Ferrosilicon Quality Review for DMS Operations | DMS Powders
DMS Powders
Key Indicators Your DMS Operation Needs a Ferrosilicon Quality Review
Dense Medium Separation (DMS) relies on controlled conditions. The density of the medium, its viscosity and its stability all influence how effectively minerals are separated. Ferrosilicon is central to that process, but using FeSi alone does not guarantee consistent results. The grade, particle characteristics and condition of the circulating medium need to suit the plant and its operating requirements.
When recovery changes, ferrosilicon consumption rises or medium behaviour becomes difficult to control, plant teams need to identify what has changed. The cause could lie with feed conditions, contamination, equipment or operating parameters. It may also be time to review the ferrosilicon being used.
For plants using ferrosilicon in Dense Medium Separation operations, the following indicators can help identify when a closer quality and performance review is warranted.
Technology:
1. Medium Density Requires Frequent Correction
Medium density is a primary process variable in DMS. Operators control it by adjusting the concentration of ferrosilicon solids in water. Increasing the amount of FeSi increases medium density, while adding water reduces it.
A plant should not automatically blame its ferrosilicon when density begins fluctuating. Water balance, dilution, feed conditions and plant control can all affect readings. Persistent changes, however, warrant investigation.
Warning signs can include:
- More frequent FeSi or water adjustments
- Difficulty maintaining the target medium density
- Unexpected density variation between operating periods
- A separation cut point that has become less predictable
- Increasing operator intervention despite similar feed conditions
Ferrosilicon particle size, shape and grade influence the physical behaviour of the suspension. If density control has changed without an obvious plant explanation, compare the current product and circulating medium with the specification and historical operating data.
DMS Powders produces specialised FeSi for DMS applications, with different ferrosilicon grades available to suit different separation requirements.
2. Separation Performance Is Drifting
Dense Medium Separation works because materials with different densities respond differently in a medium of controlled density. Particles denser than the medium report to the sinks stream, while lower-density particles report to the floats stream.
When the conditions in the separating medium change, separation can become less precise.
Plant teams may notice:
- Increasing misplaced material
- Changes in concentrate quality
- Valuable mineral reporting to discard
- More unwanted material reporting with product
- Recovery figures moving away from established operating trends
These symptoms do not identify ferrosilicon quality as the cause on their own. Feed density, particle size, separator condition, pressure, throughput and contamination should also be checked.
Ferrosilicon should form part of that investigation because the particle size distribution and shape of FeSi affect medium viscosity and stability. Consistent FeSi characteristics help produce predictable medium behaviour when other operating variables are controlled.
3. Ferrosilicon Consumption Has Increased
Ferrosilicon is magnetically recoverable, allowing a large proportion of the medium to be recovered and returned to the circuit. Fresh FeSi consumption still represents a recurring operating cost, which makes unexplained increases worth investigating.
Several mechanisms can increase FeSi losses. Medium may adhere to sink and float products, fine particles may leave with process water, or magnetic recovery equipment may not recover FeSi as effectively as expected.
An increase in consumption could also result from:
- Poor drainage or rinsing
- Excessive fines
- Changes in FeSi particle size distribution
- Feed slimes entering the medium
- Leakage or handling losses
- Magnetic separator problems
- Changes in operating density
- Different feed characteristics
DMS Powders discusses these factors in more detail in its resource on minimising ferrosilicon loss in dense media circuits.
Review fresh FeSi addition against throughput, product losses, magnetic recovery and historic consumption. A rising kilograms-per-tonne figure can reveal a developing problem long before the total purchasing cost attracts attention.
4. Medium Viscosity Appears to Be Increasing
Viscosity describes the resistance of the medium to flow. In a DMS circuit, excessive viscosity can interfere with particle movement and reduce separation efficiency.
Several factors influence medium viscosity. DMS Powders identifies solids concentration, particle size distribution, particle shape and contamination as key variables.
Finer FeSi tends to increase viscosity. Irregular particle shapes associated with milled grades can also produce higher viscosity than the more rounded particles found in atomised grades under comparable conditions. Low-density contaminating solids can create another problem because a greater solids concentration may then be required to achieve the target medium density.
A viscosity problem should therefore be assessed from more than one angle.
Check the FeSi grade, circulating solids, contamination levels and operating density. A product may still meet its specification while changes elsewhere in the circuit cause the medium to behave differently.
