A magnetic drum separator carries susceptible particles past a stationary internal magnet sector. Explore its particle paths and a separate local force estimate using an entered field, field gradient, susceptibility and particle diameter.
Linear Magnetic-Force Estimate
Enter local flux density, its local one-dimensional gradient, an effective volume susceptibility and spherical particle diameter. This ideal estimate is not a separator recovery or equipment-setting model.
Equation Used
- B and dB/dx are independently known local magnitudes at the same particle position.
- The particle is represented as a sphere with the entered diameter and effective volume susceptibility.
- The linear constitutive approximation is valid; ferromagnetic saturation, hysteresis and demagnetizing-field corrections are excluded.
The force estimate uses the magnetic field and gradient at the same particle position. It assumes a small spherical particle with a linear, unsaturated response; the illustrated particle paths do not predict capture.
Rotating drum and stationary magnetic sector
Drum-separator patents describe a cylindrical shell rotating around a stationary magnet group. Feed reaches the drum near the magnetic sector. More-susceptible particles are held at the surface and move with the shell until they leave the field; less-susceptible particles separate earlier under the actual gravity, inertia and process-fluid conditions.
The animation identifies those paths schematically. It does not predict whether any entered particle will be captured.
Topology and a local force estimate
Use the calculator only to explore the stated linear constitutive approximation when local B, local dB/dx and an appropriate effective susceptibility are already known. Recovery, grade and equipment selection require mineral characterization, liberation data, full field maps, flow conditions and validated machine tests.
Bounded linear-particle approximation
The gradient is an independent local input; it is not inferred from a drum clearance. The form applies only under the listed linear, unsaturated assumptions and does not represent a complete force balance.
Arithmetic example
For B=0.12 T, dB/dx=8 T/m, chi=0.1 and d=100 micrometres, the spherical volume is 0.524 nL, estimated force density is 76,394.4 N/m3 and estimated particle force is 0.040 micronewtons. These entered values do not establish recovery or safe machine settings.
Model boundary
Real separation depends on nonuniform three-dimensional fields, magnetization curves, particle shape and liberation, competing forces, slurry or air behavior, residence time and machine geometry.
Magnetic-separation questions
Does a larger force estimate guarantee capture?
No. Capture requires a complete trajectory and force balance plus validated material and equipment data.
Can gradient be calculated as B divided by drum gap?
Not generally. The local gradient comes from the actual magnetic circuit or a measured field map.
Does the drawing distinguish concentrate quality?
No. Its colored particle paths explain topology only and do not predict grade or recovery.
Primary references
- US Patent 3,430,870, Fast magnetic drum ore separator control: describes a rotating drum around a stationary magnet group and the distinct susceptible/non-susceptible particle paths.
- US Patent 3,327,852, Drum type magnetic separator: documents alternating stationary magnets inside a coaxial rotating drum and release of nonmagnetic material.
- US Patent 228,329, Magnetic ore-separator: Edison's falling-stream topology that deflects magnetic material into a separate receptacle.
- USGS Open-File Report 99-529, Magnetic susceptibilities of minerals: laboratory mineral-susceptibility measurements and separator context.
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