HEAP LEACH – SX / EW
validation prototype using full-sized components in a shortened stack configuration( shown in the picture) was and continues to be tested. Activities include third party validation at an established mining equipment / process validation facility near Tucson, Arizona. The basic unit serves to cost-effectively demonstrate both dimensional and stacking scaling while also enabling site-specific tailoring of salient key operational and design parameters. This facilitates refining site-specific application and provides a data driven basis for modular scale-up to target system capacities through additive summation of repeat units. The unit was shown to successfully adjust treated stream pH and eliminate target iron to low levels without generating solids and while concurrently creating ≥1.0 % sulphuric acid product as desired. Additional operational refinement is currently underway to drive cost / benefit analyses to underpin specification development and design refinement for a targeted follow-on ~ 1 / 10th capacity pilot. Application of DEMET treatment for the adjustment of the salient chemistry of leach streams generated by pressure oxidation treatment and residual metal recovery from process stream water was also recently considered in a presentation and an associated proceedings paper for the SME Annual Conference in February in Phoenix. Briefly, James explains,“ application of DEMET to a proposed gold processing facility was considered in light of the public information provided in the prefeasibility of the project. Considerable cost savings(~ 50 %: again on a feedstock basis versus using lime) were noted for the project and indicated a medium estimated IRR on DEMET implementation of + 22 % over the planned Life of Mine( LOM) when feedstock and sludge handling savings plus defrayed acid purchase costs were considered. Additional potential tertiary revenue recovery opportunities to further improve LOM economics by net ~$ 100 million of revenue were noted but not included in the IRR analysis at this point.”
The DEMET technology and treatment platform continues to rapidly evolve and find new applications treating MIW such as leach solutions to achieve cleaner and often more cost-effective solutions improving lifecycle costs. DEMET treatment may lower treatment costs, reduce sludge generation and handling costs, and provide new opportunities for revenue generation and / or cost defraying through selective saleable product generation during treatment.
SX / EW
Innovation Metals Corp( IMC) has developed the RapidSX™ process, which it says is a dramatically improved SX process for the separation and purification of rare-earth elements( REEs), nickel and cobalt, and other important metals including copper. The patentpending process significantly reduces the number of process steps required for SX as well as the physical footprint of operations. The time to reach process equilibrium is also significantly reduced, from weeks in conventional SX systems, to a few days using the RapidSX approach. The process also reduces the quantities of organic reagents required and the power requirements for equipment operation, as well as the amount of inventory required to be loaded into the system at any one time.
The process was recently applied to the separation of nickel, cobalt and other valuable metals, from a PLS produced from a bulk sample provided by a major miner of nickel-laterite ores. Commercial-grade( 99.6 %+) purities were obtained.
“ In addition to utilising IMC’ s RapidSX process for the separation and purification of these valuable metals once in solution,” said Patrick Wong, CEO of IMC,“ we have combined a unique, proprietary chloride-based leaching process for producing the PLS, with a cost-saving acidregeneration step. This allows us to extract and to monetise over 80 % of the metals present in these ores( compared to the typical 2-3 % seen with current laterite-ore processes), while reducing acid consumption and cost. We are now looking for strategic and financial partners who can see the benefit of such an approach to lateritic-ore processing.”
“ Existing nickel-sulphide deposits are being depleted through mining,” commented Gareth Hatch, President of IMC,“ with few high-quality exploration targets on the horizon. Nickel-laterite deposits are therefore set to become the most important source of nickel in the future. In addition, future demand for cobalt in Li-ion batteries is projected to grow dramatically, as electric vehicles take increasing market share in the automotive sector.”
In August, IMC announced the successful completion of a demonstration program to produce commercial-grade Pr-Nd oxide, using feedstock from the Mineração Serra Verde( MSV) deposit in Goias State, Brazil using RapidSX. Pr- Nd oxide is in increasing demand for the production of high-performance permanent magnets, used in a wide variety of industrial, automotive, defence and clean-tech applications.
Hatch explained:“ Combining the time-proven chemistry of SX with IMC’ s proprietary columnbased approach, avoids the risks associated with novelty separation approaches that require expensive resins and other complex methods, not yet demonstrated at scale.”
The demonstration project was conducted at IMC’ s pilot-plant facility in Mississauga, Canada, capable of producing 2 t / month of REEs. The high-value Pr-Nd oxide was separated to 99.5 % total REE purity using RapidSX; La oxide was also produced as a byproduct of the demonstration program, with 99.97 % total REE purity.
Although the process needs to be further demonstrated at a larger scale, these initial results indicate average separation costs of below $ 2.00 / kg for a suite of high-value separated REEs, with capital costs for a 2,500 t / y REE RapidSX-based facility in the region of $ 10- 15 million or less.
Resource Recovery Technologies( RRT) offers MSX, its centrifugal solvent extraction plant which it says“ reduces organic use by more than 95 %.” To prove the point, RRT offers an MSX 300D( 300 gallon / min or 19 litres / s PLS) demonstration plant for copper SX.“ MSX 300D pays for itself in 24 months or less by producing rich electrolyte for 1-2 Mlb / y of copper cathode,” says Randy Finfrock, RRT Founder & President,“... depending on the feed grade. We also offer membrane demonstration plants to reclaim organic from raffinate or rich electrolyte.
“ Our product and byproduct recovery systems apply centrifugal and / or membrane science to the separation of solutes from process solutions.”
RRT’ s suite of services includes: n Solution analytics and characterisation n Bench scale and prototype evaluation n Design, engineering and optimisation n Operational support and training n Centrifugal solvent extraction n Byproduct membrane extraction n Organic-aqueous membrane separation n Nanofiltration for desalinisation.
RRT’ s gravity-enhanced MSX plants use an integrated centrifugal extractor( CSX) for mixing and separating immiscible process solutions in a single annular chamber. CSX is optimised for high throughputs to achieve desired extraction efficiency, maximum loading, and net transfer. Modular CSX trains, one for extracting and one for stripping, are scaled for feeds of 315 to 1,580 litres / s( 5,000 to 25,000 g / min) simply by adding additional centrifuges.“ MSX plants are fully enclosed with low holdup volumes, so the initial organic inventory to load the plant and makeup to replace organic lost to entrainment and evaporation are reduced by more than 95 %,” Finfrock notes.
The annular CSX was originally developed by the US Department of Energy( DOE) to process uranium. DOE designed the elegantly simple centrifuge to both mix and separate process solutions in the same housing. One of DOE’ s national security labs, now a strategic technology partner of RRT, is working with RRT to optimise CSX for copper SX and scale it to a 63-litre / s( 1,000 g / min) production model for rugged mining applications. RRT initially ran feasibility tests of MSX at an Arizona copper mine. An offthe-shelf DOE centrifuge was installed and the MSX skid was automated to perform extracting
28 International Mining | NOVEMBER 2016