Magnetic Separator Overview

In mineral processing, a magnetic drum separator, also known as a drum magnet, separates non-magnetic material from magnetic material by using magnetic differences.

A Magnetic Separator is a device that utilizes a magnetic field to separate magnetic materials from non-magnetic materials.

Separators are categorized into two main processing environments:

• Wet Magnetic Separator: Uses water to wash the minerals. This is the standard for modern concentration plants.
• Dry Magnetic Separator: Uses air and gravity. This is typically used in water-scarce regions or for coarse “roughing” separation.

Whether a Low Intensity Magnetic Separator (LIMS) is needed for magnetite or a High Gradient Magnetic Separator (HGMS) for hematite, the principle remains the same: using magnetic force to conquer gravity.

Why Do We Need The Magnetic Separator?

One might ask, “Why not simply use gravity separation or flotation?” While those methods work for certain minerals, Magnetic Separation stands as the only economically viable method for extracting ferrous metals.

• 1. Revenue Increase (Upgrading):
• In iron ore mining (Magnetite), raw rock might only contain 30% iron (Fe). Steel mills typically refuse this low grade, requiring 65% Fe. A ZONEDING magnetic separator removes the waste rock (silica/quartz), upgrading 30% dirt into a 65% concentrate. This process instantly converts waste into a salable product.
• 2. Product Purification (Iron Removal):
• In the glass and ceramic industries, iron is a contaminant. Even a trace amount of iron oxide (0.1%) creates green or black spots in clear glass or white tiles. A High Gradient Magnetic Separator extracts these tiny iron contaminants from silica sand, ensuring the final product remains perfectly white.
• 3. Equipment Protection:
• In crushing plants, “Tramp Iron” (broken drill bits, shovel teeth) poses a significant risk. Equipment like an Overband Magnetic Separator lifts this scrap metal off the conveyor belt before it enters a cone crusher. Without this protection, a single piece of scrap metal could destroy a crusher’s mantle, resulting in substantial repair costs.

Magnetic Separator Classification

Magnetic separators are divided into dry magnetic separators and wet magnetic separators.

Dry magnetic separators

Advantages of the dry magnetic separators

1.No water requirement: Dry magnetic drum separators operate without a liquid medium, making them convenient and cost-effective. They are particularly advantageous in situations with limited water availability or a focus on water conservation.

2.Versatility: By adjusting magnetic field strength, drum speed, and other parameters, dry magnetic separators can process various minerals including iron ore, chromite, garnet, tantalite, and other magnetic minerals.

3.Easy maintenance: Dry high intensity magnetic separators generally have simpler designs and fewer components compared to wet separators, resulting in easier maintenance and lower maintenance costs.

Wet magnetic separators

What are Magnetic Separators Used For?

This technology finds application across almost every heavy industry sector.

• 1. Mining Industry (Beneficiation):This is the largest sector for magnetic separation.
  • Magnetite (Fe3O4): The magnetic separator acts as the heart of the plant.
  • Hematite/Limonite: These are weakly magnetic minerals. Specialized High-Intensity Magnetic Separators (10,000+ Gauss) are used to recover them.
  • Manganese: Used for upgrading manganese carbonate or oxide ores.
• 2. Industrial Minerals (Purification):
  • Quartz/Silica Sand: Removal of iron to produce glass-grade sand.
  • Kaolin Clay: Removal of titanium and iron to increase whiteness for paper and ceramics.
  • Feldspar: Reduction of iron content for ceramic glazes.
• 3. Recycling and Recovery:
  • Coal: Removal of pyrite (sulfur iron) to produce cleaner-burning coal.
  • Steel Slag: Recovery of scrap iron from smelter waste.
  • Wood/Plastic Recycling: Removal of nails and wire from shredded chips before reprocessing.

Magnetic Separator applicable materials

•  Iron ore: In iron ore beneficiation, the magnetic particles, such as magnetite or hematite, are absorbed to the drum and carried along with it. Meanwhile, non-magnetic particles continue their trajectory and are discharged separately.
• Industrial minerals: Dry drum magnetic separators remove magnetic impurities from industrial minerals like feldspar, quartz, and mica, improving the purity and quality of the minerals, so they are more suitable for industrial applications.
• Coal processing: Magnetic impurities from coal are removed via magnetic separators, improving the purity and quality of the coal.
• Sand beneficiation: Magnetic minerals such as ilmenite, rutile, zircon and garnet in heavy mineral sands are collected by magnetic separators as magnetic concentrate.

