This report presents the proposed lithium brine processing route for the Sal de Vida Project, a two-stage lithium carbonate operation planned for the Salar del Hombre Muerto in Catamarca Province, Argentina.
Report context
The Sal de Vida Project 2022 Technical Report, dated May 2022, describes the proposed design for a lithium carbonate production facility in Catamarca Province, Argentina. The report provides the project's processing route, from brine extraction through to finished lithium carbonate product. The design includes two stages of development and is supported by testwork and numerical modelling described within the report.
Processing route
Wellfield and brine distribution
Brine will be extracted from wells extending up to 300 m into the salar. The Stage 1 East Wellfield will be located over the east sub-basin of the Salar del Hombre Muerto. Stage 2 will include a Southwest Wellfield. The brine will be pumped to a booster station that will mix brine from different wells, acting as a buffer for seasonal flow changes and as a pumping station to deliver brine to the evaporation ponds.
The average design flow from the brine wells will be approximately 159 L/s for Stage 1 and 316 L/s for Stage 2. Maximum flow is expected each November at 255 L/s (summer) and minimum flow is projected for each July at 80 L/s (winter) for Stage 1. Maximum and minimum flows for Stage 2 will be 510 L/s and 160 L/s respectively. Each Stage 1 well is projected to pump at a rate of 115 m³/hr during summer and an average of 72 m³/h throughout the year.
The brine distribution system will connect all wells to the booster station, and from there brine will be pumped to the evaporation ponds. The design includes separate lines from each pump station to the booster ponds, with three booster pumps feeding a single pipeline to the evaporation ponds. Pipeline design includes section divisions at 100-m spacing for flushing and cleaning, and pipeline materials will consist of HDPE and PEX.
Solar evaporation ponds
The solar evaporation pond system will consist of halite and muriate evaporation ponds that will concentrate brine for feeding to the lithium carbonate plant. Evaporation will result from a combination of solar radiation, wind, temperature and relative humidity.
Halite ponds
Halite ponds will concentrate brine beyond the saturation point of sodium chloride, precipitating halite salts that will collect at the bottom of the ponds. Each string will contain six cells plus a buffer pond, with flow moving in a south-easterly direction from one pond to the next in series.
Key design assumptions for the halite ponds include an average evaporation rate of 2,700 mm/a, an evaporation derating factor of 0.7 for pond size, average leakage rate of 0.03 mm/d, lined ponds, and a depth of 1.2 m including 0.3 m freeboard. A 0.3 m permanent salt bed layer will be maintained on the pond base to protect the liner during harvesting, which will not be harvested. A maximum 0.3 m high harvesting layer will form on top of the salt bed, and liquid pond depth will be controlled to stay around 0.3 m above the harvest salt layer.
The Stage 1 halite system will have a total surface area of approximately 400 ha, divided evenly among three strings. Stage 2 halite evaporation ponds will cover approximately 850 ha on the northwestern corner of the Río de los Patos alluvial fan.
Muriate ponds
After liming, the clarified limed brine will be pumped to muriate ponds for further evaporation to bring the lithium concentration to 1.7% by weight. The muriate ponds operate on the same principles as the halite ponds, but the brine is evaporated beyond the saturation point of KCl, precipitating sylvite salts along with halite, with some gypsum also precipitated.
Stage 1 muriate ponds will be located south of the Stage 1 halite ponds, adjacent to the process plant. The system will consist of a muriate buffer pond, two strings of muriate ponds operating in parallel with three cells each, and two concentrated brine storage ponds. Evaporation curves were developed from pilot plant operations at the site.
Liming plant
The liming circuit will treat evaporated brine to remove magnesium, boron and sulphates. The brine will be combined with a slaked lime (Ca(OH)₂) slurry in a series of agitated mixing tanks, increasing pH and precipitating magnesium as magnesium hydroxide along with borate solids and gypsum. The limed brine will be pumped to thickeners and press filters to separate precipitated solids from the lithium-concentrated brine.
The liming plant will include mixing tanks, heat exchangers, storage tanks, hoppers, press filters, thickeners, pumps and sump pumps. The solids from this circuit will be discarded.
Softening and ion exchange
Once brine reaches the target lithium concentration of 1.7%, it will be heated to mild temperatures (~20°C) and sent to a series of six softening and mixing tanks. The addition of 25% soda ash solution will precipitate magnesium hydroxide and calcium carbonate. A plate and frame filter will remove the bulk of the solids, followed by a secondary filtration stage for final polishing.
