Selective base metals leaching from laterite ores
A process to use ferric sulphate equilibrium to reduce overall acid consumption and iron extraction, the process comprising the steps of: (i) sulphating; (ii) selective pyrolysis and (iii) selective dissolution.
1. A process for leaching base metals from laterite ores, comprising:
(i) sulphating the laterite ore to obtain ferric sulphate;
(ii) selective pyrolysis of the ferric sulphate to decompose ferric sulphate into sulphur trioxide, hematite and target metals; and
(iii) selective dissolution of the hematite and the target metals to obtain ferric oxide and a solution containing the target metals;
wherein the step of sulphating comprises a first stage of sulphuric acid dosage and a second stage of equilibrium displacement towards the ferric sulphate.
2. The process according to claim 1 , wherein the second stage of equilibrium displacement is carried out at a temperature ranging from 50 to 400° C.
3. The process according to claim 1 , wherein the first stage of sulphuric acid dosage comprises dosing from 10 to 600 kg of sulphuric acid per ton of ore.
4. The process according to claim 1 , wherein the step of selective pyrolysis is carried out at a temperature ranging from 400 to 1000° C.
5. The process according to claim 1 , wherein the target metals are nickel, cobalt and other elements.
6. The process according to claim 1 , wherein the step of selective dissolution is carried out at a temperature ranging from 15 to 100° C.
7. The process according to claim 1 , wherein the step of selective dissolution is carried out at a pH ranging from 1 to 5.
8. The process according to claim 1 , wherein the step of selective dissolution comprises filtering ferric oxide from the solution containing target metals.
9. The process according to claim 8 , wherein the solution containing target metals is a solution containing nickel sulphate.
10. The process according to claim 1 , wherein the lateritic ore comprises limonite.
11. The process according to claim 1 , wherein, prior to the step of sulphating, the ore is prepared to a size fraction below 2″.
12. The process according to claim 11 , wherein, prior to the step of sulphating, the ore is prepared to a size fraction below 0.5 mm.
13. The process according to claim 1 , wherein the solution containing the target metals is substantially devoid of iron.