Preliminary laboratory work by Reward Minerals Ltd (ASX:RWD) has confirmed the efficacy of its new processing technology for the recovery of potassium sulphate (SOP) from seawater and other high-sulphate brines.
The company has now started a follow-up program, aimed at optimising reaction times of specific technical stages in order to reliably produce high-grade SOP (>52% K2O).
This work is part of the company’s engineering scoping study (ESS), with test-work supporting the robustness and reproducibility of the new process.
It has also provided critical data for Reward’s Australian Patent Application and for inclusion in the ESS.
Reward submitted the patent application in August 2022 and intends to submit additional technical information before August 2023, to complete the international application.
About the testing
Reward’s test-work programs provided additional data for the first order SysCAD, Flowsheet and Mass Balance Model completed in the December quarter of 2022 by an independent global engineering firm.
Further to this, recent in-house laboratory evaporation, chemical analyses and Syngenite [K2Ca(SO4)2.H2O)] recovery work programs support the company’s ESS for SOP recovery using Reward’s new brine processing technology.
The company is encouraged by results so far.
Initial test-work involved evaporation of seawater-derived brine (bitterns) emanating from a solar salt operation in Western Australia (11.5g/l K, 350g/l TDS, 1.26 SG) to a magnesium content of ca. 110g/l followed by draining of the residual high manganese supernatant liquor.
The remaining crystallised salts were redissolved in water to provide a new process brine (ca. 50g/l K) suitable for reacting with gypsum [CaSO4.2H2O] to form Syngenite [K2Ca(SO4)2.H2O)].
The reaction at ambient temperature provided +50% first-pass extraction of K to the solid Syngenite salt. In operations, the residual Syngenite Reactor liquor will be recycled to the brine evaporation ponds for further SOP recovery.
Test-work conducted on Reward’s Kumpupintil Lake (KP Lake) resource brine indicated that following evaporation of resource brine to K saturation point of (ca. 45g/l K) treatment with gypsum via the Reward Process method provided a first pass K recovery to Syngenite product of around 40%.
Importantly, the 40% recovery figure for brines of composition similar to that of the KP Lake Resource brine, is possible without redissolution of precrystallised salts.
The next part of the program involved the treatment of Syngenite with water to produce a SOP solution with very low contaminants (Na, Mg, Cl) plus high-purity gypsum, which is recycled to the Syngenite reaction step. The SOP solution is evaporated to provide high-purity SOP crystal product (+52% K2O) by conventional technology.
The key benefits of the Reward Process compared to commonly used SOP brine recovery processes are:
- it does not require mechanical harvesting of mixed potash salts;
- it does not require the conventional Schoenite or Kainite flotation steps; and
- it may significantly reduce capital and operating costs per unit of SOP.
The follow-up programs will be along similar lines but use slightly different Reward Process thresholds to optimise the final flowsheet.
Upcoming test-work will also include final crystallisation of SOP from Syngenite leach liquor to confirm the SOP quality parameters.
Once complete, the ESS battery limits will be finalised so it can be advanced in the June quarter of 2023.
What happens next?
Over the coming two quarters, Reward will focus on several key activities including:
- advancement of the Reward Process, international patent finalisation and licensing to third parties;
- completion of an ESS for the KP Lake Project and typical seawater derived brines utilising the Reward Process;
- engagement with chemical, seawater solar salt, fertiliser and seawater desalination companies worldwide to discuss the application of its technology within proposed SOP developments and production joint ventures;
- receipt of results from Fortescue’s RC drilling program at the McKay Range Joint Venture.