Characterization, carbon-ash separation and resource utilization of coal gasification fine slag: A comprehensive review

Coal gasification fine slag (CGFS) from the entrained-flow coal gasification process mainly contains ash and residual carbon. Currently, the CGFS is normally stacked and landfilled in slag yards, resulting in huge resources waste and potential environmental risks. This study aims to review the research advances of the characterizations, carbon-ash separation and resource utilization of CGFS, so as to reveal the guiding role of CGFS characterizations on the process of separation and resource utilization. In this paper, the characterizations of CGFS are summarized from compositions, structures and dehydration. Methods for separating carbon-ash from CGFS are compared and analyzed. The resource utilization methods of CGFS are reviewed from direct utilization and high-value utilization. Moreover, the future research directions of carbon-ash separation and resource utilization are briefly discussed. Accordingly, this review identifies that particle size is a key factor determining the structure and composition of CGFS. Based on the analysis of the CGFS characterizations, froth flotation shows great application potential for carbon-ash separation from CGFS under the premise of reagent recycling. Blending combustion as the main direction of CGFS resource utilization should be considered. Although the synthesis of porous materials from CGFS is conducive to improving the environmental benefits of coal gasification plants, the optimization research on the preparation methods of CGFS-based porous materials is urgently needed.