Nickel Laterite Processing Overview
Nickel laterites account for approximately 60% of the world's nickel resources and are becoming increasingly important as sulfide nickel reserves decline and battery demand grows. Processing laterites is more complex than sulfides, with two main technology routes: HPAL (High Pressure Acid Leach) and RKEF (Rotary Kiln Electric Furnace).
Types of Nickel Laterite Ore
Laterite deposits are typically zoned vertically:
- Limonite layer (upper): High iron (>40%), low magnesium, contains nickel as Ni-goethite. Typical grade: 0.8-1.5% Ni.
- Saprolite layer (lower): Higher nickel (1.5-2.5% Ni), higher magnesium, lower iron. Contains nickel in silicate minerals.
- Transition zone (middle): Mixed limonite-saprolite characteristics
HPAL Technology — High Pressure Acid Leach
HPAL is the preferred process for limonite (low-magnesium) laterites. It produces a mixed nickel-cobalt hydroxide or sulfide intermediate.
Process Steps:
- Ore preparation: Crushing, grinding to -75 micron
- HPAL autoclave leaching: Sulphuric acid at 250-270°C, 40-50 bar pressure
- Counter-current decantation (CCD) washing
- Neutralization and impurity removal
- Nickel-cobalt precipitation (mixed hydroxide or sulfide)
Advantages:
- High nickel recovery (92-95%)
- Produces intermediate suitable for battery-grade nickel
- Handles high-iron, low-magnesium ores well
Challenges:
- High capital cost (autoclave is expensive)
- Scale management
- Acid consumption varies with ore chemistry
Nickel Laterite Processing — HPAL vs RKEF
RKEF Technology — Rotary Kiln Electric Furnace
RKEF is the dominant process for saprolite (high-magnesium) laterites. It produces ferronickel (FeNi) for the stainless steel industry.
Process Steps:
- Ore preparation: Crushing, screening, blending
- Rotary kiln drying and pre-reduction (800-1000°C)
- Electric furnace smelting (1500-1600°C) to produce ferronickel
- Refining to adjust ferronickel composition
Advantages:
- Well-established technology
- Handles high-magnesium, high-moisture ores
- Lower capital cost than HPAL
- Simple, reliable operation
Challenges:
- High energy consumption (electrical energy for furnace)
- Produces ferronickel (not battery-grade nickel)
- Lower overall nickel recovery (85-90%)
Selection Criteria
Choose HPAL When:
- Ore is predominantly limonite (low MgO, high Fe)
- Targeting battery-grade nickel production
- Project has sufficient capital budget
- Access to sulfuric acid is available
Choose RKEF When:
- Ore is predominantly saprolite (high MgO)
- Targeting ferronickel for stainless steel
- Capital cost constraints exist
- Low-cost power is available
WSHT provides equipment and engineering services for both HPAL and RKEF processing routes. Contact us for nickel laterite processing solutions tailored to your specific ore body.
