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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 90 (2004), No. 9

  • Expectation for Coke Quality Seen from Recent Blast Furnace Operation in Japan

    Isao OGATA, Morimasa ICHIDA

    pp. 600-608

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    Abstract

    The coke quality requested for the stable operation of a large-scale blast furnace under high production and low coke rate in the future is arranged based on a past finding concerning relation between the coke quality and the blast furnace operation analysis. And an expectation for next generation coke-making process (SCOPE21) which has the function to enable the above-mentioned coke quality and a necessary requirement are described.

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  • Strength of Coke

    Takatoshi MIURA

    pp. 609-613

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    Abstract

    The effects of non or slightly caking coal amount of blended coal and permeability of coke on coke strength have been reviewed. The optimal process control management index for the coke oven has been proposed not by the vitrinite reflactance but by the thermal plasticity based on the mechanism analysis of carbonization. The fissure formation mechanism has been clarified.
    The national project of SCOPE21 has been reviewed. An increase of plasticity has been proved by the experimentation of rapid heating rate process or mechanical pressurization.
    The mechanism of volume destruction and surface destruction has been also clarified. The simulation method of coke abrasion mechanism has been proposed in the raceway. The elucidation of a strength formation mechanism, measurement of the strength during heating process, and the estimation method of coke strength have been also shown.

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  • Development of the Innovative Cokemaking Process (SCOPE21) for the 21st Century

    Kunihiko NISHIOKA, Hironobu OSHIMA, Isao SUGIYAMA, Hideki FUJIKAWA

    pp. 614-619

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    Abstract

    Development of the innovative cokemaking process, SCOPE21 (Super Coke Oven for Productivity and Environmental enhancement toward the 21st century), had been conducted by the Japan Iron and Steel Federation (JISF) and the Center for Coal Utilization Japan (CCUJ). It had been performed from 1994 to 2003 as a ten-year research program. Some technologies for the SCOPE21 process had been developed to realize the following concepts, i.e.
    ( 1 ) Effective use of coal resources
    ( 2 ) High productivity
    ( 3 ) Energy saving
    ( 4 ) Environmental protection
    In 2002 the program was in the last stage of a pilot plant test to confirm the functions of the SCOPE21 process and to collect the scale-up data for designing a commercial plant. The pilot plant consists of a 6 t-coal/h coal pretreatment facility and a coke oven with its chamber volume of 27 m3. The specifications of the coal pretreatment facility were determined based on the test results of a 0.6 t-coal/h bench scale plant.
    The pilot plant was successfully operated on schedule for about one year until March 2003. The concepts of the SCOPE21 process were verified and the engineering data for designing a commercial plant were collected at the same time. Furthermore, the feasibility study was excuted according to the results.

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  • Coal Particle Behavior in a Continuous Fluidized Bed

    Shinichi SUYAMA, Kouji TAKATANI

    pp. 620-626

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    Abstract

    In the coal pretreatment process of SCOPE21, a continuous fluidized bed dryer is used as the first stage equipment before rapid heating in pneumatic preheaters. Since raw coal is simultaneously dried and classified into fine and coarse coal, coal particle behavior should he clarified to design the equipment. The separation behavior and RTD (residence time distribution) are studied. The separation behavior affects the fine and coarse coal ratio and RTD affects the heat efficiency for drying and heating. Both behaviors are important factors for designing the dimensions and operational conditions of the pilot and actual plant. In this paper, cold model and bench plant results are described.

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  • Development of Basic Design Model for Fluidized Bed and Study of Coal Drying, Heating and Classification Process on Fluidized Bed

    Kazunori NAGAI, Atsushi SUZUKI, Tatsunori SUNAGAWA, Shinichi SUYAMA

    pp. 627-633

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    Abstract

    SCOPE21 (Super Coke Oven for Productivity and Environmental enhancement toward 21st century) process was performed as a national project for the purpose of development of the next generation coke-making technology.
    In this process coal is pre-treated by a fluidized bed for drying, heating and classification.
    In this study, by bench plant examination and pilot plant examination, the quantitative elucidation of the phenomenon in the fluidized bed was elucidated for establishment of the basic design model of a fluidized bed process.
    As a result, by this model developed newly, a process design and process evaluation of a fluidized bed process became possible.

