Recovered Carbon Black (rCB) is mostly derived from pyrolysis of end‑of‑life tires, plastics and biomass raw materials. Waste tires contain embedded steel wire reinforcements. Even after pyrolysis, fragmented steel wire and fine iron fragments remain mixed within crude pyrolysis char feedstock. Without effective removal, these ferrous contaminants will scratch and wear grinding rotors, classifier impellers and other downstream precision equipment, and also downgrade the purity and reinforcement performance of final rCB powder. High‑intensity magnetic separation acts as the core pre‑treatment barrier to extract residual steel wire before pyrolysis char enters ultra‑fine grinding circuits.
Working Mechanism for Steel Wire Removal
High‑intensity magnetic separation leverages the physical property difference: steel wire and iron fragments are ferrous and strongly magnetic, while pyrolysis carbon char is non‑magnetic.
Crude pyrolysis char containing broken steel wire fragments is conveyed into the magnetic separation station as continuous bulk feed. Powerful magnetic coils or rare‑earth magnetic assemblies generate a deep‑penetrating high‑intensity magnetic field covering the full material flow path. When mixed feed passes through this magnetic zone, all ferrous steel wire pieces, from coarse wire segments down to micro‑fine steel shavings, are instantly captured and held onto magnetic surfaces. Non‑magnetic pyrolysis char keeps moving forward along the conveying route without magnetic attraction, and flows onward toward subsequent grinding processes.
Most industrial rCB lines adopt self‑cleaning magnetic separation configurations. Captured steel wire contaminants are mechanically stripped away from magnetic surfaces by circulating scraper belts or rotating magnetic drums, then discharged into dedicated metal collection bins. This continuous automatic discharge avoids magnetic‑surface saturation and guarantees stable separation efficiency for long‑run production.
Critical Role Within the rCB Processing Sequence
As the first core step of raw‑material pre‑treatment, high‑intensity magnetic separation delivers two core values for rCB production.
First, it protects downstream ultra‑fine grinding and air‑classification hardware. Hard steel wire fragments would cause severe impact abrasion on grinding discs, liners and classification wheels. By removing steel contaminants at the pre‑treatment stage, operators drastically cut equipment damage risk, reduce unplanned downtime and extend service life of high‑value milling systems.
Second, it secures rCB product quality. Residual steel impurities will raise ash content and compromise the structural integrity and reinforcing capability of recovered carbon black. Thorough magnetic separation delivers clean feedstock, laying foundations for achieving target particle‑size indicators such as D90 < 10 μm in later ultra‑fine grinding and air classification stages.
Adaptation for Complex Pyrolysis Feedstock
Pyrolysis char sourced from tires, plastics and biomass varies heavily in steel‑wire content, fragment size and material bulk density. High‑intensity magnetic separation systems for rCB are engineered for these variable feed conditions. Magnetic‑field strength, feeding speed and material‑layer thickness can be adjusted to catch both large steel‑wire segments and tiny iron micro‑fragments. For heavily contaminated feedstock, multi‑stage magnetic separation setups can be deployed to boost overall steel‑removal rates.
High‑intensity magnetic separation physically separates steel wire from pyrolysis‑derived char by magnetic attraction for ferrous contaminants. It serves as an indispensable front‑line pre‑treatment unit for commercial‑scale rCB grinding‑and‑classification workflows. It safeguards expensive downstream processing equipment, lowers maintenance costs, and enables high‑purity feedstock for high‑performance recovered carbon black output. Without this step, stable mass‑production of qualified rCB would be practically unachievable.
