Optimizing Phosphate Recovery: Itafos Arraias Flotation Process

Source: Itafos Inc (2026)
Website: https://itafos.com/businesses/itafos-arraias/

Critical Data

Overview

Itafos Inc. operates the Arraias Phosphate Operations in Tocantins, Brazil, a mineral processing facility designed to treat breccia ore from the Arraias deposit. The primary product is phosphate concentrate, which is further processed for fertilizer manufacture, with low-grade tailings potentially sold as agricultural product or used as mine backfill. The project’s current Preliminary Economic Assessment (effective January 30, 2026) outlines modifications to the existing beneficiation plant to process fresh breccia at a rate of 40 tonnes per hour (297,840 tonnes per year). The process design, based on extensive metallurgical testing by Eriez, integrates primary crushing with an MMD sizer, a cage mill impact crusher, hydrocyclone classification, and a multistage column flotation circuit. Key reagents include Custafloat 167 (collector), sodium silicate, starch (depressant), and NaOH for pH control. Flotation is performed in rougher, cleaner, scavenger, and scavenger-cleaner columns to achieve a concentrate grade of 27.9% P2O5 with an overall phosphate recovery of 78.1%. This modified circuit significantly enhances the value of the Arraias resource, supporting sustainable fertilizer production while minimizing freshwater consumption through advanced dewatering and water recycling systems.

Key Process Stages

• Stage 1: Primary Crushing and Stockpile – Run-of-mine breccia is dumped into a feed bin and fed via apron feeder to a single-deck vibrating grizzly with 150 mm openings. Oversize material is crushed in an MMD-500 roll crusher to -150 mm. Combined undersize and crushed rock is conveyed to a stockpile with a live capacity of approximately 50,700 tonnes, equipped with a stacker reclaimer system.
• Stage 2: Mill Grinding and Classification – Reclaimed feed is screened on a new 1.2 m x 2.4 m single-deck inclined wet screen (4-mesh). Oversize (+4 mesh x 50 mm) is crushed in a Steadman Cage Mill to 100% passing 5 mesh. The combined stream is classified by a hydrocyclone with a cut point of 106 µm. The coarse underflow reports to an existing auxiliary ball mill (2.7 m diameter x 5.7 m long, 400 kW drive) where it is milled to 90% passing 106 µm at 50% solids.
• Stage 3: Flotation Conditioning and Rougher Flotation – The conditioned slurry (pH ~9.5 using NaOH, with Custafloat 167 collector, sodium silicate, and starch depressant) is fed to a rougher flotation column (5.0 m diameter x 14.0 m high). The rougher concentrate flows to the cleaner stage; rougher tailings proceed to scavenger cells.
• Stage 4: Cleaner, Scavenger, and Scavenger-Cleaner Flotation – The rougher concentrate enters a 5.0 m diameter x 14.0 m high cleaner column. Its concentrate reports to the thickener; tailings are sent to two 4.0 m diameter x 14.0 m high scavenger columns. Scavenger concentrate feeds a 5.0 m diameter scavenger-cleaner column, whose underflow joins the tailings stream and concentrate goes to the thickener.
• Stage 5: Concentrate and Tailings Dewatering – Concentrate is thickened in a 20 m thickener and dewatered to 16.4% moisture using a 266 m² plate and frame filter. Tailings are similarly dewatered in a 266 m² filter. Recovered water is recycled to the process water tank. Concentrate is stockpiled via radial stacker; tailings (4,100 tonne capacity stockpile) are sold as low-grade agricultural product or used as backfill.

Additional Interesting Data and Summary

The Arraias phosphate beneficiation plant is designed to produce 163,812 tonnes of concentrate per year at 27.9% P2O5, with 134,028 tonnes of tailings. Annual flotation reagent consumption includes 566 tonnes of Custafloat 167, 298 tonnes of sodium silicate, and 149 tonnes of starch. The process achieves significant water sustainability: recovered water from thickener overflow and filter filtrate is returned to the raw water pond, limiting freshwater makeup to only 3.3 m³/h (equivalent to 0.0825 m³ per tonne of feed). Tailings moisture is reduced to 16.4% via plate and frame filters, enabling safe stockpiling or beneficial reuse as low-grade agricultural product or mine backfill. The power distribution system utilizes 33 kV, 11 kV, and 380 V for motors, with a total estimated connected load of 7,210 kW, subject to refinement in subsequent engineering phases. Environmentally, the modifications reduce water consumption and eliminate wet tailings disposal by leveraging dry stacking. Economically, the project supports Itafos’ phosphate fertilizer supply chain in Brazil, with the breccia feed significantly extending the life of the Arraias operation. The flowsheet design incorporates robust equipment such as the MMD crusher, Steadman cage mill, and Eriez column flotation cells, all selected to handle the abrasiveness and variability of breccia ore. Future engineering phases will optimize power infrastructure, confirm battery limits, and evaluate potential improvements in recovery and grade. Overall, the Arraias phosphate processing facility exemplifies modern, efficient beneficiation with a focus on resource conservation and operational flexibility.

Key Processes: Flotation, Gravity Separation, SAG Mill, Ball Mill, Crushing

Target Commodities: N/A