Rare earth acid bake: Controlled mixing and reaction for critical minerals.

Extracting rare earth elements from ore is a complex, multi-step process. One of the key stages in treating monazite-rich or bastnäsite-rich concentrates is the acid bake process — a thermal and chemical treatment that enables leaching of otherwise refractory minerals. Ingetecsa offers proven technologies for the drying, mixing, reaction and cooling steps required in rare earth recovery.

Following flotation and filtration, the rare earth concentrate typically retains around 20–25% moisture. This moisture must be removed to ensure a stable and controlled downstream process. Ingetecsa provides robust drying technology that delivers a reliable, low-moisture concentrate: the Spiral Flash Dryer.

After drying, the concentrate can follow three alternative routes, depending on mineralogy and process design:

• • Roasting (thermal pre-treatment): For concentrates such as bastnäsite, roasting in air at elevated temperature decomposes carbonates and fluorides, producing rare earth oxides that are more amenable to leaching.

• • Pre-leaching (PLR route): For monazite and xenotime concentrates, a chemical pre-leach removes acid-consuming impurities such as calcium, iron, and barite. This reduces acid demand and improves overall recovery in the subsequent acid bake.

• • Direct acid mixing (acid bake route): The dried concentrate bypasses pre-treatment and is fed directly into the acid mixer, where it blends with sulphuric acid. This marks the start of the sulphation roast, converting rare earth minerals into water-soluble sulphates.