Magnetic separators are the primary equipment for removing iron impurities from recovered carbon black (rCB), particularly from tire pyrolysis processes. For ultra-fine iron removal, high-intensity electromagnetic separators and specialized configurations are employed.
1. Core Magnetic Separation Equipment
Drum Magnetic Separators (Rotary Drum Magnets)
- Most widely used for primary iron removal from rCB
- Design: Stainless steel rotating drum with internal semi-circular magnet system
- Operation: Ferrous particles adhere to drum surface while carbon black flows freely; iron is discharged at non-magnetic zone
- Best for: Removing larger steel wire fragments and coarse iron particles from pyrolysis carbon black
- Advantages: Continuous operation, high throughput, low maintenance
High-Intensity Electromagnetic Separators
- For ultra-fine iron removal (down to micrometer/nanometer scale)
- Examples: Elcan’s CG/NMI Electromagnetic Separators (up to 19,500 Gauss), DGCP Series 强磁磁选机
- Design: Electromagnetic coils with vibrating magnetic matrix to prevent clogging of fine carbon black powder
- Class II Div II rating for explosive dust environments common in carbon black processing
- Best for: Battery-grade or high-purity rCB applications requiring iron content < 50 ppm
Overband Magnetic Separators
- Installed above conveyor belts carrying rCB
- Design: Suspended magnet assembly that attracts ferrous particles from moving material stream
- Best for: Pre-screening and removing large tramp iron before further processing
- Advantages: Easy installation, protects downstream equipment from damage
Plate/Grate Magnets
- Installed in chutes, hoppers, or pipelines
- Design: Stationary magnetic plates or grates that capture iron particles as material flows past
- Best for: Point-of-use protection and secondary iron removal
- Variations: Self-cleaning designs available for continuous operation
2. Specialized Equipment for Recovered Carbon Black
Multi-Stage Magnetic Separation Systems
- Combination of drum + high-intensity separators for comprehensive iron removal
- Typical configuration: Coarse magnetic separation → grinding → fine magnetic separation
- Achieves: Iron content reduction from several percent to < 100 ppm or lower
Wet Magnetic Separators (for slurry processing)
- Used when rCB is processed in liquid suspension
- Design: Magnetic drum or high-gradient magnetic separator (HGMS) in liquid flow
- Best for: Removing fine iron particles that are difficult to separate in dry state
Vibratory Magnetic Separators
- Integrated with vibration to enhance material flow
- Design: Magnetic elements combined with vibrating feeders or screens
- Best for: Sticky or bridging-prone carbon black powders
- Advantages: Prevents material buildup, improves separation efficiency
3. Complementary Iron Removal Methods & Equipment
Acid Washing Systems (for chemical iron removal)
- Equipment: Acid tanks, mixers, filters, neutralization vessels
- Process: Treats rCB with hydrochloric or sulfuric acid to dissolve iron oxides
- Best for: Removing non-magnetic iron compounds and achieving ultra-low iron levels (< 10 ppm)
- Note: Followed by thorough water washing and drying
Wind Classification + Magnetic Separation Combination
- Process: First removes lighter impurities via air classification, then magnetic separation for iron removal
- Equipment: Cyclones, air classifiers, and magnetic separators in sequence
- Advantages: Reduces magnetic separator load, improves efficiency, lowers energy consumption
4. JACAN Recommended Equipment Configuration for Tire Pyrolysis rCB
| Process Stage | Recommended Equipment | Iron Removal Target | Application |
|---|---|---|---|
| Primary Removal | Drum Magnetic Separator (10,000-12,000 Gauss) | Remove >95% of large steel wires | Post-pyrolysis, pre-grinding |
| Secondary Removal | High-Intensity Electromagnetic Separator (18,000+ Gauss) | Iron < 50 ppm | After ultrafine grinding |
| Tertiary Removal (Optional) | Acid Washing System | Iron < 10 ppm | Battery-grade or high-performance rubber applications |
5. Key Equipment Selection Factors
- Iron particle size: Larger particles (mm-cm) → drum/overband magnets; fine particles (μm) → high-intensity electromagnetic separators
- Material state: Dry powder → dry magnetic separators; slurry → wet magnetic separators
- Required purity level: General rubber → basic magnetic separation; high-end applications → multi-stage + acid washing
- Throughput capacity: From 50 kg/h (laboratory) to 50+ tons/h (industrial)
- Explosion protection: Class II Div II rated equipment for carbon black dust zones
6. Best Practices for Effective Iron Removal
- Implement multi-stage magnetic separation (coarse → fine) for optimal results
- Integrate magnetic separation before and after grinding to capture iron released during particle size reduction
- Combine with air classification to reduce ash content and improve magnetic separation efficiency
- For ultra-high purity requirements, use high-intensity electromagnetic separators (18,000+ Gauss)
- Regularly monitor iron content with magnetic susceptibility testers or chemical analysis