Field trials for the CSIRO-developed Online Gold Analyser (OLGA) are showing such positive results at a Queensland gold mine that the technology is expected to be ready for market this year, the research organisation reported recently.
OLGA is an X-ray fluorescence-based technology capable of detecting gold in slurry with around 1,000-times better accuracy than conventional methods – and in real time, according to CSIRO.#
The analyser, which will be available through technology and services company Gekko Systems, detects gold (and other elements) contained in a continuous process stream.
OLGA can detect gold in slurries at 10 parts per billion using a pair of X-ray lenses that greatly magnify the slurry’s fluorescent gold signal as it passes through a tank.
“Normally you take samples from a stream and send that sample to a laboratory,” CSIRO Research Group Leader, Yves Van Haarlem, said. “If you’re lucky the lab is onsite, but even then the turnaround time for analysis can be 10 to 12 hours. That’s probably too late to do something about it. With OLGA you can act on what you’re seeing almost immediately.”
Conventional X-ray Fluorescence is already a well-known tool in the base metals industry for the monitoring and control of concentration plants, but they tend to have less accurate detection limits – usually in the tens to hundreds of parts-per-million (ppm) range, precluding their use in precious metal concentrators, according to CSIRO.
Richard Goldberg, Gekko’s Head of Innovation and Collaboration, said that other means of detecting gold have been lacking in accuracy and/or the timely availability of results. “We’ve never had the ability to directly monitor gold flows through a plant in real time before,” Dr Goldberg said. “We know that gold grade can vary over relatively short periods and that it will do so between the samples taken as part of traditional process control regimes. As the results from those samples are also delayed, they are unlikely to accurately reflect the changes occurring in the process stream.”
Dr Goldberg said OLGA’s value stems from its ability to provide important information in near real time. In effect, the operators of a plant will no longer be blind to changes in its performance, according to CSIRO.
Andrew Dixon, Gekko’s Performance Consultant Manager, said the new system is proving its triple bottom line credentials. Economically OLGA allows the processing plant to be controlled to allow maximum efficiency of gold recovery, he said.
“This has environmental benefits as well. It will allow you to optimise reagent additions and to reduce any emissions from the plant that may have to be detoxified or treated to be made safe,” he said.
This means a plant will end up with less reagent chemicals in the tailings.
“It’s also more sustainable – the efficiency improvements will have an effect on the stability of the operation,” Dixon said. “A more stable gold processing operation is always going to be more efficient.”
Dr Goldberg said the reaction from gold mining companies that have seen OLGA work in laboratory conditions has been extremely positive and have seen considerable interest in the technology.
“We’re currently conducting field trials to ensure it’s a solid product before we fully release it to the market. To date, the trials have been extremely positive,” he said.
Dr Van Haarlem said Gekko has been the ideal partner for CSIRO on this technology. “Gekko engineered the whole structure around the analyser so that the slurry can be easily analysed, validation samples can easily be taken, and to provide the robustness required for plant installation,” he said.
OLGA is not just about detecting gold concentration. It’s about providing information, according to CSIRO.
“You could, for instance, put OLGA on the feed stream and one on the tailings,” Dr Van Haarlem said. “You could then look at what went in and what went out. If there’s too much gold in the tailings compared to the feed then the plant knows immediately that it’s losing gold. All this can then be acted upon.”
Dr Goldberg said there has been interest from potential buyers from as far away as Africa, Europe and South America. A fully supported product should be available for these regions later this year, CSIRO said.
Dr Van Haarlem said the X-ray optic system is now being tested on platinum and can be used for other metals. Its application could be much more widespread, such as for detecting toxic elements in food and water.
Yet, he believes OLGA’s future rests in its potential to revolutionise gold processing plant strategies and to refine logistics.
“It will provide a lot of data on real time gold and slurry density, which can then be correlated with other plant parameters,” he said. “It might turn out that if you don’t mill the ore sufficiently, gold recovery suffers. It’s going to show us correlations we didn’t even know were happening. This information can help us to optimise the entire production circuit.”