Where the FeSi itself is being reviewed, particle size distribution and product type deserve particular attention.
DMS Powders manufactures both atomised and milled ferrosilicon for different DMS conditions.
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5. The Medium Is Settling Differently
A DMS medium needs sufficient stability to remain suitable for the separation process.
Ferrosilicon particles are denser than the water carrying them, so settling behaviour is an inherent part of the system. Particle size, particle shape, solids concentration and contamination affect how quickly that settling occurs.
A medium that settles too readily can contribute to density gradients and the accumulation of solids in parts of the circuit. Greater stability, however, is not always better. Factors that increase stability often increase viscosity as well.
This balance is one reason FeSi grade selection cannot be based only on obtaining a certain medium density.
Changes worth investigating include:
- Faster settling than historically observed
- Solids accumulating in pipelines or process equipment
- Changes in density differential
- A medium behaving differently under similar operating conditions
- Increased viscosity alongside greater stability
Compare these observations with the grade being used and the current particle size distribution of the circulating medium.
6. Particle Size Distribution Has Become Less Consistent
Particle size distribution is one of the key physical characteristics of ferrosilicon used in DMS.
Fine and coarse FeSi particles do not behave identically in suspension. Finer particles generally increase stability but can also increase viscosity and may be more susceptible to loss from the circuit. Coarser particles can help reduce viscosity but settle more readily.
The plant therefore needs a grade whose particle characteristics support the required operating conditions.
Variation in particle size distribution can change how the medium behaves even when operators continue using the same nominal grade.
Possible symptoms include changes in:
- Settling behaviour
- Medium viscosity
- Density control
- FeSi losses
- Separation efficiency
- Magnetic recovery
DMS Powders discusses the operational effects of ferrosilicon particle size distribution and why consistency is relevant to predictable DMS performance.
Where a circuit begins behaving differently, sampling both incoming FeSi and the circulating medium can provide valuable information.
7. Contamination in the Circulating Medium Is Increasing
Not every medium-quality problem starts with the ferrosilicon supplied to the plant.
Fine solids from the feed can enter the medium through incomplete washing, degradation of feed particles and normal circulation through the process. These contaminants are commonly less dense than ferrosilicon.
As contamination increases, the plant may require a higher concentration of total solids to achieve its target medium density. The increased solids concentration can raise viscosity and change stability.
Operators may initially interpret the resulting behaviour as poor FeSi performance.
This is where fresh-product testing and circulating-medium testing should be separated.
If the fresh ferrosilicon remains consistent with its required specification but the circulating medium shows a growing proportion of contaminants, plant conditions need attention.
Desliming performance, washing efficiency, feed degradation and circuit cleanliness should then form part of the review.
8. Magnetic Recovery Is No Longer Performing as Expected
The magnetic properties of ferrosilicon make media recovery possible. After separation, magnetic recovery equipment can recover FeSi from dilute medium streams so it can return to the circuit.
When recovery efficiency drops, fresh FeSi consumption may increase.
Before changing ferrosilicon grade, check the magnetic recovery system itself. Equipment condition, loading, operating settings and process flow can affect recovery.
The circulating medium should also be assessed.
Particle characteristics can influence losses, and very fine FeSi can be more difficult to retain within the circuit. DMS Powders also notes that passage through magnetic separators can leave residual magnetisation in the medium, which can increase both viscosity and stability. Demagnetisation can be used where required.
Atomised and milled FeSi can behave differently in this area, which makes the choice of grade relevant to the complete DMS circuit rather than only the separation stage.
9. Performance Changed After a New Ferrosilicon Delivery
If plant behaviour changes soon after a new FeSi delivery enters the circuit, reviewing the material is reasonable.
Timing alone is not proof of a product issue.
Feed characteristics may have changed during the same period. Throughput could be different, operating density may have moved or maintenance work may have altered circuit conditions.
Use plant records and representative sampling to establish whether the new material differs from previous deliveries.
A review could include:
- Confirming the supplied grade
- Checking particle size distribution
- Reviewing relevant product specifications
- Comparing fresh FeSi with previous deliveries
- Checking storage and handling conditions
- Comparing consumption before and after the change
- Reviewing medium density and stability trends
- Checking separation performance over the same period
The aim is to isolate the variable that changed rather than making a decision based solely on when the performance shift occurred.
