Five 500 series cased peristaltic pumps from Watson-Marlow Fluid Technology Solutions are playing an important role in a demonstration plant at Cornish Lithium’s Shallow Geothermal Test Site in the UK.

Originally built to test the concept of extracting lithium from geothermal waters, Cornish Lithium is now working on an upgraded version of the test plant as its drilling program expands, ultimately with the aim of developing an efficient, sustainable and cost-effective lithium extraction supply chain.

The initial enquiry for pumps came from GeoCubed, a joint venture between Cornish Lithium and Geothermal Engineering Ltd (GEL). GEL owns a deep borehole site at United Downs in Cornwall where plans are in place to commission a £4 million ($5.2 million) pilot plant.

“GeoCubed’s process engineers helped us to design and commission the test plant ahead of the G7, which would run on shallow geothermal waters extracted from Cornish Lithium’s own research boreholes,” Dr Rebecca Paisley, Exploration Geochemist at Cornish Lithium, said.

Adam Matthews, Exploration Geologist at Cornish Lithium, added: “Our shallow site centres on a borehole that we drilled in 2019. A special borehole pump [not Watson-Marlow] extracts the geothermal water [mildly saline, lithium-enriched water] and feeds into the demonstration processing plant.”

The five Watson-Marlow 530SN/R2 pumps serve two different parts of the test plant, the first of which extracts lithium from the waters by pumping the brine from a container up through a column containing a large number of beads.

“The beads have an active ingredient on their surface that is selective for lithium,” Paisley explained. “As water is pumped through the column, lithium ions attach to the beads. With the lithium separated, we use two Watson-Marlow 530s to pump an acidic solution in various concentrations through the column. The acid serves to remove lithium from the beads, which we then transfer to a separate container.

“The pumps are peristaltic, so nothing but the tube comes into contact with the acid solution.”

She added: “We’re using the remaining 530 series pumps to help understand what other by-products we can make from the water. For instance, we can reuse the water for secondary processes in industry and agriculture. For this reason, we have two other columns working in unison to strip all other elements from the water as we pump it through.”

According to Matthews, flow rate was among the primary reasons for selecting Watson-Marlow pumps.

“The column needed a flow rate of 1-2 litres per minute to fit with our test scale, so the 530 pumps were ideal,” he says. “The other consideration was choosing between manual or automated pumps. At the time, because it was bench scale, we went for manual, as we knew it would be easy to make adjustments while we were still experimenting with process parameters. However, any future commercial lithium extraction system would of course take advantage of full automation.

Paisley added: “The great thing about having these five pumps is that we can use them to help evaluate other technologies moving forward. Lithium extraction from the type of waters we find in Cornwall is not undertaken anywhere else in the world on any scale – the water chemistry here is unique.

“It is really important for us to undertake on-site test work with a variety of different companies and technologies. We want to devise the most environmentally responsible solution using the optimum lithium recovery method, at the lowest possible operating cost. Using local companies is part of our strategy, particularly as continuity of supply is vital.”

To help fulfil the requirements of the next test plant, Cornish Lithium has enquired after more 530SN/R2 pumps from Watson-Marlow.

“We’ve also requested a quote for a Qdos 120 dosing pump from Watson-Marlow, so we can add a certain amount of acid into the system and achieve pH balance,” Matthews says. “We’ll be doing more drilling in the coming 12 months, which will allow us to test our technology on multiple sites.”