Structure of Magnetic Separator

What are Key Components of Magnetic Separators?

While the exterior appears simple, the interior engineering requires precision.

• 1. The Magnetic System:This is the “engine” of the unit. It consists of a stationary array of magnetic blocks arranged in a semi-circle (usually 135 degrees) inside the drum. ZONEDING typically utilizes:
  • Strontium Ferrite: For standard Low-Intensity separators (up to 1500 Gauss). This material is cost-effective and durable.
  • Rare Earth (Neodymium-Iron-Boron): For High-Intensity separators (up to 12,000 Gauss). This material is expensive but incredibly powerful.
• 2. The Rotating Drum (Shell):This cylinder rotates around the stationary magnets. It is constructed from non-magnetic 304 stainless steel. The drum must be covered with a rubber or ceramic wear layer because ore is extremely abrasive.
• 3. The Tank (Tub):The tank dictates the flow of water and slurry.
  • Half-Counter Current Tank: Best for high recovery rates and fine particles.
  • Concurrent Tank: Best for coarse particles and simple roughing operations.
• 4. The Drive System:A motor and reducer spin the drum. The speed is adjustable. Speed affects the recovery rate—if too fast, ore is thrown off; if too slow, production capacity drops.

Working principle of Magnetic Separator

How Does a Magnetic Separator Transform Raw Material Quality?

The transformation occurs in the “Separation Zone.”

• Feeding: Slurry (mixed ore and water) flows into the tank beneath the drum.
• Attraction: The magnetic minerals (Magnetite) react to the pull of the magnetic system inside the drum. They overcome gravity and fluid drag to snap onto the surface of the stainless steel drum.
• Transport: The drum rotates. The magnetic minerals stick to the drum surface and ride up out of the slurry.
• Cleaning: While adhering to the drum, the magnetic particles roll over different magnetic poles (N-S-N-S). This “Magnetic Agitation” shakes loose any non-magnetic mud trapped between the iron particles.
• Discharge: The drum carries the magnetic material to the top, where the internal magnetic system ends. Once the magnetism ceases, the iron falls off into the concentrate chute. The non-magnetic waste (tailings) flows out the bottom.

Advantages of Magnetic Separator

1. Magnetic drum separator adopts the multi-magnetic pole arrangement with short distances between poles in the internal magnetic system, which can increase the stirring of the magnetic particles and remove the gangues from minerals.
2. 180° broad-angle magnetic system can effectively prolong the separation area, and improve the recovery of iron ores.
3. Wear-resistant ceramics are stuck on the drum surface, the hardness HRA is ≥85, maximum HRA92 over
4. Simple material distribution device, which can conveniently control the grade of the concentrate and the tailing. 

What is the Cost of Magnetic Separators and Affecting Factors?

Compared to crushers, magnetic separators are relatively affordable, though high-tech magnets can drive up the price.

• Price Estimates:
  • Small Dry Drum (Laboratory/Pilot): $1,500 – $3,000 USD.
  • Standard Wet Drum (CTB-1018 – Ferrite): $6,000 – $12,000 USD.
  • High Gradient Rare Earth Separator (High Gauss): $20,000 – $60,000+ USD.
• Factors Affecting Price:
  • Field Strength (Gauss): This is the primary cost driver. A 1000 Gauss ferrite machine is inexpensive. A 12,000 Gauss Neodymium machine requires expensive rare earth metals, costing 5x-10x more.
  • Drum Size: Larger diameter drums (1200mm, 1500mm) utilize more stainless steel and magnetic material.
  • Tank Material: Standard steel tanks cost less than full stainless steel tanks required for corrosive environments.
  • Configuration: A single drum is cheaper than a double or triple drum system (used for multi-stage cleaning in one frame).

What Should You Consider Before Buying Magnetic Separator?

Purchasing the wrong strength magnet is the most common mistake made by buyers.

• 1. Know Your Mineralogy:Is the iron ore Magnetite (Strongly magnetic) or Hematite (Weakly magnetic)?
  • For Magnetite, only 1200-1800 Gauss is required. Buying a stronger magnet wastes money and will actually trap unwanted silica.
  • For Hematite or Silica cleaning, 10,000-15,000 Gauss is necessary. A standard separator will fail to pick up these minerals.
• 2. Throughput Capacity:How many tons per hour are required? A small drum (CTB-612) handles 10 tph. A large drum (CTB-1230) handles 80-100 tph. ZONEDING engineers calculate the surface area load to ensure the correct size is selected.
• 3. Separation Layout:Is the goal Roughing (discarding waste rock early) or Cleaning (achieving a final concentrate of 65%)?
  • Roughing requires a Concurrent Tank (High volume, lower grade).
  • Cleaning requires a Semi-Counter Current Tank (High grade, lower volume).

