LITHIUM exploration within Cornwall, UK has received a boost after Rockwell Automation announced it is working with Cornish Lithium on a demonstration plant to validate the sustainable production of lithium hydroxide from granite containing mica.
Thanks to its geological make-up, Cornwall has long been mined for a range of metals including tin, copper, silver, zinc and even arsenic. It’s base metal and tin production helped fuel the UK’s industrial revolution, but by the late 19th century, mining in Cornwall had significantly diminished due to plummeting tin and copper prices, and the discovery of new metal resources abroad.
However, now that countries and consumers are faced with the next revolution, the green one, mining in Cornwall is experiencing something of a revival, and a new generation of miners are now clamouring to extract a mineral that is crucial for the transition away from fossil fuels: lithium.
To hit net zero targets by 2050, it is estimated that more than 2bn electric vehicles are needed worldwide, all of which, presently, require lithium for their batteries.
But, according to the International Energy Agency (IEA), the world could face lithium shortages by 2025, a scenario that is exacerbated by a lack of lithium-rich sources around the globe. Chile has the world's largest known lithium reserves with about 8m t, followed by Australia (2.7m t), Argentina (2m t) and China (1m t).
If the evaluation of the lithium potential in the UK is correct, then Cornwall could find a spot high on that list, as studies suggest granite outcrops around St Austell could contain as much as 3.3m t of lithium.
One of the companies aiming to exploit this resource is Cornish Lithium. The other, British Lithium, has already said it has found a sizable lithium deposit in the UK, enough to produce 20,800 t/y of battery-grade lithium carbonate.
Cornish Lithium, which has secured agreements with the owners of mineral rights over a large area of the county, is currently building a demonstration plant that extracts the metal with an acid-leaching, selective precipitation, and crystallisation process developed and licensing by Lepidico, to create lithium hydroxide from micaceous granite.
The processing site will utilise two key steps to process the ore; a first pre-concentration step that will produce a lithium mica concentrate via comminution and flotation. This is followed by a hydrometallurgical acid leaching system that produces lithium sulphate, which is converted into lithium hydroxide.
The comminution section involves a feed bunker loading followed by the crushing carried out with a vibrating grizzly and a jaw crusher, clay removal via washing trommel, secondary crushing via cone crusher, rod milling with several stages of classification, and desliming, Cornish Lithium explained. Deslimed and milled material will be subjected to flotation and potentially magnetic separation to produce a lithium mica rich concentrate, the firm added.
This concentrate will then be fed into the second processing step, a hydrometallurgical process, using Lepidico’s patented processing technologies.
The hydrometallurgical section of the plant broadly consists of leaching, impurity removal, filtration and crystallisation. The primary product, lithium hydroxide, will be crystallised from solution, but by-products such as gypsum, sulphate of potash, caesium and rubidium sulphate alum can also be produced.
This process, which has already been successfully tested at a small pilot plant in Australia, is expected to be more environmentally friendly than the traditional hard rock process, as it doesn’t use the calcination step, a process whereby ore is calcined at 1,000°C, Rockwell said.
Rockwell’s role is to supply its PlantPAx modern distributed control system – a single, plant-wide control system that Cornish Lithium will use as a platform for automated control and operation of its facility.
David Moseley, process manager at Cornish Lithium said: "Rockwell Automation will play quite a crucial role in what we are doing. We want to try and simulate as much as possible, the industrial process control that we might employ at full scale. We are trying to put as much of that into the demonstration plant as possible because it is a complex multistage process with lots of recycles – and sequential operation, particularly with filtration, and process control is critical. Rockwell Automation is putting together the process control philosophy based on our instrumentation. This is a series of different process control units that must be coordinated to have a plant that will operate effectively."
The demonstration plant is currently under construction and when commissioned is expected to operate for a year.
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