The report details the processing route and expansion plans for the Olaroz lithium brine operation, based on five years of Stage 1 operating data and testwork.
Report context
This technical report, dated 2022, describes the Olaroz Project processing methods and infrastructure. Stage 1 has been in operation for approximately five years, and the report incorporates operating data and analysis from that period. A Stage 2 expansion was nearing completion at the time of the report, adding 25,000 tonnes per annum of lithium carbonate equivalent (LCE) to the existing Stage 1 production. Stage 2 was designed primarily based on experience from Stage 1 operations, supplemented by specific equipment testing for solid-liquid separation steps in the polishing area.
Processing route
Wellfields and brine supply
Northern and southern wellfields distributed over the salar properties deliver brine from 200 m or greater depth into intermediate tanks constructed as deep, compact plastic-lined ponds. Brine is pumped from the north and south tanks to the liming plant reactors. Total flow for Stage 1 is approximately 240 L/s at a grade ranging from 650 to 700 mg/L Li. For Stage 2 expansion, brine wells were drilled deeper and better equipped than Stage 1, using advanced geophysical profiling and screening technology. With a planned 15 new wells located between the existing wellfields, total flow for Stages 1 and 2 of up to 654 L/s at a minimum Li concentration of 650 mg/L is anticipated. This was supported by testing of some new wells as they became available from early 2020.
The brine is rapidly sodium chloride saturated by evaporation, with a composition primarily of sodium chloride and sodium sulphate, plus smaller concentrations of magnesium chloride, potassium chloride, lithium chloride and sodium borate.
Lime addition
Burnt lime (CaO) is delivered from the Los Tillianes plant at Vulcan, Jujuy, to the Olaroz site by tanker truck and pneumatically discharged into silos. The burnt lime is slaked with raw water in a small grinding circuit and stored in an ageing tank. From the ageing tank, the slurry is added to the brine in twin reactors in series where magnesium hydroxide and calcium sulphate are rapidly precipitated. Control of calcium and magnesium concentrations in the brine is critical to the recovery of a quality lithium product as they will co-precipitate. The precipitates are contained within the first evaporation pond for later reclamation and disposal.
Pond sequence
The reactors discharge to the first of eight halite ponds, with brine transferred by pumping from pond to pond. The ponds are baffled to minimise short circuiting, and brine levels are maintained to optimise evaporation rates on a seasonal basis. An extensive chemical and physical data set is collected, and pond performance is monitored against a mathematical model. A sequence of salts, primarily halite, Glauber salt (hydrated sodium sulphate) and complex permutations of simpler salts, are crystallised according to solubility changes induced by evaporation. The bulk of potassium and sodium salts are crystallised out as chloride salts early in the evaporation process and as sulphate salts later. Boron is precipitated by the relatively high pH (9 to 11) as tetra-borate (Na2B4O7 and CaB4O7). This may be enhanced by addition of calcium chloride.
The halite ponds flow into a series of smaller concentration ponds, originally designed to enable recovery of sylvinite salt (a mix of sylvite (KCl) and halite (NaCl)). The flotation separation of sylvite was tested early in the Olaroz Project but has never been economically feasible. At the end of the halite ponds, a secondary lime addition is used to control the final magnesium level of the plant feed brine in two intermediate ponds. The brine then flows through the eight-pond concentration system to a pair of tanks designed to minimise halite solids and control plant feed flow.
The volume of plant feed is typically one tenth of the original brine volume with a corresponding increase in Li concentration. This varies seasonally, as does the concentration of the various salts.
For Stage 2, pond design uses flat bottoms to enable salt harvesting and improved control. These ponds are dimensioned to have overall a greater area ratio to brine feed flow than the Stage 1 design. An additional 22 evaporation ponds and eight concentration ponds were completing construction at the date of the report, some of which were in operation.
Carbonation plant
The brine feed to the plant is saturated with NaCl, well below saturation of KCl, and grades 6000 to 8000 mg/L Li depending on seasonal impacts on evaporation rate. Residual calcium in the brine is precipitated with carbonate from the mother liquor recycle, and trace magnesium as hydroxide is precipitated in the polishing stage at 40 to 45 degrees C. This heating is mainly achieved by recovery from the carbonation reaction mother liquor. The precipitated solids are removed by centrifuge and specialised solution filters. Flocculant is used to improve removal of magnesium hydroxide in the centrifuges and filters. This is the first point of lithium loss as carbonate, with temperature minimised to control the loss. Some gypsum is formed.
The brine from polishing is heated indirectly with steam to approximately 85 degrees C, and 28% strength soda ash is added to precipitate the lithium as carbonate, which typically grades 99.3% Li2CO3. A small quantity of boron, sulphates and remaining magnesium are co-precipitated, with some entrapment of sulphates and chlorides in the lithium carbonate crystal and some gypsum. These are the main solids contaminants. Magnetic filters installed in various streams control iron contamination occurring from corroded components, dust ingress and equipment wear.
The underflow of the settler reactors is firstly dewatered to remove mother liquor, then the cake is water washed and dewatered. Both stages are conducted on a single belt filter, and the solid filter cake is conveyed to the drying plant. The reactor overflow solution and strong filtrate that are not re-used are returned to the ponds, and the weak filtrate from cake washing is used to mix soda ash.
