Title of Invention	PROCESS FOR PRODUCTION OF COKE AND PROCESS FOR PRODUCTION OF PIG IRON
Abstract	The present invention provides a technique of substituting reformed weakly coking coal or noncaking coal for strongly coking coal serving as coking coal, thereby enhancing the strength of resulting coke, and reducing the use amount of valuable strongly coking coal when the coke has the strength of the same level. A process for production of coke, characterized by carbonizing coking coal comprising 1 part by mass or less of substantially ash-free coal with respect to 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and the substantially ash-free coal which is contained in a coal having a carbon content (d. a. f.) of 60% or more and less than 95% is a soluble component obtained by extracting with organic solvent.

Title of Invention

PROCESS FOR PRODUCTION OF COKE AND PROCESS FOR PRODUCTION OF PIG IRON

Abstract

The present invention provides a technique of substituting reformed weakly coking coal or noncaking coal for strongly coking coal serving as coking coal, thereby enhancing the strength of resulting coke, and reducing the use amount of valuable strongly coking coal when the coke has the strength of the same level. A process for production of coke, characterized by carbonizing coking coal comprising 1 part by mass or less of substantially ash-free coal with respect to 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and the substantially ash-free coal which is contained in a coal having a carbon content (d. a. f.) of 60% or more and less than 95% is a soluble component obtained by extracting with organic solvent.

