Erratic thickener performance proves costly
Water is used in processing most minerals, from simply washing away waste solids, to leaching of target metals with acidic or basic solutions. The solids and liquids then need to be separated efficiently in order to extract the minerals.
Gravity thickeners (large tanks) are used widely for this and flocculants and suspensions assist in producing a clear liquid stream at the top of the tank and a thick sludge of settled solids, which is discharged from the bottom. Despite their importance and widespread use, thickeners can be erratic and inefficient, which costs industry time and money.
Thickeners suffer from limited throughput, poor solid-liquid separation, operational difficulties and high consumption of expensive flocculants. In tailings applications they frequently fail to deliver the desired concentration of solids, leading to the waste of water and the need for excessively large tailings disposal dams that can cause environmental issues.
Advanced modelling of thickener performance
Using our expertise in mathematical and computational fluid dynamics, we are developing the world’s first three-dimensional full thickener model, as part of the existing multi-faceted AMIRA International project.
We are applying the models to systematic studies of different designs and operating conditions (changing solids concentration, volumetric flows, and dosages) to establish best performance guidelines. We are delivering control strategies for dealing with specific issues and performance targets, and developing a new test that will give the parameters needed to characterise the settling and consolidation of a flocculated feed for process or control modelling from a series of simple cylinder tests.
The project, or series of projects, which has been running for over 25 years, has been strongly supported by Australian and international minerals industries, with sponsorship funding of more than $20 million over time.
Delivering hundreds of millions in benefit
We have delivered significant improvements to the performance of more than 150 thickeners used in processing key commodities such as alumina, copper, gold, mineral sands, nickel and uranium.
We also developed a comprehensive set of tools and techniques for improving the performance of gravity thickeners for large-scale separation of fine particles from process liquids. According to an independent assessment, this work has already delivered well over US$500 million in value to industry.
Performance improvements include higher throughputs, improved operational stability, greater underflow densities, enhanced overflow clarities and reduced flocculant consumption.
The goal is to link these to develop a full thickener model to be used to fully optimise design and operation.