Mines That Made the Switch
Detailed before-and-after data from African mines that replaced sodium cyanide with CNLITE — recovery rates, cost breakdowns, and regulatory outcomes.
Harmony Gold — Doornkop
Full CIL circuit conversion at a 1.2 Mtpa operation
Operation Details
Location
Doornkop, Gauteng
Period
Q2 2023 – Q4 2023
Scale
1.2 Mtpa (100,000 t/month)
Ore Type
Free-milling oxide & transitional ore
Process
Carbon-in-Leach (CIL)
Annual Saving
$253,200/yr
Net cost reduction after reagent price difference
Recovery improvement
+3.5%
The Challenge
Doornkop faced escalating sodium cyanide compliance costs following tightened South African environmental regulations. Monthly detoxification costs had reached R220,000 ($14,000), and the operation was under pressure from community groups over cyanide storage risks. A major tailings storage facility upgrade was also required under cyanide regulations — a capital cost of over $2M.
The Solution
CNLITE Africa conducted a 6-week bench-scale trial on Doornkop ore, confirming comparable gold recovery. A phased CIL circuit conversion was designed to minimise production disruption, converting two tanks at a time over an 8-week period. CNLITE Africa's technical team was on-site throughout commissioning.
Implementation Steps
Bench-scale leach tests confirmed 95.9% Au recovery with CNLITE vs 92.4% with cyanide
Existing cyanide stock safely disposed of under SANS 10228 dangerous goods regulations
CNLITE dosage calibrated to 0.42 kg/t through pilot-scale testing
Full CIL circuit converted over 8 weeks with zero production stoppages
Tailings management plan revised — cyanide destruction plant decommissioned
Community engagement programme launched highlighting the reagent change
Before vs After — Key Metrics
“The switch to CNLITE was the best operational decision we made in 2023. Recovery improved, costs dropped, and we've had zero cyanide-related incidents since commissioning. The CNLITE Africa team was professional and on-site whenever we needed them.”
Senior Metallurgist
Harmony Gold — Doornkop Operations
Additional Outcomes
TSF upgrade requirement waived by DMRE following reagent change
Community opposition resolved — no further objections to operating licence renewal
ISO 14001 environmental certification achieved 4 months post-conversion
Operation now qualifies for ESG-linked financing at preferential rates
Could Your Mine Be the Next Success Story?
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