The Khemisset potash project, owned by Emmerson PLC, is situated on a resource in Morocco that would be relatively easy and economical to mine. Unlike most deposits, this one lies close to the surface and has no aquifer above it, making the underground extraction fairly straightforward via a decline approach instead of a vertical shaft.
Processing that potash, however, will be more complicated than it is for other deposits. Ore in the Khemisset basin contains high levels of iron and magnesium, and removing those metals will require an extra processing step. In addition, the ore’s complex chemistry requires different approaches to materials of construction, treatment of wastewater effluent, and management of tailings.
When Emmerson was first contemplating the Khemisset project, one of Barr’s longtime potash clients recommended bringing in our plant design team during the prefeasibility study to complement work being performed by Golder on the mine and infrastructure. Barr was chosen to replace another plant-design firm that had conducted the scoping work for the project.
Initially we developed and evaluated options for plant configuration, including ways to refine the potassium chloride (muriate of potash, or MOP) in the ore and reject the deleterious iron and magnesium present in the feed. We worked closely with Emmerson’s in-house process engineer and used key test data from a third-party laboratory to develop and compare the process options in terms of complexity, cost, and risk. This included not only the process plant, but disposal of the waste brine and process tailings.
Using the go-forward case from the options study, Barr developed the feasibility-level designs and cost estimates that provided Emmerson with the necessary input for a JORC-compliant feasibility study on the entire project. Our work included a full mass and energy balance model in METSIM, process flow diagrams, a mechanical equipment list, preliminary equipment specifications and quotes, a preliminary 3D model of the plant, and feasibility-level designs for electrical, controls, structural, and civil works.
Under Barr’s direction, a project partner developed an AACE Class 4 capex estimate from our material takeoff lists and in-country labor rates. We developed a commensurate estimate of plant and process opex costs based on estimated values for reagent usage, utility demand, plant labor, and other indirect factors.
Appreciative of our high-quality work, project-specific innovations, and on-time delivery, Emmerson awarded Barr a contract in 2021 to complete basic engineering for the MOP plant. Our process, mechanical, electrical, controls, structural, and civil engineers advanced the feasibility-level designs for the project to 30% completion, coordinating with Moroccan mine-engineering firm Reminex, which developed basic engineering for the mine and infrastructure in parallel with Barr’s work. We also updated the capex and opex for the project based on the 30% design deliverables.
Throughout the feasibility study and basic engineering, Barr worked closely with Emmerson to meet its funding timelines while optimizing design. We also engaged in clear communications with Emmerson and Reminex to confirm schedules and tie-points between the design packages and minimize the chances of details being missed or duplicated. We conducted this work successfully across multiple time zones with multiple parties for whom English wasn’t a primary language.
Creating detailed METSIM mass and energy balance models allowed Barr to demonstrate how modifying processes could deliver additional value. From the base model, we developed a series of what-if models to explore (1) incorporating a circuit that would produce market-quality sodium chloride (road salt) and (2) options for obtaining salt of different purity levels. In each case, the models helped us quickly calculate corresponding changes in equipment, costs, and operational scale.
Following that, Barr worked closely with Emmerson’s team to develop alternative processes for the iron- and magnesium-bearing brines. Concepts and laboratory test work brought forth by Emmerson were discussed, and Barr developed new circuits to manage the iron and magnesium and produce additional value-added products. This approach significantly minimized the projected water-usage and brine-disposal requirements for the project.
