Why DNi?

  • The only commercially available, internationally implemented, process which can match DNi’s flexibility in output is High Pressure Acid Leaching (HPAL) but that process cannot treat both limonite and saprolite in one stream and is incapable of treating the entire saprolite profile – the more saprolite added the less profitable the process is.
  • The DNi Process™ is protected by registered patents.
  • The DNi Process™ is the only process available which can treat the whole limonite/saprolite ore profile (from 90% limonite to 100% saprolite) enabling maximum recovery of saleable products from the mine.
  • The DNi Process™ is also able to treat just the limonite (provided 3-4% (by weight) magnesium is added to the feed).
  • The DNi Process™ can easily adapt to changing market demands with the simple addition of different refining units on the back end. The principal markets for DNi’s output, currently, are:
    • The Stainless Steel market: Nickel metal, Cobalt metal or Cobalt oxide;
    • The Battery market: NiCO3 and other Ni/Co products.

 

The DNi Process™ is a recently-developed, potentially disruptive hydrometallurgical process for extracting nickel from laterite deposits with an efficiency, we believe, that is unparalleled. It is the first process capable of treating the full laterite profile, from limonitic to saprolitic ores in any ratio using a single flowsheet.

 

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1. DNi Process™ leach is operated at atmospheric pressure in 304 stainless steel tanks at temperatures below the boiling point. Leaching is very rapid (typically 2-4 h).
2. Insoluble residue is separated from the pregnant leach solution (PLS), which now contains most of the Ni, Co, Fe, Al and Mg. The residue goes to a tailings disposal facility.
3. Iron Hydrolysis takes the PLS and removes the iron and chromium, making a hematite (Fe2O3) product. This is separated from the PLS by filtration.
4. Aluminium is precipitated by MgO addition and filtered from the solution.
5. A Mixed Hydroxide Product (MHP) is precipitated using MgO and filtered out of the solution. This MHP (35-40wt%Ni, ~2% Co) is the final product from the process and can be treated via conventional flowsheets, typically through to Ni and Co metal. The solution after filtration, primarily magnesium nitrate (Mg(NO3)2), is known as the barren solution.
6. The barren solution is passed through a series of evaporation vessels and then through thermal decomposition where the magnesium nitrate converts to MgO and NOx gases. These gases are recycled back to nitric acid and reused in the leach circuit. Some of the produced MgO is recycled back to aluminium precipitation and mixed hydroxide precipitation, the remainder is available for sale as a high quality magnesia product.
Reagent Recycling Mixed Nickel/Cobalt Hydroxide Precipitation Aluminium precipitation Iron hydrolysis solid liquid separation 1 Leaching

Key Features of the DNi Process™ are:

  • 13076-0357The opex and capex is less than half those of traditional HPAL processes because the DNi Process™ does not need high pressures or high temperatures. The minimum threshold plant size is, at 5,000tpa nickel, a fraction of the scale competitors must start from.
  • DNi’s technical partners, Teck Resources and the CSIRO, are world-class experts in the field and both are positive about the DNi Process™.
  • The DNi Process™ has been hugely de-risked with the help of these expert partners and rigorous testing of the breakthrough reagent recycle process at demonstration scale.
  • The DNi Process™ is most efficient for extracting nickel from laterites and the first to treat both of the layers that comprise a laterite deposit in any proportion – meaning better utilisation of the resource.
  • The DNi Process™ is environmentally friendly because almost all the reagent is captured and recycled. Tailings are benign and can boost plant growth.

Capital Savings

The DNi Process™ leach operates at atmospheric pressure hence there is no need for costly high-pressure autoclaves and their associated infrastructure. Basic stainless steels (304 and 316) are passivated by nitric acid, hence materials of construction are amenable to ‘welding rod construction’ and therefore quite simple and low cost. Most of the process is conducted in a series of simple stirred tanks.

The test plant is controlled via a custom iPad app
The test plant is controlled via a custom iPad app

Operating Cost Efficiencies

  • High recoveries of nickel and cobalt from all parts of the ore body;
  • High recovery of nitric acid leads to low consumption of 20-60kg/t of nitric acid compared to +500kg/t of sulphuric acid in the HPAL Process where recycling is not possible;
  • Various marketable products can be produced (MHP, MOP, MSP, metal) to maximise marketability and revenue;
  • Valuable co-products are produced and  provide revenue streams which assist the economics of the DNi Process™;
  • Maintenance costs are reduced by the low intensity of the process, the simple materials of construction and the straightforward plant layout.

Environmental Benefits

  • All NOx gases are captured and converted to reuseable nitric acid
  • Leach residue is mainly silicates with minor residual nitrate content
  • Nitrates in residue break down to usable nitrogen for plant growth and return to the natural Nitrogen Cycle
  • Production of saleable magnesia solves the magnesium disposal problem experienced by HPAL operations.
  • The mass of waste residues is less than half that of HPAL processes due to minimal disposal of reagent and neutralising agents – and production of saleable co-products. This is a major advantage in high-rainfall tropical environments.

In summary, a highly-efficient and elegant solution to the world’s nickel supply problems.