I. Basic Principle

The drum permanent magnetic separator uses a strong magnetic field on the surface of the drum, created by an internal fixed system of permanent magnets. When the pulp with magnetic minerals passes through the rotating drum, magnetic particles are attracted to the drum surface and transported by rotation to the discharge zone, while non-magnetic particles are carried away with the pulp flow, achieving separation.

II. Main Operating Mechanism

1. Magnet System

Permanent Magnet System Inside the drum, permanent magnets (neodymium-iron-boron or ferrite) are fixed in place, arranged in a specific pattern with alternating N-S poles. The magnetic system is stationary; only the outer shell of the drum rotates. Magnetic field lines emerge through the drum surface, forming the working magnetic field.

Field Distribution The field intensity is uneven around the drum circumference—maximum in the pole areas (working zone), weak between poles (discharge zone), with penetration depth up to 200-300 mm.

2. Cyclic Separation Process

Stage 1: Feeding and Dispersion

Pulp is evenly fed into the housing from the feed hopper (concentration 25-35%, particle size 0.074-6 mm), dispersed inside the housing, with magnetic and non-magnetic particles suspended.

Stage 2: Magnetic Attraction and Separation

Magnetic Field Zone (Adsorption Zone) Pulp passes through the lower strong magnetic field zone under the drum; magnetic particles are attracted to the drum surface by magnetic force, overcoming gravity and flow resistance. Strong magnetic, large, and nearby particles are mainly attracted, forming a magnetic layer on the surface.

Non-magnetic Particle Discharge Non-magnetic particles are not affected by magnetic force, continue moving with the pulp flow, and are discharged through the tailings outlet.

Transportation of Magnetic Particles Attracted magnetic materials rotate with the drum, leave the pulp zone, enter the air, are held by magnetic force, and move to the discharge zone.

Stage 3: Concentrate Washing (if available)

The surface of the magnetic layer is washed with sprayed water to remove mechanically trapped non-magnetic particles and clay impurities between magnetic particles, improving concentrate quality. Multi-stage washing with adjustable pressure and water flow is possible.

Stage 4: Concentrate Discharge

Magnetic Field Weakening Zone The drum rotates into the area between magnetic poles where field intensity significantly decreases, magnetic force on particles sharply reduces, and gravity becomes dominant.

Concentrate Separation Magnetic materials separate from the drum under gravity (a scraper, if installed, assists), fall into the concentrate chute, and are discharged through the concentrate outlet.

Continuous Cycle The drum continues rotating, the surface re-enters the strong field zone, attracts new magnetic particles, realizing continuous separation.

3. Types of Housings

Counter-current Housing The feed direction is opposite to drum rotation, suitable for large particles (3-20 mm), high efficiency, thorough separation, high recovery.

Semi-counter-current Housing The feed direction is at an angle to drum rotation, suitable for medium and small particles (0.5-5 mm), high separation accuracy, good quality, wide application, balance of performance and effect.

III. Key Technical Elements

Field Intensity and Distribution 800-1200 Gs (strong magnetic minerals), 1200-1800 Gs (common magnetite), 1800-3000 Gs (weak magnetic minerals), >3000 Gs (very weak magnetic minerals).

Drum Rotation Speed 15-35 rpm, low speed for large particles (15-20 rpm), high for small particles (25-35 rpm). Too low - low productivity, too high - low recovery, optimal - balance of adsorption and discharge.

Pulp Concentration 25-35% (usual), 30-40% (large particles), 20-30% (small particles). Too low - low productivity, too high - settling, poor adsorption.

Feed Particle Size 3-20 mm (counter-current), 0.5-5 mm (semi-counter-current), 0.074-3 mm (special design). Large particles are easily attracted but may carry impurities, small particles tend to agglomerate.

IV. Technical Specifications

Continuous operation (feeding-separation-discharge simultaneously), stable separation (constant field, decay <5% over 10 years), energy saving (zero energy consumption by magnets, only drive), environmentally friendly (no radiation, low noise), easy operation (simple design, high automation, low maintenance).

V. Factors Affecting Separation Effect

Ore Properties Magnetic susceptibility, particle size distribution, density difference, degree of liberation.

Equipment Parameters Field intensity, drum speed, housing type, magnetic system configuration.

Operating Conditions Pulp concentration, feed uniformity, wash water consumption, equipment condition.