Improving uranium recovery by utilising compressor waste heat

Abstract

Leaching is the key process used for uranium extraction in a slurry mixture. Heat is often introduced in the leaching process to increase the uranium extraction yield. However, acquiring heat is expensive due to electricity tariff increases and is thus seldom feasible. Therefore, this study investigated alternative heating strategies for the leaching process. Different heat sources such as photovoltaic systems, heat pumps, boilers and compressor waste heat were considered. Waste heat was selected since the waste heat on mine compressed air systems is often available to be utilised and was proven to be the most cost-effective option. A method was created to assess the impact of waste heat on the extraction of uranium. The approach involved examining and simulating a standard heat recovery system. The simulation was verified using gathered data. Additionally, a potential heat source was assessed and simulated, with the possibility of incorporating it into heat recovery. An empirical model of the uranium plant was constructed and validated with relevant literature, enabling an analysis of the impact of the recovered heat. Finally, the validated models were integrated into a single system to evaluate the influence of a heat recovery system. The South African uranium processing mine implemented the suggested method, with each model being utilised to simulate current operations. The resulting accuracy level of the models was around 95%. The integrated model was used to simulate a heat recovery system that could potentially use the heat recovered from the mine compressors and quantify the impact by evaluating the transferred heat to the uranium plant. An economic feasibility analysis showed an annual benefit of R8.0m, with a total revenue of R48.2m over a life of mine of six years, resulting in a payback period of 2.6 years.