What are the best practices for magnetic separation of fine particles?

Magnetic separation is a widely used technique in mineral processing to separate valuable minerals from gangue or impurities. However, when dealing with fine particles, magnetic separation can be challenging and require some best practices to achieve optimal results. In this article, you will learn about the factors that affect the magnetic separation of fine particles, the types of magnetic separators available, and the tips and tricks to improve the efficiency and selectivity of your magnetic separation process.

1 Factors affecting magnetic separation

The magnetic separation of fine particles depends on several factors, such as the magnetic properties of the minerals, the particle size and shape, the pulp density and viscosity, the magnetic field intensity and gradient, and the operating conditions. Generally, the finer the particles, the lower the magnetic susceptibility and the higher the surface forces that can hinder the separation. Therefore, it is important to optimize the feed preparation, the magnetic field configuration, and the separation parameters to achieve the desired separation.

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Michael McClintock, P.Eng.

Founder & Principal @ McClintock Group| Co-Founder EOC | Enhancing Mineral Projects, Advocating for Shareholders
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One item I would mention that is not always discussed is water quality. From my experience water quality can affect how particles clean, especially as material becomes more fine. Effectively as particles get smaller the drag forces per unit of mass, that increases the drag force on particles making two different particles increasingly harder and harder to seperate. Anything that increases the likelyness of particles sticking together, will make it more difficult for the magnetics to do thier job.

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2 Types of magnetic separators

Depending on the application and feed characteristics, there are various types of magnetic separators that can be used for fine particle separation. Wet high-intensity magnetic separators (WHIMS) are suitable for particles with low to medium magnetic susceptibility, like hematite, ilmenite, chromite, and wolframite, that require a high magnetic field gradient. Dry high-intensity magnetic separators (DHIMS) utilize a high magnetic field intensity to separate strongly magnetic minerals from weakly magnetic or non-magnetic ones and are appropriate for coarse and fine particles with high magnetic susceptibility, such as magnetite, pyrrhotite, and garnet. Wet low-intensity magnetic separators (WLIMS) employ a low magnetic field intensity to separate moderately magnetic minerals from non-magnetic ones and are suitable for coarse and fine particles with medium to high magnetic susceptibility, such as magnetite, pyrrhotite, and limonite. Lastly, dry low-intensity magnetic separators (DLIMS) use a low magnetic field intensity to separate weakly magnetic minerals from non-magnetic ones and are effective for coarse and fine particles with low to medium magnetic susceptibility like hematite, ilmenite, and rutile.

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Michael Wheatland

RMIT University - Senior Manager STEM College - Engineering
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Magnetic separation is crucial beyond iron ore, particularly in extracting impurities from critical mineral ores. WHIMS effectively process low to medium susceptibility minerals like ilmenite, while DHIMS excel in separating strongly magnetic minerals like garnet. WLIMS are suited for moderately magnetic minerals such as limonite, and DLIMS focus on weakly magnetic ones like hematite. These diverse separators ensure optimal purity and efficiency in processing a range of critical minerals, highlighting their versatility in modern mineral processing.

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3 Tips and tricks for magnetic separation

To maximize the performance of your magnetic separation process, there are certain tips and tricks to consider. Choosing the right type of magnetic separator is important, as it should match the magnetic properties, particle size distribution, and moisture content of your feed material and target minerals. Additionally, you should adjust the feed rate, pulp density, and viscosity to avoid overloading, clogging, or diluting the separator. To ensure the desired separation force and selectivity, it's necessary to control the magnetic field intensity and gradient. This can be done by using different pole configurations, matrix elements, or gap settings. To monitor product quality and recovery, sampling and analysis of the feed, concentrate, and tailings streams should be conducted. Online or offline instruments such as magnetic susceptibility meters, X-ray fluorescence analyzers, or mineralogical scanners can measure composition and grade. Regular maintenance and cleaning of your magnetic separator is also essential to prevent wear and tear, corrosion, or contamination. Water jets, air blasts, or mechanical scrapers can be used to remove trapped particles from the separator. By following these best practices you can optimize your magnetic separation process and improve mineral processing performance.

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What are the best practices for magnetic separation of fine particles?

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1 Factors affecting magnetic separation

2 Types of magnetic separators

3 Tips and tricks for magnetic separation

Mineral Processing

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