10. Your Plant Has Changed but Your FeSi Grade Has Not
Plants do not remain static throughout their operating lives.
Ore characteristics change. Throughput targets increase. Cyclones are replaced. Process equipment is modified. Feed size can shift and the required separation density may change.
Ferrosilicon purchasing specifications, however, can remain unchanged for long periods.
That creates a valuable question for plant teams: does the FeSi grade still suit the circuit as it operates now?
DMS Powders identifies operating density as a major consideration in medium selection. Once the required operating density has been established, the balance between stability and viscosity helps determine the appropriate grade.
Feed characteristics and the separating vessel also need to be considered.
A grade that performed well under earlier plant conditions may need reassessment after substantial process changes.
11. Density Differential Has Moved Away From Normal Plant Behaviour
The difference between medium densities at different points in a separator can provide useful information about process conditions.
In bath-type separators, low or zero differentials are generally desirable. Dynamic separators such as cyclones operate differently, and some positive differential can assist the separation process.
The relevant warning sign is therefore not the existence of a differential itself. It is an unexplained movement away from the operating behaviour expected for that particular circuit.
Changes in FeSi grade, medium stability, contamination and operating conditions can affect the differential.
Review it alongside plant pressure, feed rate, density, viscosity and separation results. It can form part of a broader diagnosis of whether the circulating medium still suits the process.
For detailed information about these relationships, plant teams can refer to DMS Powders’ technical support information covering medium density, viscosity, stability and FeSi grade selection.
What Should a Ferrosilicon Quality Review Check?
A good FeSi quality review should connect laboratory information with what operators are seeing in the plant.
Testing incoming ferrosilicon without considering circuit conditions provides only part of the picture. Testing the circulating medium without checking the fresh material can create the opposite problem.
Start by comparing the supplied FeSi with its agreed specification. Then compare its physical characteristics with previous material that performed well in the same circuit.
The review may consider:
- Ferrosilicon grade
- Particle size distribution
- Particle shape and product type
- Medium density behaviour
- Viscosity and stability
- Magnetic recovery
- Contamination
- FeSi consumption per tonne processed
- Product and discard performance
- Changes to operating conditions
Historical plant data can be particularly useful. If FeSi consumption, density control and separation results were previously stable under comparable conditions, identifying what changed can narrow the investigation considerably.
The result may show that the ferrosilicon is performing correctly and another section of the plant requires attention. It may instead identify a grade, consistency or recovery issue that needs correction.
Both outcomes are useful because the plant can act on evidence.
Ferrosilicon Quality Starts with the Correct Product for the Process
Ferrosilicon for Dense Medium Separation needs controlled chemical and physical properties. DMS Powders produces specialised FeSi powders for this purpose, with both atomised and milled products available for different DMS applications.
Our atomised grades include Coarse, Fine, Cyclone 60, Cyclone 40 and DMS 70. Our milled grades include 65D, 100D, 150D, 270D and 270F.
The choice between these products should reflect the operating density, separator, required stability, viscosity, feed characteristics and broader circuit conditions.
DMS Powders has been involved in the production of ferrosilicon for Dense Medium Separation since the business began as part of Amcor in 1949. Today, we manufacture and supply FeSi for DMS operations internationally, supported by technical knowledge developed specifically around dense medium applications.
Read more about DMS Powders, our ferrosilicon specifications and grades and our DMS technical information when reviewing your plant’s current medium requirements.
Is It Time to Review Your DMS Ferrosilicon?
Higher FeSi consumption, unstable density, changing viscosity or weaker separation performance should not automatically lead to the conclusion that the ferrosilicon is defective. They are signals that something in the process needs to be checked.
A structured review can establish whether the issue lies with incoming FeSi, grade selection, contamination, magnetic recovery, operating conditions or another part of the circuit.
When the physical properties of the ferrosilicon are matched correctly to the separation process, the plant is better positioned to maintain predictable medium behaviour and control FeSi consumption.
Contact DMS Powders to discuss your current ferrosilicon grade, DMS operating conditions and product requirements.
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Ferrosilicon is often treated as a standard consumable, yet its characteristics have a direct impact on plant efficiency. Consistent particle size distribution supports stable operation, reduces losses, and improves recovery outcomes. Working with a manufacturer that maintains strict quality standards contributes to reliable, long-term performance within DMS circuits.
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