❖ DATA (Assumed)
- Before doing design, you need some baseline data often from lab tests or pilot tests. For example
❖ Volume & Tank Design
You need to design your vats so that 10 tonnes of ore fits in each.
Step A: Estimate the volume of ore in each vat (solid only)
- Ore density = 2.5 t/m³
- So 10 t of ore → volume = 10 / 2.5 = 4 m³
- But with 10% shrinkage / voids when wetted → effective volume required = 4 × 1.1 = 4.4 m³
So each vat must hold ~4.4 m³ of ore.
Step B: Vat geometry
Let’s pick a vat depth of 1.5 m (common in vat design)
- If depth = 1.5 m, then cross-sectional area needed = 4.4 / 1.5 = 2.93 m²
- Suppose we choose a square vat (for simplicity)—side length = √2.93 ≈ 1.71 m
- Or a circular vat: area = π * (r²) = 2.93 → r ≈ 0.965 m, diameter ≈ 1.93 m.
Step C: Solution freeboard & drainage
- Add 0.1 m solution height → total depth ~1.6 m
- Slope at 0.8% bottom improves drainage toward outlet.
- floor above bottom (~0.1–0.2 m) for filtering layer or supporting media
❖ Scheduling & Throughput
With 72-hour retention:
- Cycle time = 3 days.
- You have 6 vats, so ideally every day one vat is loaded, one is leached, one drained, etc.
- Throughput per day = 60 t / 3 = 20 t/day
- Monthly (30 days) throughput = 20 × 30 = 600 t/month
❖ Gold Recovery & Revenue Estimate
Using the assumption:
- Grade = 5 g/t
- Recovery = 85%
- Throughput per day = 20 t → gold content = 20 t × 5 g/t = 100 g
- Recovered = 100 g × 0.85 = 85 g/day
If gold sells at (assume) USD 60 per gram:
- Daily revenue = 85 × 60 = USD 5,100
- Monthly revenue = 5,100 × 30 = USD 153,000
(This is ideal—ignores losses, operational costs, taxes, etc.)
❖ Reagent & Operating Cost Estimation
- NaCN consumption = 1 kg/ton → 20 kg/day
- Lime, water, power, labor, maintenance, etc.
- NaCN cost at USD 5 / kg → 20 × 5 = USD 100/day
- Other reagents & utilities = USD 200/day
- Labor, maintenance, overhead = USD 300/day
Total OPEX = ~ USD 600/day
Profit before capex = 5,100 – 600 = USD 4,500/day
❖ Capital Cost Estimation
Key cost items:
- Tanks (6 vats with liners, civil works)
- Pumps, piping, solution tanks
- Gold recovery system (carbon columns or zinc plant)
- Crushing unit
- Laboratory, building, site works
- Safety, spill control, waste collection
Let’s assume capital cost ~ USD 200,000
At that rate and profit, you recover capital in under 50 days (if ideal). In practice, scaling
inefficiencies, downtime, etc will lengthen payback.
❖ Optimization & Sensitivity
- If recovery drops to 80% → revenue drops
- If cyanide cost increases → margins shrink
- If throughput fluctuates → smooth scheduling is needed
- Monitor pH, cyanide concentration daily, adjust loading, agitation (if used), aeration, etc.
Use response surface methodology (RSM) from lab tests to optimize cyanide concentration, pH,
particle size.
❖ Risk & Mitigation
Risks include:
- Ore variability
- Channelling / non-uniform flow
- Cyanide losses / environmental damage
- Power interruption, equipment failure
Mitigations:
- Pilot test different zones of ore
- Use liner & monitoring sensors
- Tailings detoxification
- Backup power, maintenance plans
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