Elevate reports results from U-pgrade pilot plant in Namibia

U-pgrade is a sequential five-stage process with all stages operating and undergoing continuous optimisation.

Results from the first four stages show a cumulative mass rejection of about 88% of the original ore mass achieved using Stages 1 to 4, in line with the design basis and confirming the mass rejection performance previously demonstrated at historical bench-scale testing in 2013.

Uranium recovery of 79% is reported using Stages 1 to 4, in line with expectations from historical bench-scale testing.

An upgrade ratio of seven times achieved using Stages 1 to 4 is in line with the ratio achieved at the equivalent point in historical bench-scale testing.

A further six to eight times increase in grade was demonstrated from Stage 5 in the historical bench-scale testing.

Calcite flotation (Stage 4) has removed the carbonate mineral that would preclude acid leaching, thereby allowing a simpler acid leach route at ambient temperature over four to six hours, which reduces the size, energy demands and operating costs compared with a conventional leach plant.

Marenica ore was upgraded from a head grade of 89 ppm uranium to 590 ppm uranium using Stages 1 to 4.

Results from the final stage, uranium flotation (Stage 5), which achieved a final concentrate grade of about 4 240 ppm uranium during bench-scale testing, are due in the fourth quarter.

Plant availability and operation has improved as freight and delivery constraints become less critical as the inventory of spare parts and reagents have increased.

Results generated will be incorporated into a Marenica scoping study work programme.

“All five stages of the pilot plant are now operating on ore from Elevate’s Marenica uranium project. The pilot plant is rejecting 88% of the ore mass and thereby upgrading the ore from 89 ppm to 590 ppm, before it reaches the final concentration stage which is in line with historical bench-scale results,” MD Murray Hill explains.

The answer to the question – ‘does U-pgrade work?’ was never a binary answer. We knew that U-pgrade would work, we just weren’t certain how the results from the bench-scale testwork would translate to a pilot plant.

“The low volumetric flows of a pilot plant produce operating challenges that aren’t evident in a full-scale operating plant. This has resulted in several challenges which the team in Namibia has now resolved,” he explains.

Importantly, Stage 4 calcite flotation has also removed the primary acid consumer from the leach feed, Hill highlights, noting that by removing the calcite, U-pgrade produces a feed that can be simply leached in acid at ambient temperature in four to six hours.

“That single outcome fundamentally changes the size, energy demands, operability and operating costs of a leach plant using the U-pgrade process – which is a major structural advantage we have regardless of the final concentrate grade,” he avers.