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  • Effect of Rapid Heating Conditions on Crack of Coal Particle

    Masaru NISHIMURA, Kazuma AMAMOTO

    pp. 634-640

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    Abstract

    In the SCOPE21 coke making process, there is a preheating process which raise the temperature of coal particles up to about 400°C before coal charging. It is known that coal particles are broken into pieces when they are heated rapidly to over 1000°C in the DIOS process1). It is undesirable that coal particles break into fine powder in preheating process of the SCOPE21. Because fine powder causes various troubles in coke making process such as carry over phenomenon. Then, effect of rapid heating condition on crack of coal particles from room temperature up to 380°C was investigated. Down flow type experimental apparatus was used in this study, and 6 kinds of coals were investigated about heat crack. From this investigation, next results were obtained.
    1) Crack of wet coal particles, in the case of direct rapid heating from room temperature up to 380°C, was remarkable.
    2) Degree of the heat crack of wet coal samples that Ro were about 0.70.8 was low in rapid heating.
    3) Degree of the heat crack of coal particles, in the case of rapid heating up to 380°C after heating and drying below 250°C, became lower.
    Preheating process was divided to two stages in the SCOPE21 coke making process. The first stage is the drying and preheating process in which coal particle is heated and dried and fine coal powder is separated in the same time. The second stage is the rapid heating tower process after the drying process. Obtained results were applied to the heating condition in two preheating processes.

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  • Thermoplastic Behavior of Coal under Rapid Heating Conditions

    Kiyoshi FUKADA, Shozo ITAGAKI, Izumi SHIMOYAMA

    pp. 641-647

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    Abstract

    The thermoplastic behavior of coal under various heating conditions was investigated using the rapid heating plastometer that was developed in this study. Coal samples were heated at a rate of 3-1800K/min with this instrument and the torque applied to the stirrer, which rotated at a constant speed, was measured. This torque was converted to apparent viscosity of coal in a plastic state.
    As the thermoplastic behavior of coal, minimum apparent viscosity and all the characteristic temperatures corresponding to softening, maximum fluidity and resolidification state observed by Gieseler method was estimated.
    Coal thermoplasticity was strongly dependent on the heating rate under the condition of rapid heating. All the characteristic temperatures were shifted to higher values remarkably while the minimum apparent viscosity decreased with the increase of heating rate. The minimum apparent viscosity decreased in case of weathered coal, which never shows Gieseler plasticity, over the heating rate of 1000K/min. The additivity of the minimum apparent viscosity was also examined for blended coals. Though no additivity was observed at low heating rate, with the increase of heating rate the difference between additive value and observed value became small.

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  • Heating-up Performance of the Coal Rapid Heating Process with Gas Flow Heating Tower

    Yuichi MATSUDA, Masahiko YOKOMIZO, Masaki SASAKI, Makoto MATSUURA

    pp. 648-655

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    Abstract

    Specifically, the method using a rapid heating is effective from the standpoints of reducing equipment cost and aiming at a simple process. The national project, "SCOPE21", is believed to be rendered highly practicable through the process of drying and classifying by the fluidized bed prior to the rapid heating.
    This paper clarifies, by the conduct of a pilot-plant test, the basic heating characteristics of the rapid heating tower, which is the principal one of the processes involved in the SCOPE21 process.
    By the results of temperature measurement of coarse coal and fine coal in the rapid heater, the effectiveness of the simulation model of the rapid heating process were verified, and temperatures were inferred for each particle size, using this model. As a result, we have been able to attain the target coal-heating rate of higher value than 2000°C per minute and also the target of temperature uniformity of coal particles to less than 50°C, thereby obtaining a good prospect for achieving the expected heating performance.
    Regarding the behaviors of coal particles within the sectional heater in the pilot plant, from the good dispersion of coal particles inside the tower, we have ascertained that biased distribution of coal particles charged into the heater become approximately uniform at the top of the tower 25 m in height.
    Cracking of coal particles within the rapid heater and other basic engineering data for the design of commercial plant have been gathered and tasks sorted out.

