Overview
Nestled in the mineral-rich state of Minas Gerais, Brazil, the Minas-Rio iron ore operation stands as a flagship project for global mining giant Anglo American plc. This world-class facility represents one of the largest integrated iron ore mining and processing projects developed in the 21st century. Commissioned in 2014, the Minas-Rio complex was designed with a nominal capacity to process 48 million tonnes of ore annually, producing a premium, high-grade iron concentrate essential for global steel production. The project’s significance extends far beyond its impressive scale; it is a marvel of modern engineering, integrating a sophisticated mineral processing plant with a record-setting 529-kilometer slurry pipeline that transports the final product to the Port of Açu on Brazil’s Atlantic coast. This pipeline is the longest of its kind for iron ore concentrate in the world, a critical piece of infrastructure that defines the project’s logistics and economic viability. Operating in a challenging topography, the facility transforms itabirite ore—a lower-grade iron-bearing rock—into high-quality Direct Reduction Pellet Feed (DRPF) and Blast Furnace Pellet Feed (BFPF) for international markets. The ongoing operation, backed by a comprehensive NI 43-101 Technical Report, underscores Anglo American’s commitment to long-term, sustainable resource development in Brazil, leveraging cutting-edge technology in crushing, grinding, and flotation to maximize recovery and product quality while implementing significant projects to enhance yield and environmental stewardship.
Key Process Stages
The Minas-Rio beneficiation plant employs a complex and highly automated circuit designed to upgrade itabirite ore into a saleable iron concentrate. The process is a sequential journey of size reduction, liberation, and separation, optimized for efficiency and recovery. Here is a detailed breakdown of the key stages in this advanced mineral processing flowsheet.
- Stage 1: Primary & Secondary Crushing: Run-of-mine ore is delivered by haul trucks to one of two dump pockets, each fitted with an 800 mm grizzly. An apron feeder directs the material to a primary jaw crusher at a design rate of 8,440 tonnes per hour, reducing the ore to approximately 150 mm. The product is then screened, with oversize material undergoing secondary crushing to achieve a target size of about 25 mm before being conveyed to a crushed ore stockpile.
- Stage 2: High-Pressure Grinding Rolls (HPGR) & Primary Grinding: The crushed ore is further comminuted by multiple 4.8 MW High-Pressure Grinding Rolls (HPGRs), a highly energy-efficient technology that reduces the ore to about 1 mm. The HPGR product is fed into the primary grinding circuit, which consists of two parallel ball mills. Each massive mill is 7.9 meters in diameter and 12.2 meters long, powered by a 15 MW motor, and operates in closed circuit with banks of hydrocyclones. This stage grinds the ore to a target P80 of 120 micrometers, liberating the iron minerals from the waste gangue.
- Stage 3: Two-Stage Desliming: The ground slurry reports to a two-stage desliming cyclone plant. The primary stage uses 8 clusters of 11 cyclones, with the overflow feeding a secondary stage of 8 clusters of 60 smaller (100 mm) cyclones. This process removes fine, low-value silicate slimes (ultra-fine particles) that can interfere with downstream separation. The combined underflow, containing the coarser valuable material, advances to flotation, while the slime-rich overflow is sent to the tailings thickener.
- Stage 4: Reverse Cationic Flotation: The deslimed feed enters a twin-stream flotation circuit, the heart of the chemical separation process. The slurry is conditioned in large 180 m³ tanks where reagents are added: starch acts as a depressant for iron oxides, and amine acts as a collector for the unwanted silica. The circuit is configured with rougher, cleaner, and scavenger banks of 160 m³ tank cells. The amine-coated silica particles attach to air bubbles and are skimmed off as froth (tailings), while the iron-rich pulp sinks and becomes the concentrate. This “reverse flotation” method is highly effective for producing a super-high-grade iron product.
- Stage 5: Concentrate Regrinding & Thickening: The final flotation concentrate is classified in cyclones ahead of a regrind circuit comprising 16 vertical mills (Vertimills). The cyclone overflow, ground to an ultra-fine P80 of 40 micrometers, reports to a large concentrate thickener. This fine grinding is crucial not for liberation, but to reduce particle size for safe hydraulic transport, minimizing the risk of settlement in the long-distance pipeline. The thickener underflow is pumped at 69.5–71.0% solids to homogenization tanks.
- Stage 6: Slurry Pipeline Transport: This is the defining stage of the Minas-Rio operation. A concentrated slurry is pumped into a 529 km buried pipeline—the world’s longest for iron ore. The system uses positive displacement piston diaphragm pumps at two stations to maintain a flow velocity of ~1.7 m/s. The slurry is conditioned to a pH >11 to prevent corrosion and settlement. The pipeline itself contains approximately 80 hours of production volume, acting as a massive buffer storage system as it traverses varied topography to the coast.
