Coal Washery Magnetic Recovery Equipment
Magnetic Separator for Coal Washery Magnetite Recovery
John Finlay’s LF-HMDS series wet drum magnetic separators deliver separation efficiency up to 99.9%, engineered for reliable, continuous magnetite medium recovery in dense medium coal preparation plants.
Definition & Overview
What is a Magnetic Separator in Coal Washery?
A magnetic separator in a coal washery, also called a wet drum magnetic separator or magnetic medium recovery unit, is a permanent magnet drum device used to recover magnetite (the dense medium) from coal products and refuse streams after dense media separation (DMS).
In every dense medium coal preparation plant, magnetite slurry is used as the separation medium in DMS cyclones and dense medium baths. After separation, both the clean coal overflow and the refuse underflow carry magnetite that must be recovered and recycled back into the circuit. Without efficient magnetic separation, magnetite consumption costs would be prohibitive. John Finlay’s LF-HMDS series achieves separation efficiency up to 99.9%, maximizing magnetite recovery and minimizing medium consumption costs.
John Finlay’s magnetic separators use a permanent magnet drum with a full counter-flow tank design, the most effective configuration for dense medium coal preparation plants. High coercivity magnetic blocks generate a strong magnetic field with high density and a large flux gradient, ensuring effective separation throughout the machine’s internal body.
LF-HMDS Series | Key Performance Data |
|---|---|
Screening Efficiency | Up to 99.9% |
Magnetic System (914mm) | Main poles + 5 pairs, 132° angle |
Magnetic System (1219mm) | 750 gauss, 7 main + 6 pairs, 123° |
Cylinder Diameters | 914 mm & 1219 mm |
Tube Lengths Available | 1829, 2134, 2438, 2743, 2972 mm |
Solid Mass (%) | 10–25% |
Magnetic Content (Feed) | 13% (recommended) |
Non-Magnetic Content (Feed) | 12% (recommended) |
Motor Power (914 mm) | 4 kW |
Motor Power (1219mm) | 5.5 kW |
Drum Material | High-Grade 304 Stainless Steel |
Tank Design | Full Counter-Flow (HFC) |
Key Features
LF-HMDS Series
Key Features & Performance Highlights
John Finlay's wet drum magnetic separators are built for continuous, high-efficiency magnetite recovery in demanding coal preparation environments incorporating three critical engineering features.
Permanent Magnet Drum | Full Counter-Flow Design
The full counter-flow (HFC) tank configuration ensures maximum recovery of magnetic media. Slurry flows counter to drum rotation, maximizing residence time in the magnetic field. High-coercivity magnetic blocks generate a strong magnetic field with high density and a large flux gradient, delivering effective separation throughout the machine's internal body. Separation efficiency up to 99.9%.
High-Grade 304 Stainless Steel Drum
The nonmagnetic drum shell is fabricated from high-grade 304 stainless steel, ensuring it is nonmagnetic, highly wear-resistant, and serviceable throughout the separator's operating life. The drum shell can be replaced independently, extending overall equipment life without replacing the full magnetic assembly. Assembled using imported original components to ensure long-term reliability and consistent performance.
Tailings Tank Liquid Level Adjustment
An integrated liquid level control device ensures consistent separation conditions throughout operation regardless of feed rate fluctuations. A rinsing port at the base of the tailings tank allows for efficient cleaning and sediment flushing, preventing build-up that would otherwise degrade separation performance over time. Delivers automated reliability in high-performance coal preparation plants.
Working Principle
How a Wet Drum Magnetic Separator Works in Coal Processing
Understanding the wet drum magnetic separator working principle helps coal washery engineers optimize the dense medium recovery circuit for maximum magnetite recovery and minimum medium loss.
01
Feed Entry
02
Magnetic Attraction
03
Concentrate Discharge
04
Tailings & Rinsing
Technical Specifications
HFC Series Magnetic Separator | Full Process Performance Table
John Finlay’s HFC series wet drum magnetic separators are available in two cylinder diameters (914mm and 1219mm), each with five tube length options, covering the full range of magnetite recovery duties in coal preparation plants.
| Cylinder Dia. | Tube Length | Magnetic System | Counterflow Type (Recommended Amount) | Solid Mass (%) | Feed Pulp Solid Content (%) — Recommended | Motor Power | ||
|---|---|---|---|---|---|---|---|---|
| Quantity of Pulp | Concentrate Quantity | Magnetic Content | Non-Magnetic Content | |||||
| 914 mm | 1829 mm | Main poles and 5 pairs of poles, Envelop Angle 132° | 177 | 33 | 10–25% | 13% | 12% | 4 kW |
| 914 mm | 2134 mm | 207 | 39 | |||||
| 914 mm | 2438 mm | 236 | 44 | |||||
| 914 mm | 2743 mm | 267 | 50 | |||||
| 914 mm | 2972 mm | 295 | 55 | |||||
* Pulp quantity and concentrate quantity values are indicative. Actual performance depends on feed characteristics and operating conditions.
| Cylinder Dia. | Tube Length | Magnetic System | Counterflow Type (Recommended Amount) | Solid Mass (%) | Feed Pulp Solid Content (%) — Recommended | Motor Power | ||
|---|---|---|---|---|---|---|---|---|
| Quantity of Pulp | Concentrate Quantity | Magnetic Content | Non-Magnetic Content | |||||
| 1219 mm | 1829 mm | 750 gauss, 7 Main poles and 6 pairs of poles, Angle 123° | 212 | 60 | 10–25% | 13% | 12% | 5.5 kW |
| 1219 mm | 2134 mm | 248 | 70 | |||||
| 1219 mm | 2438 mm | 283 | 80 | |||||
| 1219 mm | 2743 mm | 319 | 90 | |||||
| 1219 mm | 2972 mm | 354 | 100 | |||||
* Specifications sourced from John Finlay LF-HMDS series product brochure. Contact JFI for application-specific sizing and selection.
