Optimising Diamond Recovery with High-Quality Milled Ferrosilicon
DMS Powders
How to Minimise Ferrosilicon Loss in Dense Media Circuits
In dense media separation (DMS), the stability and efficiency of the separating medium are critical to achieving accurate density-based classification of minerals. Ferrosilicon (FeSi), a magnetic alloy of iron and silicon, remains the most common medium in DMS due to its ideal properties: high density, magnetic recoverability, and chemical stability. However, ferrosilicon is a recurring operational cost, and minimising its loss is essential for maintaining the economics of the process. Excessive FeSi loss increases consumables expenditure, complicates medium stability, and can lead to inefficiencies in separation performance.
This article presents scientifically supported strategies to reduce ferrosilicon loss in dense media circuits across multiple points of the process, from feed preparation to magnetic recovery systems.
Technology:
1. Understanding the Causes of Ferrosilicon Loss
Minimising ferrosilicon loss starts with understanding how and where losses occur. Loss mechanisms can be broadly categorised into three areas:
Adherence to Sink and Float Particles:
Ferrosilicon particles can physically adhere to the surfaces of separated materials.
Slimes and Fines Interference:
Clay, ultra-fine particles, and suspended solids can destabilise the medium, resulting in ferrosilicon loss.
Inefficient Magnetic Recovery:
Magnetic separators may be improperly configured, worn, or overloaded, allowing ferrosilicon to pass through with waste streams.
Identifying these sources allows for targeted operational improvements and process monitoring.
2. Use of the Correct Ferrosilicon Grade
Choosing the right grade of ferrosilicon, both in terms of particle size distribution and alloy composition, directly influences loss rates.
- Atomised vs. Milled Ferrosilicon: Atomised ferrosilicon is spherical, smooth, and less prone to degradation, making it suitable for most mineral separation applications. Milled ferrosilicon has angular particles that are more prone to breakdown and loss but may offer better stability in some circuits.
- Size Range Selection: Using a narrow particle size distribution centred around 65–250 microns reduces the risk of fine particles being lost through drainage or non-magnetic flows.
Finer ferrosilicon grades (<45 microns) are highly susceptible to loss and should be used with caution unless necessary for specific process demands.
3. Improving Magnetic Recovery Efficiency
The magnetic recovery circuit is the most critical control point for ferrosilicon loss. High-gradient magnetic separators (HGMS), low-intensity magnetic separators (LIMS), or wet drum separators are commonly used.
Key variables to monitor:
- Drum Speed: The rotational speed of magnetic drums affects particle pickup. Speeds that are too high reduce contact time; speeds that are too low limit throughput.
- Magnetic Field Strength: The field intensity should be appropriate for the grade of ferrosilicon used. Atomised FeSi requires stronger fields compared to milled FeSi.
- Magnet Positioning: Internal magnet alignment must be optimised to ensure maximum capture of the ferrosilicon across the full width of the drum.
- Maintenance: Magnetite scaling, worn magnets, or misaligned drums can significantly reduce magnetic recovery.
Routine calibration and inspection of these components help ensure the maximum recovery of ferrosilicon.
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4. Medium Density and Viscosity Control
Maintaining an optimal medium density and viscosity is essential for limiting loss. A medium that is too dense or too viscous can promote increased adherence of ferrosilicon to the sink product, leading to greater losses.
Operational steps to mitigate this:
- Automated Density Control: Online densitometers help keep the medium within a narrow density range, typically between 2.65 and 2.75 g/cm³, depending on the mineral being treated.
- Medium Dilution and Recirculation: Periodic dilution with water and recirculation of the medium helps reduce viscosity and suspend ferrosilicon more effectively.
- Flocculant Management: Overuse of flocculants or the wrong type can thicken the medium, leading to ferrosilicon trapping and sedimentation losses.
A clean and consistent medium delivers better separation precision and reduces medium loss downstream.
5. Managing Slimes and Fines
Fines present a significant challenge to ferrosilicon stability. They increase the viscosity of the slurry, coat ferrosilicon particles, and inhibit magnetic recovery.
Recommendations:
- Pre-Screening of Feed: Installing high-frequency vibrating screens or hydrocyclones to remove slimes before the material enters the DMS circuit can dramatically reduce losses.
- Upstream Classification: Ensuring that only correctly sized feed enters the separation unit reduces fine particle loading.
- Water Quality: Recycled water systems should be monitored and treated to prevent the build-up of suspended solids.
Effective fines management reduces wear on equipment, maintains sharp cut points, and lowers the rate of ferrosilicon attrition and entrainment
Frequently Asked Questions about Ferrosilicon
6. Preventing Mechanical Losses
Mechanical loss of ferrosilicon can occur through leaks, pipe flushing, or spillage.
Control measures include:
- Piping Design: Use of proper pipe diameters and smooth transitions minimises turbulence and dead zones where ferrosilicon can settle.
- Settling Sumps: Installing properly designed sumps and traps ensures any spilled ferrosilicon is recovered and returned to the system.
