The Farim Phosphate Project in Guinea-Bissau uses a physical separation process flowsheet with scrubbing, desliming, classification, and dewatering to produce a filtered concentrate for drying and ship loadout at a nearby Mineral Terminal.
Article Body
The Farim Phosphate Project process design covers the beneficiation plant and the relevant equipment at the Mineral Terminal facility. The process is designed to accommodate material from both South and North pits, with the design criteria based on testwork managed by KEMWorks and using Ausenco's reference project database and in-house modelling programs.
The plant receives run-of-mine (ROM) ore delivered from the open pit by 36 t dump trucks. Ore is deposited on a ROM stockpile with an operating storage capacity of five weeks, or 175,000 t. Oversize material is reclaimed by a front-end loader. For metallurgical accounting and plant control, a weightometer and moisture analyzer are installed on the scrubber feed conveyor.
The process design has an annual throughput of 1,750,000 dry t/a for each pit. Scrubbing and classification availability is 91%, and mass yield to concentrate is 77.5% for South Pit and 74.3% for North Pit. Annual concentrate production is 1,356,250 t/a for South Pit and 1,300,250 t/a for North Pit. Over the mine life, average concentrate production is 1.32 Mt per annum.
The plant discharges waste streams including tailings and oversized rejects. During Years 1 to 7, the plant produces between 280,000 t/a of tailings and 113,750 t/a of oversized rejects; from Years 8 to 25, it produces 379,750 t/a of tailings and 70,000 t/a of oversized waste. Ore is fed at a moisture content of 23% to 25%.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Annual Throughput (South Pit) | 1,750,000 | dry t/a | Design |
| Annual Throughput (North Pit) | 1,750,000 | dry t/a | Design |
| Concentrate Produced (South Pit) | 1,356,250 | t/a | Design |
| Concentrate Produced (North Pit) | 1,300,250 | t/a | Design |
| Operating Availability | 7,972 | h/a | Design |
| Mass Yield (South Pit) | 77.5 | % w/w | Design |
| Mass Yield (North Pit) | 74.3 | % w/w | Design |
| ROM Stockpile Capacity | 175,000 | t | 5 weeks operating capacity |
| Scrubber Feed Moisture | 23 to 25 | % | Feed condition |
| Process Water Demand (Years 1–7) | 2,202 | m³/h | Design |
| Process Water Demand (Years 8–25) | 2,221 | m³/h | Design |
| Tailings Production (Years 1–7) | 280,000 | t/a | Design |
| Tailings Production (Years 8–25) | 379,750 | t/a | Design |
| Oversized Rejects (Years 1–7) | 113,750 | t/a | Design |
| Oversized Waste (Years 8–25) | 70,000 | t/a | Design |
| Shiploading Capacity | 1,200 | t/h | Maximum |
| Concentrate Shipments | 28 | no. per annum | Average |
Project website: https://itafos.com/news/2023/itafos-completes-updated-feasibility-study-for-the-farim-phosphate-project/
Overview
The Farim Phosphate Project process design covers the beneficiation plant and Mineral Terminal equipment. The flowsheet uses physical separation processes rather than chemical flotation. Feed is classified by size, and impurities are rejected through scrubbing, desliming, and classification stages. The resulting bulk concentrate is filtered, then trucked to the Mineral Terminal for drying and shiploading. Power is provided by a hybrid solar and diesel generation system.
The plant feed is sourced from two open pits, the South Pit and the North Pit. The South Pit is mined during the first seven years, and the North Pit from Year 8 onward. The process design criteria for both pits are identical in throughput, but the feed characteristics result in different concentrate yields and grades.
Key Process Stages
ROM ore is reclaimed from the stockpile and fed to horizontal drum scrubbers. The scrubbers are 3.6 m in diameter by 10 m in length. The scrubbed slurry is screened, with oversize material reporting to a rejects stockpile. The screen undersize is then deslimed and classified.