Counter-Flow vs Semi Counter-Flow Magnetic Separator
John Finlay recommends the full counter-flow (HFC) design for dense medium coal washery applications where magnetite recovery is critical. Here is how it compares:
Counter Flow (HFC) Design
John Finlay LF-HMDS SeriesSemi Counter Flow Design
Standard market alternativeApplications
Applications of Magnetic Separators in Coal & Mineral Processing
John Finlay's wet drum magnetic separators serve critical roles across every stage of the dense medium coal preparation plant circuit.
Primary Magnetite Recovery (Product Circuit)
Primary wet drum magnetic separators recover magnetite from the clean coal product drain screen underflow, the highest-volume magnetic separation duty in the DMS circuit. John Finlay's LF-HMDS units achieve up to 99.9% recovery to minimize magnetite losses in the product stream.
Secondary Magnetite Recovery (Rinse Circuit)
Secondary magnetic separators treat the rinse screen underflows from both product and refuse circuits, recovering residual magnetite that was not captured in the primary stage. Two-stage magnetic separation is standard practice in all high-efficiency coal preparation plants.
Refuse Circuit Medium Recovery
Magnetic separators on the refuse (reject) circuit recover magnetite from the dense media refuse stream, preventing medium losses to the tailings pond and maintaining the overall medium balance in the DMS circuit. Critical for maintaining consistent medium density and reducing top-up costs.
Dense Medium Coal Preparation Plants
John Finlay magnetic separators are integral to complete DMS coal washery circuits, working in conjunction with dense media cyclones, banana screens, and medium conditioning systems. Supplied to Coal India subsidiaries (BCCL, SECL, MCL, CCL) and private coal mining companies across India and internationally.
Ferrosilicon Recovery (Mineral Processing)
Wet drum magnetic separators also recover ferrosilicon from dense medium mineral processing circuits (iron ore, diamond, platinum beneficiation), where ferrosilicon replaces magnetite as the dense medium. High recovery efficiency reduces the operating cost of ferrosilicon-based DMS circuits.
Magnetite Ore Concentration
Beyond DMS medium recovery, John Finlay wet drum magnetic separators can be used for the concentration of magnetite ore in mineral processing plants, separating ferromagnetic magnetite from nonmagnetic gangue material in slurry feed circuits.
About John Finlay
Magnetic Separator Manufacturer in India
Why John Finlay?
John Finlay is a leading magnetic separator manufacturer offering wet drum magnetic separators for coal washeries and mineral processing backed by 50+ years of DMS coal washery experience.
Magnetic Separator | Frequently Asked Questions
Common questions from coal washery process engineers and plant operators about wet drum magnetic separators, magnetite recovery, and medium management.
In a coal washery, a magnetic separator (specifically a wet drum magnetic separator) recovers magnetite, the dense medium used in DMS cyclones and baths from the drain and rinse screen underflows after coal washing. Magnetite is a significant operating cost in any dense medium plant, so recovering and recycling it via magnetic separation is essential for economic operation. John Finlay’s LF HMDS series achieves up to 99.9% separation efficiency, minimizing magnetite consumption and reducing medium make-up costs significantly.
A wet drum magnetic separator works by feeding magnetite-bearing slurry (solid mass 10–25%) into a tank where a rotating non-magnetic 304 stainless steel drum contains a stationary permanent magnet assembly inside. Magnetite particles are attracted to the drum surface by the strong magnetic field (750 gauss for 1219mm models), carried around by drum rotation to the discharge zone, and collected as magnetic concentrate (recovered medium). Non-magnetic coal fines and water pass through the tank to the tailings outlet. John Finlay uses a full counter-flow tank design for maximum recovery.
In a full counter-flow (HFC) magnetic separator, the slurry flows in the opposite direction to drum rotation; this maximizes the residence time of magnetite particles in the magnetic field, giving the highest possible recovery (up to 99.9%). In a semi counter-flow design, slurry partially flows with drum rotation, reducing the effective contact time with the magnetic field. John Finlay recommends and supplies the full counter flow (HFC) design for all dense medium coal preparation applications where magnetite recovery efficiency is critical.
Selection depends on the volumetric flow rate of pulp requiring treatment. John Finlay offers 914mm diameter models (with pulp quantities from 177 to 295, motor 4 kW) and 1219mm diameter models (pulp quantities from 212 to 354, motor 5.5 kW), each in five tube lengths (1829mm to 2972mm). The 1219mm models have a stronger magnetic system (750 gauss, 7 main poles, and 6 pairs) and handle higher pulp volumes. Contact John Finlay’s engineers with your drain and rinse screen underflow rate for correct sizing.
John Finlay Engineering & Tech. Group of Companies is a global supplier of equipment for coal washing, founded in 1974 in Brisbane, Australia, with operations in India. With 130+ coal washery projects completed and 50+ years of experience, John Finlay supplies industrial centrifuge machines to Coal India subsidiaries (BCCL, SECL, MCL, and CCL) and private coal mining companies across India and globally. John Finlay’s JFH and JFCB centrifuge series each carry four national patents.