Journal of the Japan Institute of Energy
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ONLINE ISSN: 1882-6121
PRINT ISSN: 0916-8753

Journal of the Japan Institute of Energy Vol. 77 (1998), No. 9

  • Mechanism of Asphaltene Formation in Thermal Cracking of Athabasca bitumen

    pp. 877-887

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    DOI:10.3775/jie.77.877

    Insolubilization of pentane-soluble fraction from Athabasca bitumen in thermal cracking at 673 K was examined in N2 and H2 atmosphere and in the presence and absence of solvent. Reaction products were analyzed by 13C-nmr and VPO. In the absence of solvent, insolubilization occurred through two types of mechanisms; polymerization and dehydrogenation. The results of the thermal cracking of pentane-solubles in N2 and H2 atmosphere indicated that polymerization was dominant in the initial stages, while dehydrogenation took place predominantly in the later stages for nitrogen atmosphere. It was also observed that in the absence of solvent the main chemical reactions of pentane-solubles were naphthenic ring opening and consequential cracking of alkyl side chains. Whereas in the presence of solvents, 13C-nmr results indicated that aromatization of products without the naphthenic ring opening and gas formation by the cracking of alkyl side chains occurred in the both atmospheres . However, in the presence of tetralin as a solvent, yield of pentane-insolubles indicated that insolubilization of pentane-solubles was restricted, which could be due to the hydrogen donor ability and the dispersion of bitumen molecules in tetralin .
  • A Study on Optimal Repowering System of Recombustion Type

    pp. 888-895

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    DOI:10.3775/jie.77.888

    The repowering which is combined gas turbine to the used fossil power plant has an increasing effect of electric power supply and the thermal efficiency of power plant. In the repowering, the question now arises the more increasing parts of power plant remodels the more increasing cost of repowering.
    This paper is proposed a repowering system of recombustion type with minimized parts of power plant remodels and high thermal efficiency of total power plant system. The optimal repowering system is maximized performance index represented a thermal efficency of the repowering system. The system is satisfied with the constraint for operating the repowering plant. And we proposed the optimization for quantity of heat transfer at each parts of the boiler by the burner combustion control of upper and under stage for less remodeling parts of the power plant.
    A result of analysis, this repowering system has higher thermal efficiency of total fossil power plant system in spite of minimum parts of plant remodels. This system has an advantage to cost performance, and it will be applied the repowering to used fossil power plants extensively.
  • Study on Desulfurization of Coke Oven Gas by Diluted Ammonia Water

    pp. 896-905

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    DOI:10.3775/jie.77.896

    Reaction factor β is essential to analyse the performance of gas purification by means of chemical absorption. However, it is very difficult to calculate β which is expressed by complicated functions composed of several factors; order of chemical reaction, rate constant for chemical reaction, equilibrium constant for reaction, diffusivity of solvent gas and so on.
    Therefore, simple calculation method for β was studied in this work, and approximate equations were introduced to estimate β by means of H* and H. H* is ordinary Henry's law constant and H is Henry's law constant with chemical reaction.
    For HCN-NH3-H2O system, Henry's law constant with chemical reaction was measured by dynamic method. In case of H2S-NH3-H2O and CO2-NH3-H2O systems, constants were calculated based on Van Krevelen's experimental data.
  • Appearance of Rapid Carbon on Hydrogasification of Coal

    pp. 906-908

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    DOI:10.3775/jie.77.906

    The interesting behavior of so-called rapid carbon was examined in the hydrogasification of Taiheiyo coal at 5.0 MPa and 1173 K using rapid heating apparatus. The amount of rapid carbon was as much as about 40% of raw coal at an appropriate flow rate of hydrogen. However, when there was no flow, the rapid carbon appeared a little. This could be due to the chemical equilibrium between hydrogen -methane - carbon reactions or to the hindrance of hydrogen access by the cloud of volatile matter surrounding coal.
    When the char, which had been obtained after reaction in no hydrogen flow, was reacted again in a stream of hydrogen, the rapid carbon recovered. The char prepared at rapid heating in nitrogen also produced it in the reaction in hydrogen.

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