Refining of platinum group metals concentrates

Abstract

This invention relates to a process in which a Platinum Group Metal (PGM)-rich residue from a BMR (Base Metals Refinery) process is subjected to a high temperature roast to remove contaminants, typically volatile elements (for example Se, Te, As, S, Bi, Os) and obtain a roast product. The roast product is smelted with a flux to form a slag phase and an alloy phase, and to vaporize sulphates and heavy metals like Pb, Te, and remove stable oxide compounds such as Si02 and oxides of Fe, Ni, Co, Cu, Cr, Te, Bi to the slag phase. The alloy and the slag phase are separated, and the alloy phase is then melted and atomized with a gas or liquid atomization process to form fine alloy particles that can be dissolved in water and treated in a hydrometallurgical PMR (Precious Metals Refinery) process.

Description

BACKGROUND TO THE INVENTION[0001]This invention relates to the production of Platinum Group Metals (PGMs) (which includes Pt, Pd, Rh, Ru, Ir) and gold (Au), which normally consists of a floatation step during which most of the PGMs and sulphidic minerals are concentrated in slurry. Floatation is quite selective and typical PGM recoveries >80% can be achieved with mass pull (mass % of feed reporting as concentrate) figures of 1.8% to 4%. Unfortunately, some elements are often associated with the sulphide or PGM mineralogy (elements like As, Se, Te, Bi, Cd, Hg, Pb) and some of these elements also carry over with the floatation concentrate to become smelter feed material.[0002]In the typical smelting step of PGM production, concentrates are first melted in an AC or DC furnace where the sulphide minerals separate from the oxide minerals to form a distinct furnace matte and slag layer respectively. These layers are tapped separately on different elevations in the furnace. PGMs tend to...

AI Technical Summary

Benefits of technology

The invention is a process for removing contaminants from a pyrometallurgical process using PGM materials at high temperatures. The process allows for the formation of a PGM alloy phase that can be atomized, resulting in a high purity alloy containing Pt, Pd, Rh, Ru, Ir, and Au. The process also includes adding a synthetic slag to the melt, which helps dissolve stable spinel type compounds in the roast feed material. The slag can be added in various amounts, but typically around 20 g per 100 g of roast product feed is used. The alloy can be atomized using methods such as gas or liquid cooling, with high pressure water jets being a common method for achieving fine particulate. The process can also be done with high pressure inert gas or centrifugal gas cooling. The particles are more spherical and cooling is less rapid with inert gas.

Problems solved by technology

Unfortunately, some elements are often associated with the sulphide or PGM mineralogy (elements like As, Se, Te, Bi, Cd, Hg, Pb) and some of these elements also carry over with the floatation concentrate to become smelter feed material.

Complete physical separation between these two phases is seldom feasible so that the alloy phase is normally treated with acids and alkalis under oxidising environments to remove the intergrowths of base metal contaminants.

These residues need to be retreated with associated processing cost, inventory time, etc.

The contaminants might also negatively impact on overall recoveries of Precious Metals and pipeline time for delivery of the metals to the market.

Most refineries have pyrometallurgical process steps on recycle / residue / toll materials, but there is no existing Pyrometallurgical process slotted to treat the main feed material stream after the bulk of the Cu, Ni and S are removed and before the material is brought into dissolution for a PMR process.

Images