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  • Effects of Coal Blend Type and Preheating Temperature in Coal Rapid Preheating Process on Coke Strength

    Makoto MATSUURA, Masaki SASAKI, Kenji KATO, Yoshiaki NAKASHIMA

    pp. 656-660

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    Abstract

    In order to develop a coal preheating process, the effects of coal type and preheating conditions on coke strength were investigated. The blended coal of poor-coking coal 50% and coking coal 50% were preheated rapidly and carbonized by laboratory scale test. The following results were obtained.
    ( 1 ) As a result of investigation of three kind of poor-coking coal, the rapid preheating treatment improves coke strength irrespective of coal type.
    ( 2 ) It was found that rapid preheating treatment of coal improves coke strength in the case of coal blend which consists of six kind of coal.
    ( 3 ) The preheating condition to raise the coke strength has been revealed as follows; first of all, coal has to be heated up to 330-400°C; secondly, it is nessesally to prevent fault heating of coal over 400°C.

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  • Effect of Hot Briquetting Conditions on Briquette Quality

    Koji HANAOKA, Koichi NUSHIRO, Katsutoshi IGAWA

    pp. 661-666

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    Abstract

    Hot fine coal briquetting with using double roll press in diameter 400 mm in several briquetting conditions were tested in order to research fundamental phenomena in SCOPE process. Effects of hot briquetting conditions and coal qualities to briquetting yields and briquette strengths were researched. The followings were found that: (1) Briquetting yields and briquette strengths were increased with the increase of briquetting temperature, and with the decrease of cup volume. (2) Briquetting yields and briquette strengths were increased with the increase of the number of rotation of screw feeder, which was used to supply compulsorily coal. (3) Briquetting yields and briquette strengths were decreased with the increase of the number of rotation of rolls. But increasing the number of rotation of screw feeder was recovered briquetting yields and briquette strengths. (4) Briquette strengths were increased with using more fluidity coal for coking and non- or slightly coking coals. (5) Briquetting yields and briquette strengths were increased little in wider coal diameter distribution.

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  • Effect of Hot Briquetting Conditions on Briquettability of Preheated Fine Coals

    Makoto MATSUURA, Masaki SASAKI, Kenji KATO, Yoshiaki NAKASHIMA

    pp. 667-672

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    Abstract

    A double-roll briquetting machine was selected to conduct hot briquetting of the preheated fine coal without binder. Since a scale-up theory for the briquetting machine has not been established, its diameter was set at 1200 mm as the same size as that of commercial scale machine.
    We were obtained as following findings about the effects of hot briquetting conditions on briquettability.
    (1) The relation between the residence time of coal in a hopper and gas pressure in a void of packed bed was clarified. Enough residence time is effective means to prevent increase of gas pressure during hot briquetting of the preheated fine coal.
    (2) When the briquetting temperature is more than 360°C, gas pressure in a void of packed bed rises rapidly over 5 kPa and the yield of briquette is decreased. In order to control gas pressure in a packed bed to 5 kPa or less, it is necessary to control the briquetting temperature 360°C or less.

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  • Development of Hot Coal Transport and Charging into Coke Ovens

    Hisashi KURIYAMA, Shuhei YOSHIDA, Hirofumi TAKETOMI, Shinichi SUYAMA

    pp. 673-678

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    Abstract

    One of the targets of the SCOPE21 process was to enhance the environment around coke ovens. In this process, the charging coal was preheated to about 380°C and charged into the coke oven. Because the fine coal tends to disperse at high temperature, it was necessary to convey and charge into coke ovens with closed system. So that, the plug transport system was tested in order to clarify the properties of the transportation and to find the design parameter by the fundamental transport test and the combined element bench scale test. The transport system of pilot plant was designed based on the results, and the test was carried out. It was confirmed that the properties of the transportation and the design parameter are appropriate. Moreover, the charging property of the preheated coal into a hot coke oven chamber was made clear, and it was confirmed that the plug transport system provides smokeless and safe charging of preheated coal.

