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Dry nickel suphate hexahydrate recovery and resale for Zimplats Base Metals Refinery.

Proxa recovers dry nickel suphate hexahydrate

THE CHALLENGE

PROXA was tasked to recover dry nickel suphate hexahydrate from nickel catholyte liquor as part of the Zimbabwe Platinum Base Metal Refinery refurbishment project. The dry nickel sulphate is loaded into 1-ton bulk bags for sale into the local market.

OUR SOLUTION

Our solution for Zimplats focussed on a number of key areas: We ensured that crystallisation is achieved at low temperature in a forced circulation crystalliser operating under vacuum, and that the evaporative process is driven using a steam thermocompressor to improve the overall steam economy. We also recognised that the fluidised bed dryer design was critical in order to avoid blockages and to allow adequate residence time for drying. And, by incorporating a 2-stage scrubbing process, we were able to meet the very stringent specifications for dryer off-gas emissions. What’s more, our wealth of experience in plant construction in super duplex stainless steels, titanium and SAF2205, meant that we selected high grade materials for the project, which is essential for plant longevity due to the highly corrosive nature of the feed.

HOW PROXA ADDED VALUE

Given that PROXA has a number of nickel sulphate crystalliser reference plants around the globe, we were able to deliver a complete energy efficient package for the crystalliser and fluidised bed dryer with confidence. Our experience also meant that we are familiar with working in remote locations and taking complete responsibility for the entire project train – within budget and on time.

FEED WATER

Nickel sulphate solution containing impurities of cobalt iron, sulphuric acid and chlorides.

PRODUCT WATER

76 tons/day dry nickel sulphate hexahydrate

PERFORMANCE TARGET

Evaporation rate: 4754 kg/hr

PROCESS

  • Forced circulation crystalliser
  • Fluidised bed dryer
  • Pusher centrifuge
  • Thermocompressor

PROCESS RELIABILITY

The robust plant design caters for impurities in the feed stream and allows for remote operation. Ideal for a mine located in a remote part of Africa.


Client: Zimbabwe Platinum Mines
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