A sensor to detect gold on-line while a processing plant is running opens up a real-time window for operators to monitor their product quality and capture value from going to waste. ADAM COURTENAY reports
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.
OLGA is an X-ray fluorescence-based technology capable of detecting gold in slurry with around 1000-times better accuracy than conventional methods – and in real time.
The analyser, which will be available through technology and services company Gekko Systems, detects gold (and other elements) contained in a continuous process stream.
Partnering with Gekko Systems
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, says.
“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.
Real-time gold data in slurry streams for the first time
Richard Goldberg, Gekko’s head of innovation and collaboration, says 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 says.
“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 says 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.
Delivering productivity while reducing emissions and improving safety
Andrew Dixon, Gekko’s performance consultant manager, says the new system is proving its triple bottom line credentials. Economically it allows you to control the processing plant to allow maximum efficiency of gold recovery, he says.
“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.”
This means that 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,” Mr Dixon says.
“A more stable gold processing operation is always going to be more efficient.”
Dr Goldberg says the reaction from gold mining companies who have seen OLGA work in laboratory conditions has been extremely positive and they 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.”
Dr Van Haarlem says Gekko, which is known for its ability to industrialise technologies, has been the ideal partner for CSIRO on this technology.
He and his X-ray team developed the OLGA technology, but it was Gekko which made it ready for the field and robust.
“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,” Dr Van Haarlem says.
Information to inform decision-making to optimise plant processes
OLGA is not just about detecting gold concentration. It’s about providing information.
“You could, for instance, put OLGA on the feed stream and one on the tailings,” Dr Van Haarlem says.
“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 says 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.
Dr Van Haarlem says 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.
Potential to transform gold processing
Dr Van Haarlem 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 says.
“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.”