Nickel laterite: the HPAL–neutralise–precipitate family

Nickel laterites — the oxide-ore half of the nickel world — are treated by high-pressure acid leaching and a precipitation back end. The flowsheet composes from mechanisms taught earlier, and this page assembles them, naming each contribution rather than re-teaching it.

The flowsheet in one line

Leach the laterite in sulfuric acid in an autoclave, neutralise the leach liquor in stages to throw out the iron and aluminium, and precipitate the nickel and cobalt as a mixed product: HPAL–neutralise–precipitate.

What each stage is doing

The leach is high-pressure acid leaching — the pressure-leaching mechanism of topic 4.6, the autoclave acting as the leach itself — dissolving the nickel and cobalt out of the laterite with sulfuric acid at high temperature and pressure. Neutralisation is precipitation by pH control, topic 6.2: lime or limestone raises the pH in stages so that iron and aluminium drop out as hydroxides first, ahead of the value, and the free acid is consumed. Precipitation of the product is topic 7.4: the nickel and cobalt are precipitated together as a mixed hydroxide (MHP) or mixed sulfide (MSP) intermediate, the form in which much laterite nickel is sold for downstream refining.

The defining numbers

The staged neutralisation lands on the lime slurry preparation calculator below — the reagent that consumes the free acid and lifts the pH. The autoclave leach itself reads on the sulfuric acid hub for the lixiviant property data; the nickel sulfate hub carries the property data for the dissolved value and the refined sulfate product. The autoclave heat balance is the pressure-leaching mechanism’s own subject (topic 4.6).

Where it differs from the others

Nickel laterite leads with an autoclave, like the copper concentrate (POX) variant, but its back end is precipitation rather than electrowinning: it makes an intermediate precipitate, not a finished metal. Cobalt rides with the nickel through the circuit and is separated downstream — often by the solvent extraction of topic 6.6 — which is why a nickel reader meets SX next.