509 • Since early 2022, mechanical issues with the Phase I grinding line ball mills have constrained throughput. Chinalco is addressing these issues. • In May 2020, Phase II grinding line commenced operations (mean of 1,890 tph in 2021) • Since then, the throughput of the Phase II grinding line has steadily increased up to 2,220 tph. The design throughput (2,550 tph) has not been reached but should be achievable after implementation of all Hatch recommendations from the Phase II grinding line optimization study. • An audit and debottlenecking of the flotation circuit was carried out in parallel to the Phase II grinding circuit optimization study in May 2023. • Implementation of quick wins and several of the mid to longer-term initiatives has already delivered measurable improvements in throughput, operational stability, and metallurgical performance. This paper documents the structured methodology and practical implementation of the integrated Mine-to-Process strategy at Toromocho, from conceptual opportunity identification to implementation across drill and blast, comminution, and flotation. 2. METHODOLOGY The integrated optimization project at the Toromocho operation was executed using a structured Mine-to-Process methodology implemented progressively across the mining and processing value chain. The structured methodology takes an integrated approach, avoiding optimization of processes in isolation, which can result in suboptimal results for the overall operation. This approach considers the impact of variable feed ore characteristics on each stage (mining, comminution and flotation) as well as the interactions between each stage. The approach combined ore characterization, operational audits, plant surveys, analysis of historical operating data, development of semi-mechanistic and site-specific models, and integrated simulations, with a strong emphasis on implementation feasibility and sustainability of results. 2.1 Integrated Mine-to-Process Optimization The optimization project was structured into sequential and interlinked stages, each building upon the outcomes of previous work: • Mine and ROM fragmentation optimization, including review and optimization of drill and blast practices. • Phase I grinding circuit assessment and optimization, supported by plant surveys, modelling, and throughput forecasting. • Phase II grinding circuit modelling and optimization, following commissioning of the second grinding line in 2020. • Flotation circuit auditing, modelling, and debottlenecking, to manage the downstream impacts of increased throughput and coarser grinding product size. • Implementation and validation, including prioritization of quick-win initiatives and definition of major CAPEX projects. This staged approach ensured technical consistency and progressive implementation. 2.2 Ore Characterization and ROM Fragmentation Ore hardness and breakage characteristics are key drivers of blasting and comminution performance. Available ore characterization data were consolidated and expanded over time, including Bond Ball Work Index (BWi), SAG Power Index (SPI), Drop Weight Index (DWi), and JK Axb parameters. During early optimization stages, where detailed test work was limited, validated Hatch in-house comminution relationships were applied to derive representative breakage parameters. This was subsequently complemented by a comprehensive geometallurgical testing program, including SMC and Bond tests across
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