- Stage 7: Filtration & Ship Loading: At the Port of Açu, the slurry is dewatered in a dedicated filtration plant. It is first thickened to about 76% solids, then filtered using 14 large ceramic filters, each with a 144 m² filtration area, to achieve a final moisture content of approximately 9%. This is critical to meet the Transportable Moisture Limit (TML) for safe ocean shipping. The filter cake is stockpiled and later loaded onto vessels for export to global customers.
Critical Data
The operational excellence of the Minas-Rio circuit is quantified by its key performance indicators. The table below summarizes the critical technical and production data extracted from the NI 43-101 Technical Report, highlighting the scale and efficiency of this world-class operation.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Nominal Plant Capacity | 48.0 | Mt/a | Original design capacity |
| Average Plant Feed Rate | 5,995 | t/h | Recent operating average (2020-2025) |
| Average Concentrate Production | 2,887 | t/h (dry) | Recent operating average |
| Primary Ball Mill Power | 15.0 | MW (each) | Two mills, each 7.9m x 12.2m |
| HPGR Unit Power | 4.8 | MW (each) | Multiple units in operation |
| Target Primary Grind Size (P80) | 120 | µm | Ball mill circuit product |
| Target Regrind Size (P80) | 40 | µm | Vertimill circuit product for pipeline |
| Pipeline Length | 529 | km | Longest iron ore concentrate pipeline globally |
| Pipeline Flow Velocity | ~1.7 | m/s | To prevent solids settlement |
| Specific Energy Consumption | 17-19 | kWh/t (dry concentrate) | Total for beneficiation and filtration |
| Plant Availability (“Up Time”) | 85% | – | Beneficiation plant average |
| Concentrate Solids to Pipeline | 69.5 – 71.0 | % | Thickener underflow density |
Additional Interesting Data and Summary
Beyond the core processing stages, the Minas-Rio operation is characterized by continuous innovation and a strong focus on sustainability and risk management. Since 2022, several key metallurgical enhancement projects have been implemented. The magnetic separation plant, commissioned in November 2022, processes a feed stream at 737 t/h and contributes a 38% yield to the final concentrate, improving overall recovery. The Vertimill regrind project has been crucial in refining the concentrate size for safer pipeline transport. Looking forward, a major tailings filtration project is under construction, with commissioning slated for Q1 2026. This initiative is central to the site’s water management strategy, aiming to increase water recycling, reduce the wet tailings footprint, and enhance dam safety—a critical aspect of modern ESG (Environmental, Social, and Governance) compliance in mining.
The operation’s water management is a model of efficiency, with approximately 85-90% of process water demand met through internal recycling from the tailings storage facility (TSF) thickener overflow and filtrate recovery. Freshwater is sourced from the Peixe River system, but the closed-loop design minimizes external abstraction. Energy consumption, while significant due to the energy-intensive grinding and pumping processes, is managed through a reliable supply from the regional CEMIG grid, with specific consumption averaging 17-19 kWh per tonne of dry concentrate produced.
The 529-km pipeline is not just a transport solution but an engineering asset requiring meticulous care. Its integrity is maintained through a rigorous monitoring regime, including a “smart pig” inspection every five years to measure wall thickness and bi-annual “pigging” to clear sediment. Following an incident in 2018, the monitoring system was significantly upgraded with advanced leak detection and pump monitoring technologies. At the port, the filtration plant ensures the product meets strict shipping moisture specifications, with the TML monitored quarterly. Interestingly, the filtration plant makes the port site “water positive,” as it extracts all transported process water, which must then be treated and managed.
In summary, the Minas-Rio operation is a testament to large-scale, integrated mineral processing. It successfully combines brute-force comminution with sophisticated chemical separation and groundbreaking logistics to deliver a high-quality product from a challenging ore body. The project’s ongoing investments in magnetic separation, fine grinding, and tailings filtration demonstrate Anglo American’s commitment to optimizing recovery, reducing environmental impact, and ensuring the long-term, sustainable operation of this pivotal asset in the global iron ore supply chain.
Source: NI 43-101 Technical Report | Feasibility Study | Project: Rio Property | Date: November 2025
Further Reading
- Major Mines & Projects | Minas-Rio Mine
- Minas-Rio Iron Ore Project, Rio de Janeiro, Brazil
- Minas-Rio: World’s longest iron concentrate pipeline