- Maintenance Protocols: Operators must be trained to manage hose flushing and valve operations to prevent excessive discharge of the medium during cleaning or shut-downs.
A well-maintained circuit with minimal manual intervention offers better control over ferrosilicon usage.
7. Enhancing Process Monitoring and Control
Data-driven process control helps reduce variability, detect ferrosilicon loss early, and maintain system performance.
Tools that support loss minimisation:
- Medium Density Meters: Inline density meters provide real-time feedback to dosing systems.
- Ferrosilicon Loss Monitors: Sensors can be installed in tailings lines to detect magnetic content, serving as early warnings for recovery issues.
- SCADA Integration: Linking field devices to a central control system allows for automated adjustments based on real-time data, improving consistency and reducing operator error.
Facilities with advanced process automation tend to report lower average ferrosilicon consumption per tonne treated.
8. Ferrosilicon Recycling and Replenishment Practices
Losses will always occur to some degree, but effective recycling and replenishment strategies mitigate their impact.
- Settling Ponds and Recovery Tanks: Tailings streams can pass through settling tanks where FeSi is recovered from underflow before waste discharge.
- Bleed-and-Feed Systems: This approach involves continuous replenishment of small amounts of fresh ferrosilicon while removing fines and degraded particles from the circuit. It keeps the medium in optimal condition without complete replacement.
- Screening of Recycled Medium: Removing degraded and non-magnetic particles ensures that recycled ferrosilicon retains its magnetic response and density.
Controlled recycling helps maintain the medium’s quality while reducing the volume of fresh ferrosilicon required.
9. Supplier and Quality Assurance Considerations
Sourcing high-quality ferrosilicon from a reputable manufacturer can reduce consumption rates.
What to look for in a supplier:
- Consistent particle sizing
- Verified density specifications (e.g., 6.7–7.1 g/cm³)
- Low content of tramp materials or residual oxidised metal
- Technical support for optimising usage in specific DMS applications
Engaging with a supplier, like DMS Powders, who understands your plant’s needs allows for better matching of product grade to operational parameters.
Ferrosilicon loss is a manageable operational cost that can be reduced with a combination of sound process engineering, regular equipment maintenance, fines management, and proper recovery systems. Operators who maintain tight control over particle size distribution, separation circuit parameters, and magnetic recovery efficiency tend to experience lower FeSi consumption per tonne processed.
While total elimination of ferrosilicon loss is not feasible, consistently implementing these proven practices will yield measurable reductions in material wastage and operating cost over time.
Why DMS Powders is the Trusted Global Supplier of Ferrosilicon
When reliability, consistency, and quality matter, DMS Powders stands out as the industry’s leading manufacturer and global distributor of ferrosilicon for dense media separation. With decades of experience serving mineral processing operations across the globe, we offer a complete range of atomised and milled ferrosilicon products that meet the demanding requirements of DMS applications, from coal and diamond separation to base metal pre-concentration.
Precision-Engineered Products
Our ferrosilicon grades are manufactured to strict specifications, ensuring optimal density, magnetic recovery, and minimal degradation. DMS Powders produces both atomised and milled ferrosilicon in several density classes and particle size distributions to suit various DMS circuit designs and separation objectives.
- Atomised Ferrosilicon: Spherical particles with excellent reusability, reduced degradation, and strong magnetic response - ideal for high-efficiency dense media circuits.
- Milled Ferrosilicon: Angular particles providing enhanced medium stability in specific applications, with tightly controlled size ranges to minimise loss and maximise recovery.
Global Distribution Network
From our manufacturing base in South Africa, we supply ferrosilicon to customers across Africa, Europe, Asia, the Americas, and Australia, ensuring consistent stock availability, fast turnaround times, and dependable logistics support. Whether you're a diamond processor in Botswana or a coal plant in Colombia, we have the reach and infrastructure to deliver exactly what you need.
Ongoing Technical Support
We don’t just sell ferrosilicon, we support our clients with technical advice, performance audits, and best-practice guidance to reduce consumption and optimise plant performance. Our team collaborates closely with mineral processors, plant operators, and metallurgical consultants to ensure every tonne of ferrosilicon performs as expected.
Quality Control You Can Trust
All batches undergo rigorous quality assurance testing, including:
- Chemical composition analysis
- Density testing
- Particle size distribution verification
- Magnetic susceptibility profiling
This attention to detail results in highly stable products that perform consistently over repeated DMS cycles, helping you maintain precise cut-points and reduce operational downtime.
Committed to Long-Term Value
Working with DMS Powders means building a partnership that values operational efficiency, cost control, and process performance. Our ferrosilicon products are designed to reduce your loss rate, lower your medium consumption per tonne, and contribute to better metallurgical outcomes.
Contact DMS Powders Today
Whether you are designing a new plant, upgrading an existing circuit, or simply looking for a more stable and cost-effective ferrosilicon supplier, DMS Powders is ready to support your operation. Get in touch with our team to discuss your specific requirements or request a product sample.
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