Separation of Residual Combustible Matter from Coal Gasification Fine Slag Using a Combined Supergravity-Sieving Process Enhanced by Ultrasonic Dispersion

The resource utilization of coal gasification fine slag (CGFS) is critical for reducing solid waste and promoting its high-value use in the coal chemical industry. To address the challenge of tight interlocking between residual combustible matter (coke) and glass microspheres, which limits the effectiveness of conventional physical separation, this study proposes a combined supergravity-sieving separation process enhanced by ultrasonic dispersion. The effects of the strong mechanical shear force generated by ultrasonic cavitation on the disaggregation and surface cleaning of heterogeneous agglomerates in CGFS were systematically investigated, and the settling separation mechanism of the liberated particles in the centrifugal field was examined. The experimental results demonstrate that ultrasonic pretreatment can disrupt the physical encapsulation and agglomeration constraints between combustible matter and ash particles, creating favorable prerequisites for efficient separation in the subsequent supergravity field. Under the optimized pretreatment conditions, the loss on ignition (LOI) of the final concentrate obtained by the combined ultrasonic-supergravity-sieving process was 84.04%, which was 18.52% higher than that from supergravity separation alone. Furthermore, with the addition of wet sieving, the micro-fine inorganic ash liberated by ultrasonication was effectively removed, contributing to the enrichment and recovery of residual combustible matter. This study provides microscopic evidence consistent with the proposed mechanism of the combined process and offers a feasible technical pathway for the efficient recovery of valuable combustible matter from CGFS.