Quantification of the existence ratio of non-adhesion grain boundaries and factors governing the strength of coke containing low-quality coal

Tetsuya Kanai, Yoshiaki Yamazaki, Xiaoqing Zhang, Ataru Uchida, Yasuhiro Saito, Masakazu Shoji, Hideyuki Aoki, Seiji Nomura, Yukihiro Kubota, Hideyuki Hayashizaki, Shigeto Miyashita

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19 Citations (Scopus)

Abstract

"Non-adhesion grain boundaries" are formed when low-quality coal grains do not adhere to other grains in the carbonization process because of the low dilation of coke. To better understand the effects of non-adhesion grain boundaries on coke strength, the relationship between the existence ratio of non-adhesion grain boundaries and coke strength was investigated quantitatively. The existence ratio of non-adhesion grain boundaries were measured quantitatively by observing the fracture cross-section of coke using scanning electron microscopy (SEM). Coke strength was measured with a diametral-compression test and an I-shape drum index test. As a result, non-adhesion grain boundaries increased with an increase in the blending ratio of low-quality coal. In particular, non-adhesion grain boundaries increased rapidly when the blending ratio of low-quality coal was over 50%. When the ratio was less than 50%, low-quality coals adhered to other caking coal. However, not many low-quality coals adhered to other caking coals when the ratio was over 50%. The tensile strength of coke was not affected by the porosity of coke. However, the tensile strength and the drum index were affected by the existence ratio of non-adhesion grain boundaries. Tensile strength decreased rapidly even for a few non-adhesion grain boundaries because significant defects caused a fracture in the diametral-compression test. However, the I-shape drum index decreased linearly with the existence ratio of the non-adhesion grain boundaries because many fractures occurred during 600 rotations in the drum. The strength of coke containing low-quality coal is governed by the existence ratio of non-adhesion grain boundaries rather than mean values such as the porosity of coke.

Original languageEnglish
Pages (from-to)351-363
Number of pages13
JournalJournal of Thermal Science and Technology
Volume7
Issue number2
DOIs
Publication statusPublished - 2012 Aug 15

Keywords

  • Coke
  • Coke strength
  • Fracture cross-section
  • Low-quality Coal
  • Non-adhesion grain boundaries
  • Tensile strength

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Instrumentation
  • Engineering (miscellaneous)

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    Kanai, T., Yamazaki, Y., Zhang, X., Uchida, A., Saito, Y., Shoji, M., Aoki, H., Nomura, S., Kubota, Y., Hayashizaki, H., & Miyashita, S. (2012). Quantification of the existence ratio of non-adhesion grain boundaries and factors governing the strength of coke containing low-quality coal. Journal of Thermal Science and Technology, 7(2), 351-363. https://doi.org/10.1299/jtst.7.351