Experimental and Mechanistic Analysis of Bastnaesite Pelletization in the Context of Carbochlorination

Abstract

Rare earth elements, as strategic resources, have garnered global attention. Among these elements, bastnaesite stands out as one of the most abundant rare earth resources. It has various production processes, with carbochlorination being one of the most effective for rare earth recovery. We propose a carbochlorination process for bastnaesite using aluminum chloride produced in situ from alumina, which serves as the fluorine-fixing agent, and coke, which serves as the reducing agent. In the carbochlorination process, to prevent raw material from splashing during the reaction in the packed bed, a binder is typically added, and a reducing agent is used for balling. The impact of various binders on the strength of bastnaesite pellets was investigated, and the bonding mechanisms of the binders were analyzed and discussed. With pellet strength as the primary focus, an experimental investigation was conducted on the factors affecting binder addition, raw material particle size, water addition, and drying temperature. The results indicated that a raw material particle size of 100 mesh, a binder additive amount of 3%, a water addition of 11%, and a drying temperature of 100 ℃ were optimal experimental conditions. Under these conditions, the dry and wet ball drop strengths were 52.5 times and 10.5 times greater, respectively, and the wet and dry compressive strengths were 760.71 N/cm² and 2.79 N/cm², respectively. To reduce experimental costs, the composite binder and its doping ratio were explored. Finally, pellets prepared with the three binders were selected for experimental verification of carbochlorination.