Desliming uses hydrocyclones. The classification cyclone cluster uses canister-style cyclones. Underflow at 45% w/w reports to a fine concentrate pump tank for transfer to the fine concentrate thickener. Oversize material from the vibrating screen reports to the rejects stockpile via the same conveyor as the +5,000 µm rejects.
The fine concentrate stream is classified using hydrosizers. The hydrosizers use an upflow current to drive fine particles to the overflow and allow coarse particles to settle and discharge as underflow. The resulting fine concentrate is nominally 106 x 20 µm. The -20 µm cyclone overflow is sent to the tailings thickener.
Dewatering includes both fine and coarse concentrate filtration. Ancillary equipment includes filter feed tanks, pumps, and compressors. Concentrate is filtered to a cake, with the filtrate returned to the process water circuit. The filter presses use filter cloth rated at 5,000 cycles per unit and pressing diaphragms rated at 80,000 cycles per unit.
The filtered concentrate is trucked to the Mineral Terminal. At the terminal, a stockpile and storage shed manage the concentrate. When a ship is berthed, front-end loaders transfer dried concentrate from the storage shed into five concentrate hoppers. The shiploading system is a traversing radial telescoping shiploader with a retractable conveyor discharge spout and a maximum capacity of 1,200 t/h. A sampler collects material prior to shiploading for quality accounting purposes.
The process water system is a mostly closed circulating loop to minimize makeup water requirements. Tailings thickener overflow, tailings reclaim return water, fine concentrate thickener overflow, and filtrate are recycled. Ninety-three percent (Years 1 to 7) to 90% (Years 8 to 25) of process water demand is sourced from thickener and filtrate processes. The balance is made up from the tailings storage facility decant, the environmental control dam, and sediment control dam. Excess process water is sent to a reverse osmosis water treatment plant.
An event pond captures all untreated process water and slurry spillage, returning it to the treatment plant by two pumps. Instrument and plant air are distributed at a design pressure of 750 kPag. A centralized dust collector is installed at all material handling transfer points to prevent fine concentrate dust from entering the working environment.
Additional Interesting Data and Summary
The plant uses consumables including flocculant at 35 g/t, filter cloth, pressing diaphragms, and filter plates. High-pressure diesel is consumed by the dryer circuit. Raw water consumption is 54.6 m³/h (South Pit) and 69.9 m³/h (North Pit). The plant also consumes drum scrubber liners, pressing diaphragms, and filter plates on a regular basis.
The annual average concentrate production of 1.32 Mt requires 28 shipments per year. The shiploading maximum capacity of 1,200 t/h dictates port loading time. The process plant design throughput of 1.75 Mt/a is unchanged across the mine life, with the feed source switching from the South Pit to the North Pit.
The process design accounts for the different ore characteristics of the two pits. Concentrate grades are 33.9% P₂O₅ for the South Pit and 32.3% P₂O₅ for the North Pit. These concentrations show the design criteria for the beneficiation plant.
Key Processes
- Feed receipt and reclaim from a 175,000 t ROM stockpile delivered by 36 t dump trucks
- Horizontal drum scrubbing with 3.6 m diameter by 10 m length scrubbers
- Vibrating screen size separation with +5,000 µm rejects reporting to a stockpile
- Hydrocyclone desliming and classification with canister-style cyclones
- Hydrosizer classification using upflow currents to separate fine and coarse fractions
- Fine concentrate thickening and filtration with filter presses
- Process water recovery through a closed-loop system with makeup from tailings storage facility decant
- Concentrate transport by truck to the Mineral Terminal
- Drying and stockpiling at the terminal
- Shiploading using a traversing radial telescoping shiploader with 1,200 t/h capacity
- Dust collection at all transfer points to prevent fine concentrate dust release
Source: Farim Phosphate Project , 2023 Technical Report, June 23, 2023.
—
Editorial note: The source text contains a possible typographical error in the process water recovery figures. One portion states "93% (Years 1 to 7) to 90% (Years 8 to 25)" while another portion states "93% (Years 1 to 7) to 90% (Years 18 to 25)". The first is more consistent with the Years 8 to 25 period used elsewhere.
Project website: Farim Phosphate Project, 2023 Technical Report
