Synergistic effects on pyrolysis of binary and ternary coal blends studied by means of dynamic mechanical thermal analysis and Gieseler plastometer

Desirable values of technological indices of cokes produced from blends containing poor coking coals are expected due to mutual interactions between components during pyrolysis. The aim of this work was to study a synergistic effects postulated to occur during thermal decomposition of the binary (50:50) and the ternary blends of weakly-caking coals (from the Szczygłowice and Krupiński coal mines, Poland), blended with strongly caking coal (from the Zofiówka coal mine, Poland) of increasing content from 10 wt.% up to 100 wt.% with step of 10 wt.%. Pyrolysis of the blends was studied by means of the dynamic mechanical thermal analysis (DMTA) (shortened form is DMA) and the Gieseler plastometer. The results were related to the structure ordering degree of cokes performed from the blends mentioned above. Synergistic effects were detected in all blends, but strength of above was not the same. Divergences between temperature dependence of fluidity measured by the Gieseler plastometer and calculated one from the data of initial coals and their content in a blend under assumption of additivity, were higher for the binary blends in comparison with those of the ternary ones. The greatest synergistic effects were observed for the blends with the strongly caking coal content of 30–50 wt.%, for which high ordering of structure was registered. For these blends the greatest dissipation of the oscillation energy supported by the DMA apparatus was observed.

► Thermal decomposition of bituminous coal blends was studied with DMTA and Gieseler plastometer.
► Results were related to those obtained by means of XRD, TEM and Raman spectroscopy.
► Synergistic effects were detected on pyrolysis of all blends.
► Blends with 30–50 wt.% of strongly caking coal were characterized by the greatest synergistic effects.
► Blends of the greatest synergistic effects resulted in the most ordered cokes.