1. INTRODUCTION The global phosphate industry is facing a dual challenge: the exhaustion of high-grade deposits and the imperative for more resource-efficient operations. At the Miski Mayo concentrator, the projected decline in ROM grade from 18.2% to 15.0% P2O5 necessitates a 76% increase in mass pull for wet feed to maintain concentrate output. In these complex brownfield environments, traditional static mass balances often fail to account for the stochastic nature of equipment availability and the dynamic interaction of surge capacities or buffers (Noiseux & Côté, 2010; Tapia, Mendoza, Callejas, Muñoz, & Rosales, 2009). This paper describes the application of Discrete Event Simulation (DES) to map the migration of constraints under low-grade stress. While static models provide a snapshot of nominal capacity, the proposed dynamic framework incorporates MTBF/MTTR probability distributions and real-world control logic to identify "hidden" bottlenecks (Lavoie, Navarra, & Kuhne, 2008; Nikkhah, Wiseman, Dry, & Huang, 2019). The objective of this work is to define a scalable roadmap that prioritizes low-capital interventions and determines the technical-economic optimal point for capacity expansion. 2. PROCESS DESCRIPTION AND STUDY BASIS 2.1 Operational Context: Miski Mayo Plant The operation processes phosphate through a purely physical beneficiation method, without the use of chemical reagents or flotation. The flowsheet is based on size-based segregation, utilizing successive stages of washing in scrubbers, classification via vibrating screens, and two stages of high-efficiency hydrocyclones. The final product is dewatered in belt filters prior to dispatch. This configuration makes plant capacity extremely sensitive to volumetric and pulp density variations. 2.2 The Low-Grade Ore Challenge The primary driver of this study is the inevitable transition toward ore bodies with significantly lower P2O5 grades. As illustrated in Figure 1, the shift from high-grade ROM (4.56 Mtpa) to low-grade conditions (3.24 Mtpa) results in a 30% reduction in concentrate output if the current plant configuration remains unchanged. The simulation results further demonstrate that conventional operational improvements, categorized as "Quick Wins," are insufficient to bridge this production gap. Even with optimized availability and reduced MTTR, capacity only marginally recovers to 3.64 Mtpa, failing to meet the strategic design targets. This production deficit is not merely a logistical bottleneck but a fundamental volumetric constraint: to sustain production, the system must process a 76% increase in mass pull, a challenge that requires the deep-dive debottlenecking analysis provided by the stochastic dynamic simulation in the subsequent sections of this paper.
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