Lithium: the spodumene and brine flowsheet families

Lithium reaches the market by two published routes — a hard-rock route from spodumene and an evaporite route from brine — and both compose from mechanisms taught earlier. This page assembles them from the public process literature, naming each mechanism and what it contributes rather than re-teaching it.

The flowsheet in one line

The hard-rock route: calcine spodumene to make it leachable, leach it, purify the liquor, and crystallise a lithium salt — calcine–leach–purify–crystallise. The brine route: concentrate a lithium brine by solar evaporation, purify it, and crystallise the salt — evaporate–purify–crystallise. Two front ends feeding the same purify-and-crystallise back end.

What each stage is doing — spodumene route

Calcination is the thermal pre-treatment of topic 3.2: spodumene is calcined to flip the mineral from a leach-resistant form to a reactive one, the standard published example of a phase change driven purely by heat. The leach follows — in the common acid-bake variant the calcine is mixed with sulfuric acid and roasted, then the soluble lithium sulfate is leached into water — the dissolution-and-stoichiometry and tank-leaching mechanisms of topics 4.1 and 4.3. Purification is precipitation by pH control (topic 6.2): impurities such as iron, aluminium, magnesium and calcium are dropped out as hydroxides and carbonates, the impurity-management discipline of topic 6.8 applied to a lithium liquor. Crystallisation is topic 7.3: the purified liquor is reacted with soda ash to crystallise lithium carbonate, or processed to lithium hydroxide, by the fall in solubility.

What each stage is doing — brine route

In the brine route the front end is solar evaporation: a continental brine is concentrated in a series of evaporation ponds, which both removes water and drops out unwanted salts as it goes — evaporative concentration by solubility, the published counterpart to the crystallisation mechanism of topic 7.3. The concentrated brine is then purified of residual magnesium, calcium and boron by precipitation (topic 6.2) and crystallised to lithium carbonate with soda ash, the same back end as the hard-rock route.

The defining numbers

The spodumene calciner is sized by residence time on the kiln residence-time calculator below — the same rotary-kiln relation as any calcination. The acid-bake reagent demand reads on the leach reagent consumption calculator. The lithium-carbonate precipitation reads on the sodium carbonate hub for the soda-ash property data, and the acid-bake lixiviant on the sulfuric acid hub. The bicarbonation gas loop used to purify lithium carbonate by re-dissolution is the subject of topic 6.9.

Where it differs from the others

Lithium is the family where the product is a high-purity salt — carbonate or hydroxide — recovered by crystallisation, not a metal recovered by electrowinning. The brine route is distinctive in using solar evaporation as its concentration step, which no other family on this path does at scale. Both routes lean heavily on precipitation purification, because the product specification for a battery-grade salt is tight on exactly the impurities (magnesium, calcium, boron, iron) the circuit must reject.