NORTHWEST TERRITORIES – Toronto-based Avalon Rare Metals says recent tests have indicated that heavy rare earth elements (HREE) recovery from the Nechalacho REE project near Thor Lake will be in excess of 80% compared to 42% as reported in the April 2013 feasibility study. The study considered combined results from both flotation and hydrometallurgical circuits.
The company says that preliminary estimates of the capital and operating costs associated with the improved processes are higher than those estimated in the flowsheet. However, those costs will be offset by the increased revenues from higher HREE recoveries. An updated technical report is due in early 2014.
SGS Minerals Services conducted the concentrator tests using a flowsheet without de-sliming ahead of flotation, with no gravity enrichment of the final concentrate, and with no recycling of tails from the four cleaner stages. The result is a simpler to use and less capital intensive plant. What changed was the choice of reagents used in the flotation tests.
The original sulphuric acid baking process proposed for the hydrometallurgical plant has been abandoned in favour of an alkali cracking process. The cracking process alters the zircon in the flotation concentrator and that enables the contained HREE (and most of the zirconium) to be released into solution. The process produces zirconium basic sulphate, a product for which there are established markets.
The Nechalacho project is planned as a 2,000 t/d underground mine with adjacent mill. Concentrates will be barged across Great Slave Lake to the hydrometallurgical plant in Pine Point, NT.
Readers may enjoy the Nechalacho project animation posted at AvalonRareMetals.com.