How to Recover Value When Grind Size Is Off Target

How to Recover Lost Value When Grind Size Is Out of Spec

For many mining operations, grind size is a hidden variable with massive consequences. When grind size fluctuates outside its target range - whether too coarse or too fine - recovery rates drop, energy use increases, and throughput is compromised. This article explores how much value is lost when grind size is out of spec and outlines what mining teams can do to prevent it.

Why Grind Size Matters

Grind size directly affects mineral liberation, which in turn controls flotation efficiency and recovery rates. If ore particles are too coarse, valuable minerals remain locked within waste rock. If too fine, particles may be lost to slimes or overconsume reagents. Studies show that a consistent, optimized grind size can improve recovery by several percentage points, translating to millions in recovered value (JXSC, n.d.; 911Metallurgist, n.d.).

In one Zambian copper operation, recovery improved dramatically by adjusting the grind from 75 µm to 65 µm, underscoring the tight margins on which plants operate (GSSRR, 2015). Small misalignments in grind size can create cascading inefficiencies across flotation, dewatering, and downstream processing.

Root Causes of Off-Spec Grinding

Maintaining target grind size isn’t just a matter of equipment - it’s a system-wide challenge. Common contributors include:

• Ore Variability: Changes in ore hardness, density, or moisture content affect how material breaks down in the mill.

• Lack of Real-Time Monitoring: Without continuous grind size feedback, operators make reactive or overly conservative adjustments.

• Disconnected Systems: Sensor data may be collected but not translated into actionable control inputs.

In a Chilean case study, machine learning techniques helped optimize SAG mill operations by identifying the link between ore characteristics, mill settings, and optimal throughput - improving both energy use and output quality (MDPI, 2023).

Strategies to Recover Lost Value

1. Implement Inline Particle Size Analyzers
   Modern sensors provide real-time grind size measurements, enabling automatic adjustments to mill speed, load, and feed.

2. Use Predictive Control Systems
   AI and machine learning models can anticipate grind size drift based on ore input characteristics and operational conditions (MDPI, 2023).

3. Integrate Mill Data with Flotation Performance
   Closing the loop between grind and recovery metrics helps teams understand true economic impact—not just particle size deviations.

At NTWIST, our AI-driven process optimization tools are designed to close these gaps. By tying together real-time sensor data, ore variability, and downstream KPIs, we help operations recover lost value with precision and confidence.

Conclusion

When grind size drifts out of spec, mines lose more than recovery - they lose predictability, efficiency, and profitability. Recovering that value means going beyond reactive corrections. With integrated data, real-time feedback, and predictive analytics, operations can optimize grind size consistently and systematically, unlocking measurable gains.