Full Text	DESCRIPTION TECHNICAL FIELD [0001] The present invention relates to techniques for production of coke using reformed coking coal, and a technique for production of pig iron using the techniques. BACKGROUND ART [0002] As coking coal for producing coke for blast furnaces, blended coal of high quality strongly coking coal and low quality weakly coking coal or noncaking coal have been used. By blending the high quality strongly coking coal, the strength of the resulting coke can be improved and gas permeability at the time of operation in a blast furnace can be secured. However, the high quality strongly coking coal has gradually been exhausting and a material cost of the coal has been increasing. Thus, techniques for reforming the low quality weakly coking coal and noncaking coal, which exist in a large amount, have been studied (Japanese Patent Laid-open Publication No. 51- 107301, Japanese Patent Laid-open Publication No. 51-107302, Japanese Patent Laid- open Publication No. 7-53965, Japanese Patent Laid-open Publication No. 8-269459, and Toru Nishi et al., "Use of SRC as Coking Coal," The 72nd Preliminary Presentation Report of Coke Special Meeting, pp. 46-49 (1982)) (hereinafter, simply referred to as "The 72nd Preliminary Presentation Report of Coke Special Meeting"). [0003] For example, Japanese Patent Laid-open Publication No. 51-107301 and Japanese Patent Laid-open Publication No. 51-107302 disclose that a caking filler having 60 to 25% of a volatile component and a caking index of 90% or more, which is obtained by mixing dust coal and a solvent under normal pressure or increased pressure, or optionally heating the mixture in a hydrogen atmosphere to obtain a coal reformed product and treating the coal reformed product, is blended with weakly coking coal or noncaking coal. Japanese Patent Laid-open Publication No. 7-53965 and "The 72nd Preliminary Presentation Report of Coke Special Meeting" disclose a method in which brown coal and the like is mixed with a hydrogen donor solvent to obtain a slurry, the slurry is hydrogenated and liquefied at high temperature under high pressure using a catalyst, then finally purified SRC (solvent refined coal) is separated and extracted, and the obtained product is used as coking coal for coke. DISCLOSURE OF THE INVENTION [0004] Under these circumstances, the present invention has been made and an object thereof is to provide techniques of enhancing the strength of resulting coke, and reducing the use amount of valuable strongly coking coal as the coke producing material when the coke has the strength of the same level and increasing the use amount of weakly coking coal or noncaking coal. [0005] A gist of the process for production of coke of the present invention lies in the use of coking coal comprising 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and 1 part by mass or less of substantially ash-free coal. Coal is commonly classified into anthracite, strongly coking coal, caking coal, weakly coking coal, noncaking coal, brown coal, peat and the like, but the definition is not necessarily clear. A portion of the coking coal may be sometimes referred to as caking coal. In the present invention, anthracite, strongly coking coal, caking coal, weakly coking coal, noncaking coal and the like are classified according to a carbon content (d. a. f.). For example, the anthracite is coal having a carbon content (d. a. f.) of more than 91%. The strongly coking coal is coal having a carbon content (d. a. f.) of 85% or more and 91% or less. The caking coal is coal having a carbon content (d. a. f.) of 83% or more and less than 85%. The weakly coking coal is coal having a carbon content (d. a. f.) of 80% or more and less than 83%. The noncaking coal is coal having a carbon content (d. a. f.) of 78% or more and less than 80%. The brown coal is coal having a carbon content (d. a. f.) of 70% or more and less than 78%. The peat is coal having a carbon content (d. a. f.) of less than 70%. As used herein, the carbon content (d. a. f. = dry ash free) refers to a carbon content (% by mass) of organic components (C, H, O, S, N) excluding a moisture content and an ash content of coal, and can be measured in conformity with JIS M8819. In the following description, coal having a carbon content (d. a. f.) of 85% or more and 91% or less may be sometimes simply referred to as "strongly coking coal", and coal having a carbon content (d. a. f.) of 60% or more and less than 85% may be sometimes simply referred to as "noncaking coal". [0006] In the present invention, when coking coal containing substantially ash-free coal in an amount within the above predetermined range to the blended coal is used, the strength of the resulting coke is improved. For example, it is preferred to use, as the substantially ash-free coal, a soluble component extracted from coal having a carbon content (d. a. f.) of 60% or more and less man 95% with an organic solvent(s). The organic solvent(s) is, for example, an organic solvent(s) containing a dicyclic aromatic compound(s) as a main component. The present invention includes a process for production of pig iron using coke obtained by the above process for production of coke. [0007] According to the present invention, coal obtained by reforming weakly coking coal or noncaking coal having a carbon content (d. a. f.) of 60% or more and less than 95% can be used as a substitute of a portion of strongly coking coal as a coke producing material, and thus the present invention can cope with problems such as exhaust of strongly coking coal and an increase in a material cost. Further, the resulting coke has excellent strength, and thus can be preferably used for producing pig iron in a blast furnace. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING [0008] Fig. 1 is an explanatory view showing an apparatus and a process for production of ash-free coal used in the present invention. BEST MODE FOR CARRYING OUT THE INVENTION [0009] The process for production of coke of the present invention comprises carbonizing coking coal comprising 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and 1 part by mass or less of substantially ash-free coal. [0010] First, substantially ash-free coal (hereinafter, sometimes simply referred to as "ash-free coal") used in the present invention will be described. The ash-free coal may be any substantially ash-free coal, but may contain a trace amount of ash. In this case, the ash content is preferably 5,000 ppm or less, and more preferably 2,000 ppm or less. In addition, the ash is an inorganic substance left when coal is converted into ash by heating at 815°C. For example, the ash includes silica, alumina, iron oxide, lime, magnesia and an alkali metal(s). [0011] In the present invention, it is preferred to use, as the ash-free coal, a soluble component(s) extracted from coal having a carbon content (d. a. f.) of 60% or more and less than 95% (more preferably 60% or more and less than 85%) with an organic solvent(s). This is because the process is not influenced by a problem such as exhaust of strongly coking coal when noncaking coal and the like is used as a starting material. In the present invention, it is particularly preferred to use, as the coal to be extracted with an organic solvent(s), weakly coking coal, noncaking coal, brown coal or a mixture thereof having a carbon content (d. a. f.) of 70% or more and less than 83%. [0012] More particularly, the ash-free coal can be obtained by mixing coal having a carbon content (d. a. f.) of 60% or more and less than 95% (more preferably 60% or more and less than 85%) with an organic solvent(s) to prepare a slurry, heating and aging the slurry, thereby extracting a soluble component(s) in the organic solvent(s), separating the resulting slurry into a overflow and a concentrated liquid in which a solid phase component(s) is concentrated, filtrating the overflow, and evaporating to remove the organic solvent(s). Fig. 1 is an explanatory view showing an apparatus and a process for production of ash-free coal. In a tank 1, a slurry is prepared by mixing coal having a carbon content (d. a. f.) of 60% or more and less than 95% with an organic solvent(s). The resulting slurry is supplied to an extraction vessel 4 which performs an extraction treatment using a pump 2. In this case, the slurry is heated to a predetermined temperature by a pre-heater 3. In the extraction vessel 4, a soluble component is extracted in the organic solvent(s) while stirring the slurry using a stirrer 10, and the slurry is supplied to a gravity precipitation vessel 5. In the gravity precipitation vessel 5, gravity precipitation is carried out so as to precipitate (an arrow 11) a solid phase component, and the slurry is separated into an overflow and a concentrated liquid in which the solid phase component is concentrated. The resulting overflow is supplied to a filter unit 8, and the solid phase component concentrated liquid precipitated in the gravity precipitation vessel 5 is recovered by a solid phase component concentrated liquid receiver 6. The overflow is filtered with a filter member 7 of the filter unit 8, and the resulting filtrate is recovered by an overflow receiver 9 for recovering an overflow. Then, ash-free coal can be obtained by evaporating to remove the organic solvent(s) from the recovered overflow. A method of evaporating to remove the organic solvent(s) from the overflow is, for example, a common drying method such as a spray dry method, an evaporating method or a vacuum drying method. [0013] A coal concentration in the slurry is properly 10 to 35% by mass. As for the conditions to heat and age the slurry so as to extract the soluble component(s) in the organic solvent(s), for example, the slurry is kept at 300°C to 420°C for 5 to 120 minutes so as to solubilize the soluble component(s) in coal. When the temperature is lower than 300°C, it is insufficient to weaken the bond between molecules constituting coal, and the ratio of a soluble component(s) which can be extracted from coal decreases. In contrast, when the temperature is higher than 420°C, a thermal decomposition reaction of coal becomes active, and the generated thermally decomposed radical is re-bonded. Thus, the ratio of an extracted soluble component(s) decreases also in this case. On the other hand, when the temperature is within a range from 300 to 420°C, the bond between molecules constituting coal is loosened so as to generate mild thermal decomposition, and thus the ratio of a soluble component(s) extracted from coal increases. At this time, due to mild thermal decomposition of coal, a component(s) with abundant aromatic groups having an average boiling point (Tb50: 50% distillation temperature) of 200 to 300°C is mainly produced and can be effectively used as a portion of an organic solvent(s). [0014] The temperature at which the resulting slurry is separated into the overflow and the solid phase component(s) concentrated liquid by gravity precipitation is preferably 300°C or higher to 420°C or lower. When the temperature is lower than 300°C, a portion of a component(s) dissolved in the liquid phase component(s) is precipitated, and thus the yield of ash-free coal may decrease. [0015] The organic solvent(s) is preferably a solvent(s) having a high dissolving power for coal, and is preferably an organic solvent(s) mainly containing a dicyclic aromatic compound(s) which is similar to a coal structure unit. Further, the organic solvent(s) preferably has a boiling point of 180°C to 330°C. When the boiling point is lower than 180°C, the recovery rate of the organic solvent(s) evaporated to remove from the overflow may decrease. On the other hand, when the boiling point is higher than 330°C, it is difficult to separate coal and the organic solvent(s), and thus the recovery rate of the organic solvent(s) may decrease. Specific examples of the dicyclic aromatic compound(s) include naphthalene (boiling point: 218°C); naphthalenes having an aliphatic side chain(s), such as methylnaphthalene (boiling point: 241 to 242°C), dimethylnaphthalene (boiling point: 261 to 272°C) and trimethylnaphthalene; biphenyl; biphenyls having an aliphatic side chain(s) or an aromatic substituent(s); or a mixture thereof. [0016] As coal (noncaking coal and the like) having a carbon content (d. a. f.) of 60% or more and less than 95%, as a starting material for producing ash-free coal, for example, coal having the following properties is preferably used. A volatile content of the noncaking coal and the like is preferably 30% or more, more preferably 32% or more, and preferably 40% or less, more preferably 36% or less. An average reflectance of the noncaking coal and the like is preferably 0.6 or more, more preferably 0.8 or more, and preferably 1.0 or less, more preferably 0.9 or less. A total inert of the noncaking coal and the like is preferably 5% or more, more preferably 15% or more, and preferably 35% or less, more preferably 20% or less. A Gieseler maximum fluidity (logMFD) of the noncaking coal and the like is preferably 3.0 (logddpm) or more, more preferably 3.3 (logddpm) or more, and preferably 4.5 (logddpm) or less, more preferably 3.6 (logddpm) or less. The volatile content is measured by a method defined in JIS M8812, the average reflectance is measured by a method defined in JIS M8816, and the Gieseler maximum fluidity (logMFD) is measured by a Gieseler plastometer method defined in JIS M8801. Further, the total inert (TI) can be calculated using the proportion of a semi-fusinite and the proportion of a fine composition component group (maceral group) among analyzed values of a coal fine composition component (maceral) in JIS M8816 by the following equation. [0017] In the equation, "MM" (mineral matter) denotes a mineral component, "A" denotes an ash content (dry basis, measured in conformity with JIS M8812), and "S" indicates a total sulfur content (dry basis, measured in conformity with JIS M8813). [0018] In a process for production of coke in the present invention, it is preferable to use coking coal containing 1 part by mass or less, preferably 0.7 parts by mass or less, and more preferably 0.5 parts by mass or less of ash-free coal based on 100 parts by mass of blended coal to be described later. The minimum content of the ash-free coal is not especially limited, but is preferably 0.2 parts by mass or more. [0019] By containing 0.2 parts by mass or more of ash-free coal, the strength of the resulting coke is substantially and significantly improved. Particularly, when