Leaching and Precipitation
The process of leaching (atmospheric or pressure) is the primary step in most hydrometallurgical processes. The overall recovery of the valuable species is thus directly affected by the efficiency of the leach, and optimisation of the leach parameters is therefore of critical importance.
HMD is able to select and optimise leaching conditions for a variety of ores. Mintek’s expertise in this field includes an understanding of the intricate chemistry involved, as well as process simulation modelling and process optimisation.
Precipitation techniques are often used to purify or concentrate process streams. In these cases, both product purity and recovery need to be considered. Mintek’s hydrometallurgy division is able to provide a number of techniques that can readily be integrated into new or existing processes. Special expertise is available in base metal precipitation and the removal of iron and manganese from process streams via air/SO2.
Mintek has facilities, resources and more than 75 years of experience to undertake projects from basic flowsheet design through to laboratory test work, piloting and full-scale plant commissioning. The services include process design, and optimisation of process conditions and economics, based on computer simulation and experimental work.
SAVMIN – AMD WATER TREATMENT
HMD developed the SAVMINTM process during the 1990’s. However, a demonstration plant campaign that was done during 2007 by Atomaer for Western Utilities Corporation (WUC) indicated that the capital expenditure and operational expenditure of the process is too high, like most other acid mine drainage processes. Mintek has recently improved the SAVMINTM process which resulted in a significant capital cost reduction as compared to the previous values. Mintek also entered into a collaborative agreement with an international water treatment company, Veolia Water Solutions & Technologies, to conduct preliminary feasibility studies for three separate types of acid mine drainage water. Mintek will operate a pilot plant, demonstrating the SAVMINTM process on a 4m3/h scale at the start of 2012.
The price for rare earth elements has increased significantly in the last year and Mintek has, as a result, received a considerably increase in rare earth projects. HMD is currently involved in a number of rare earth projects, which involves various stages of leaching and precipitation to remove the impurities from the rare earth containing process stream and thereby obtaining a concentrated stream suitable for further purification.
Platinum Group Metals (PGM)
HMD has been involved in numerous projects to upgrade low grade PGM alloys to concentrate the alloy so that it would be suitable to for refining. Some of these projects also involved detailed flowsheet development and optimisation. The processes involved the removal of impurities via numerous leaching steps in different lixiviants to obtain a more concentrated PGM alloy.
The following facilities are available to perform the world-class work done in the Extraction group:
- Multi-purpose 4-stage (40 L) stirred-tank cascade for batch or continuous leaching and precipitation.
- Multi-purpose 6 stage (1 L to 20 L) stirred-tank cascade for batch or continuous leaching and precipitation.
- Mechanically agitated, rubber lined tanks with volumes ranging from 100 L to 2,000 L for leaching or precipitation test work.
- Small-scale batch autoclaves (Ti-lined): the internal parts are manufactured from grade 2 titanium. These vessels are suitable for leaching and precipitation work in sulphate media up to 240ºC and 45 bar.
- Air agitated Pachuca tanks (3,500 L) for bulk leaching of slurries.