > a' x log MFp + b where a' is a constant equal to 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend. In the formula, b is a constant equal to or more than but not more than 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from brands used in obtaining the linear regression line. [0045] (C) The permeation distance range is greater than 2.0 times the weighted average permeation distance of the coal blend to which the caking additive is to be added. [0046] (D) The permeation distance range is greater than 15 mm according to a value observed when a sample of the caking additive prepared by pulverizing the caking additive so that particles having a diameter of 2 mm or less account for 100 Our.Ref.,2011S01226 - 41 mass% and packing a vessel with the pulverized caking additive at a packing density of 0.8 g/cm 3 to a layer thickness of 10 mm is heated in an inert gas atmosphere from room temperature to 550'C at a heating rate of 3 0 C/min while a load is applied from above glass beads having a diameter of 2 mm placed on the sample so that the pressure is 50 kPa. [0047] Caking additives that have a permeation distance within the ranges defined in (A) to (D) above leave coarse defects and form a thin pore wall structure during coking when used as the coke-making material mixed with coals for coke making according to typical operation, and thus adversely affect the coke strength. Accordingly, it is convenient and effective to use caking additives that have a permeation distance outside the ranges of (A) to (D) in order to maintain the coke strength. Note that since caking additives are used to improve the fluidity of the coal blend, their Gieseler fluidity log MF is particularly preferably 2.5 or more and the influence of the permeation distance is significant with such caking additives. [0048] Here, four approaches, (A) to (D), for determining the control range are described. This is because the value of the permeation distance changes with the measurement condition settings, e.g., load, heating rate, type of Our.Ref.,2011S01226 - 42 material having through-holes, configuration of the instrument, etc. Considering that there may be measuring conditions different from the examples described in the present invention, the inventors have found that it is effective to determine the control range according to the approaches set forth in (A) to (D) above. [0049] The constants a and a' of the formulae used in determining the ranges in (A) and (B) are set so that each constant is within a range of 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend. This is because in the range of log MF < 2.5, a substantially positive correlation is observed between the maximum fluidity and the permeation distance of the coal; however, a brand that decreases the strength is a brand having a permeation distance highly deviated from this correlation in the positive direction. The inventors have conducted extensive investigations and found that brands having a permeation distance more than 1.3 times the permeation distance determined based on log MF of the coal by the above-described regression formula are the brands Our.Ref.,2011S01226 - 43 that induce the decrease in strength and thus the range is defined as described in (A). In attempting to detect brands that deviate from the regression formula in the positive direction beyond the measurement errors, the inventors have found that brands in the range beyond the sum of the value obtained by the regression formula and a value 1 to 5 times the standard deviation observed by measuring the same sample a plurality of times are the brands that decrease the strength. Thus, the range is defined as in (B) above. Accordingly, the constant b is a value 1 to 5 times the standard deviation observed by measuring the same sample a plurality of times. Under the measurement conditions set forth in the present invention, this value is about 0.6 to 3.0 mm. Here, the permeation distance range that causes the decrease in strength is set based on the log MFp value of the caking additive. This is because the permeation distance generally increases with MF and thus the extent of deviation from the correlation is critical. Note that the linear regression line may be plotted by a known linear regression least square estimation. The number of coals used in regression is preferably as large as possible since the regression errors are reduced. In particular, brands having small MF have small permeation distances and the error tends to be large. Accordingly, it is particularly preferable to draw a linear regression line by using at Our.Ref.,2011S01226 - 44 least one coal in the range of 1.75 < log MF < 2.50. [0050] The ranges of the constants a, a', and b are defined here in order to more