If your ball mill is crushing gold ore into particles that are too fine, it can lead to issues like slurry viscosity problems, gold losses in tailings, or inefficient leaching/recovery. Here’s how to address the problem:
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Potential Causes & Solutions:
1. Over-Grinding (Excessive Milling Time)
– Reduce grinding time by optimizing the residence time in the mill.
– Use a coarser grind setting if downstream processes (e.g., gravity separation, leaching) don’t require ultra-fine particles.
2. Ball Size & Charge Issues
– Use larger grinding media (bigger steel balls) to promote coarser crushing rather than excessive pulverization.
– Adjust the ball-to-ore ratio—too many small balls can over-grind the material.
3. Mill Speed Too High
– Lower the rotational speed (critical speed %) to reduce excessive impact forces that create fines.
4. Ore Feed Size Too Small
– Ensure feed material isn’t already too fine before milling; consider pre-screening or adjusting crusher settings upstream.
5. Incorrect Slurry Density
– A too-thick slurry can cause over-grinding; maintain optimal pulp density (~65-75% solids for gold ores).
6. Classification Circuit Problems
– Install or adjust a screen or hydrocyclone to remove fine particles early and recycle oversize back to the mill (closed-circuit grinding).
7. Alternative Recovery Methods for Fine Gold
– If fines are unavoidable, improve recovery by:
– Using flotation for free gold fines.
– Optimizing cyanide leaching (ensure proper agitation, oxygen levels).
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a gravity circuit (centrifugal concentrators like Knelson/Falcon).
Testing & Optimization:
– Conduct a grind size vs. recovery test (e.g., bottle roll or leach tests) to find the optimal particle size for your process.
– Monitor the P80 (80% passing size) and adjust mill parameters accordingly.
Would you like recommendations specific to your ore type or processing setup?