Interactions between vitrinite and solid additives including inertinite during pyrolysis for coke-making considerations

Macerals (vitrinite and inertinite) were separated from a coal to understand the mechanism of interaction between them during coking. Macerals were blended in various ratios and their viscoelastic properties and expansion/contraction behaviour measured using rheometry. Inertinite increases the viscosity of vitrinite exponentially. To understand why, various solid additives were also blended with vitrinite. Additionally, the solid additives were mixed with a high viscosity liquid that does not generate volatiles (silicone oil). Results show that meso-porous solids increase viscosity exponentially, however, the exponent is far greater. Interestingly, the exponent for meso-porous and non-porous solids is the same for silicone oil, showing that volatiles are playing a role in viscosity development. Thermogravimetric analysis showed that far more volatiles are being retained for mesoporous solids, providing evidence to support the hypothesis that volatile adsorption is occurring. It is proposed that adsorption increases the driving force for liquid evaporation, which causes viscosity to increase. Only a small amount of adsorption occurred for the inertinite studied here and its effect on viscosity was mild and similar to graphite. The exponents in the viscosity vs % solid relationships could be used to evaluate solid additives, and hence, their effect on expansion/adhesion behaviour and pore structure development.