reliably detect caking additives that decrease the strength, by decreasing these values. These values can be adjusted to satisfy the operating requirements. However, excessively decreasing these values will excessively increase the number of caking additives assumed to adversely affect the coke strength and there is a risk that even caking additives that do not actually decrease the strength will be mistaken as ones that decrease the strength. Accordingly, a and a' are each preferably 0.7 to 1.0 times the slope of the linear regression line and b is preferably 1 to 5 times the standard deviation obtained by measuring the same sample a plurality of times. [0051] The coals and caking additives used in coal blends are usually used after various properties of each brand are measured. The permeation distance also may be measured in advance for each lot of the brand. The mean permeation distance of the coal blend may be determined by measuring the permeation distances of various brands in advance and averaging the measured values in accordance with the blending ratio or by making the coal blend and measuring the permeation distance of the coal blend. In this manner, it Our.Ref.,2011S01226 - 45 becomes possible to identify caking additives that have extremely large permeation distances compared to the mean permeation distance of the coal blend. The coal blend used in making the coke may contain oil, coke powder, petroleum coke, resin, wastes, etc., in addition to the coal and caking additive. [0052] Since the caking additives in the ranges defined in (A) to (D) above leave coarse defects in the coke, they are preferably not added to the coal blend. This effect is notable when the particle size of the caking additive added is large. In other words, a caking additive that has coarse particles and a large permeation distance is particularly disfavored since it is likely to generate larger defects. In contrast, when the particle size of the caking additive is small, the difference in coke strength caused by the permeation distance is not significant. Accordingly, the method of judging the quality of the caking additive according to the present invention is particularly useful when the particle size of the caking additive is large. [00531 The measurement of the permeation distance has made it possible to distinguish caking additives preferable for increasing the coke strength from those that are not preferable. On the basis of such findings, the inventors Our.Ref.,2011S01226 - 46 have attempted to improve the properties of unfavorable caking additives by modifying the properties of the caking additives. [0054] The inventors have found that even when coal blends containing caking additives in the ranges described in (A) to (D) above are used as the raw material for making coke, the decrease in strength can be suppressed by controlling the permeation distance and the maximum fluidity by naturally weathering or forcibly weathering by heating, and modifying the caking additives in the ranges of (A) to (D) in advance. Properties of coal and caking additives gradually change when the coal and caking additives are exposed to air. The caking properties (maximum fluidity etc.), the heat quantity, and the coking property are also degraded and the quality as raw material for coke making is deteriorated. This phenomenon is called weathering. When a coal or caking additive is weathered, the permeation distance decreases with the progress of weathering. Moreover, the caking property is known to decrease also by heating in an inert gas atmosphere such as nitrogen. The inventors have conducted extensive studies and found that, in the case where the caking additives in the ranges of (A) to (D) are naturally weathered or forcibly weathered by heating and modified in advance, the treatment method and Our.Ref.,2011S01226 - 47 the progress of the treatment may be controlled so that the permeation distance and the maximum fluidity of the coal after weathering and modification are outside the ranges defined in (A) to (D) above and so that the decrease in coke strength can be effectively suppressed. [0055] In order to produce high-strength coke, the process is preferably controlled so as to decrease the permeation distance while suppressing the decrease in maximum fluidity as much as possible. The reason why a high maximum fluidity is preferred is that when coal softens and melts, particles appropriately bond to each other. Accordingly, the maximum fluidity of the caking additive after modification is preferably within the range of log MF > 2.5. In this manner, the decrease in strength can be effectively suppressed without causing bonding failure. [0056] It is generally known that the rate of progress of weathering of the coal