Addition of cyanide solution (Sodium Cyanide (NaCN)), lime, and protective alkalinity to pregnant leach solution. Uniform mixing maintains protective alkalinity for cyanide stability and consistent gold extraction.
Coefficient of Variation (CoV) ≤0.05 at pH/CN monitoring point. Protective alkalinity must be maintained uniformly across flow cross-section. Lime slurry (Calcium Hydroxide / Lime (Ca(OH)₂)) scales mixer elements — KE-R removable mandatory. Wide turndown for seasonal heap leach operation.
Preferred MOC: FRP or HDPE-lined carbon steel throughout — no bare carbon steel in cyanide service. PVDF injection quill for cyanide. Rubber-lined for lime slurry.
KE-R removable elements mandatory for lime slurry (Calcium Hydroxide / Lime (Ca(OH)₂) scaling). Double-containment on cyanide injection line. HCN gas monitoring in all enclosed installations. Emergency cyanide destruction system upstream. pH monitoring 5D downstream.