the content of ash-free coal is 0.5 parts by mass, the strength of the resulting coke is the maximum value. On the other hand, when the content of ash-free coal is more than 0.5 parts by mass and 1 part by mass or less, the coke strength is more excellent than in the case of not adding ash-free coal. However, when the content of ash-free coal increases more, the coke strength tends to further decrease. Further, when the content is more than 1 part by mass, the coke strength rather decreases as compared with the case of adding no ash-free coal. [0020] The blended coal used in the present invention, which contains coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, will now be described. [0021] The blended coal is not especially limited as long as the blended coal contains coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%. The more preferable coal having a carbon content (d. a. f.) of 60% or more and less than 85% is weakly coking coal, noncaking coal or a mixture of these having a carbon content (d. a. f.) of 78% or more and less than 83%. A combination of coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85% is, for example, a combination of strongly coking coal and weakly coking coal, a combination of strongly coking coal and noncaking coal, and a combination of strongly coking coal, weakly coking coal and noncaking coal. [0022] The coal (strongly coking coal) having a carbon content (d. a. f.) of 85% or more and 91% or less in the blended coal is blended for increasing the coke strength to be obtained, and a blending amount is preferably 10 parts by mass or more, and more preferably 40 parts by mass or more with respect to 100 parts by mass of the whole blended coal. When the blending amount of strongly coking coal is less than 10 parts by mass, a caking component is too insufficient. Thus, even when 1 part by mass or less of ash-free coal is added to 100 parts by mass of blended coal, desired coke strength may not be obtained. On the other hand, the maximum of the blending amount of strongly coking coal is not especially limited, but is preferably 100 parts by mass, more preferably 90 parts by mass, and even more preferably 60 parts by mass. When the blending amount of strongly coking coal is too large, a raw material cost at the time of producing coke increases. On the other hand, the coal (noncaking coal and the like) having a carbon content (d. a. f.) of 60% or more and less than 85% is preferably blended so as to have a total blending amount of the coal and strongly coking coal to be 100 parts by mass. [0023] In the present invention, blended coal obtained by blending strongly coking coal and noncaking coal and the like preferably has the following properties. The volatile components of the blended coal is preferably 15% or more, more preferably 26% or more, and preferably 35% or less, more preferably 29% or less. The average reflectance of the blended coal is preferably 0.65 or more, more preferably 1.00 or more, and preferably 1.60 or less, more preferably 1.10 or less. The total inert of the blended coal is preferably 15% or more, more preferably 20% or more, and preferably 35% or less, more preferably 23% or less. The Gieseler maximum fluidity (logMFD) of the blended coal is preferably 0.7 (logddpm) or more, more preferably 2.0 (logddpm) or more, and preferably 3.5 (logddpm) or less, more preferably 2.3 (logddpm) or less. As for the particle size constitution of the blended coal, particles of 3 mm or less are preferably 50% or more, more preferably 75% or more, and preferably 90% or less, more preferably 85% or less. The wide value range of the above each property is proper to use each coal as a raw material of cake for a blast furnace. When the value range of each property is narrower, coke substantially having no problem in strength can be obtained. [0024] A process for production of coke of the present invention comprises carbonizing coking coal comprising 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and 1 part by mass or less of substantially ash-free coal. [0025] The condition of carbonizing the coal is not especially limited, and a common carbonizing condition for producing coke using a coke furnace can be used. For example, the temperature is preferably 950°C or higher, more preferably 1,000°C or higher, and preferably 1,200°C or lower, more preferably 1,050°C or lower. The carbonizing time is preferably 8 hours or more, more preferably 10 hours or more, and more preferably 24 hours or less, more preferably 20 hours or less. [0026] The present invention includes a process for production of pig iron, in which coke obtained by a process for production of coke of the present invention is used. Since coke obtained by the production process of the present invention has excellent strength, the coke can be suitably used for producing pig iron in a blast furnace. That is, when the coke obtained by the production process of the present invention is used, gas permeability at the time of producing pig iron in a blast furnace is improved. In addition, as the process for production of pig iron in a blast furnace, a publicly known process can be used. For example, the process includes the steps of alternately stacking iron ore and coke in a blast furnace so as to have a layer state, and blowing hot blast and dust coal if necessary into the blast furnace from a lower part of the blast furnace. EXAMPLES [0027] The present invention will now be described in detail by way of examples. However, the present invention is not limited to these examples, and includes all modifications and embodiments within the range not separating from the objective of the present invention. [0028] As shown in Table 1, coking coal was prepared by adding ash-free coal to blended coal. The ash-free coal was a soluble component (having an ash content of 600 ppm) extracted from caking coal from Australia (having a carbon content (d. a. f.) of 84%) by using 1-methylnaphthalene. In addition, the ash-free coal was prepared using an apparatus of Fig. 1 by the following process. A slurry was prepared by mixing the caking coal from Australia (having a carbon content (d. a. f.) of 84%) and 1-methylnaphthalene in a tank 1 (caking coal from Australia: 1-methylnaphthalene = 20% by mass: 80% by mass). The resulting slurry was heated with a pre-heater 3 to 370°C and a soluble component was extracted from the caking coal from Australia in an extraction vessel 4. The slurry subjected to an extraction treatment was supplied to a gravity precipitation vessel 5 at a flowing rate of 15 kg/h and then the slurry was separated into an overflow and a solid phase component concentrated liquid by gravity precipitation. Then, the overflow was supplied to a filter unit 8 at a flowing rate of 3 kg/h, and the solid phase component concentrated liquid was discharged from a bottom part of the gravity precipitation vessel 5 to a solid phase component concentrated liquid receiver 6 at a flowing rate of 12 kg/h. The overflow was filtrated by the filter unit 8, and recovered by an overflow receiver 9. Then, an organic solvent was evaporated and removed from a recovered liquid by a spray drying method so as to obtain ash-free coal (having an ash content of 600 ppm). [0029] The coking coal was put into a can container having a width of 378 mm, a length of 121mm and a height of 114 mm so as to attain a desired density (720 kg/m3 and 780 kg/m3). The four can containers were taken into a steel retort (size: 380 mm in width x 430 mm in length x 350 mm in height) while arranging the containers, and the retort was taken into a both-faces-heating-type electric furnace capable of heating the can containers in the width direction so as to carbonize the coking coal. The carbonizing was carried out at conditions of 1,000°C for 10 hours. Then, the retort was taken out from the electric furnace, and naturally cooled for about 16 hours. [0030] The four can containers were taken out from the cooled retort, and a piece of coke, which is at a portion apart 189 mm from the side edge of the carbonized coking coal, was cut. This length was equivalent to the half of the width direction. When both-faces-heating was carried out, a portion at the center of the width direction was referred to as a center of plastic layer, coke burned from a heated face to the center of plastic layer was referred to as a head, a body, and a tail from a portion close to the heated face in order. It is known that a difference of strength of the coal was generated by a difference of the heating rate at the time of heating the head, the body and the tail. Therefore, the coke cut at the 189 mm portion equivalent to the half of the width direction was divided into three portions at about 60 mm. The divided portions corresponded to the head, body, and tail portions. Then, an approximately rectangular parallelepiped body (one side: about 20 mm ± 1 mm) was cut out from each divided portion so as to obtain coke in which a particle size was regulated. The particle size-regulated coke was washed with distilled water so as to remove fine particles of coke adhered at the time of regulating a particle size (cutting out). Then, the coke was dried with a dryer at 150°C±2°C. The dried and particle size-regulated coke pieces were made into samples for measuring strength by selecting 12 pieces from the head portion, 12 pieces from the body portion, and 11 pieces from the tail portion when the bulk density of coking coal was 780 kg/m3, or by selecting 12 pieces from the head portion, 13 pieces from the body portion, and 11 pieces from the tail portion when the bulk density of coking coal was 720 kg/m3 to make the total amount 200 g. [0031] An I-type strength was measured by using the resulting samples for measuring strength. An apparatus used for the I-type strengdi test was a cylindrical container made of a SUS material (length: 720 mm, bottom face diameter of the circle: 132 mm). 200 g of the samples were put in this container, rotated for 30 minutes at the rotating rate of 20 times per one minute, and impact was given to the samples by 600 times of rotation movements in total. The cylinder was rotated by providing a rotary shaft at a portion apart 360 mm from the side, which was a center of the lengdi of the cylinder of 720 mm, and rotating the cylinder centering on the rotary shaft so mat the bottom face of the cylinder takes a circle movement having a diameter of 720 mm. After the samples were impacted by the specified rotation of 600 times, the samples were taken out from the cylindrical container, and sieved by a sieve having openings of 9.5 mm. Then, the mass of the samples left on the sieve was measured. At this time, the samples caught on the sieve were regarded as the samples left on the sieve and the mass thereof was also measured. The I-type strengdi index was calculated by the following equation.The calculated results were shown in Table 1 [0032] I-type strength index I6009.5 = Mass on sieve of 100 x 9.5 mm (unit: g)/200 g In addition, the rotational strength of coke is generally classified into the evaluation of volume destruction in which coke blocks are broken as large blocks, and the evaluation of surface destruction due to abrasion on the surface of coke. The I- type strength index I6009.5 used in the present invention was considered to be an index used for evaluating the surface destruction. As is apparent from the results of Table 1, when coke No. 1 to No.5 are compared with coke No. 8 to No. 10, the coke strength is improved by adding 1 part by mass or less of ash-free coal based on 100 parts by mass of blended coal. Particularly, the coke strength obtained in the case of adding ash-free coal in an amount of 0.5 parts by mass based on 100 parts by mass of blended coal showed the highest value. Further, as is apparent from the results of coke No. 6 and No. 7, the coke strength decreased on the contrary when the addition amount of ash-free coal was more than 1 part by mass with respect to 100 parts by mass of blended coal. [0034] In the case of comparing the case where the bulk density of coking coal is 780 kg/m (coke No. 1 and No. 3) with the case where the bulk density is 720 kg/m (coke No. 8 and No. 9), the coke strength improving effect in the case where the bulk density of coking coal is 720 kg/m3 is more improved than the case where the bulk density is 780 kg/m3. [0035] As for the coke No. 12, the ratio of strongly coking coal was lower than that of the coke No. 8, and the resulting coke strength decreased. However, when 0.5 parts by mass of ash-free coal was added, the coke strength was improved (coke No. 13). [0036] Further, when the coke No.9 is compared with the coke No. 11, it is found out that the strength improving effect by ash-free coal used in the present invention is higher than the strength improving effect of asphalt based pitch. INDUSTRIAL APPLICABILITY [0037] The present invention can be suitably applied to the production of coke and the production of pig iron in a blast furnace. WE CLAIM: 1. A process for production of coke, characterized by carbonizing coking coal comprising 1 part by mass or less of substantially ash-free coal with respect to 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and the substantially ash-free coal which is contained in a coal having a carbon content (d. a. f.) of 60% or more and less than 95% is a soluble component obtained by extracting with organic solvent. 2. The process for production of coke as claimed in claim 1, wherein the organic solvent contains a dicyclic aromatic compound as a main component. 3. A process for production of pig iron, which comprises using coke obtained by the process for production of coke as claimed in claims 1 or 2. ABSTRACT PROCESS FOR PRODUCTION OF COKE AND PROCESS FOR PRODUCTION OF PIG IRON The present invention provides a technique of substituting reformed weakly coking coal or noncaking coal for strongly coking coal serving as coking coal, thereby enhancing the strength of resulting coke, and reducing the use amount of valuable strongly coking coal when the coke has the strength of the same level. A process for production of coke, characterized by carbonizing coking coal comprising 1 part by mass or less of substantially ash-free coal with respect to 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and the substantially ash-free coal which is contained in a coal having a carbon content (d. a. f.) of 60% or more and less than 95% is a soluble component obtained by extracting with organic solvent.

