A sustainable process for vanadium recovery from stone coal: efficient enrichment via alkali melting–carbothermal reduction

Abstract

With the continuous growth of vanadium market demand, it has become increasingly urgent to promote research on sustainable and efficient vanadium resource utilization. Stone coal vanadium ore has remained underutilized due to its low grade and complex composition. This study proposes a calcium oxide (CaO)-assisted fusion and carbothermal reduction process for the efficient release and enrichment of vanadium from stone coal. The experiment systematically investigated the effects of reduction temperature, slag composition, reducing agent dosage, and smelting time on vanadium recovery efficiency. Calculation results indicate that vanadium pentoxide (V₂O₅) begins to decompose at 288 °C, and reduction to elemental vanadium (V) requires a temperature of approximately 1600 °C. Below 1468 °C, iron and vanadium form a continuous solid solution. Above 1538 °C, molten iron exhibits a strong affinity for vanadium, acting as a collector. Under optimized conditions (1600 °C for 2 h, 35 % calcium oxide, 5 % carbon, and 9 % ferric oxide), the vanadium enrichment ratio reaches 97.84 %. The resultant vanadium-iron alloy contains 4.09 % V and 78.35 % total iron (TFe). The chemical composition of the tailings closely resembles that of rock wool raw materials, indicating significant potential for resource utilization. The stability and industrial application prospect of the process were further confirmed by pilot test. This study serves as a technical reference for the sustainable and efficient development of stone coal vanadium ore, as well as the high-value utilization of vanadium resources.