and caking additive is dependent upon oxygen concentration, pressure (atmospheric pressure), temperature, coal particle size, coal moisture content, etc. In carrying out weathering of the caking additive to control the permeation distance and maximum fluidity, these weathering factors are preferably appropriately controlled. [0057] Our.Ref.,2011S01226 - 48 The atmosphere in which weathering is conducted needs to be an oxidizing atmosphere. The oxidizing atmosphere here means an atmosphere that contains oxygen or a substance capable of performing oxidation by dissociating oxygen. There are an infinite number of such conditions but a gas atmosphere containing 02, Ca 2 , and/or H 2 0 is preferred considering availability and ease of control. As long as a gas atmosphere is used, the oxidizing power can be easily controlled by adjusting the concentration and the pressure of the oxidizing gas and the process time can be freely set since the progress of oxidation of the coal and the caking additive can be immediately stopped by substituting the oxidizing gas with inert gas after the treatment. Here, weathering progresses fast with higher oxidizing gas concentrations and higher pressures. In contrast, when an oxidizing liquid atmosphere is used, it is difficult to rapidly separate the liquid atmosphere from the coal and the caking additive after the weathering treatment and thus the oxidizing liquid atmosphere is not preferred for controlling the progress of weathering. [0058] The oxidizing atmosphere that is least expensive and easily available in large quantities is air in the ambient atmosphere. When industrial mass treatment is desired, it is preferable to use air in the ambient atmosphere as the Our.Ref.,2011S01226 - 49 oxidizing atmosphere. [0059] The treatment temperature during weathering may be any temperature in the range of room temperature to a temperature immediately before onset of thermal plasticization. Since the weathering progresses faster with the increasing temperature, the treatment time required decreases with the increase in treatment temperature. The inventors have investigated the influence of the treatment temperature on the properties of weathered coal and have found that the rate at which the permeation distance decreases becomes higher relative to the rate at which the maximum fluidity decreases as the treatment temperature increases. In other words, it is possible to preferentially decrease the permeation distance without significantly decreasing the maximum fluidity when weathering is conducted at higher temperatures. In other words, they have found that the preferred and effective treatment temperature and treatment time are high temperature and short treatment time. [0060] When a caking additive is rapidly weathered, spontaneous ignition caused by exothermic oxidation may occur and thus measures for preventing spontaneous ignition such as spraying water must be taken. If the treatment temperature is excessively high, the weathering occurs fast Our.Ref.,2011S01226 - 50 and it becomes difficult to control the properties after weathering. Moreover, since the caking additive starts releasing volatile matter due to pyrolysis beyond about 300'C, the thermal plasticity changes. The weathering treatment in a temperature range in which volatile matter is released involves a risk of explosion since combustible gas exists under heating conditions in the oxidizing atmosphere. [0061] For the reasons described above, the treatment temperature during weathering is preferably 100 0 C to 300 0 C and the treatment time is preferably 1 to 120 minutes. Most preferably, the treatment temperature during weathering is 180'C to 220'C and the treatment time is 1 to 30 minutes. [0062] The modification of the caking additive can be carried out by a heat treatment in a nitrogen atmosphere. Since the permeation distance and fluidity decrease by heating at a temperature near 400 0 C, the properties of the modified caking additive can be controlled by adjusting the temperature and time. [0063] In sum, the inventors have found that the decrease in coke strength can be suppressed by choosing the caking additives that decrease the coke strength, treating the caking additives under appropriate conditions, and modifying Our.Ref.,2011S01226 - 51 the caking additives so that an appropriate coking property is exhibited before blending, and made the present invention. [EXAMPLES] [EXAMPLE 1] [0064] The permeation distance was measured by using the instrument shown in Fig. 1. Since a high-frequency induction heating method was used as the heating method, a heater 8 shown in Fig. 1 was an induction heating coil and the material of the vessel 3 was graphite, which is a dielectric material. The diameter of the