Lake Way hosts several sources of hypersaline brine, which contains the metal salts which are then concentrated and converted into SOP. The brine is abstracted using bores and trenches on the lake surface. The 88 production bores tap into several different resource components, the deepest being the main paleochannel sequence at around 120m below ground level, then with intermediate resources in gravel lenses and siltstone deposits which are between 30 and 60m below ground level.
The bores are connected by the Brine Transfer System (BTS) which transports the brine to the required destination in a completely enclosed pipeline. The 86km of trenches extend to the North, East and South of the pond system on the lake surface, terminating in sumps from where the brine is pumped to its destination depending on requirements.
The requirement for brine supply to the evaporation ponds is seasonal, peaking in the Summer when evaporation rates can exceed 22mm/day, and at its lowest in the Winter, where 2 – 5mm/day is more normal. To manage this variability SO4 uses a disused gold mine in the centre of the lake to store brine. Wiliamson Pit acts as a buffer between the brine supply which is kept as constant as possible, and the pond demand which varies with the seasonal evaporation. With a working capacity of 6.5Gl it is an asset to the site.
At the beginning of 2025, Lake Way had 1,132ha of pond area. During 2025, SO4 will further expand this and combine the current two train system into one train, realising efficiencies in brine delivery and salt harvesting.
The first ponds to receive brine are the preconcentration ponds, P1 and P3, with P2 to be constructed in 2025 connecting the two pond trains. These ponds are designed to increase the concentration of the brine to a point just before the crystallisation of salts begins. Brine is continuously pumped into the P ponds and transferred through the system in balance with the evaporation rate and to maintain the correct concentration profile through the train.
The “P” ponds feed the halite ponds, H1, H4, H5 and H6. These ponds crystallise halite salt (sodium chloride, NaCl) as the brine concentration increases through the system. Approximately 5 million tonne of halite will be crystallised and removed from these ponds each year. The halite is returned to the salt lake system.
When the brine reaches the concentration where potassium (K) containing salts start to crystallise, it is transferred to the “K” ponds. These ponds are sequentially filled with high concentration brine and then allowed to evaporate and produce “K salts” until the salt has formed a pavement in the pond that is of sufficient depth for efficient harvesting. When this point is reached the K pond is taken off-line and “de-brined” so that the valuable high concentration brine is conserved in the pond system. The K salt layer is then harvested and delivered to the Process Plant.
Brine which reaches high concentration when the K pond is still operating is transferred to carnalite ponds (CA ponds). Due to the very high concentration, these ponds crystallise a different balance of K salts. The CA ponds are then harvested in a similar way to the K ponds, and then the different salts are blended to provide a consistent feed to the Process Plant.
Finally, brine from the CA ponds, which has crystallised out almost all of the K salts, is transferred to the bitterns pond, where the final concentration of the remaining brine occurs. This mainly produces magnesium chloride (MgCl2), which has uses in several areas.The final ponds in the system are the recovery ponds. These consist of the “RB” ponds, where a waste salt, bloedite, is crystallised, and “RK” ponds where salts are produced with a higher concentration of K than in all the other ponds. The RK ponds are harvested in a similar way and the salts blended as required to give a consistent feed to the Process Plant.
The feed to the RB ponds is the spent conversion brine from the Process Plant. This is a relatively dilute brine, that still contains a significant quantity of K, as well as greater amounts of Mg and sulphate (SO4). This brine must be purged from the Process Plant to prevent the build-up of Mg and SO4 particularly. Bloedite and other high Mg and SO4 containing salts are crystallised in the RB pond, and then the brine is transferred to the RK ponds when the concentration reaches the point where additional K salts are crystallised.
The Process Plant has been designed to purify the specific blend of salts from the Lake Way brine and produce a very high-quality SOP product. The plant consists of several recirculating loops where the chemistry of the brine and salt slurry is manipulated to remove the NaCl, Mg, and excess SO4 from the salt finally producing a very pure SOP.
The first step is crushing and attritioning of the blended harvest salt. In this step, the large agglomerations of crystals from the harvest ponds are reduced in size and separated to provide the correct presentation of the salt crystals to the flotation step. The salt is mixed with recirculating brine at saturation, so that it forms a salt/brine slurry. This slurry is conditioned for pH (making the slurry slightly acidic) and a “collector” is added which makes the halite crystals in the slurry more hydrophobic, encouraging the air in the flotation step to adhere to these crystals preferentially.
The Upstream Project expansion marks an exciting phase of growth, focused on significantly enhancing our borefield and pond infrastructure to support increased production capacity.
Central to this expansion is the construction of the P2 evaporation pond, a critical addition that will enable greater brine concentration and storage. The project also involves the integration of the current two-train pond system into a more efficient single-train configuration, streamlining operations and improving flow dynamics. Complementing these upgrades is the expansion of the brine supply network, designed to ensure a consistent and scalable feed into the processing plant.
Together, these developments lay a strong foundation for operational excellence and long-term sustainability.
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