Purification
A proportion of the primary technical grade lithium carbonate is purified to meet battery grade specification. The primary lithium carbonate is reacted with dissolved carbon dioxide at 5 degrees C in absorption reactors to form soluble bicarbonate, enabling removal by filtration of insoluble solid impurities. Both liquid and gaseous CO2 are utilised and injected at various points in the absorber feed and into the reactors.
The solution is further purified by removal of trace Mg, Ca and B in solution by ion exchange (IX). This solution is then heated to 85 to 90 degrees C to re-precipitate Li2CO3, releasing CO2 which is partly recovered and recycled to the absorbers. The Li2CO3 is separated by cycloning, with cyclone underflow filtered and washed with pure water before being dried and bagged. The cyclone overflow feeds a thickener, from which any settled solids are fed to the product filter.
The crystalliser performance achieves reaction equilibrium levels (dictated by temperature and carbonate concentration) of 2500 to 3500 mg/L of Li as Li2CO3, causing some losses of Li2CO3 in terms of strong filtrate directed back to the primary carbonation circuit.
Drying and packaging
The lithium carbonate filter cake at approximately 35% moisture is de-agglomerated and dried to approximately 0.5% moisture in a gas-fired spray drier. The dried solids are micronised if required by the customer. The dried product is bagged in 1 tonne lots with extensive quality control sampling and analysis.
Stage 2 plant design features
The Stage 2 expansion plant is similar in its general process flowsheet and chemistry to the Stage 1 plant but has been designed to provide higher quality product and improved recovery. This is achieved by: washing of solid precipitates in the polishing circuit to minimise Li loss; inclusion of improved ultra-fine filtration technology in the polishing circuit; removal of trace Ca and Mg by ion exchange processing of carbonation reactor feed, with an anticipated improvement from technical to battery grade; improved control of washing and filtration of final product by the use of air-blown plate and frame filters; and improved process control by enhanced instrumentation and increased process buffer storage. A gas-fired rotary drying kiln was used in the expansion drying plant, along with additional micronising capacity.
Stage 2 and Naraha supply
Allkem (75%) and TTC (25%) have constructed a plant in Japan to convert lithium carbonate (Li2CO3) to lithium hydroxide monohydrate (LiOH.H2O). This is achieved by reacting LCE with lime (Ca(OH)2), resulting in the formation of LiOH in solution. The solution is purified by ion exchange, concentrated by evaporation, crystallised as the monohydrate and dried. Stage 2 will supply 9,500 tpa LCE for 10,000 tpa lithium hydroxide production.
Infrastructure
The Olaroz site is managed on a drive-in drive-out basis, with personnel coming from regional centres, primarily Salta and San Salvador de Jujuy. A substantial camp with mess, clinic and nursing staff is maintained. Access is via highways 9 and 52 from Jujuy, with secondary connections at Salar Grande or Cauchari. The highway enters Chile via Paso de Jama. A gas spur line from the Norte Andino Gasoducto at Tres Cruces provides all site energy requirements other than diesel for mobile equipment. Electrical power is generated on a contract basis in a gas-fired generator plant. Water supply is from a five-hole wellfield in the Archibarca alluvial sediments, pumped to the plant for process use and purified by three reverse osmosis plants. A new water supply wellfield was being established in the Rosario Delta area north of the salar.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Stage 1 brine flow | ~240 L/s | Design/operating |
| Stage 1 brine grade | 650 – 700 mg/L Li | Design/operating |
| Combined Stages 1 & 2 brine flow | Up to 654 L/s | Design (supported by well testing from early 2020) |
| Minimum Li concentration for combined flow | 650 mg/L | Design |
| Carbonation plant feed grade | 6,000 – 8,000 mg/L Li | Operating (seasonally dependent) |
| Brine volume reduction to plant feed | ~90% (one tenth original volume) | Operating |
| Polishing stage temperature | 40 – 45 °C | Design/operating |
| Carbonation reactor temperature | ~85 °C | Design/operating |
| Lithium carbonate product grade | Typically 99.3% Li2CO3 | Operating |
| Crystalliser equilibrium Li concentration | 2,500 – 3,500 mg/L Li as Li2CO3 | Operating |
| Filter cake moisture (drier feed) | ~35% | Operating |
| Dried product moisture | ~0.5% | Operating |
| Stage 2 expansion capacity | 25,000 tpa LCE | Design |
| Stage 2 supply to Naraha | 9,500 tpa LCE for 10,000 tpa LiOH.H2O | Design |
| Number of Stage 2 new wells | 15 (planned) | Design |
| Number of Stage 2 evaporation ponds | 22 | Under construction |
| Number of Stage 2 concentration ponds | 8 | Under construction |
| Sylvinite flotation separation | Tested but never economically feasible | Historical testwork |
Technical qualifications
The report states that the Stage 2 expansion has been designed primarily based on experience gained from five years of operating development and data analysis from the Stage 1 plant. Some equipment-specific testing was conducted, mostly the new solid-liquid separation steps in the polishing area. The pond design for Stage 2 uses flat bottoms to enable salt harvesting and improved control. The Stage 2 expansion plant is similar in its general process flowsheet and chemistry to the Stage 1 plant.
A Stage 3 expansion concept is noted as being considered based upon acquisition of resources, further exploration potential, and emerging higher efficiency technologies, but no design or performance details are provided for Stage 3.
Source: Olaroz Resource Update , 2022 Technical Report, Section 17 Recovery Methods, pages 153-159.
