Name and Location
Dougou potash project, Republic of Congo.

Client
Elemental Minerals.

Project Description
Production at the Dougou deposit will be undertaken in three distinct project phases:
• Phase 1 – 400 000 t/y at a K60 potassium concentration of muriate of potash (MoP), (0% granular).
• Phase 2 – 800 000 t/y at a K60 MoP (67% granular).
• Phase 3 – 1.2-million tonnes a year K60 MoP (89% granular).

The scoping study completed on the project envisages a solution mining operation. Water is pumped down a well to dissolve the carnallite, resulting in production of a potassium, magnesium and sodium mineralised brine. This brine is continuously displaced by further pumping and transferred to the brine processing plant for processing into a MoP product. To increase potassium chloride content in the brine, a hot-solution mining operation is planned using dual well caverns, with a cavern radius of about 50 m and 70 m between the cavern wells.

Phase 1 production will comprise 12 operating caverns. To maintain steady-state production, 2.5 caverns a year have to be mined out, requiring the drilling of five new solution mining wells a year.

Completing the expansion of the full Phase 3 operation will increase the number of operating caverns to 22 in Phase 2 and to 32 in Phase 3, with five and 7.5 caverns respectively being depleted a year. The pipeline network required for the solution mining operation has been designed for a 400 000 t/y operation, and will be duplicated for each subsequent production phase.

The brine produced will be processed at a centrally located process plant facility. The processing concept will continually add carnallite (produced at a later stage) to the incoming brine, which will result in the precipitation of halite and sylvite. The solid slurry is separated from the brine and processed using hot leaching, and potassium chloride crystallisation to produce a K60 product.

The K60 product is dried and partially compacted during Phase 2 and Phase 3 before being transported to the storage facility. The brine from the carnallite decomposition is evaporated to produce carnallite, which is recycled to the carnallite decomposition stage. The remaining magnesium chloride brine and solid sodium chloride will be disposed into deep injection wells or mined-out caverns.

It is planned that Phase 2 and Phase 3 will each have installed compaction capacity of 532 000 t/y to produce an increasingly larger volume of granular product in each phase. The process has a conservative recovery ratio of 90% of potassium chloride from the incoming brine, transformed to product. It is planned to undertake full core dissolution and process testwork in the next study phase.

Net Present Value/Internal Rate of Return
The project has an after-tax net present value at a 10% discount rate of 10% of $880-million and an internal rate of return of 21.67%.

Value
The project has an unleveraged Phase 1 capital expenditure of $429.68-million.
Phase 2 capital expenditure is estimated at $450.93-million, while Phase 3 is estimated at $422.77-million.

Duration
It is expected that Phase 1 construction will take about two years, with preparation of the first solution mining wells taking place in the second year. First production is expected in the second half of 2019.

Phase 2 will start production five years after Phase 1.

Phase 3 will start production three years after Phase 2.

Latest Developments
The project has been recommended to proceed to the feasibility study phase.

Key Contracts and Suppliers
None stated.

On Budget and on Time?
Not stated.

Contact Details for Project Information
Elemental Minerals (South Africa), tel +27 11 469 9140.