Journal of the Japan Institute of Energy
Online ISSN : 1882-6121
Print ISSN : 0916-8753
ISSN-L : 0916-8753
Volume 89 , Issue 4
Showing 1-2 articles out of 2 articles from the selected issue
Original Paper
  • Kei TAKAHASHI, Naohiro OHYAMA, Yuichiro DEGUCHI, Toshihiko NAKATA
    2010 Volume 89 Issue 4 Pages 355-363
    Published: 2010
    Released: May 12, 2010
    Bioethanol is expected as a prospective alternative to fossil fuels for mitigating greenhouse gas emissions. The study aims to design bioethanol production system utilizing energy crops in restorable fallow land in Japan and evaluate system performance based on energy balances, costs, and carbon emissions. The energy system has three processes such as cultivation, transportation, and manufacturing. In the analysis, energy potential in the area is calculated considering crop species, yields, chemical components, available land areas, and conversion efficiency. Then, the system performance is derived focusing on a local prefecture as a case study. The result shows that sorghum is expected to have the highest energy potential in most regions except for northern prefectures, and the amount of bioethanol produced from crops in fallow land is estimated to be about 2 million kl. Net energy value reaches -1.09 to 15.9 MJ/l. The total cost producing bioethanol is 2.4 to 8.9 times higher than petroleum fuel on calorific value basis. It is concluded that it is important to improve the productivity of the cultivation process of energy crops and to design optimized energy system to meet social requirements in near future.
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  • Yukihiko OKUMURA, Ken OKAZAKI
    2010 Volume 89 Issue 4 Pages 364-372
    Published: 2010
    Released: May 12, 2010
    A coal pyrolysis experiment under atmospheric and elevated pressure conditions using a thermobalance is carried out to clarify the yields of devolatilization products in many coals (i.e., coal ranks from low [C :73.1wt%, daf] to high [C: 90.6 wt%, daf, semi-anthracite]) and to clarify the effect of pressure on pyrolysis yields (tar and gas yields). As a result, a method for predicting the product yields of many coals is presented. Even coal containing almost the same percentage of carbon varies greatly in yield of volatile components and/or tar, but the use of H/C and O/C allows for systematic sorting. The yields of volatile and tar increase almost linearly with increasing H/C. CH4 and C2H4 yields also increase with increasing H/C. The yield of heavier gases such as C2H6, C3H6, and C3H8 cannot, however, be sorted by H/C. CO2 and CO yields are predictable since they increase linearly with increasing O/C. The yields of devolatilization products can be estimated with favorable accuracy for many types of coal by H/C and O/C. In addition, the tar yield decreases and the total yield of gas shows increasing behavior at elevated pressure conditions in all types of coal.
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