Abstract:
Gasification slag is the main solid waste produced in the modern coal chemical process. To efficiently extract and utilize the strategic metal resources contained in the coal gasification slag, and realize its high-value utilization, has become a current research hotspot. Currently, the occurrence state and migration rules of strategic metal elements in gasification slag are not well understood. In this study, ICP-MS, SEM-EDS and XRD were employed to analyze the content and mineral phase composition of strategic metals including Li, Ga, Ge and In in gasification slag. Subsequently, the occurrence state of these strategic metals in gasification slag was investigated using a step-by-step chemical extraction method. Moreover, the chemical morphology evolution of Li, Ga, Ge and In during gasification was simulated by Factsage thermodynamic software. The results indicate that compared to Yulin coal, Li and Ga are enriched in both fine slag and coarse slag. Ge and In are highly volatile during the gasification process and are mostly enriched in the gasification fine slag as the syngas cools. The strategic metals Li, Ga, Ge and In in the gasification slag mainly exist in the form of metal oxidation state, organic binding state and residue state, and a small part of Li exists in the ion exchange state and acid soluble state. The strategic metals Li, Ga, Ge and In in the gasification slag primarily exist in the form of metal oxidation state, organic binding state and residue state, with a small portion of Li existing in the ion exchange state and acid soluble state. These findings contribute to elucidating the occurrence state of strategic metal elements in coal gasification slag and the migration law of gasification process, thereby providing a theoretical reference for the comprehensive utilization of coal gasification slag.