The De Beers Group of Companies’ innovation division, De Beers Technologies South Africa (DebTech SA), has developed a novel density measurement system that can provide process plants with fast and accurate data on the material density profiles of particle samples.

The availability of this data, in turn, can facilitate timeous plant adjustments that make for better plant performance and higher recoveries.

The RhoVol densimetric measurement system has been in development for three years and has now been made commercially available.

The system determines the density of an ore sample by measuring the mass and volume of individual particles.

Notably, the system allows plant operators to conduct density tests on site and to generate the data they need within about an hour, rather than sending samples to third-party laboratories and waiting days or even weeks for the results.

DebTech research and development manager Dr Grant High explains that the usual delay in receiving results presents a lost opportunity for metallurgical plants as, by the time the results of the sample tests are returned to the plant, it is often too late to adjust the setup of a process to achieve the optimal effect.

Further, the density profile of the material passing through the plant may have changed since the last sample was taken.

“The metallurgical industry has, for many years, been looking for [a solution] to measure the density of incoming material in real time, so that the plant’s settings can be optimised in time to make a difference,” he says, stressing that the key advantage of the RhoVol system is the accurate, timeous information it provides.

In the RhoVol, DebTech has combined its vision size frequency distribution (VSFD) technique – which is a camera-based system for measuring the size of particles – with a rapid weight measurement device. This allows for the mass and the volume to be determined with significant accuracy and speed, providing data from which the density of each particle can be calculated.

The system’s software creates a three-dimensional (3D) model of each particle, so that any physical dimensions or ratios can be derived.

High explains that information about the shape of the particle – such as elongation, flatness and compactness – can be valuable in understanding the particular behaviour of a metallurgical process.

“The simplicity of operation of the RhoVol means that a plant does not require any specialised laboratories on site, and a relatively unskilled operator can conduct the measurements,” he adds.

Processing plants can also use the RhoVol to audit the density profile of the run-of-mine material entering the plant, as well as material on the output side, thereby facilitating more effective monitoring of plant performance.

The machine is available in two sizes to accommodate coarse and fines-size fractions – one for material sized 3 mm to 8 mm, and a larger machine for material sized 8 mm to 25 mm.

DebTech is considering the development of a system capable of measuring very fine fractions of between 1 mm and 3 mm.

Further, DebTech aims to, in future, add additional sensor measurements to the RhoVol, such as a magnetic susceptibility measurement, High tells Mining Weekly.

The RhoVol has an optional sorting functionality and can even raise the resolution of the 3D models by accommodating multiple passes of material through the system. By matching and merging images of the same particle, a high-fidelity 3D model can be generated, High explains.

The system, which provides accurate measurement of the mass, volume, density and shape of particles, can be applied across a range of commodities, as any mineral or material can be measured for its volume and mass. High notes that the density measurement range is not restricted and can be programmed to suit the product.

The RhoVol has a process rate of about 1 000 particles an hour, which is generally sufficient for a representative sample. The advantages of the measurement system include high levels of repeatability.

Data is displayed live as it is captured and made available in a standard spreadsheet format on a per-particle basis.

Notably, no consumables are required in the testing process and no toxic liquids are involved in the testing, as in some sink float processes.

High further notes that critical components of the system are 3D-printed locally.

Market Uptake
Since the RhoVol’s development, about eight systems have been deployed in the South African iron-ore industry, while one system is currently operational at a diamond mine in Botswana.

DebTech retains two systems for densimetric profiling of samples sent from universities and other tertiary education institutions.

Meanwhile, smaller laboratories have also expressed an interest in the system.

“There has been reasonable uptake of the system in the short time it has been available commercially,” High concludes.