THE CHALLENGE

The Largo Resources Vanadio de Maracas project needed the recovery of sodium sulphate from a concentrated mother liquor stream containing sodium and ammonium sulphates, chlorides and saturated with calcium sulphate. The sodium sulphate needed to be reused in their on-site vanadium extraction process, thereby reducing the fresh reagent required and resulting in a direct cost saving. Furthermore, the complexity of the plant operation was increased due to the presence of impurities associated with the vanadium process.

OUR SOLUTION

As global leaders in crystallisation technology and experts in vanadium processing, PROXA designed a sodium sulphate crystalliser to process barren liquors derived after ammonium metavanadate precipitation. The product from the crystalliser contains a slurry of crystals which we separated into a damp crystal cake (<5% moisture) using a screen bowl type centrifuge. The remaining barren is also recycled back to the process for utilisation of valuable ammonium sulphate. A small purge is maintained from the entire circuit to control the build-up of chlorides.

HOW PROXA ADDED VALUE

We included 2-stage mechanical vapour recompression fans (MVR), which resulted in a highly energy efficient plant. And, given our extensive experience in crystallisation, we ensured that the crystals grew to a desired size for efficient separation. We also provided the crystalliser in corrosion-resistant materials such as super duplex stainless steel and titanium, in order to manage potential damage due to the aggressive nature of the high temperature, low pH chloride containing liquors. What’s more, our design ensures that the collected clean process condensate is not contaminated by carryover salts and – even though it contains traces of ammonia – can still be reused within the overall process.

PROCESS INNOVATIONS

Sodium sulphate/ammonium sulphate solution containing chlorides, and saturated with calcium.

PRODUCTS

PERFORMANCE TARGET

PROCESS RELIABILITY

The plant has been in continuous operation since 2014 and is meeting all client’s key performance objectives.
Client: Largo Resources – Vanadio de Maracas