Mine-to-Mill optimisation at Mont Wright

In 2019, ArcelorMittal Exploitation Minière (AMEM) and Hatch conducted a Mine-to-Mill (M2M) integration and optimisation project at Mont Wright (MW) iron ore complex in Canada. The aim was to increase production with little or no capital expenditure. In 2020 and 2021, the recommendations resulting from the M2M project were implemented by MW with assistance and refinement from Hatch. Throughout the M2M project, site-specific models of the mine and plant (blast fragmentation, crushing, grinding, gravity separation) were developed and calibrated based on historical data, and audits and surveys carried out by MW and Hatch personnel. The models were integrated and used to simulate and determine optimised strategies across the entire value chain from the mine through to the plant, to increase production while minimising overall costs. Optimisation strategies were trialled and refined during implementation, accounting for the limitations encountered in the mine and plant. During the project, ore domains were defined based on rock structure and strength, and blasting guidelines were developed for each to improve Run-of-mine (RoM) fragmentation for production blasts across multiple pits and reduce feed variability. Crushing and grinding simulations were conducted to assess the impact of finer RoM fragmentation and to optimise operating strategies for the finer feed. Simulations indicated an expected throughput increase of 7 to 26 % for the different grinding lines depending on the ore domain. One of the main recommendations in the plant was conversion of Mill 7 from Autogenous (AG) to Semi-Autogenous (SAG) grinding to fully utilise the available power, capitalising on the finer fragmentation from the mine and increasing throughput. Implementation of the new operating strategies began in late 2020, including additional ore characterisation, refinement of domain definition, establishment of updated blasting guidelines to accommodate operational constraints, and conversion of Mill 7 to SAG (12 % ball charge). A composite (rubber/steel) mill liner design was also investigated to allow a higher ball charge in Mill 7. Throughput improvements of up to 10 % (overall, for all ore types) have been achieved to date and further benefits are expected when the refinements to blasting guidelines and all recommended M2M operating strategies are fully implemented.