The Carina Project technical report describes a proposed processing plant designed to recover rare earth elements from ionic clay ore through washing, ion exchange, thickening, filtration, and precipitation stages, with supporting mass balance data from laboratory testwork.
Report context
This NI 43-101 Technical Report for the Carina Project, located in Goiás, Brazil, is dated 2025 and was prepared with contributions from Hatch and Aclara. The report presents a pre-feasibility level design for the processing facility, including a proposed average production rate of 4,265 tonnes per year of rare earth oxide equivalent, excluding ramp-up and ramp-down periods. Process design details, mass balance parameters, and capital and operating cost estimates are included in the report.
Processing route
Ore Feeding and Conditioning
Mined ionic clays will be fed into each of four process lines via static grizzlies to reject oversized material such as vegetation and rocks. A temporary run-of-mine stockpile will be used when the process plant is offline for maintenance. Discarded material from the grizzlies will be temporarily stacked and sent to final disposal at the Deposition Zone. The mined material passing through each grizzly falls into a hopper and is transferred by conveyor to the associated washing drum.
Ore from the washing belt conveyor feeds the washing drum feed chute, where wash solution is added. The discharge from the washing drum passes through a trommel to remove coarse particles before further washing with clean alkaline water. The coarse material is discharged to a portable truck hopper for subsequent final disposal. The resulting slurry reports to the wet screening stage.
Clean solution is used at the first wet screen to further wash particles, achieve the desired slurry concentration, and improve screening efficiency. The first wet screen separates fine particles from coarse particles. Fine particles pass through the first wet screen and flow via gravity to a slurry transfer box before being pumped to the thickening area for clay leaching. Coarse particles are directed to a second wet screen, where they are washed with clean water. The second wet screen undersize is discharged via gravity to the same first screen undersize transfer box. The oversize stream is discharged to the spent material conveyor belt.
Thickening Area
Slurry from each feed preparation process line area is pumped into one of four thickeners, where flocculant is added to enhance sedimentation of solids and achieve a slurry concentration of approximately 50% w/w, as required for feeding the press filters. The overflow, a rich solution, from the thickeners flows by gravity to the overflow tank. From here, most of the overflow is pumped to the reactors in the primary precipitation area, with a portion sent back to the primary wet screening area to enhance size separation performance. The underflow from the thickeners is pumped to the filter press holding feed tanks and then to membrane type filter presses.
Dewatering (Press Filter)
The underflow stream from each thickener will be pumped to pressure filter feed holding tanks, from where the slurry will be pumped by independent pumps and pipelines to plate and frame pressure filters. The filters will use clean wash water at the end of each filtration cycle to displace any residual REEs remaining in the filter cake. Washed clay will be discharged via gravity from each filter to respective feeders, which discharge to a shared spent material belt conveyor that sends the cake to the Deposition Zone. The filtrate from each filter flows via gravity to the primary precipitation area before being sent to the impurities removal area.
Primary Precipitation
The REE solution from the filters will be fed to primary precipitation reactor #1, where anhydrous ammonia and ammonium carbonate will be added to adjust the pH and precipitate some impurities. The final primary precipitation slurry will be pumped to polishing filters to produce a filtrate with high total dissolved solids concentration. The filtrate will then be pumped to the polishing filter discharge boxes and then to the water treatment plant.
The precipitate slurry generated from the polishing filter will flow by gravity to polishing filter discharge tanks. From here, it is pumped to a decanter centrifuge, with reverse osmosis permeate solution from the centrifuge wash tank also added for washing. The centrifuge produces a thickened material that is sent to the redissolving tank and then to the impurity precipitation and removal area. The liquid phase from the centrifuge, the centrate, is sent to the co-precipitation centrate tank and pumped back to primary precipitation reactor #3.
Impurity Precipitation
The REE-rich solution from the redissolving tank will be sent to the first of two reactors. Reagents are to be added to adjust the pH and promote precipitation of impurities such as aluminum and iron. The solution containing impurities will be pumped to an impurity precipitation polishing filter to capture impurities for final disposal. Off-gas from the reactors will be drawn from the tanks under vacuum and directed to the plant scrubber due to the potential for ammonia gas generation.
The clean solution generated from the impurities filter will be sent to the REE precipitation reactors, while the precipitated impurities will be discharged to the impurities slurry receiving tank. From here, the impurity slurry will be pumped to the centrifuge filtration system. The impurities filtrate is discharged to the impurities filtrate tank and recirculated to the primary precipitation system, whereas the filter cake is disposed together with the spent clay.
REE Precipitation
The clean solution from the impurity precipitation polishing filters will be fed to REE precipitation reactors arranged in series. Ammonium carbonate will be added to achieve the desired process conditions for REE carbonate precipitation. Any off-gases produced will be sent to the plant scrubber.
The solution containing precipitated REEs will be pumped to product polishing filters, which will also be fed with clean water. The polishing filters generate a filtrate and a product slurry: the filtrate is sent to a receiver tank and pumped back to co-precipitation tank #1 located in the primary precipitation area, whereas the slurry containing the precipitated REEs is discharged to the polishing filter product transfer tank. From here, it is pumped to product tube press filters to produce a filter cake with high REE content. A clean water stream feeds the tube press cake and filter-cloth wash water tanks.