Full Text

DESCRIPTION
TECHNICAL FIELD
[0001]
The present invention relates to techniques for production of coke using
reformed coking coal, and a technique for production of pig iron using the techniques.
BACKGROUND ART
[0002]
As coking coal for producing coke for blast furnaces, blended coal of high
quality strongly coking coal and low quality weakly coking coal or noncaking coal
have been used. By blending the high quality strongly coking coal, the strength of the
resulting coke can be improved and gas permeability at the time of operation in a blast
furnace can be secured. However, the high quality strongly coking coal has gradually
been exhausting and a material cost of the coal has been increasing. Thus, techniques
for reforming the low quality weakly coking coal and noncaking coal, which exist in a
large amount, have been studied (Japanese Patent Laid-open Publication No. 51-
107301, Japanese Patent Laid-open Publication No. 51-107302, Japanese Patent Laid-
open Publication No. 7-53965, Japanese Patent Laid-open Publication No. 8-269459,
and Toru Nishi et al., "Use of SRC as Coking Coal," The 72nd Preliminary
Presentation Report of Coke Special Meeting, pp. 46-49 (1982)) (hereinafter, simply
referred to as "The 72nd Preliminary Presentation Report of Coke Special Meeting").
[0003]
For example, Japanese Patent Laid-open Publication No. 51-107301 and
Japanese Patent Laid-open Publication No. 51-107302 disclose that a caking filler

