Experimental and mechanism research on carbothermal reduction of spodumene ore via vacuum

Abstract

Considering the low resource utilisation rate and high environmental pollution afflicting the current technology for extracting Li from spodumene ore, this report proposes a clean process for the vacuum carbothermal reduction of spodumene ores for Li extraction, ferrosilicon alloy preparation, and alumina recovery. Thermodynamic analysis indicated that vacuum conditions can significantly promote the carbothermic reduction of spodumene ores and that the initial reaction temperature can be reduced by 480 K when an environmental pressure of 20 Pa is applied. According to the experimental results, two important factors in the above procedure are the reduction temperature and reduction time. When the reduction temperature was 1648 K and the reduction time 3 h, the reduction rate of Li in the spodumene ore exceeded 90%. Furthermore, the ferrosilicon alloy and alumina slag could be effectively separated from the reduction residue. The thermodynamic equilibrium simulation of the reduction process was combined with the experimental results to assess the vacuum carbothermal reduction mechanism of spodumene ores. Compared with the existing Li extraction approach, this method has the advantages of a straightforward process flow, almost zero waste water/waste residue production, environmental compatibility, and increased resource exploitation. Based on the above, this work provides new insights for advancing the conventional technology used for Li extraction from spodumene ores.

Keywords

• spodumene ore
• carbothermal reduction
• vacuum
• lithium
• ferrosilicon alloy
• alumina