Premium sulphate of potash (SOP)
The Colluli Potash Project is located within the Danakil region of Eritrea, approximately 177km south-east of the capital city Asmara. The owner and developer of the project is the Colluli Mining Share Company (CMSC), a 50:50 joint-venture between Danakali and the Eritrean National Mining Company (ENAMCO).
The mine is estimated to have a production life of more than 200 years. The current proposal, however, is to develop the mine in two phases for the first 60 years, and use the capital gained from them to develop the subsequent phases.
The preliminary feasibility study (PFS) for the project was completed in March 2015, whereas the definitive feasibility study (DFS) was completed in November 2015. Construction works for Phase I are scheduled to commence in 2017, and first production is anticipated in late-2018. Production from Phase II is anticipated after five years of beginning Phase I operations.
The total development cost for Phase I is estimated to be $198.2m, while Phase II will require an additional $175.1m. Phase I is expected to produce approximately 425 kilotonnes per annum (ktpa) of premium sulphate of potash (SOP) product, while Phase II will double the production capacity.
The potash project also has the potential to produce potassium magnesium sulphate and potassium chloride.
The geology at the site is composed of a shallow sequence of evaporites, with the mineralisation occurring at just 16m below surface. The mineralisation lies below a clastic overburden and an upper rock salt layer.
The mineralised horizons are arranged as sylvinite, upper carnallitite, bischofitite, lower carnallitite, and kainitite respectively. These potash-bearing layers further overlie the lower rock salt, which forms the lower extent of the mineralisation.
As of February 2015, the potash mine is estimated to hold a combined measured, indicated and inferred resource of 1,289Bt, with an average grade of 11% K2O, containing 260Mt of SOP.
As of November 2015, the combined proven and probable reserves are 1,113 billion tonnes (Bnt), with an average grade of 10% K2O, containing 216 million tonnes (Mt) of SOP.
The project envisages the development of a single open-pit using conventional truck and shovel methods, complemented by continuous surface miners.
The processing plant, using proven technologies, will primarily integrate ore receival, secondary crushing, ore storage and reclaim facilities, ore pulping and deslime units, sylvinite, carnallite and kainite processing units, SOP production facilities incorporating, drying, sizing and compaction units, and product load-out and haulage facilities.
The project will involve the construction of evaporation ponds, a run-of-mine (ROM) pad, a sewage treatment plant, fuel storage tanks, and installation of communications facilities.
Infrastructure at the site will further include an accommodation camp and site buildings integrating a main administration building, a clinic and emergency response building, workshops, warehouse, reagent store, ablution blocks and crib rooms, laboratory, and gatehouse.
The required water for the site is proposed to be extracted from the groundwater present in the clastic and upper rock salt layers, and via an 85km desalinated water pipeline from a reverse osmosis desalination plant located at Anfile Bay on the Red Sea coast.
The electricity requirements will be met by installing an 11kV heavy fuel oil on-site power plant, with distribution via both underground and overhead power lines.
The output from the project will be stored in twenty foot equivalent (TEU) shipping containers at the site of the processing plant and conveyed to the Port of Massawa, which is located approximately 180km from the project site, by road haulage vehicles.
The existing 50km product haulage road connecting the site to the main road leading to the port will be upgraded as part of the project.
The DFS was performed by Lycopodium with assistance from Knight Piésold for the pond and tailings study and AMC Consultants Geotechnical for the mine design. Global Potash Solutions provided technical support to Lycopodium, while Saskatchewan Resource Council assisted in product test work and piloting, Ausenco performed the water abstraction and logistics study, and MBS Environmental handled the social and environmental aspects.
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