having 60 to 25% of a volatile component and a caking index of 90% or more, which
is obtained by mixing dust coal and a solvent under normal pressure or increased
pressure, or optionally heating the mixture in a hydrogen atmosphere to obtain a coal
reformed product and treating the coal reformed product, is blended with weakly
coking coal or noncaking coal. Japanese Patent Laid-open Publication No. 7-53965
and "The 72nd Preliminary Presentation Report of Coke Special Meeting" disclose a
method in which brown coal and the like is mixed with a hydrogen donor solvent to
obtain a slurry, the slurry is hydrogenated and liquefied at high temperature under high
pressure using a catalyst, then finally purified SRC (solvent refined coal) is separated
and extracted, and the obtained product is used as coking coal for coke.
DISCLOSURE OF THE INVENTION
[0004]
Under these circumstances, the present invention has been made and an
object thereof is to provide techniques of enhancing the strength of resulting coke, and
reducing the use amount of valuable strongly coking coal as the coke producing
material when the coke has the strength of the same level and increasing the use
amount of weakly coking coal or noncaking coal.
[0005]
A gist of the process for production of coke of the present invention lies in
the use of coking coal comprising 100 parts by mass of blended coal containing coal
having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a
carbon content (d. a. f.) of 60% or more and less than 85%, and 1 part by mass or less
of substantially ash-free coal. Coal is commonly classified into anthracite, strongly
coking coal, caking coal, weakly coking coal, noncaking coal, brown coal, peat and

the like, but the definition is not necessarily clear. A portion of the coking coal may
be sometimes referred to as caking coal. In the present invention, anthracite, strongly
coking coal, caking coal, weakly coking coal, noncaking coal and the like are
classified according to a carbon content (d. a. f.). For example, the anthracite is coal
having a carbon content (d. a. f.) of more than 91%. The strongly coking coal is coal
having a carbon content (d. a. f.) of 85% or more and 91% or less. The caking coal is
coal having a carbon content (d. a. f.) of 83% or more and less than 85%. The weakly
coking coal is coal having a carbon content (d. a. f.) of 80% or more and less than
83%. The noncaking coal is coal having a carbon content (d. a. f.) of 78% or more
and less than 80%. The brown coal is coal having a carbon content (d. a. f.) of 70% or
more and less than 78%. The peat is coal having a carbon content (d. a. f.) of less than
70%. As used herein, the carbon content (d. a. f. = dry ash free) refers to a carbon
content (% by mass) of organic components (C, H, O, S, N) excluding a moisture
content and an ash content of coal, and can be measured in conformity with JIS
M8819. In the following description, coal having a carbon content (d. a. f.) of 85% or
more and 91% or less may be sometimes simply referred to as "strongly coking coal",
and coal having a carbon content (d. a. f.) of 60% or more and less than 85% may be
sometimes simply referred to as "noncaking coal".
[0006]
In the present invention, when coking coal containing substantially ash-free
coal in an amount within the above predetermined range to the blended coal is used,
the strength of the resulting coke is improved. For example, it is preferred to use, as
the substantially ash-free coal, a soluble component extracted from coal having a
carbon content (d. a. f.) of 60% or more and less man 95% with an organic solvent(s).
The organic solvent(s) is, for example, an organic solvent(s) containing a dicyclic

aromatic compound(s) as a main component. The present invention includes a
process for production of pig iron using coke obtained by the above process for
production of coke.
[0007]
According to the present invention, coal obtained by reforming weakly
coking coal or noncaking coal having a carbon content (d. a. f.) of 60% or more and
less than 95% can be used as a substitute of a portion of strongly coking coal as a coke
producing material, and thus the present invention can cope with problems such as
exhaust of strongly coking coal and an increase in a material cost. Further, the
resulting coke has excellent strength, and thus can be preferably used for producing
pig iron in a blast furnace.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
[0008]
Fig. 1 is an explanatory view showing an apparatus and a process for
production of ash-free coal used in the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0009]
The process for production of coke of the present invention comprises
carbonizing coking coal comprising 100 parts by mass of blended coal containing coal
having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a
carbon content (d. a. f.) of 60% or more and less than 85%, and 1 part by mass or less
of substantially ash-free coal.
[0010]

First, substantially ash-free coal (hereinafter, sometimes simply referred to as
"ash-free coal") used in the present invention will be described. The ash-free coal
may be any substantially ash-free coal, but may contain a trace amount of ash. In this
case, the ash content is preferably 5,000 ppm or less, and more preferably 2,000 ppm
or less. In addition, the ash is an inorganic substance left when coal is converted into
ash by heating at 815°C. For example, the ash includes silica, alumina, iron oxide,
lime, magnesia and an alkali metal(s).
[0011]
In the present invention, it is preferred to use, as the ash-free coal, a soluble
component(s) extracted from coal having a carbon content (d. a. f.) of 60% or more
and less than 95% (more preferably 60% or more and less than 85%) with an organic
solvent(s). This is because the process is not influenced by a problem such as exhaust
of strongly coking coal when noncaking coal and the like is used as a starting material.
In the present invention, it is particularly preferred to use, as the coal to be extracted
with an organic solvent(s), weakly coking coal, noncaking coal, brown coal or a
mixture thereof having a carbon content (d. a. f.) of 70% or more and less than 83%.
[0012]
More particularly, the ash-free coal can be obtained by mixing coal having a
carbon content (d. a. f.) of 60% or more and less than 95% (more preferably 60% or
more and less than 85%) with an organic solvent(s) to prepare a slurry, heating and
aging the slurry, thereby extracting a soluble component(s) in the organic solvent(s),
separating the resulting slurry into a overflow and a concentrated liquid in which a
solid phase component(s) is concentrated, filtrating the overflow, and evaporating to
remove the organic solvent(s). Fig. 1 is an explanatory view showing an apparatus
and a process for production of ash-free coal. In a tank 1, a slurry is prepared by

