Enhancement of lignite microwave dehydration by cationic additives

Abstract The addition of materials with high dielectric parameters can improve lignite’s microwave absorption, thereby, enhancing lignite microwave dehydration. In order to explore the promotion effect of cationic additives on this process, five kinds of same and different valence state additives were studied in this paper. The physicochemical properties of the solid and liquid products under each condition were compared and analyzed in detail. Process characteristics, dehydration kinetics, and moisture diffusion coefficient results showed that the higher the cationic valence, the weaker the promotion effect of additives on lignite dehydration. When the cationic valence was the same, the promotion effect of additives was affected by the hydration radius of cations and solubility of additives. After microwave treatment, the pore structure of solid products at first decreased, then increased, ultimately developing into mesopore and micropore regions. Their absorption capacity was weakened according to contact angle tests. The significance was that the combustion of solid products was more complete, and the number of pollutants released was reduced. For liquid products, the content of organic matter and inorganic ions increased greatly. The surface tension first increased, followed by a decrease, indicating that the removal of organic matter gradually exceeded that of inorganic matter, and that additive had an effect on the microwave process of lignite sequentially through dehydration, dissolution of inorganic substances, and destruction of organic structure.