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  • Development of Low NOx Combustion Structure in Coke Oven

    Shuhei YOSHIDA, Shoji TAKASE, Makoto UCHIDA, Takafumi SAJI, Hiroyuki KOYAMA, Masaaki YAMAMOTO

    pp. 679-685

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    Abstract

    One of the targets of the SCOPE21 process was to improve theproductivity. To achieve high productivity, the process was applied the following items; (1) ultra super dense brick, (2) thin wall (70 mm), (3) hot coal charging, (4) medium temperature carbonization. As the heat flux for carbonization was needed about 2 times as much as a conventional coke oven, the combustion technologies to achieve high productivity were investigated by using the actual scale combustion test oven. The combustion conditions to achieve low NOx in the waste gas and uniform heating for carbonization were clarified. The coke oven of the pilot plant was designed based on these results. The combustion targets of the low NOx and uniform heating were achieved in the test operation.

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  • Evaluation of Coke Strength and Coke Size in the SCOPE21 Process

    Yukihiro KUBOTA, Takashi ARIMA, Kenji KATO, Makoto MATSUURA, Hiroki NAKAI, Masaki SASAKI, Isao SUGIYAMA

    pp. 686-693

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    Abstract

    In the SCOPE21 pilot plant, it was verified whether the target of coke strength and coke mean size were attainable, when the proportion of poor coking coal in coal charge was 50%.
    As a result of the tests, it was confirmed that DI15015 was improved by 2.5 compared with a conventional process, which was higher than the coke strength, 84, usable for blast furnaces. The improvement of DI15015 is thought to be due to the increase of bulk density of coal charge, coking property improvement of coals by rapid preheating of coals and homogenization effect of coke texture.
    Moreover, it was confirmed that the appropriate coke mean size, 43 mm, was obtained by an anthracite addition even at the highest productivity (flue temperature: 1250°C) of the SCOPE21 process.

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  • Further Heating of Medium Temperature Carbonization Coke

    Kazuya UEBO

    pp. 694-700

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    Abstract

    Medium temperature carbonization is one of the technologies to increase productivity of a coke oven. However, strength of lower temperature coke is lower than that of high temperature coke. Then technology covering the decrease of coke strength will be necessary for accompanying the medium temperature carbonization. Heating medium temperature coke further to the high temperature carbonization level after pushed off the oven is one of the methods to modify coke quality.
    Medium temperature coke was made in a test coke oven and then heated further in a vessel by an electric heater passing model heating gas. The effect of heating conditions and of reactions with reactive gas on coke strength was investigated. It took coke less than one hour to be fully modified at the heating temperature. Carbonized coke below 750°C in a coke oven at oven center did not sufficiently recover its strength even in the non-reactive gas. Coke strength decreased in proportion to the weight loss by the reaction with carbon dioxide or steam similarly. However, coke strength slightly decreased in a reaction with oxygen.
    Change in gas composition along with flow was measured in a coke bed of more than 1.0 m. From the behavior of reactions between coke and reactive gas, their reaction rates were analyzed. Following these results, further heating situation in coke dry quencher (CDQ) by air injection was simulated and it is confirmed that medium temperature coke can be modified in its strength to that of high temperature coke in spite of the weakening of the coke strength by the reaction loss.

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  • Research on Upgrading of Low Temperature Coke by Air Blowing in Operating CDQ

    Hirofumi TAKETOMI, Isho YAMAGUCHI, Shozo ITAGAKI

    pp. 701-706

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    Abstract

    One of the targets in the SCOPE21 process was to enhance the productivity of coke ovens. For the high productivity, it was investigated to push the coke at a low temperature and to upgrade the low temperature coke by reheating in a CDQ. The coke reheating in this research, reheating of coke by air blowing was tested in an operating CDQ and some useful data were obtained by measurement probe. A three dimensional simulation model was developed based on those data, and this model could simulate the conditions of CDQ and upgrading effect of coke precisely.