vessel was 18 mm and the height was 37 mm. Glass beads having a diameter of 2 mm were used as a material that has through-holes extending from the lower to upper surface. Into the vessel 3, 2.04 g of a coal sample pulverized to a particle size of 2 mm or less and vacuum-dried at room temperature was placed and the sample 1 was packed in the vessel 3 by dropping a 200 g weight onto the coal sample from a dropping distance of 20 mm five times (the thickness of the sample layer in this state was 10 mm) . Next, glass beads having a diameter of 2 mm were laid to a thickness of 25 mm on the sample 1 packed layer. A sillimanite disk having a diameter of 17 mm and a thickness of 5 mm was placed above the glass bead packed layer, a quartz bar serving as the dilatation detecting rod 13 was placed on the sillimanite disk, and a Our.Ref.,2011S01226 - 52 1.3 kg weight 14 was placed on top of the quartz bar. As a result, the pressure applied to the sillimanite disk was 50 kPa. Nitrogen gas was used as the inert gas and heating was conducted at a heating rate of 3 0 C/min to 550 0 C. After completion of the heating, the sample was cooled in a nitrogen atmosphere and the mass of the beads that did not consolidate with plastic coal was measured from the cooled vessel. Note that while the measurement conditions given above have been determined as the conditions preferred by the inventors for measuring the permeation distance in comparison with the measurement results under various other conditions, the method for measuring the permeation distance is not limited to this method. [0065] The thickness of the glass bead layer is to be equal to or larger than the permeation distance. In the cases where the softening and melting product had permeated to the top of the glass bead layer during measurement, the measurement is conducted again by increasing the amount of the glass beads. The inventors have carried out experiments in which the thickness of the glass bead layer was changed and confirmed that as long as the thickness of the glass bead layer is equal to or more than the permeation distance, the observed values of the permeation distance of the same sample are the same. In measuring the permeation distance Our.Ref.,2011S01226 - 53 of a caking additive that has a large permeation distance, a larger vessel was used and the amount of glass beads packed was increased. [0066] The height of the consolidated bead-packed layer was assumed to be the permeation distance. The relationship between the height and mass of a glass bead packed layer was determined in advance so that the height of the consolidated bead-packed layer could be derived from the mass of the beads bonded to the plastic coal. The result is formula (4) and the permeation distance was determined from formula (4): L = (G - M) x H ... (4) where L represents the permeation distance [mm], G represents mass [g] of the glass beads packed, M represents the mass [g] of the beads not consolidated with the plastic matter, and H represents the packed layer height [mn/g] per gram of glass beads packed in this experimental instrument. [00 67]1 The coals and caking additives used as raw materials for making coke were blended as below. According to a conventional coal blend theory for estimating the coke strength, the coke strength was considered to be determined mainly by the mean maximum vitrinite reflectance (Ro) and the logarithm of Gieseler maximum fluidity (log MF) (for example, refer to Non-Patent Literature 2). Based on this Our.Ref.,2011S01226 - 54 approach, coal blends in which various coals were blended so that the weighted average Ro of the whole coal blend was 0.99 and the weighted average log MF was 2.2. Each coal was pulverized so that coal particles having a diameter of less than 3 mm accounted for 100 mass% and the moisture content of the whole coal blend was adjusted to 8 mass%. To 16 kg of each coal blend, a caking additive pulverized to the same size as the coal was added at a blending ratio of 3%, and the resulting mixture was packed in a carbonization can so that the bulk density was 750 kg/m. A 10 kg weight was placed thereon, and carbonization was conducted for 6 hours in an electric furnace at a furnace wall temperature of 1050'C. The carbonized material was discharged from the furnace and cooled in nitrogen to obtain coke. Three types of caking additives were used: caking additive A with a permeation distance of 11.0 mm (log MF = 3.4): ash content: 0.2 mass%, melting range: 360'C to 500 0 C caking additive B with a permeation distance of 20.0 mm (log MF = 3.5): ash content: 0.2 mass%, melting range: 350'C to 505 0 C caking additive C with a permeation distance of 45.6 mm (log MF = 4.8): ash content: 0.1 mass%, melting range: 250'C to 530 0

