Project Overview
The Nigeria Kaduna State Gold CIL Carbon-in-Leach Plant processes refractory gold ore from the Nigerian Shield greenstone belt. WSHT Mining Group delivered a complete CIL facility including three-stage crushing, SAG/ball milling, and 8-stage carbon-in-leach circuit designed for high gold recovery from sulfide-bearing ore.
Ore Characteristics
The ore is a banded iron formation (BIF) hosted gold deposit with gold finely disseminated in pyrite and arsenopyrite. Average grade: 3.8 g/t Au. The ore is refractory (72% recovery by direct cyanidation) requiring fine grind and extended leach time for acceptable recovery. Bond Work Index: 15.8 kWh/t.
Process Flow
Crushing: Three-stage crushing circuit: C120 jaw crusher (primary) → HP500 cone crusher (secondary) → HP300 cone crusher (tertiary). Product: P80 = 8 mm at 60 t/h. Total installed crushing capacity: 180 t/h.
Grinding: A Φ4.0×6.0 m SAG mill (2,200 kW) operates in closed circuit with a vibrating screen, reducing ore to P80 = 2 mm. A Φ3.2×4.5 m ball mill (1,500 kW) grinds to 80% passing 53 microns (finer grind for refractory ore). Combined grinding power: 3,700 kW.
CIL Circuit: Ground slurry is thickened to 50% solids and pumped through 8 CIL tanks (5.0 m diameter × 5.5 m height, 108 m³ each). Extended leach time: 48 hours (vs 24 hours for non-refractory). Cyanide concentration: 350 ppm NaCN. Lime consumption: 4.0 kg/t (higher due to acid-generating sulfides).
Gold Recovery: Loaded carbon is stripped in a split ADR elution circuit. Gold recovery: 92-94% (improved from 72% direct cyanidation). Doré bars produced: 98.2% Au purity.
Key Equipment
| Equipment | Specification | Capacity |
|---|---|---|
| C120 Jaw Crusher | 1200×900 mm feed opening | 180-350 t/h |
| HP500 Cone Crusher | Secondary, medium cavity | 100-200 t/h |
| HP300 Cone Crusher | Tertiary, fine cavity | 60-120 t/h |
| Φ4.0×6.0 m SAG Mill | 2,200 kW, gearless | 60 t/h |
| Φ3.2×4.5 m Ball Mill | 1,500 kW, rubber liners | 45 t/h |
| 8× CIL Tanks | 5.0 m dia × 5.5 m, 108 m³ | 48 h residence |
| Split ADR Elution | 3-stage, 120°C | 15 t carbon |
| EW Cell Bank | 36 cathodes, stainless | 80 kg Au/day |
Project Highlights
- Capacity: 1,000 TPD (300,000 TPA) refractory ore
- Gold Recovery: 92-94% CIL (vs 72% direct CN)
- Product: Doré bars 98.2% Au purity
- Power: 5.5 MW (dual-fuel generators)
- Water: 75% recycling, 2.8 m³/t ore
- Camp: 200-person accommodation facility
- Timeline: 18 months EPC delivery
- Location: Kaduna State, Nigeria
