Extensive collaborative test work is being carried out by Greenland and major shareholder Shenghe Resources Holding Co Ltd, a leading rare earth company.
A low temperature hydrochloric acid (HCl) leach circuit has been developed that allows for fewer processing steps and smaller equipment but delivers very high rare earth extractions.
The new methodology opens the opportunity for cost‐effective import of reagent rather than on site production.
A leading producer of key magnet metals
Kvanefjeld is projected to be one of the largest producers globally of key magnet metals including neodymium, praseodymium, dysprosium and terbium.
It is underpinned by resource of more than 1 billion tonnes and an ore reserve estimate of 108 million tonnes to sustain an initial 37 year mine life.
John Mair, managing director, said: “The simplified refining circuit will bring numerous benefits to the project.
“It draws on guidance from Shenghe to utilise Kvanefjeld’s unique qualities to establish a highly competitive cost structure and align the project with downstream processing.
“Coupled with major flotation improvements to produce a higher‐grade, lower‐mass mineral concentrate, the simplified refining circuit will result in smaller equipment sizing and less support infrastructure.
“This will lead to a reduction of capital and operating costs.
“These enhancements will reduce the project’s in‐country footprint and impacts, whilst serving to increase the profitability.”
The tests carried out in China and Australia are aimed at optimising and simplifying the refining circuit that has been developed for the project.
Test work to develop a simpler, enhanced leaching methodology was conducted in Australian laboratories.
Hydrochloric acid key to revised strategy
Key to the revised processing strategy has been evaluation of HCl for direct concentrate leaching.
This is a departure from the process outlined in the feasibility study which uses sulphuric acid for direct leaching and HCl acid for secondary leaching.
Previous attempts to use direct HCl met with issues owing to silica contamination.
Greenland has now devised a method which allows the silica in the concentrate to be controlled in a single leaching step.
This occurs while still extracting high levels of rare earths and uranium from the concentrate.
Viscous paste is formed
The new method mixes HCl directly with mineral concentrate to produce a viscous paste, which is then mixed for 30 minutes before being dissolved in water.
In the viscous paste, the rare earths are dissolved and the silica is controlled by precipitation in a favourable form.
This simple extraction method is not dependent on high temperature, high pressure or extreme chemical treatment that is otherwise the norm in rare earth production.
Elimination of sulphuric acid will remove the requirement for a sulphuric acid plant on site. Further investigations reveal that it will be possible to transport HCl directly to Greenland for use in the refinery, which will also remove the requirement for a HCl plant.
Removal of reagent production facilities in Greenland will reduce capital costs.
Test work has established a method for the effective removal of uranium from the leach solution, allowing for the generation of saleable uranium product in Greenland.
Feasibility studies will quantify the benefit of shipping an intermediate rare earth product as a chloride solution, which is ideal feedstock for latest technology separation plants.
This approach eliminates solids handling and releaching steps common with other solid feedstocks, resulting in cost benefits across the overall supply chain.
Last month the company and Shenghe also achieved substantial improvements to the flotation circuit and mineral concentrate grades.