mixing coal having a carbon content (d. a. f.) of 60% or more and less than 95% with
an organic solvent(s). The resulting slurry is supplied to an extraction vessel 4 which
performs an extraction treatment using a pump 2. In this case, the slurry is heated to a
predetermined temperature by a pre-heater 3. In the extraction vessel 4, a soluble
component is extracted in the organic solvent(s) while stirring the slurry using a stirrer
10, and the slurry is supplied to a gravity precipitation vessel 5. In the gravity
precipitation vessel 5, gravity precipitation is carried out so as to precipitate (an arrow
11) a solid phase component, and the slurry is separated into an overflow and a
concentrated liquid in which the solid phase component is concentrated. The resulting
overflow is supplied to a filter unit 8, and the solid phase component concentrated
liquid precipitated in the gravity precipitation vessel 5 is recovered by a solid phase
component concentrated liquid receiver 6. The overflow is filtered with a filter
member 7 of the filter unit 8, and the resulting filtrate is recovered by an overflow
receiver 9 for recovering an overflow. Then, ash-free coal can be obtained by
evaporating to remove the organic solvent(s) from the recovered overflow. A method
of evaporating to remove the organic solvent(s) from the overflow is, for example, a
common drying method such as a spray dry method, an evaporating method or a
vacuum drying method.
[0013]
A coal concentration in the slurry is properly 10 to 35% by mass. As for the
conditions to heat and age the slurry so as to extract the soluble component(s) in the
organic solvent(s), for example, the slurry is kept at 300°C to 420°C for 5 to 120
minutes so as to solubilize the soluble component(s) in coal. When the temperature is
lower than 300°C, it is insufficient to weaken the bond between molecules
constituting coal, and the ratio of a soluble component(s) which can be extracted from

coal decreases. In contrast, when the temperature is higher than 420°C, a thermal
decomposition reaction of coal becomes active, and the generated thermally
decomposed radical is re-bonded. Thus, the ratio of an extracted soluble component(s)
decreases also in this case. On the other hand, when the temperature is within a range
from 300 to 420°C, the bond between molecules constituting coal is loosened so as to
generate mild thermal decomposition, and thus the ratio of a soluble component(s)
extracted from coal increases. At this time, due to mild thermal decomposition of coal,
a component(s) with abundant aromatic groups having an average boiling point
(Tb50: 50% distillation temperature) of 200 to 300°C is mainly produced and can be
effectively used as a portion of an organic solvent(s).
[0014]
The temperature at which the resulting slurry is separated into the overflow
and the solid phase component(s) concentrated liquid by gravity precipitation is
preferably 300°C or higher to 420°C or lower. When the temperature is lower than
300°C, a portion of a component(s) dissolved in the liquid phase component(s) is
precipitated, and thus the yield of ash-free coal may decrease.
[0015]
The organic solvent(s) is preferably a solvent(s) having a high dissolving
power for coal, and is preferably an organic solvent(s) mainly containing a dicyclic
aromatic compound(s) which is similar to a coal structure unit. Further, the organic
solvent(s) preferably has a boiling point of 180°C to 330°C. When the boiling point is
lower than 180°C, the recovery rate of the organic solvent(s) evaporated to remove
from the overflow may decrease. On the other hand, when the boiling point is higher
than 330°C, it is difficult to separate coal and the organic solvent(s), and thus the
recovery rate of the organic solvent(s) may decrease. Specific examples of the

dicyclic aromatic compound(s) include naphthalene (boiling point: 218°C);
naphthalenes having an aliphatic side chain(s), such as methylnaphthalene (boiling
point: 241 to 242°C), dimethylnaphthalene (boiling point: 261 to 272°C) and
trimethylnaphthalene; biphenyl; biphenyls having an aliphatic side chain(s) or an
aromatic substituent(s); or a mixture thereof.
[0016]
As coal (noncaking coal and the like) having a carbon content (d. a. f.) of
60% or more and less than 95%, as a starting material for producing ash-free coal, for
example, coal having the following properties is preferably used. A volatile content of
the noncaking coal and the like is preferably 30% or more, more preferably 32% or
more, and preferably 40% or less, more preferably 36% or less. An average
reflectance of the noncaking coal and the like is preferably 0.6 or more, more
preferably 0.8 or more, and preferably 1.0 or less, more preferably 0.9 or less. A total
inert of the noncaking coal and the like is preferably 5% or more, more preferably
15% or more, and preferably 35% or less, more preferably 20% or less. A Gieseler
maximum fluidity (logMFD) of the noncaking coal and the like is preferably 3.0
(logddpm) or more, more preferably 3.3 (logddpm) or more, and preferably 4.5
(logddpm) or less, more preferably 3.6 (logddpm) or less. The volatile content is
measured by a method defined in JIS M8812, the average reflectance is measured by a
method defined in JIS M8816, and the Gieseler maximum fluidity (logMFD) is
measured by a Gieseler plastometer method defined in JIS M8801. Further, the total
inert (TI) can be calculated using the proportion of a semi-fusinite and the proportion
of a fine composition component group (maceral group) among analyzed values of a
coal fine composition component (maceral) in JIS M8816 by the following equation.
[0017]

In the equation, "MM" (mineral matter) denotes a mineral component, "A"
denotes an ash content (dry basis, measured in conformity with JIS M8812), and "S"
indicates a total sulfur content (dry basis, measured in conformity with JIS M8813).
[0018]
In a process for production of coke in the present invention, it is preferable to
use coking coal containing 1 part by mass or less, preferably 0.7 parts by mass or less,
and more preferably 0.5 parts by mass or less of ash-free coal based on 100 parts by
mass of blended coal to be described later. The minimum content of the ash-free coal
is not especially limited, but is preferably 0.2 parts by mass or more.
[0019]
By containing 0.2 parts by mass or more of ash-free coal, the strength of the
resulting coke is substantially and significantly improved. Particularly, when the
content of ash-free coal is 0.5 parts by mass, the strength of the resulting coke is the
maximum value. On the other hand, when the content of ash-free coal is more than
0.5 parts by mass and 1 part by mass or less, the coke strength is more excellent than
in the case of not adding ash-free coal. However, when the content of ash-free coal
increases more, the coke strength tends to further decrease. Further, when the content
is more than 1 part by mass, the coke strength rather decreases as compared with the

