Research on extraction of carbon from coal gasification fine slag using hydrophobic-hydrophilic separation: Efficient separation, molecular dynamics simulation, and model optimization

Abstract

Disposing of coal gasification fine slag (CGFS) in piles and landfills result in enormous resource wastage and potential environmental risks. The precondition for CGFS resource utilization is separating residual carbon and ash materials. However, froth flotation products are heavily entrained, and gravity separation is not targeted for fines. This research introduced Hydrophobic-Hydrophilic Separation (HHS) as a solution to achieve efficient separation of residual carbon and ash materials. We investigated the surface morphology, elemental composition, and functional group species of residual carbon and ash materials by various testing methods. Additionally, molecular dynamics simulations were employed to reveal the visualization mechanism of CGFS in HHS. Response surface methodology analyzed the effects of mixing time, stirring speed, and n-heptane dosage on HHS carbon/ash separation. Furthermore, the sequence and interaction relationships of factor effects were analyzed, and optimal parameter values were determined. The advantages of HHS over froth flotation and gravity separation were briefly discussed. Finally, research directions were proposed for the process design of HHS and resource utilization with HHS products. This research would provide the theoretical basis and technical support for the efficient separation of residual carbon and ash materials, the large-scale resource utilization of CGFS, and the high-value processing of HHS products, which was beneficial to clean production, sustainable development, and environmental management.