Changes in Viscosity of Single Coals and Their Blends upon Heating

摘要

Thermoplasticity of two different coals and their blends was investigated upon isothermal and non-isothermal heating at temperatures of 600—800 K. Changes in viscosity (η) and the fraction of liquid (φ_L, defined as that of mobile hydrogen) of softening coal in a form of disk were successfully measured by means of a variable-force-loading needle penetrometry coupled with a volumetric dilatometry and a proton nuclear magnetic resonance, respectively, η and φ_L changed with the temperature and time over ranges of 10~4—10~(10) Pa s and 0.03—0.53, respectively, depending upon the blending ratio and also the heating mode. For every single-coal/ blend, a single linear relationship between log η and φ_L i.e., log η = a — bφ_L, was confirmed over the temperature range and regardless of the heating mode, which indicated that the softening coal behaved as a mixture of liquid and "deformable" solid. It was found that both the parameters a and b were linear functions of the blending ratio, and the log η-φ_L relationships for the blends were thus predictable from those for the single coals. Furthermore, log η of the blends was reasonably approximated over the temperature/viscosity ranges only from those of the single coals by assuming additivity of log η.