The clarified softened brine will be conditioned before feeding a Ca/Mg IX circuit in a lead–lag–regeneration configuration using three columns. Small amounts of HCl and NaOH or RO water will be used for stripping and resin regeneration. The treated softened brine will be stored in two softening filtrate tanks for feedstock to crystallisation.
Lithium carbonate crystallisation
Lithium carbonate will be recovered by reacting purified brine with sodium carbonate at elevated temperatures of about 84°C. Sodium carbonate will be added as a 25% solution. The reaction will occur in a series of heated mixing tanks (crystallisers) operated at 84°C. A seed recycle stream of lithium carbonate crystals will be used to improve crystal growth.
After crystallisation, lithium carbonate solids will be recovered from the mother liquor by a hydrocyclone and centrifuge. The solid cake will be subjected to a displacement wash on the centrifuge before being conveyed to product finishing.
Product finishing
The product finishing circuit will dry the lithium carbonate solids to <1% moisture, after which they will be filtered, cooled, micronized and processed through magnetic removal of iron contaminants. The micronized product will then be bagged for transport.
Process plant infrastructure
The process facilities will be located adjacent to the muriate ponds. The plant will operate year-round with a planned availability of 8,000 hours per year. Surge capacity of the buffer ponds will allow constant plant throughput while evaporation rates and pond throughput vary seasonally.
Power generation will consist of a centralised power generation centre combining diesel and solar generation, with overhead powerline distribution to the geographically-isolated facilities. Raw water will be sourced from well SVWF12_19 and treated using reverse osmosis.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Well depth | Up to 300 m | Design |
| Stage 1 average brine flow | 159 L/s | Design |
| Stage 2 average brine flow | 316 L/s | Design |
| Stage 1 summer maximum brine flow | 255 L/s | Design |
| Stage 1 winter minimum brine flow | 80 L/s | Design |
| Stage 1 well pump rate (summer) | 115 m³/hr | Design |
| Stage 1 well pump rate (annual average) | 72 m³/hr | Design |
| Target lithium concentration after halite evaporation | 0.7 wt% (8.9 g/L) | Design |
| Target lithium concentration after muriate evaporation | 1.7 wt% | Design |
| Halite pond average evaporation rate | 2,700 mm/a | Design assumption |
| Evaporation derating factor | 0.7 | Design assumption |
| Pond leakage rate | 0.03 mm/d | Design assumption |
| Pond depth | 1.2 m including 0.3 m freeboard | Design |
| Permanent salt bed layer | 0.3 m | Design |
| Maximum harvest salt layer | 0.3 m | Design |
| Stage 1 halite pond area | ~400 ha | Design |
| Stage 2 halite pond area | ~850 ha | Design |
| Stage 1 muriate pond area | ~26 ha | Design |
| Stage 2 muriate pond area | ~52 ha | Design |
| Stage 1 halite salt harvest | 1.4 Mtpa | Design |
| Stage 1 muriate salt harvest | 79,000 tpa | Design |
| Stage 2 halite salt harvest | 2.8 Mtpa | Design |
| Stage 2 muriate salt harvest | 158,000 tpa | Design |
| Brine transfer weir width | 5 m | Design |
| Maximum brine flow (pumps/pipelines) | 450 m³/hr | Design |
| Crystallisation temperature | ~84°C | Design |
| Product moisture target | <1% | Design |
| Lime softening circuit tanks | 6 mixing tanks in series | Design |
| IX configuration | Lead-lag-regeneration | Design |
| Planned plant availability | 8,000 hr/a | Design |
| Halite pond harvesting frequency | ~1 harvest per year | Design |
| Halite pond availability derating | ~91% average | Design |
Project website: https://idbinvest.org/en/projects/sal-de-vida
Project website: https://www.riotinto.com/en/operations/south-america/sal-de-vida
Technical qualifications
The process design is based on testwork discussed in Section 13 of the report and numerical modelling described in Section 15. The evaporation pond model used an internally-developed tool together with a METSIM simulation of the process plant. Evaporation derating for brine activity was based on empirical correlations with magnesium and lithium concentrations. A set of evaporation curves was developed by evaporating limed brine from the pilot plant at the site. The pond design assumed lined ponds with HDPE geomembrane, and the salt harvest estimates and operating parameters are derived from these models and testwork.
Source: Sal de Vida Project NI 43-101 Technical Report, May 2022, Sections 1.15, 17.1.4, 17.2, and 17.2.2.