case of adding no ash-free coal.
[0020]
The blended coal used in the present invention, which contains coal having a
carbon content (d. a. f.) of 85% or more and 91% or less and coal having a carbon
content (d. a. f.) of 60% or more and less than 85%, will now be described.
[0021]
The blended coal is not especially limited as long as the blended coal
contains coal having a carbon content (d. a. f.) of 85% or more and 91% or less and
coal having a carbon content (d. a. f.) of 60% or more and less than 85%. The more
preferable coal having a carbon content (d. a. f.) of 60% or more and less than 85% is
weakly coking coal, noncaking coal or a mixture of these having a carbon content (d.
a. f.) of 78% or more and less than 83%. A combination of coal having a carbon
content (d. a. f.) of 85% or more and 91% or less and coal having a carbon content (d.
a. f.) of 60% or more and less than 85% is, for example, a combination of strongly
coking coal and weakly coking coal, a combination of strongly coking coal and
noncaking coal, and a combination of strongly coking coal, weakly coking coal and
noncaking coal.
[0022]
The coal (strongly coking coal) having a carbon content (d. a. f.) of 85% or
more and 91% or less in the blended coal is blended for increasing the coke strength to
be obtained, and a blending amount is preferably 10 parts by mass or more, and more
preferably 40 parts by mass or more with respect to 100 parts by mass of the whole
blended coal. When the blending amount of strongly coking coal is less than 10 parts
by mass, a caking component is too insufficient. Thus, even when 1 part by mass or
less of ash-free coal is added to 100 parts by mass of blended coal, desired coke

strength may not be obtained. On the other hand, the maximum of the blending
amount of strongly coking coal is not especially limited, but is preferably 100 parts by
mass, more preferably 90 parts by mass, and even more preferably 60 parts by mass.
When the blending amount of strongly coking coal is too large, a raw material cost at
the time of producing coke increases. On the other hand, the coal (noncaking coal and
the like) having a carbon content (d. a. f.) of 60% or more and less than 85% is
preferably blended so as to have a total blending amount of the coal and strongly
coking coal to be 100 parts by mass.
[0023]
In the present invention, blended coal obtained by blending strongly coking
coal and noncaking coal and the like preferably has the following properties. The
volatile components of the blended coal is preferably 15% or more, more preferably
26% or more, and preferably 35% or less, more preferably 29% or less. The average
reflectance of the blended coal is preferably 0.65 or more, more preferably 1.00 or
more, and preferably 1.60 or less, more preferably 1.10 or less. The total inert of the
blended coal is preferably 15% or more, more preferably 20% or more, and preferably
35% or less, more preferably 23% or less. The Gieseler maximum fluidity (logMFD)
of the blended coal is preferably 0.7 (logddpm) or more, more preferably 2.0
(logddpm) or more, and preferably 3.5 (logddpm) or less, more preferably 2.3
(logddpm) or less. As for the particle size constitution of the blended coal, particles of
3 mm or less are preferably 50% or more, more preferably 75% or more, and
preferably 90% or less, more preferably 85% or less. The wide value range of the
above each property is proper to use each coal as a raw material of cake for a blast
furnace. When the value range of each property is narrower, coke substantially having
no problem in strength can be obtained.

[0024]
A process for production of coke of the present invention comprises
carbonizing coking coal comprising 100 parts by mass of blended coal containing coal
having a carbon content (d. a. f.) of 85% or more and 91% or less and coal having a
carbon content (d. a. f.) of 60% or more and less than 85%, and 1 part by mass or less
of substantially ash-free coal.
[0025]
The condition of carbonizing the coal is not especially limited, and a
common carbonizing condition for producing coke using a coke furnace can be used.
For example, the temperature is preferably 950°C or higher, more preferably 1,000°C
or higher, and preferably 1,200°C or lower, more preferably 1,050°C or lower. The
carbonizing time is preferably 8 hours or more, more preferably 10 hours or more, and
more preferably 24 hours or less, more preferably 20 hours or less.
[0026]
The present invention includes a process for production of pig iron, in which
coke obtained by a process for production of coke of the present invention is used.
Since coke obtained by the production process of the present invention has excellent
strength, the coke can be suitably used for producing pig iron in a blast furnace. That
is, when the coke obtained by the production process of the present invention is used,
gas permeability at the time of producing pig iron in a blast furnace is improved. In
addition, as the process for production of pig iron in a blast furnace, a publicly known
process can be used. For example, the process includes the steps of alternately
stacking iron ore and coke in a blast furnace so as to have a layer state, and blowing
hot blast and dust coal if necessary into the blast furnace from a lower part of the blast
furnace.

EXAMPLES
[0027]
The present invention will now be described in detail by way of examples.
However, the present invention is not limited to these examples, and includes all
modifications and embodiments within the range not separating from the objective of
the present invention.
[0028]
As shown in Table 1, coking coal was prepared by adding ash-free coal to
blended coal. The ash-free coal was a soluble component (having an ash content of
600 ppm) extracted from caking coal from Australia (having a carbon content (d. a. f.)
of 84%) by using 1-methylnaphthalene. In addition, the ash-free coal was prepared
using an apparatus of Fig. 1 by the following process. A slurry was prepared by
mixing the caking coal from Australia (having a carbon content (d. a. f.) of 84%) and
1-methylnaphthalene in a tank 1 (caking coal from Australia: 1-methylnaphthalene =
20% by mass: 80% by mass). The resulting slurry was heated with a pre-heater 3 to
370°C and a soluble component was extracted from the caking coal from Australia in
an extraction vessel 4. The slurry subjected to an extraction treatment was supplied to
a gravity precipitation vessel 5 at a flowing rate of 15 kg/h and then the slurry was
separated into an overflow and a solid phase component concentrated liquid by gravity
precipitation. Then, the overflow was supplied to a filter unit 8 at a flowing rate of 3
kg/h, and the solid phase component concentrated liquid was discharged from a
bottom part of the gravity precipitation vessel 5 to a solid phase component
concentrated liquid receiver 6 at a flowing rate of 12 kg/h. The overflow was filtrated
by the filter unit 8, and recovered by an overflow receiver 9. Then, an organic solvent