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  • Numerical Analysis of Effect of Partial Combustion Air Introduction on Coke Re-heating Behavior in CDQ

    Yohsuke MATSUSHITA, Tetsuya YAGI, Yoshio MOROZUMI, Hideyuki AOKI, Takatoshi MIURA, Yukihiko MAENO

    pp. 707-714

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    Abstract

    In this study, the mathematical model for the solid-gas two phase combustion simulation is developed in order to analyze the effect of partial combustion air introduction on coke re-heating behavior in Coke Dry Quencher (CDQ). By introducing combustion air into the pre-chamber of CDQ, the coke quality is expected to be improved. Thus, it is necessary to understand the effect of partial air introduction on transport phenomena in CDQ.
    The difference of the transport phenomena such as gas flow, gas and coke temperature and concentration of chemical species in CDQ between with and without partial combustion is mainly discussed in this paper.
    Temperature is about 370K higher in both solid and gas phase with partial air than that without partial combustion around the surface of coke bed due to heat release of volatile matters combustion. In the middle of CDQ, however, the simulation results with partial combustion air introduction show the larger decreasing rate of coke temperature than that without air introduction because not only heat transfer between coke and quenching gas but also endoergic reactions such as C-CO2 and C-H2O are yielded due to higher temperature and more CO2 and H2O. Coke temperature is almost the same, that is 500K, at the bottom of CDQ, coke outlet.

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  • Effect of Hot Briquetting of Preheated Coal on Carry-over during Charging

    Makoto MATSUURA, Hiroki NAKAI, Masaki SASAKI, Kenji KATO

    pp. 715-720

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    Abstract

    Carry-over during coal charging is a significant factor in the increase of the carbon deposition in the coke oven chamber. Therefore, the technology of hot briquetting of fine coal has been developed in the SCOPE21 project, and the pilot scale test has been made in 2002. The main results of this study are shown below.
    (1) The ratio of particle 100 μm or less in coal charge could be decreased by hot briquetting of fine coal. As a result, it was confirmed that the amount of carry-over during coal charging could be reduced about 60% compared with the case of non-briquetting.
    (2) The gas velocity that passes through the free space of coke oven chamber affects carry-over particle size. In 75% period during coal charging, the gas velocity in the coke oven was 1 m/s or less. On that condition, it was hard that coal particle of 100 μm or more disperse.
    (3) The hot briquetting technology developed in this study was shown to be a valuable one even in commercial operation to reduce amount of carry-over on the during coal charging.

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  • Carbon Deposition in a Coke Oven Chamber at High Productivity Operation

    Kazuya UEBO, Hideyuki KUNIMASA, Shinichi SUYAMA

    pp. 721-727

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    Abstract

    SCOPE21 process uses thin oven wall of high thermal conductivity dense brick and pre-heated coal charging to achieve high coking rate. This suggests critical trouble by the increase of carbon deposits. Carbon deposition in a coke oven at high coking rate of SCOPE21 process was investigated in this study. The influences of temperature, fine coal and water existence on carbon deposition were studied in laboratory tests. Carbon deposition in coal charging and after charging was investigated in the pilot plant oven using test brick pieces.
    Carbon deposition rate in top space after charging was mainly affected by temperature and was little affected by fine coal briquetting. This is supported by the laboratory test. However, considering no moisture content, the rate was smaller than the one expected by the laboratory test. The amount of carbon deposits in top space in one carbonization period was small by means of the shorter coking time and the lower top space temperature. The amount of carbon deposits in coal charging was larger than the one after charging at ordinal operation of the pilot plant oven. The deposits in the top space derived from coal had been reduced by about one-half due to the fine coal briqetting.
    By applying the relationship between the carbon deposition rate in the top space and the temperature it was estimated that carbon deposits on chamber wall are not so large.
    From these results, it was concluded that the carbon deposition of SCOPE21 process is not such a serious problem.

