Mesa Minerals Limited
Granulated Manganese Sulfate

Mesa’s patented sulfur dioxide leach process is highly efficient and could be used to extract a very high percentage of the manganese in any given oxide ore irrespective of that ore’s grade. This efficiency makes it ideal for the productions of a highly pure solution of manganese sulfate from which a fertilizer grade granulated manganese sulfate (GMS) product can be produced. Importantly, GMS could be produced as an interim product prior to expanding the plant to produce either electrolytic manganese dioxide (EMD) or electrolytic manganese metal (EMM), thus facilitating the financing of a new electrolytic plant by financing the later stage capital spend from GMS cash flows.

By utilizing the Mesa sulfur dioxide leach process, a manganese electrolytic plant, can continue to produce GMS as a co-product of EMD or EMM on a long term basis, as an alternative to micro nutrient fertilizer (MNF) production as the co-product. The choice of either GMS or MNF as a co-product will be predominantly driven by prevailing prices for these products at the time of the investment decision, local market demand and access to export markets, as the capital involved will be relatively similar in each case. A secondary but potentially important consideration will be the production of a benign silica tailing where the GMS route is chosen that will need to be disposed of compared with zero tailings make when the MNF route is chosen.

Existing manganese electrolytic plants that depend on manganese oxide ores could obtain the same benefits as a new plant, namely the ability to switch to a low grade ore feed located much closer that would cost far less and to create a second revenue stream by co-producing a fertilizer product, by replacing their current roast/acid dissolution circuits with a Mesa sulfur dioxide leach circuit. The capital cost of replacing a roast circuit with a leach circuit and the provision of a new GMS or MNF circuit would be readily repaid out of increased revenues and lower costs. Plants undertaking such a retro-fitting would be effectively rejuvenated and could look forward to decades of additional life irrespective of the urbanization that inevitably intensifies around them. An additional bonus may also be possible where the old tailings dams can be reclaimed and the land reused or sold off.

The following example process flowsheet provides an overview of the steps in a joint EMD/GMS production plant:

A typical composition of an GMS product derived from a ferruginous 25% manganese oxide, sourced from Mesa’s Ant Hill mining lease as feed for an EMD/GMS plant, would be a manganese sulphate monohydrate, containing:

  • Mn 32% minimum; and
  • S minimum 18%.

Production of GMS by this method has several advantages over the more commonly used methods:

  • the elimination of roasting and thus a reduction in energy usage;
  • the elimination of particulate and metalion pollution;
  • the elimination of carbon dioxide emmissions; and
  • the ability to utilize low cost manganese oxide ore as the plant feedstock.

The form of the final GMS product would also depend firstly on the local area demand and then on export demand if that is the chosen route.

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