An Investigation of the Mechanism of Influence of Coal-tar Pitch Additive on Changes in the Ordered Structure of Caking Coals during Pyrolysis

Abstract

The quantitative X-ray phase analysis and scanning electron microscopy were used to determine the influence of coal tar pitch on structural changes in co-pyrolyzed Polish coals—P, Z, and B—with good caking properties. It was stated that coal tar pitch weakened interactions between fragments of coal macromolecules and favored their higher mobility at the stage of swelling of the coal grains, which contributed to making the removal of plasticizing substances from these grains easier. It reduced the mobility of the macromolecular structure at the viscous-liquid stage. The decrease in the amount of the crystalline phase was influenced by the coal tar pitch at the temperature of re-solidification of the co-pyrolyzates of coals P and B. The intracrystalline ordering was blocked in the plastic layer of the co-pyrolyzates of coal Z and evaluated by an increase in the d₀₀₂ parameter.

Keywords:

• coal structure
• coal tar pitch
• scanning electron microscopy
• texture
• X-ray diffraction