was evaporated and removed from a recovered liquid by a spray drying method so as
to obtain ash-free coal (having an ash content of 600 ppm).
[0029]
The coking coal was put into a can container having a width of 378 mm, a
length of 121mm and a height of 114 mm so as to attain a desired density (720 kg/m3
and 780 kg/m3). The four can containers were taken into a steel retort (size: 380 mm
in width x 430 mm in length x 350 mm in height) while arranging the containers, and
the retort was taken into a both-faces-heating-type electric furnace capable of heating
the can containers in the width direction so as to carbonize the coking coal. The
carbonizing was carried out at conditions of 1,000°C for 10 hours. Then, the retort
was taken out from the electric furnace, and naturally cooled for about 16 hours.
[0030]
The four can containers were taken out from the cooled retort, and a piece of
coke, which is at a portion apart 189 mm from the side edge of the carbonized coking
coal, was cut. This length was equivalent to the half of the width direction. When
both-faces-heating was carried out, a portion at the center of the width direction was
referred to as a center of plastic layer, coke burned from a heated face to the center of
plastic layer was referred to as a head, a body, and a tail from a portion close to the
heated face in order. It is known that a difference of strength of the coal was
generated by a difference of the heating rate at the time of heating the head, the body
and the tail. Therefore, the coke cut at the 189 mm portion equivalent to the half of
the width direction was divided into three portions at about 60 mm. The divided
portions corresponded to the head, body, and tail portions. Then, an approximately
rectangular parallelepiped body (one side: about 20 mm ± 1 mm) was cut out from
each divided portion so as to obtain coke in which a particle size was regulated. The

particle size-regulated coke was washed with distilled water so as to remove fine
particles of coke adhered at the time of regulating a particle size (cutting out). Then,
the coke was dried with a dryer at 150°C±2°C. The dried and particle size-regulated
coke pieces were made into samples for measuring strength by selecting 12 pieces
from the head portion, 12 pieces from the body portion, and 11 pieces from the tail
portion when the bulk density of coking coal was 780 kg/m3, or by selecting 12 pieces
from the head portion, 13 pieces from the body portion, and 11 pieces from the tail
portion when the bulk density of coking coal was 720 kg/m3 to make the total amount
200 g.
[0031]
An I-type strength was measured by using the resulting samples for
measuring strength. An apparatus used for the I-type strengdi test was a cylindrical
container made of a SUS material (length: 720 mm, bottom face diameter of the
circle: 132 mm). 200 g of the samples were put in this container, rotated for 30
minutes at the rotating rate of 20 times per one minute, and impact was given to the
samples by 600 times of rotation movements in total. The cylinder was rotated by
providing a rotary shaft at a portion apart 360 mm from the side, which was a center
of the lengdi of the cylinder of 720 mm, and rotating the cylinder centering on the
rotary shaft so mat the bottom face of the cylinder takes a circle movement having a
diameter of 720 mm. After the samples were impacted by the specified rotation of
600 times, the samples were taken out from the cylindrical container, and sieved by a
sieve having openings of 9.5 mm. Then, the mass of the samples left on the sieve was
measured. At this time, the samples caught on the sieve were regarded as the samples
left on the sieve and the mass thereof was also measured. The I-type strengdi index
was calculated by the following equation.The calculated results were shown in Table 1

[0032]
I-type strength index I6009.5 = Mass on sieve of 100 x 9.5 mm (unit: g)/200 g
In addition, the rotational strength of coke is generally classified into the
evaluation of volume destruction in which coke blocks are broken as large blocks, and
the evaluation of surface destruction due to abrasion on the surface of coke. The I-
type strength index I6009.5 used in the present invention was considered to be an index
used for evaluating the surface destruction.

As is apparent from the results of Table 1, when coke No. 1 to No.5 are
compared with coke No. 8 to No. 10, the coke strength is improved by adding 1 part
by mass or less of ash-free coal based on 100 parts by mass of blended coal.
Particularly, the coke strength obtained in the case of adding ash-free coal in an
amount of 0.5 parts by mass based on 100 parts by mass of blended coal showed the
highest value. Further, as is apparent from the results of coke No. 6 and No. 7, the
coke strength decreased on the contrary when the addition amount of ash-free coal
was more than 1 part by mass with respect to 100 parts by mass of blended coal.
[0034]
In the case of comparing the case where the bulk density of coking coal is
780 kg/m (coke No. 1 and No. 3) with the case where the bulk density is 720 kg/m
(coke No. 8 and No. 9), the coke strength improving effect in the case where the bulk
density of coking coal is 720 kg/m3 is more improved than the case where the bulk
density is 780 kg/m3.
[0035]
As for the coke No. 12, the ratio of strongly coking coal was lower than that
of the coke No. 8, and the resulting coke strength decreased. However, when 0.5
parts by mass of ash-free coal was added, the coke strength was improved (coke No.
13).
[0036]
Further, when the coke No.9 is compared with the coke No. 11, it is found
out that the strength improving effect by ash-free coal used in the present invention is
higher than the strength improving effect of asphalt based pitch.
INDUSTRIAL APPLICABILITY

[0037]
The present invention can be suitably applied to the production of coke and
the production of pig iron in a blast furnace.

WE CLAIM:
1. A process for production of coke, characterized by carbonizing coking coal
comprising 1 part by mass or less of substantially ash-free coal with respect to 100 parts by
mass of blended coal containing coal having a carbon content (d. a. f.) of 85% or more and
91% or less and coal having a carbon content (d. a. f.) of 60% or more and less than 85%, and
the substantially ash-free coal which is contained in a coal having a carbon content (d.
a. f.) of 60% or more and less than 95% is a soluble component obtained by extracting with
organic solvent.
2. The process for production of coke as claimed in claim 1, wherein the organic solvent
contains a dicyclic aromatic compound as a main component.
3. A process for production of pig iron, which comprises using coke obtained by the
process for production of coke as claimed in claims 1 or 2.

ABSTRACT

PROCESS FOR PRODUCTION OF COKE AND PROCESS FOR PRODUCTION
OF PIG IRON
The present invention provides a technique of substituting reformed weakly coking
coal or noncaking coal for strongly coking coal serving as coking coal, thereby enhancing the
strength of resulting coke, and reducing the use amount of valuable strongly coking coal when
the coke has the strength of the same level. A process for production of coke, characterized by
carbonizing coking coal comprising 1 part by mass or less of substantially ash-free coal with
respect to 100 parts by mass of blended coal containing coal having a carbon content (d. a. f.)
of 85% or more and 91% or less and coal having a carbon content (d. a. f.) of 60% or more
and less than 85%, and the substantially ash-free coal which is contained in a coal having a
carbon content (d. a. f.) of 60% or more and less than 95% is a soluble component obtained
by extracting with organic solvent.

PROCESS FOR PRODUCTION OF COKE AND PROCESS FOR PRODUCTION OF PIG IRON

Documents:

Inventors:

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