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  • Effect of Coking Conditions on Rankin Coefficient of Coke Cake

    Takashi ARIMA, Koichi FUKUDA, Kenji KATO

    pp. 728-733

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    Abstract

    An innovative cokemaking process, SCOPE21 (Super Coke Oven for Productivity and Environmental enhancement toward the 21st century), has been developed by JISF (The Japan Iron and Steel Federation) and CCUJ (Center for Coal Utilization, Japan). As a cokemaking process, it is important to guarantee safe and stable pushing. Coke pushing behavior was studied by using a pilot-scale coke oven and influence of coking conditions on the Rankin coefficient was investigated. It was found that Rankin coefficient was dependent on lateral shrinkage and fissure density in coke cake and that it can be controlled by controlling the fissure density in SCOPE21 process.

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  • Effect of Coking Conditions on Coke Pushing Force at the SCOPE21 Pilot Plant

    Takashi ARIMA, Yukihiro KUBOTA, Kenji KATO, Makoto MATSUURA, Hirotaka NAKAI, Masaki SASAKI, Isao SUGIYAMA, Masaaki YAMAMOTO

    pp. 734-738

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    Abstract

    An innovative cokemaking process, SCOPE21 (Super Coke Oven for Productivity and Environmental enhancement toward the 21st century), has been developed by JISF (The Japan Iron and Steel Federation) and CCUJ (Center for Coal Utilization, Japan). A test plant has been constructed in Nippon Steel's Nagoya Works as the final phase of the project. Coke pushing behavior was studied at the pilot plant and influence of coking conditions on the pushing force was investigated.

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  • Interrelation between Blend Ratio and Heating Rate on Thermoplasticity of Coal Blends

    Toshimasa TAKANOHASHI, Kensuke MASAKI, Takahiro YOSHIDA, Koji HANAOKA, Atsushi DOBASHI

    pp. 739-742

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    Abstract

    Thermoplasticity for coal blends of a high-caking Goonyella coal and a slightly-caking Witbank coal was evaluated by a dynamic viscoelastic technique using a temperature-variable rheometer. At several blend ratios, effect of heating rate on the thermoplasticity for blends was investigated. At a heating rate of 3°C/min, for the coal blends containing 50% Witbank coal, the thermoplasticity was almost the same as Witbank coal alone, suggesting that Witbank coal has any negative effect for thermoplasticity of the blends with Goonyella coal. In contrast, in the cases of less than 30% Witbank coal contained, a sufficient thermoplasticity to produce metallurgical cokes was observed. On the other hand, when the heating rate was increased to 10°C/min, even for the blend containing 70% Witbank coal, a high thermoplasticity was obtained. This result indicates that the slight increase in heating rate greatly affected the thermoplasticity of coal blends. In addition, it is suggested the coal blend containing 70% slightly-caking Witbank coal can be used for cokemaking, when the heating rate is increased to 10°C/min during heating.

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  • Production of Metallurgical Coke from Low Grade Coals by Utilizing the Coal Extract Obtained at 350°C

    Ryuichi ASHIDA, Toshitaka NAKAI, Hiroyuki NAKAGAWA, Kouichi MIURA

    pp. 743-750

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    Abstract

    We have recently presented a new coal solvent extraction method that enhances the extraction yield dramatically. The method extracts coal using a flowing stream of a non-polar solvent such as tetralin under 10 MPa at 350°C. The extract yield reached 65 to 80% for bituminous coals at 350°C, and the extract was separated into about 25 to 40% of soluble fraction at room temperature (soluble) and about 40% of solid fraction which precipitated from the extract at room temperature (deposit). It was found that the soluble and the deposit were almost free from inorganic materials. In this paper we clarified by the thermomechanical analyses that the extracts had remarkable fusibility when heated. To utilize the characteristics of the extract, we investigated the possibility to produce metallurgical coke from slightly caking or non-caking coal by carbonizing it with the extract (5 to 1 mixing ratio). The carbonized material obtained by the co-carbonization was much harder than that prepared from coal itself even in the case of non-caking coal, indicating the possibility of producing metallurgical cokes from only slightly caking coals or non-caking coals. We also succeeded in preparing mesophase from the extract. This suggested the possibility of utilizing the extract as a feedstock of high performance carbon materials.

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  • © 2004 The Iron and Steel Institute of Japan

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