Lofdal Heavy Rare Earths Recovery: Crushing, Flotation, Refinery

Source: Namibia Critical Metals Inc (2026)
Website: https://www.namibiacriticalmetals.com/projects/lofdal-heavy-rare-earths-project

Critical Data

Overview

Namibia Critical Metals Inc. is advancing the Lofdal Heavy Rare Earths Project 2B-4 in Namibia, a strategic source of heavy rare earth elements (HREOs) including dysprosium and yttrium. The Preliminary Feasibility Study (PFS), dated April 2024, outlines a comprehensive recovery plant designed to process 3.01 million tonnes per annum (Mtpa) of run-of-mine ore through crushing and sorting, with 1.482 Mtpa fed into the concentrator and refinery. Located approximately 2.5 km west-northwest of Area 4, the project benefits from established infrastructure and nearby uranium producers, enabling a unique by-product recovery stream. The significance of Lofdal lies in its high HREO-to-TREO ratio, with indicated resources of 0.09% HREO and inferred resources of 0.07% HREO, positioning it as a critical supplier for clean energy and defense technologies. The recovery process begins with dual high-grade and low-grade crushing circuits, incorporating X-ray transmission (XRT) ore sorting to upgrade feed. The concentrator uses ball milling to a P80 of 38 µm, followed by a flotation circuit consisting of roughers, cleaners, and re-cleaners to produce a rare earth concentrate. The refinery section employs a sulphation roast at 600°C, water leach, impurity precipitation, and uranium ion exchange before final REE carbonate precipitation. Water is recycled extensively, and tailings are thickened and sent to a dedicated storage facility. This integrated flowsheet achieves overall REO recovery of 59.4% and HREO recovery of 62.2%, demonstrating robust metallurgical performance for a complex heavy rare earth deposit.

Key Process Stages

• Stage 1: Crushing and XRT Ore Sorting – High-grade ore undergoes primary jaw crushing (P80 79 mm), secondary cone crushing in closed circuit (P80 24 mm), and tertiary VSI crushing (P80 17 mm). Low-grade ore uses a separate circuit with similar stages plus XRT sorting at coarse (50–25 mm) and fine (25–10 mm) sizes, rejecting fines (<10 mm) to waste. Sorter product reports to the crushed ore stockpile.
• Stage 2: Ball Milling – Crushed ore (F80 12 mm) feeds a single-stage ball mill in closed circuit with flat-bottom cyclones. The mill operates wet with 250% recirculation load, achieving a final product P80 of 38 µm. The Bond ball mill work index is 16.7 kWh/t, and the circuit availability is 90%.
• Stage 3: Flotation Circuit – The milled slurry is conditioned at 35% solids with high-intensity mixing (1,800 rpm). Rougher flotation uses five 70 m³ tank cells, followed by three 20 m³ cleaner cells and two 5 m³ re-cleaner cells. Collectors (Florrea 3900Z at 1,235 g/t and Florrea 3000 at 260 g/t) and depressant (sodium silicate at 213 g/t) are added. Overall mass pull is 3.78% with TREO recovery of 52–68%.
• Stage 4: Refinery – Sulphation Roast and Water Leach – Flotation concentrate cake is mixed with concentrated H₂SO₄ (1,500 kg/t concentrate) in a pug mill and fed to a rotary kiln at 600°C for 1.5 hours. The sulphated product is cooled and leached in four tanks at 50°C for one hour at 16–18.4% solids, selectively dissolving rare earth sulphates.
• Stage 5: Purification and REE Precipitation – Leach liquor undergoes primary impurity removal with MgCO₃ (707 kg/t conc.) followed by secondary neutralization. Uranium is recovered via ion exchange (99.9% recovery) and precipitated as ammonium di-uranate (ADU) using NH₄OH at pH 7.3. REEs are precipitated with Na₂CO₃ at pH 6.75, thickened, filtered, dried, and packaged as mixed rare earth carbonate.

Additional Interesting Data and Summary

Beyond the core flowsheet, the Lofdal project incorporates several critical design features that enhance sustainability and economic viability. The concentrator section includes a tailings thickener producing underflow at 50% solids, with overflow water recycled to the process water dam. The refinery employs a closed-loop sulphuric acid recovery system via kiln off-gas scrubbing, minimizing reagent consumption. Uranium by-product recovery is a key economic driver: ion exchange captures 99.9% of uranium from the leach liquor, and the resulting ADU slurry is shipped to a local Namibian uranium producer, generating additional revenue while reducing waste. The process water balance is optimized through thickener overflows and filtrate returns, with separate front-end and back-end water storage facilities to manage quality. Environmental controls include neutralization of tailings using milk of lime, and all spillages are directed back to process or neutralization tanks. Reagent handling is designed for safety: sulphuric acid storage includes desiccant dryers and spill containment, while flocculant and collectors are prepared in dedicated mixing areas. The plant’s design criteria are based on extensive testwork by Mintek, SGS Lakefield, Geolabs SA, and other laboratories, confirming the suitability of the flowsheet for Lofdal’s mineralogy. The PFS assumes a 90% availability for the ball mill and 68% for crushing circuits, with a 250% recirculation load in milling. Future optimization work may focus on reducing acid consumption and improving flotation selectivity, particularly for low-grade ores. The project’s location in Namibia provides access to established mining infrastructure, skilled labor, and existing uranium processing facilities, reducing capital and operational risks. With a total indicated resource of 4.4 kt TREO and inferred resources of 6.6 kt TREO at a cut-off of 0.1% TREO, the Lofdal project represents a significant opportunity for heavy rare earth supply chain diversification. The recovery methods outlined in the PFS demonstrate a technically robust and environmentally conscious approach to processing a complex HREO deposit, positioning Namibia Critical Metals to become a key Western-world supplier of dysprosium and other strategic rare earths.

Key Processes: Flotation, Ball Mill, Crushing

Target Commodities: Uranium