Optimising Heap Leach Operations with CNLITE: A Technical Deep-Dive

Heap leaching with CNLITE Gold Leaching Agent offers significant advantages over conventional cyanide heap leach — but achieving optimal results requires careful attention to key operating parameters. This guide shares insights from over 15 heap leach operations across Africa.

Key Operating Parameters

Solution pH

Maintain pH between 9.5 and 11.0. Unlike cyanide which requires strict pH 10.5–11.5, CNLITE operates effectively across a wider range, reducing lime consumption by 15–25%.

Application Rate

Typical application rates range from 8–15 L/m²/hr depending on ore permeability. Start at the lower end and increase based on drainage monitoring.

Reagent Concentration

Optimal CNLITE concentration in the leach solution is 0.8–1.5 g/L. Higher concentrations do not proportionally improve recovery and increase reagent costs.

Dissolved Oxygen

Maintain DO above 4 mg/L in the pregnant leach solution. CNLITE requires less oxygen than cyanide, reducing aeration costs by up to 20%.

Common Pitfalls and Solutions

Problem: Slow leach kinetics in the first 48 hours

This is often caused by insufficient wetting of the ore bed. Solution: Increase application rate by 20% for the first 48 hours, then reduce to target rate.

Problem: Inconsistent recovery across the pad

Usually indicates uneven ore stacking or preferential flow channels. Solution: Ensure uniform lift heights (6–8m maximum) and consider drip emitter spacing of 0.5m × 0.5m.

Problem: Recovery drop in cold weather

CNLITE performance is less temperature-sensitive than cyanide, but recovery can drop 2–3% below 10°C. Solution: Increase reagent concentration by 15% during cold periods.

Case Study: Heap Leach Operation, Zimbabwe

A 3,500 t/day heap leach operation in Zimbabwe switched from cyanide to CNLITE in Q1 2024. Results after 6 months:

• Gold recovery improved from 74% to 79%
• Reagent cost per ounce reduced by 8% (despite higher reagent price per kg)
• Detoxification costs eliminated: $18,000/month saving
• Zero environmental incidents vs 2 minor incidents in the previous 6 months

Conclusion

With proper parameter optimisation, CNLITE consistently delivers equal or superior heap leach performance compared to cyanide, with significant cost and compliance advantages. Our technical team is available for on-site optimisation support at no charge for operations processing 500+ t/day.