C

Our.Ref.,2011S01226 - 55 [0068] The coke strength of the obtained coke was calculated by measuring the mass ratio of the coke particles having a diameter of 15 mm or more after rotated 150 turns at 15 rpm in accordance with the drum strength test method set forth in JIS K 2151 and calculating the ratio of the obtained mass ratio to the ratio before rotating to determine the drum strength DI 150/15. Since the weighted average permeation distance of this coal blend was 7.5 mm, the caking additives B and C comply with the conditions of (C) and (D) above. [0069] The constants a and a' in formulae (1) and (2) were each set to 4.0 which was coincident with the slope of a linear regression line calculated on the basis of the values of the permeation distance and maximum fluidity of coals constituting a coal blend in which a plurality of coals were mixed and to which the caking additive was to be added. The constant b in formula (2) was set to 3.0 which is five times the value of standard deviation, i.e., 0.6, under the measurement conditions of the present invention. Based on these formulae, the positional relationships between the permeation distance and the maximum fluidity of the caking additives A and B used in this example and the ranges defined in (A) and (B) above are shown in Figs. 5 and 6. As shown in Figs. 5 and 6, the caking additive B is in the Our.Ref.,2011S01226 - 56 ranges of conditions of defined in (A) and (B). Although the caking additive C is not indicated in the graphs, it is in the ranges of conditions defined in (A) and (B). In contrast, the caking additive A is outside the ranges defined in (A) and (B) and has a fluidity within a preferable range of fluidity, i.e., log MF 2.5. [0070] The results of coke strength measurement are shown in Table 1. For reference, CSR (coke strength after CO 2 reaction measured in accordance with ISO 18894) and micro strength (MSI +65) were also measured. These examples show that the coke strength is greatly improved when the caking additive A having a permeation distance of 11.0 mm and outside the ranges defined in (A) to (D) was used although the coke strength is improved by addition of any caking additive. [0071] Our.Ref.,2011S01226 - 57 [Table 1] 1-1 1-2 1-3 1-4 No. Comparative Example Comparative Comparative Example Example Example Caking additive None A B C DIl150/15(-) 81.1 83.5 82.2 81.6 CSR (%) 53.0 60.2 56.0 54.7 MSI +65 (%) 53.1 56.2 54.3 53.7 [EXAMPLE 2] [0072] Cokes 2-1 to 2-6 were produced as in Example 1 except that the mean particle diameter of the caking additive was changed. The strength of the obtained cokes were evaluated (Table 2). [0073] [Table 2] 2-1 2-2 2-3 2-4 2-5 2-6 No. Comparative Example Example Comparative Comparative Comparative Example Example Example Example CaditiA A A B B B Average particle diameter 0.3 0.5 1.5 0.3 0.5 1.5 (mm) DI 150/15 83.1 83.4 83.3 82.8 82.0 81.3 [0074] These examples show that the influence of the mean particle diameter on the coke strength is negligible when the caking additive A having a permeation distance of 11.0 Our.Ref.,2011S01226 - 58 mm is used but the strength decreases with the increase in the particle diameter when the caking additive B having a permeation distance of 20.0 mm is used. If the mean particle diameter is 0.3 mm, the difference between the caking additives A and B is small but the difference widens when the mean particle diameter is 0.5 mm or more. In other words, the coke-strength-improving effect is large when a caking additive having a small permeation distance is used in the cased where a caking additive having a mean particle diameter of 0.5 mm or more is added. [EXAMPLE 3] [0075] The caking additive B having a permeation distance of 20.0 mm used in Example 1 was heat-treated in air at 150'C for 20 minutes to produce a modified caking additive Bl. The permeation distance of this caking additive was 14.1 mm and the maximum fluidity was 2.9. The same caking additive was heated in a nitrogen atmosphere at 385'C for 20 minutes to produce a modified caking additive B2. The permeation distance of this caking additive was 13.2 mm and the maximum fluidity was 3.1. Cokes were produced as in Example 1 except that the modified caking additives Bl and B2 were added. The strength of the resulting cokes was evaluated (Table 3). [0076] Our.Ref.,2011S01226 - 59 Since the weighted average permeation distance of each coal blend was 7.5 mm, the modified caking additives B1 and B2 obtained by modifying the caking additive B do not satisfy the conditions described in (C) or (D). The constants a, a', and b in formulae (1) and (2) were the same as in Example 1. Based on these formulae, the positional relationships between the permeation distance and the maximum fluidity of the modified caking additives used in this example and the ranges defined in (A) and (B) were investigated and the results are shown in Figs. 7 and 8. As shown in Figs. 7 and 8, the modified caking additives B1 and B2 are outside the ranges defined in (A) and (B) . They also have a fluidity in a preferred fluidity range, i.e., log MF > 2.5. [0077] [Table_3] 1-3 3-1 3-2 No. Comparative Example Example Example Example _ Example Caking additive B B1 B2 DI 150/15 (-) 82.2 83.6 83.4 [0078] These examples clearly show that when the permeation distance of a caking additive is adjusted to be below the ranges defined in (A) to (D) by heating the caking additive or leaving the caking additive in an oxygen-containing atmosphere at room temperature or higher, the strength of - 60 the coke can be improved by addition of the caking additive to the coal blend for making coke. [0078a] It is to be understood that, if any prior art 5 publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. [0078b] 10 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, is i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. Reference Signs List [0079] 1 caking additive 2 material having through-holes extending from the upper to lower surface 3 vessel 5 sleeve 7 thermometer 8 heater 9 temperature detector 10 temperature controller 11 gas inlet 12 gas outlet 13 dilatation detecting rod 14 weight 15 displacement meter 16 circular through-hole 17 packing particles 18 packing columns CXNRPortbl\GHMatters\KRSTENA\5183503_1 doox 7/03/14