Wet Magnetic Separator vs. Dry Magnetic Separator: Which Suits Your Material?

This decision typically depends on geography and particle size.

Feature	Wet Magnetic Separator	Dry Magnetic Separator
Medium	Water	Air
Particle Size	Fine (< 3mm)	Coarse (up to 20mm) or Fine Powder
Efficiency	High (Cleaner separation)	Lower (Dust and static interfere)
Resource Need	Requires Water	Requires Dust Collection
Throughput	High Volume	Lower Volume
Application	Final Concentrate Production	Roughing / Pre-concentration

How to Choose Between Permanent Magnets and Electromagnetic Separators?

• 1. Permanent Magnetic Separator (ZONEDING Standard):
  • Mechanism: Uses blocks of solid magnet material (Ferrite/Neodymium).
  • Pros: Uses no electricity for the magnet (only for the motor). Constant field. Zero maintenance. No heat generation.
  • Cons: The magnetic strength is fixed and cannot be adjusted.
  • Best For: 95% of all mineral processing applications.
• 2. Electromagnetic Separator:
  • Mechanism: Uses copper coils and electricity to create a field.
  • Pros: Extremely deep magnetic penetration. Strength can be adjusted by changing the voltage.
  • Cons: Consumes significant amounts of electricity. Requires cooling systems (oil or water) because the coils generate heat. If power fails, the iron drops.
  • Best For: Suspended Overband Magnets (removing heavy tramp iron from deep conveyor belts) or specialized heavy-duty applications.

What is the Impact of Particle Size on Magnetic Separation Recovery Rates?

Size matters significantly, as physics behaves differently at different scales.

• Coarse Particles (> 5mm):Heavy particles possess high momentum. The magnetic force must be very strong to hold them against gravity and centrifugal force. However, coarse particles often contain “Locked” minerals—a piece of iron attached to a piece of silica. Separating these often results in lower grade concentrate because the silica is carried along.
• Fine Particles (< 0.074mm / 200 mesh):This is where high grade is achieved (Liberation). However, if particles are too fine (slimes), they form non-selective aggregates. Also, fine particles struggle to break the surface tension of water.
• Optimization:Magnetic separators are usually installed in stages.
  • Stage 1: Coarse separation (Cobbing) to remove pure waste.
  • Stage 2: Grind in a Ball Mill.
  • Stage 3: Fine wet separation to obtain the final high-grade powder.

How Does ZONEDING Design Magnetic Systems for Maximum Field Depth?

Not all magnets are created equal. Two machines might both claim “2000 Gauss” but perform differently.

• 1. Multi-Pole Design:ZONEDING does not simply use one large magnet. The design incorporates alternating poles (N-S-N-S) arranged closer together. This increases the “Magnetic Agitation” frequency. The ore flips over more times as it travels the drum, shaking off more silica.
• 2. Large Wrap Angle:Standard drums might have a 120-degree magnetic system. ZONEDING utilizes a 127 to 135-degree system. This provides the material a longer path to separate, increasing recovery rates by 2-3%.
• 3. Gauss Stability:Cheaper magnets lose strength over time. ZONEDING uses high-grade Strontium Ferrite and sintered NdFeB that guarantees demagnetization of less than 5% over 8 years. The machine will function as effectively in 2030 as it does today.

Technical Parameter of Magnetic Separator

Model	Shell diameter （mm）	Shell lenght （mm）	Shell rotation speed（r/min）	Feeding size （mm)	Processing capacoty （t/h）	Power（kw）
CTB6012	600	1200		2-0	10-20	1.5
CTB6018	600	1800		2-0	15-30	2.2
CTB7518	750	1800		2-0	20-45	2.2
CTB9018	900	1800		3-0	40-60	3
CTB9021	900	2100		3-0	45-60	3
CTB9024	900	2400		3-0	45-70	4
CTB1018	1050	1800		3-0	50-75	5.5
CTB1021	1050	2100		3-0	50-100	5.5
CTB1024	1050	2400		3-0	60-120	5.5
CTB1218	1200	1800		3-0	80-140	5.5
CTB1224	1200	2400		3-0	85-180	7.5
CTB1230	1200	3000		3-0	100-180	7.5
CTB1530	1500	3000		3-0	170-280	11

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