Simulating the Use of a Smelter Off-Gas in the Precipitation Stage of the Pedersen Process

The Pedersen process is an alumina production process, which combines pyrometallurgical and hydrometallurgical methods. In the pyrometallurgical stage, limestone is calcined and CO2 is generated. This off-gas can be captured with a high CO2 concentration. At the end of the hydrometallurgical process, aluminum hydroxides, like bayerite, are precipitated using CO2. In this paper, experimental work on precipitation of aluminum hydroxides through the addition of a mixture of CO2, O2 and N2 is presented. The parameters varied, as were the percentages of each gas and the temperature. The indicators measured were the time until the beginning of precipitation and the time that the precipitation lasts. These tests simulate the use of a smelter furnace off-gas in the precipitation stage of the Pedersen process and have shown promising results

Assessing a two-stage heap leaching process for Platreef flotation concentrate

Samples of low-grade flotation concentrate derived from Platreef ore were treated with a two-stage heap leach process to determine the potential to run this process parallel to the convential concentrate–smelt–refine process for extracting platinum group metals, thereby adding value to the convential process via economic treatment of low-grade materials. Using bench-scale columns, a first stage bioleach achieved extractions of 91.1% Cu, 98.5% Ni and 83.5% Co in a space of 88 days at a temperature of 65 °C. Samples of residual concentrate from this process were similarly treated via columns in a second stage leach using cyanide solution, achieving extractions of up to 96.5% Pd, 97.5% Au and 35% Pt in a space of 45 days at 50 °C. Mineral liberation analysis of a sample of concentrate from the cyanide leach experiment revealed that the bulk of the remaining Pt was in the form of sperrylite which appeared to leach very slowly in cyanide solution. Further to this, analysis of the cyanide leachate solution showed high levels of thiocyanate

A conceptual flowsheet for heap leaching of platinum group metals (PGMs) from a low-grade ore concentrate

This research proposes a new conceptual process to economically extract platinum group metals (PGMs), and as a secondary aim, base metals (BMs) from a low-grade concentrate originating from typical PGM concentrator plants. Slurry made from the concentrate was coated onto granite pebbles and packed into a column, in which it was bioleached with a mixed culture of thermophiles and mesophiles at 65 °C. After 30 days the extractions achieved were 52% copper, 95% nickel and 85% cobalt. The residual concentrate material was subsequently subjected to a cyanide leach also in a packed column operating at a room temperature of 23 °C. After 21 days 20.3% Pt, 87% Pd and 46% Rh were extracted. Using these results and projected extractions over longer operating times, a conceptual flowsheet was proposed for a possible process route to recover PGM values circumventing the problematic smelter route for this material