I. Basic Principle

A high-gradient magnetic separator creates a strong magnetic field (background field 1.5-2.0T) through a magnetizing coil; the separation space is filled with a magnetic concentrating medium (steel wool, rods, plates), which is magnetized in the strong field, forming local ultra-high-gradient magnetic fields at the edges and ends. When pulp with weakly magnetic minerals passes through the medium, weakly magnetic particles are captured by the high-gradient field and adsorbed on the surface of the medium, while non-magnetic particles are carried away with the pulp flow, achieving separation.

II. Main Operating Mechanism

1. Magnetic System

Strong background field from the coil The magnetizing coil creates a strong field (1.5-2.0T+) filling the entire separation space, providing an environment for magnetizing the concentrating medium.

High-gradient local field from the medium The magnetic concentrating medium (steel wool, rods) is magnetized by the background field; at the edges, ends, and corners of the medium, the gradient is extremely high (10⁶-10⁷ A/m²), forming many microscopic high-gradient capture zones, with gradients 100-1000 times higher than ordinary separators.

Key Advantages The strong background field overcomes the weak magnetism of minerals; the high gradient creates sufficient force to capture microparticles; the dense medium forms a dense capture network.

2. Separation Process

Stage 1: Feeding and Dispersion

Pulp is evenly fed from the feed hopper into the separation chamber (concentration 20-35%, particle size 0.02-3mm for microfine weakly magnetic minerals), evenly distributed in the separation space, flow velocity controlled (usually 0.1-0.5 m/s), ensuring contact of all particles with the medium.

Stage 2: Magnetic Capture

Capture of weakly magnetic particles When the pulp passes through the magnetic concentrating medium, weakly magnetic particles are subjected to the high-gradient field; the magnetic force is much greater than gravity and flow resistance; weakly magnetic particles are adsorbed on the surface of the medium; even microfine particles <0.02mm are effectively captured.

Factors of Magnetic Force Field intensity (the stronger the background field, the greater the force), field gradient (the higher the gradient, the greater the force), particle magnetism (the higher the magnetization coefficient, the greater the force), particle size (the larger, the greater the force).

Removal of Non-Magnetic Particles Non-magnetic particles are not affected by magnetic force, pass through the medium layer with the pulp, and are discharged through the tailings outlet.

Formation of Magnetic Material Layer Captured magnetic particles gradually accumulate on the surface of the medium, forming a layer of certain thickness; the thickness of the layer is related to the feed amount and magnetic particle content; when a certain thickness is reached, washing is required.

Stage 3: Washing and Unloading

Power off and demagnetization Stop feeding, turn off magnetizing power, background field disappears, magnetic concentrating medium loses magnetism, adsorbed magnetic particles lose magnetic retention.

Washing with water flow Washing the medium with high-pressure water (or air-water mixture), captured magnetic particles are washed off, forming magnetic concentrate pulp, discharged through the concentrate outlet.

Pulsating washing   (optional): Using intermittent pulsating water flow to create shocks; vibration loosens magnetic agglomerates, removes non-magnetic inclusions, improves concentrate quality.

Thoroughness of cleaning Multiple washings ensure medium cleanliness, avoid residue from the previous cycle, prepare for the next separation cycle.

Stage 4: Cyclic Separation

Re-magnetization After washing is completed, power is turned on again, background field restored, medium re-magnetized, restoring capture ability.

Continuous operation Feeding restarts, entering a new separation cycle, periodic or continuous operation, achieving continuous production.

3. Types of Operation

Vertical ring high-gradient separator The ring separation chamber is arranged vertically, divided into several sector zones (usually 4-8); the ring rotates or is fixed; each zone sequentially passes through feeding-separation-washing-unloading positions, realizing quasi-continuous or continuous operation, high capacity, high efficiency.

Horizontal ring The ring chamber is arranged horizontally, divided into sector zones; the ring rotates horizontally; processes are performed sequentially; continuous operation; compact design; small footprint.

Disk type Several disk separation disks are stacked, each filled with medium; disks rotate or are fixed; pulp passes sequentially through the disks; multiple separations; gradual enrichment; high concentrate quality; suitable for cleaning.

III. Key Technical Elements

Field Parameters: 1.0-1.5T (medium magnetism), 1.5-2.0T (weak magnetism), >2.0T (very weak magnetism); gradient at the edges of the medium 10⁶-10⁷ A/m², capture of minerals with a magnetization coefficient from 10×10⁻⁸ m³/kg.

Magnetoconcentrating Medium Steel wool (thin wire, high gradient, for ultrafine particles), steel rods (high strength, large gradient, versatile), steel plates (high productivity, medium gradient), combined medium. Material: low-carbon or stainless steel, diameter/thickness 0.05-5mm, filling 5-15% (by volume).

Process Parameters Concentration 20-35% (typical), flow rate 0.1-0.5 m/s, washing pressure 0.1-0.6 MPa, cycle time 2-6 minutes (feeding 1-3 min, washing 0.5-2 min).

IV. Technical Specifications

Advantages High gradient, strong ability to capture weakly magnetic minerals, high recovery (85-95%) of microfine weakly magnetic particles, wide adaptability (hematite, limonite, manganese, ilmenite), wide particle size range (0.02-3mm), high separation accuracy.

Limitations Periodic operation (limited productivity by cycle), medium clogging (fine sludge or magnetic agglomerates), high energy consumption (strong magnetizing coil), large consumption of washing water, complex operation (high requirements for parameter adjustment).

V. Application

Suitable for weakly magnetic minerals (hematite, limonite, manganese, ilmenite, wolframite), particle size 0.02-3mm, magnetization coefficient 10×10⁻⁸ - 500×10⁻⁸ m³/kg, cleaning-recleaning-iron removal operations, productivity 50-500 t/h.