TRENDS IN ISR TECHNOLOGY

摘要

After a 60-years history, the development of ISR technology enters into its fourth stage: ISR 4.0. The challenges and possibilities of applying ISR to produce metals in general - and technology metals in particular - are outlined by (i) systematizing the feasibility criteria (ore morphology/grade distribution, hydrogeology, mineralogy, groundwater chemistry, microbiology), (ii) characterizing the combination of ISR wellfield hydrology and leaching chemistry (including thermodynamics and kinetics) both determining achievable production rates, and (iii) generically describing the dependence of ISR projects economics on key variables (including deposit criteria and design parameters). By referring mainly to recent advancements in the ISR of uranium, the overview on the following key areas of ISR project development and application includes: (i) ISR-specific exploration/delineation methodology and 3D deposit modelling (ii) State-of-the-art and innovative test procedures, ISR-specific requirements and model-based up-scaling to field conditions (iii) ISR wellfield design, optimization and control, in particular, emphasizing: a. model-based software tools (overview) b. potential of permeability enhancement (e.g. by fracturing) c. chemical pre-conditioning options (iv) Metal processing in ISR operations (also reviewing model-based software tools for control and optimization) (v) Post-mining measures and ISR aquifer restoration In the case of reduced minerals (e.g. tetravalent U minerals and metal sulfides), leaching involves redox processes to oxidize the metal-bearing minerals and to dissolve the metals of interest. The underlying thermodynamic conditions and specific kinetics of these redox reactions (including competing processes) are characterized and discussed with reference to practical applications (feasibility at industrial scale). Recent core assays and tests demonstrate the role of mineral texture and relevant reactive surfaces for leaching kinetics, whereas the degree of hydrological heterogeneities at various scales (studied by tomographic methods) determines the achievable effective contact of leachant and mineral. The ISR productivity in general and the time dependence of metal leaching from wellfields in particular depend on this interplay between pore-volume exchange rate and leaching kinetics. The potential of (model-based) ISR wellfield design and performance and constraints of ISR productivity are systematically demonstrated. The role of microorganisms in the in-situ recovery of technology metals, in particular by acid leaching from reduced ores, attracts increasing interest. Based on electron-balance criteria and practical application conditions the potential of bioleaching in ISR applications is characterized. Finally, the review provides a summary of key factors to implement ISR 4.0.