Claims

1. A method for producing a metallurgical coke by carbonizing coal, the method comprising measuring a permeation distance of a caking additive to be added to coal and conducting carbonization by adding a caking additive having a permeation distance equal to or lower than a predetermined value to the coal.

2. The method for producing a metallurgical coke according to Claim 1, wherein the coal is a coal blend that contains a plurality of types of coal and the predetermined value of the permeation distance is defined by formula (1) below: Permeation distance = 1.3 x a x log MFp (1) where a is a constant equal to 0.7 to 1.0 times a coefficient of a common logarithm, log MF, of a Gieseler maximum fluidity MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value. Our.Ref.,2011S01226 - 62

3. The method for producing a metallurgical coke according to Claim 2, wherein a is a constant equal to 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend.

4. The method for producing a metallurgical coke according to Claim 1, wherein the coal is a coal blend that contains a plurality of types of coal and the predetermined value of the permeation distance is defined by formula (2) below: Permeation distance = a' x log MFp + b (2) where a' is a constant equal to 0.7 to 1.0 times a coefficient of a common logarithm, log MF, of a Gieseler maximum fluidity MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in the coal blend; b is a constant equal to or more than but not more than 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from Our.Ref.,2011S01226 - 63 brands used in obtaining the linear regression line; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value.

5. The method for producing a metallurgical coke according to Claim 4, wherein a' is a constant equal to 0.7 to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend.

6. The method for producing a metallurgical coke according to Claim 1, wherein the coal is a coal blend that contains a plurality of types of coal and the predetermined value of the permeation distance is 2.0 times a weighted average permeation distance of the coal blend.

7. The method for producing a metallurgical coke according to Claim 1, wherein the predetermined value of the permeation distance is 15 mm according to a value observed when a sample of the caking additive prepared by pulverizing the caking additive so that particles having a diameter of 2 Our.Ref.,2011S01226 - 64 mm or less account for 100 mass% and packing a vessel with the pulverized caking additive at a packing density of 0.8 g/cm 3 to a layer thickness of 10 mm is heated in an inert gas atmosphere from room temperature to 550 0 C at a heating rate of 3 0 C/min while a load is applied from above glass beads having a diameter of 2 mm placed on the sample so that the pressure is 50 kPa.

