Spanish potash developer Highfield Resources recently reported significant progress as it prepares to begin construction at its flagship Muga potash project. The company has essentially doubled the mine life by improving operational efficiencies over the projections made in the definitive feasibility study (DFS). Life of mine increased from 24 years to 47 years at a production rate of 1.08 million metric tons per year (mt/y) of K60 granular muriate of potash (MoP). The proven and probable ore reserves for the project were increased from 146 million mt at an average grade of 12.7% K2O to 253 million mt with an average grade of 11.5%, an increase of 73% from the DFS.
“We have had a very productive six-month period, taking our Muga mine from a DFS to a mine ready to be built and operated,” said Anthony Hall, managing director, Highfield Resources. “Our initiatives have resulted in a doubling of mine life, as well as a mine that will be significantly better to operate long term. We have factored in expansion to our Muga mine design and also have further mine life potential that sits in our substantial Muga project exploration target.”
“We now have contracts ready to be executed for more than 25% of the direct costs of the mine,” Hall said. “This pricing is below budget without any contingency, which suggests we are well on track to delivering the mine within our capex estimate.”
Following the completion of the DFS, Highfield focused on preparing the Muga project for construction and, ultimately, production of potash. This work has further optimized the project, with a focus on underground design and equipment selection to improve operational efficiencies.
The mine plan has been altered to include an additional sylvinite seam (Capa A). Management decided to use a combination of continuous miners and road headers to increase productivity in production and infrastructure development. The number of main infrastructure galleries in the mine plan was increased from one to three to reduce ramp-up risk and increase likely operational efficiency. The size of the underground conveyor belt system was increased to accommodate an increase in underground tonnage and to enable better expansion options. Similarly, the size of underground storage was increased to enable more flexibility in smoothing grade profile to the processing plant.
The original DFS envisioned the principal mining horizons being accessed via two straight-line declines, approximately 2.5 km and 2.6 km in length, respectively. The total cross sectional area of each decline is 35.7 m2, a slight increase from the DFS. The declines will access the same mining horizon at two different points. The eastern decline reaches the mineralized horizon at 440 m below surface and the western decline approximately 452 m below surface.
Underground extraction will be via room-and-pillar mining using a combination of continuous miners and road headers to optimize extraction efficiency and selectivity in varying ore body heights. Additionally, continuous miners will be used for the ongoing mining development, including new transport drifts and main transport galleries. The change in machinery selected for underground mining is reflected in the higher capital cost for the underground elements of the mine.
The underground design and equipment sizing contemplates the delivery of an average of approximately 550,000 mt of RoM ore per month (6.6 million mt/y) to the process plant. The ROM tonnages delivered to the process plant are variable over the life of mine and depend on location within the ore body taking into the account grade, mineralization type and expected metallurgical performance of each panel being mined.