The tube press filtrate reports via gravity to the product filtrate tank and is pumped back to co-precipitation tank #1 in the primary precipitation area. The REE product tube press filter cakes are discharged to the packing system feeder through a shared chute located below the tube press, which transfers the wet cake to the product belt conveyor. From here, the wet product is transferred to the packing system, where flexible intermediate bulk container bags are filled with the final wet REE concentrate. The bags are removed from the bagging system via forklift and stored in the product storage and dispatch warehouse, ready for shipment via truck.
Washed Clay Handling
A washed clay belt conveyor receives washed clay from various parts of the plant. Two weightometers are used: the first, located at the beginning of the conveyor belt, measures the wet screen oversize, and the second, located after the press filter discharge, measures the wet screen oversize production. The ion exchange filter press cake weight is calculated as the difference between the two streams.
The discharge from the washed clay belt conveyor feeds a temporary stockpile. From here, the material will be dried and placed in the Deposition Zone. Oversize material from the washing drum trommels will be transported in trucks directly to the drying area before final disposal.
Water Treatment Plant
A water treatment plant is included as part of the process design to minimise the consumption of fresh water and avoid the need for a plant liquid discharge stream. The process system will recover water and remove impurities that could affect the quality of the final product. The design features chemical precipitation, nanofiltration, reverse osmosis, and ion exchange.
Fresh and Process Water Distribution
The process water distribution system will collect and store water rejected from different process streams into water tanks. Treated water will be pumped to the pressure filters, wet screens, and washing drums.
Fresh water from the water supply area will be received into a freshwater pond and distributed to the potable water tank, firefighting water tank, wash solution tank (start-up only), mine services, mining vehicle services, and vehicle washing facilities. All drainage and rainwater are collected by a sump. Excess water is sent to leaching solution tank #1 located in the reverse osmosis area of the water treatment plant.
Off Gas Scrubbing
The process plant will use scrubbers to treat off-gases from the impurities and REE precipitation area, redissolving stage, reagent preparation tanks, neutralization reactor, water recovery system clarifier, water recovery system filter press feed tank, and water recovery system recovered solution tank. Clean gas from the scrubber is released to the atmosphere, and the acid solution is pumped back to the leaching solution tank.
Systems and Utilities
Compressed air is required to meet plant, process, and instrumentation air requirements. It is generated as required to ensure a constant air supply. The process plant main air destinations are ion exchange, impurities, product handling, and water recovery system areas. The main items of equipment requiring air supply are the filter presses, polishing filters, and product tube press filters. Compressed air for instrumentation will be fed to air dryers and filters and then stored in dedicated instrument air receivers.
A tank truck will be used to feed the potable water tank. From here, potable water will be pumped to the process plant safety showers and other areas where it is required for human use and consumption, such as the dining room, offices, and restrooms. In areas where the eyes and/or bodies of people may be exposed to hazardous or corrosive materials, emergency showers with eyewashes will be provided.
Fresh water is pumped to various plant areas to feed the firefighting system water tank. The location and configuration of the fire detection and protection elements for each area are to be defined.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Processed wet mineral feed rate | 1,400 t/h (total, four lines at 350 t/h each) | Design |
| Dry mineral feed rate | 1,232 t/h | Mass balance |
| Fresh mineral moisture | 12% | Mass balance |
| REE grade | 1,454 ppm | Mass balance input |
| REO grade | 1,722 ppm | Mass balance input |
| Average REE plant recovery (mean, with Ce) | 26.5% total recovery | Testwork and mass balance |
| Overall plant recovery | 96.1% | Testwork and mass balance |
| Desorption efficiency (mean, without Ce) | 37.7% | Testwork |
| Desorption efficiency (mean, with Ce) | 26.5% | Testwork |
| Wet MREC production | 13,284 t/year | Mass balance |
| MREC carbonate grade | >95% (98.2%) | Vendor/testwork |
| Purity (rare earth oxide equivalent) | >95% (97.7%) | Vendor/testwork |
| Fresh water consumption | 220.7 m³/h | Mass balance |
| Total initial project CAPEX | US$680.5 million | Estimate |
| Life-of-mine operating costs | US$2,156.1 million (US$13.03/t ore) | Estimate |
| Reclamation and closure costs | US$78 million (2025) | Estimate |
| Fresh water supply | ~100 L/s from Paranã River, 7.5 km away | Design |
| Transmission line | 100 km overhead, conceptual engineering phase | Design |
Project website: https://www.aclara-re.com/carina-project
Technical qualifications
The report states that the REE recovery model derived from the initial drilling dataset satisfies the level of detail required for a pre-feasibility study. The ion-exchange desorption protocol employed has been successfully implemented in previous REE test programs targeting ion-adsorbed clay deposits.
The efficiencies of the solid/liquid separation and washing systems reported by vendors are being verified through tests with specialized companies. The parameters used in mass balance calculations were obtained from laboratory tests conducted in accordance with the mining plan.
Capital expenditures were estimated by combining unit rates for equipment, materials, labour, and subcontracts with unit quantities from various engineering deliverables. Unit costs were based on a combination of vendor budget quotes, reference costs from similar projects, factored costs, and allowances.
Environmental licensing is pending for some items. SEMAD approval for land-use changes and vegetation suppression is pending, based on technical studies like the Forest Inventory and the Vegetation Suppression Project. Environmental studies for the transmission line corridor are underway, with field surveys, stakeholder engagement, and impact assessments to be conducted during the Feasibility Study phase.
Source: NI 43-101 Technical Report – Carina Project, Goiás, Brazil, Hatch, 2025.
