Extraction process for metals like gold and platinum including fine grinding, pulping and oxygenating
This invention relates to a process for obtaining metal values, typically base metals, platinum or gold from a feed material. In a first step of the process of the invention, feed material containing metal values is ground to a particle size d 90 of 100 microns or less to form an ultra fine pulp. In a second step of the process of the invention, the ultra fine ground pulp from the first step is oxygenated by pumping it in multiple passes through an in-line high shear static oxygenation device ( 30 ), while re-circulating it on a tank ( 28 ) or any other vessel. The process of the invention results in a significant reduction in the required leach time, improved recoveries, reduced cyanide consumptions, a steadier gold tail, as well as reduced capital and operational expenditure.
1. A process for obtaining metal values from a feed material, the process including the steps in sequence:
1) obtaining a feed material in the form of a pulp with a particle size of d 90 of 100 microns or less;
2) passing the pulp through an oxygenating device in ten or more passes, wherein oxygen is introduced into the oxygenating device in the form of bubbles; and
3) passing the oxygenated pulp through a leach step.
2. The process of claim 1 , wherein the metal values are base metals, platinum or gold.
3. The process of claim 1 , wherein the feed material is a pulp with a particle size of d 90 of 50 microns or less.
4. The process of claim 3 , wherein the feed material is a pulp with a particle size of d 90 of 25 microns or less.
5. The process of claim 4 , wherein the feed material is a pulp with a particle size of d 90 of 15 microns or less.
6. The process claim 1 , wherein the oxygenating device of step 2) is operated at a pressure of from above 1 bar (1×10 5 Pa).
7. The process of claim 6 , wherein the oxygenating device of step 2) is operated at a pressure of up to about 10 bar (1×10 6 Pa).
8. The process of claim 7 , wherein the oxygenating device of step 2) is operated at a pressure of about 2.5 bar (2.5×10 5 Pa).
9. The process of claim 1 , wherein the bubbles have a size of from 1 micron to 1000 microns.
10. The process of claim 9 , wherein the bubbles have a size of from 1 micron to 500 microns.
11. The process of claim 1 , wherein the bubbles have an average size of 100 microns.
12. The process of claim 1 , wherein the oxygenating device provides high shearing to the pulp.
13. The process of claim 1 , wherein the oxygen line pressure at the point of injection of oxygen in the oxygenating device is above the pressure of the oxygenating device.
14. The process of claim 13 , wherein the oxygen line pressure is about 10 bar (1×10 6 Pa).
15. The process of claim 1 , wherein the oxygen consumption of the oxygenating device of step 2) is from 20 kg/t to 200 kg/t pulp.
16. The process of claim 1 , wherein the pulp is re-circulated through the oxygenation device in step 2) in from 10 to 300 passes.
17. The process of claim 16 , wherein the pulp is re-circulated through the oxygenation device in step 2) in from 20 to 200 passes.
18. The process of claim 17 , wherein the pulp is re-circulated through the oxygenation device in step 2) in from 50 to 200 passes.
19. The process of claim 18 , wherein the pulp is re-circulated through the oxygenation device in step 2) in from 100 to 150 passes.
20. The process of claim 1 , wherein the pulp is re-circulated through the oxygenation device in step 2) via a tank and the pH of the material in the tank should be maintained between 10 and 11.