Techno-economic evaluation of an environmental-friendly processing route to extract rare earth elements from monazite

Abstract

The relatively high concentration of thorium and uranium in monazite poses significant environmental issues in the extraction process of rare earth elements from monazite if left untreated. A new process route that recovers both thorium and uranium as oxides has been proposed, and an analysis of its economic feasibility is presented in the current paper, based on analysis and processing of a Korean monazite sample. Comparative evaluations with existing acidic and alkaline routes have also been carried out. It was estimated that the largest proportion of the operational cost for the new process related to the materials and reagent costs. Sensitivity analysis predicted that the value of neodymium oxide followed by Heavy Rare Earth Oxides (HREO) and praseodymium oxide affect the revenue significantly. Increasing the average basket price of the total rare earths oxide by 1.5 times would result in revenues of US$158.8 million/year for the proposed route, compared to US$161.5 and US$156.3 million/year for the alkaline and acidic routes, respectively. The discounted cash flow analysis and the resulted Net Present Value (NPV) suggested that the proposed processing route was in fact the only process estimated to be economically feasible with the payback period expected to be around 4.5 years. The sale of thorium oxide and uranium oxide by-products of the proposed route contributed to the positive discounted NPV. It was also estimated that a minimum sale price of US$20/kg total rare earth oxide is required to ensure all the processes generate a positive discounted NPV. These results shown that the proposed new processing route is estimated to be economically feasible.