The L-Max® process technology employed in the downstream chemical plant has been developed over
a six year timeframe through an extensive program of laboratory, mini-plant and pilot plant programs. Coupled with extensive flowsheet modelling and vendor testwork, a robust process has evolved that produces lithium chemical, high value by-product chemicals of caesium and rubidium (extracted by a separate proprietary process) and a range of bulk by-products, in an efficient low energy approach. Patent protection was received in fiscal 2020 for the L-Max® technology in Australia, Europe, Japan and the United States.
The Phase 1 chemical plant is designed to process 56,700tpa (dry basis) of lithium mica/amblygonite concentrate at a feed grade of up to 4.0% Li2O for production capacity of 5,600tpa of lithium hydroxide. The overall lithium recovery from concentrate to lithium hydroxide is estimated at 90%.
A key aspect of the L-Max® process is the direct leaching of the lithium bearing mineral from the feed without the need for an energy intensive thermal treatment step preceding the leach, which is employed by many other hard rock lithium conversion processes. The leach conditions are such that very little energy is required to keep the process at temperature. Optimising the leaching conditions has been an important part of the development process.
Handling of the leached slurry is a unique part of the L-Max® process and the embedded intellectual property. The slurry is filtered at moderate temperature to yield a solution containing the valuable alkali metals and a silica- rich filter cake. Selective washing of this cake is required to achieve high lithium recovery to the liquor moving downstream.
The filtered leach liquor, which is rich in aluminium, is cooled resulting in the crystallisation of an alum solid. This alum crystallisation step achieves the separation of lithium from the other monovalent cations. The monovalents, potassium, rubidium and caesium all form alums, whereas lithium does not. Filtering the alum slurry results in the potassium, rubidium and caesium, and most of the aluminium reporting to the solids, and a liquor containing the lithium and small amounts of other impurities. The alum solids are further treated to yield potassium, caesium and rubidium products.
The impure lithium-rich liquor is treated through a series of pH controlled precipitation stages, with limestone and lime, to sequentially remove the remaining impurities, namely iron, aluminium, manganese, and magnesium. The resulting lithium sulphate solution is of su cient quality to allow the recovery of a high specification lithium product.
LOH-Max® is a proprietary process for the production of lithium hydroxide without the co-production of sodium sulphate. The unique chemistry of this process has been able to directly produce high purity lithium hydroxide monohydrate in a cost effective manner. The process takes the lithium sulphate liquor produced from the L-Max® process as feed and involves hydrometallurgical reactions to produce lithium hydroxide and a gypsum containing residue. Provisional patent applications advanced in
fiscal 2020 for LOH-Max® and the separate process for production of caesium and rubidium chemicals. More recently a provisional patent application was lodged by Lepidico for the production of nominal battery grade specification lithium carbonate from a LOH-Max® intermediate crude lithium hydroxide via the sequestration of carbon dioxide – planned to be captured from the upstream L-Max® process – followed by refining. The new process is designed so that it can be integrated with either L-Max® and/or LOH-Max® or potentially in the chemical conversion of spodumene concentrates.
Chemical Plant layout