8. The method for producing a metallurgical coke according to any one of Claims 1 to 7, wherein a mean particle diameter of the caking additive to be added is 0.5 mm or more.

9. The method for producing a metallurgical coke according to any one of Claims 1 to 8, wherein the caking additive to be added is an organic substance that has an ash content of 1 mass% or less and becomes plastic in a temperature range within a range of 300 0 C to 550 0 C.

10. The method for producing a metallurgical coke according to any one of Claims 1 to 9, wherein the caking additive is heat-treated or treated at room temperature or higher in an atmosphere that contains at least one component selected from 02, C0 2 , and H 2 0 so that the caking additive added to the coal comes to have a permeation distance smaller than Our.Ref.,2011S01226 - 65 the permeation distance before the treatment.

11. The method for producing a metallurgical coke according to Claim 10, wherein the caking additive to be added has been subjected to a treatment in an oxygen-containing atmosphere at a treatment temperature of 100'C to 300'C for a treatment time of 1 to 120 minutes.

12. The method for producing a metallurgical coke according to Claim 11, wherein the caking additive to be added has been subjected to a treatment in an oxygen-containing atmosphere at a treatment temperature of 180'C to 220'C for a treatment time of 1 to 30 minutes.

13. The method for producing a metallurgical coke according to any one of Claims 10 to 12, wherein log MF of the caking additive that has been heat-treated or treated at room temperature or higher in an atmosphere that contains at least one component selected from 02, C0 2 , and H 2 0 is 2.5 or more.

14. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF > 2.5, and a permeation distance equal to or less than a value Our.Ref.,2011S01226 - 66 defined by formula (1) below: Permeation distance = 1.3 x a x log MFp (1) where a is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among types of coal contained in a coal blend; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value.

15. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to be equal to or lower than a predetermined value defined by formula (1) below, the caking additive being prepared by heat-treating or treating at room temperature or higher in an atmosphere containing at least one component selected from 02, C0 2 , and H 2 0 an organic substance that becomes plastic in a temperature range within the range of 300'C to 550'C: Permeation distance = 1.3 x a x log MFp (1) where a is a constant equal to 1.0 times a coefficient of Our.Ref.,2011S01226 - 67 log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among types of coal contained in a coal blend; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value.

16. The caking additive for producing a metallurgical coke according to Claim 14 or 15, wherein a is a constant 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend.

17. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF > 2.5, and a permeation distance equal to or less than a value defined by formula (2) below: Our.Ref.,2011S01226 - 68 Permeation distance = a' x log MFp + b (2) where a' is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among the types of coal contained in a coal blend; b is a constant equal to 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from brands used in obtaining the linear regression line; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value.

18. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to be equal to or lower than a predetermined value defined by formula (2) below, the caking additive being prepared by heat-treating or treating at room temperature or higher in an atmosphere containing at least one component selected from 02, C0 2 , and H 2 0 an organic substance that becomes plastic in a temperature range within the range of 300'C to 550'C: Our.Ref.,2011S01226 - 69 Permeation distance = a' x log MFp + b (2) where a' is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of log MF < 2.5 among types of coal contained in a coal blend; b is a constant equal to 5 times a mean value of standard deviations obtained by measuring the same sample a plurality of times, the same sample being a sample of at least one brand selected from brands used in obtaining the linear regression line; and MFp is a Gieseler maximum fluidity (ddpm) of the caking additive, where if the maximum fluidity of the caking additive exceeds a detection limit, MFp is the highest detectable value.

19. The caking additive for producing a metallurgical coke according to Claim 17 or 18, wherein a' is a constant equal to 1.0 times a coefficient of log MF determined from a linear regression line passing through the origin, the linear regression line being obtained by using measured permeation distance and log MF of at least one type of coal having a log MF in the range of 1.75 < log MF < 2.50 among the types of coal contained in the coal blend. Our.Ref.,2011S01226 - 70

20. A caking additive for producing a metallurgical coke wherein the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF 2.5, and a permeation distance equal to or lower than a predetermined value defined by processes (a) and (b) below: (a) determining in advance types of coal that constitute a coal blend to which the caking additive is to be added and a blending ratio of each type of coal; and (b) setting the predetermined value to be 2.0 times a weighted average permeation distance of the coal blend.

21. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to be equal to or lower than a predetermined value defined by processes (a) and (b) below, the caking additive being prepared by heat treating or treating at room temperature or higher in an atmosphere that contains at least one component selected from 02, CO 2 , and H 2 0 an organic substance that becomes plastic in a temperature range within the range of 300 0 C to 550 0 C: (a) determining in advance types of coal that constitute a coal blend to which the caking additive is to be added and a blending ratio of each type of coal; and (b) setting the predetermined value to be 2.0 times a Our.Ref.,2011S01226 - 71 weighted average permeation distance of the coal blend.

22. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less, a Gieseler maximum fluidity satisfying log MF > 2.5, and a permeation distance of 15 mm or less according to a value determined through processes (c) to (f) below: (c) pulverizing the caking additive or a coal so that particles having a diameter of 2 mm or less account for 100 mass% and packing a vessel with the pulverized caking additive or coal at a packing density of 0.8 g/cm3 to a layer thickness of 10 mm to prepare a sample; (d) placing glass beads 2 mm in diameter on the sample to a layer thickness equal to or more than the permeation distance; (e) heating the sample from room temperature to 550'C at a heating rate of 3 0 C/min in an inert gas atmosphere while applying a load from above the glass beads so that a pressure is 50 kPa; and (f) measuring a permeation distance of the softening and melting sample that has permeated into the glass bead layer.

23. A caking additive for producing a metallurgical coke, wherein the caking additive has an ash content of 1 mass% or less and a permeation distance decreased to 15 mm or less Our.Ref.,2011S01226 - 72 according to a value determined by steps (c) to (f) below, the caking additive being prepared by heat-treating or a treating at a temperature equal to or more than room temperature in an atmosphere containing at least one component selected from 02, C0 2 , and H 2 0 an organic substance that becomes plastic in a temperature range within the range of 300'C to 550 C: (c) pulverizing the caking additive or a coal so that particles having a diameter of 2 mm or less account for 100 mass% and packing a vessel with the pulverized caking additive or coal at a packing density of 0.8 g/cm 3 to a layer thickness of 10 mm to prepare a sample; (d) placing glass beads 2 mm in diameter on the sample to a layer thickness equal to or more than the permeation distance; (e) heating the sample from room temperature to 550'C at a heating rate of 3 0 C/min in an inert gas atmosphere while applying a load from above the glass beads so that a pressure is 50 kPa; and (f) measuring a permeation distance of the softening and melting sample that has permeated into the glass bead layer.

24. The caking additive for producing a metallurgical coke according to Claim 15, 18, 21, or 23, wherein the treatment at room temperature or higher in the atmosphere containing - 73 at least one component selected from 02, C02, and H 2 0 is conducted at a treatment temperature of 100*C to 300*C for a treatment time of 1 to 120 minutes.

25. The caking additive for producing a metallurgical coke according to Claim 24, wherein the treatment at room temperature or higher in the atmosphere containing at least one component selected from 02, C02, and H 2 0 is conducted at a treatment temperature of 180*C to 220*C for a treatment time of 1 to 30 minutes.

26. The caking additive for producing a metallurgical coke according to Claim 15, 18, 21, 23, 24, or 25, wherein the caking additive has a log MF of 2.5 or more after being heat-treated or treated at room temperature or higher in the atmosphere containing at least one component selected from 02, C02, and H 2 0.

27. The method for producing a metallurgical coke according to claim 1, or the caking additive for producing a metallurgical coke according to any one of claims 14, 15, 17, 18, 20, 21, 22 or 23, substantially as herein described with reference to any one of the Examples and/or Drawings.