How to Separate Ultra-Fine Particles from Calcined Coke During Shaping

Calcined coke is hard, brittle and highly abrasive. During shaping in the JCSM-V circulating spheroidizer, edge friction continuously generates ultra-fine debris. If these ultra-fines remain mixed with near-spherical calcined coke precursors, D10 will drop, BET surface area rises sharply, tap density becomes unstable, and the final graphite anode suffers high electrolyte consumption and low initial coulombic efficiency. The goal is online continuous removal of ultra-fines during spheroidization, rather than only post-processing separation. JACAN JCSM-V integrates built-in dynamic classification, fine extraction airflow and secondary classification to isolate ultra-fine coke without losing qualified near-spherical product.

Source & Risks of Ultra-Fines in Calcined Coke Shaping

Ultra-fine particles are produced by abrasive edge chipping and brittle fracture of calcined coke during particle-to-particle rubbing.

• Too many ultra-fines: D10 decreases, PSD span widens, BET increases.
• Fines easily re-adhere onto shaped particle surfaces when moisture is high.
• Excessive fines create false high tap density, misleading quality judgement.

Core Separation Principle

The JCSM-V closed-loop system uses centrifugal force from the built-in dynamic classifier plus adjustable airflow to split powder into three streams simultaneously:

1. Under-shaped coarse calcined coke: returned back to the shaping chamber for re-polishing.
2. Qualified near-spherical calcined coke (D50 6–18 μm): sent to product collection.
3. Edge-generated ultra-fine debris: carried by fine extraction airflow out of the shaping loop and captured separately by dust collector.

Step-by-Step Method for In-Line Ultra-Fine Separation During Shaping

1. Pre-remove excess fines before entering JCSM-V

Do not rely entirely on the spheroidizer for fines removal. The upstream air classifier mill must strip most pre-existing ultra-fines before feeding calcined coke powder into the shaping machine.

• Control calcined coke moisture ≤0.3%. Adsorbed moisture causes agglomeration; agglomerated fines stick on particles and escape separation.
• Install magnetic separators upstream to remove metal impurities, which cause random particle breakage and extra fine generation.
• Keep feed PSD span ≤0.9. A broad incoming PSD increases the fine load entering the spheroidization loop.

2. Built-in dynamic turbo classifier inside JCSM-V (primary separation)

This is the core online fine separation unit during shaping:

• Adjust classifier wheel rotational speed and airflow to define the fine cut point.
• Increase classifier wheel speed: stronger centrifugal interception; only ultra-fine fragments can pass through with airflow into the fine collection circuit.
• Avoid excessive classifier speed, which will carry medium-sized qualified calcined coke into fines and reduce product yield.
  The classifier differentiates intact near-spherical particles from tiny abrasive fragments.

3. Tune fine extraction airflow and negative pressure balance

Airflow acts as the carrier to transport ultra-fines away immediately after generation.

• Increase fine extraction airflow to boost submicron and micro-fines capture capacity.
• Avoid over-high airflow that entrains qualified medium particles.
• Maintain stable full-system negative pressure. Pressure fluctuation triggers fines back-mixing and unstable separation efficiency.
• Proper airflow cools the chamber and reduces static adhesion of fine coke powder.

4. Secondary air classification after JCSM-V (polishing separation)

For high-spec anode precursors, add an independent multi-stage air classifier downstream:

1. Coarse separation: intercept residual under-rounded coarse particles and return them to JCSM-V.
2. Fine cutting: further strip residual ultra-fines that bypassed the built-in classifier.
   This two-stage classification greatly stabilizes D10 and compresses PSD span.

5. Pulse dust collection for isolated ultra-fine collection

Ultra-fine coke carried by airflow enters high-efficiency pulse bag dust collectors with fine filter media. Separated ultra-fines are collected as by-products and isolated from qualified product. Regular filter bag cleaning prevents blockage, pressure drop and fines re-contamination.

Parameter Tuning Rules for JCSM-V

1. Main rotor speed: Keep at the minimum speed to reach target sphericity (0.80–0.86). Higher rotor speed fractures calcined coke and generates more ultra-fines, overloading the classification system.
2. Classifier wheel speed: Raise moderately to enhance fines interception; reduce if qualified product loss occurs.
3. Fine extraction airflow: Increase when D10 drifts down; reduce when yield loss appears.
4. Circulation cycles: Avoid redundant circulation passes, which continuously produce more abrasive fine debris.

Common Troubleshooting

1. Ultra-fines cannot be fully separated, D10 continuously drops
   Cause: Insufficient fine extraction airflow; improper classifier cut point; rotor speed too high generating excess fines.
   Solution: Boost fine extraction airflow, adjust classifier wheel speed, reduce main rotor speed.
2. Product yield loss; qualified calcined coke is discharged with ultra-fines
   Cause: Extraction airflow too high or classifier wheel speed too high.
   Solution: Reduce airflow and moderately lower classifier speed.
3. Fines re-adhere onto particle surfaces
   Cause: Feed moisture exceeds 0.3%.
   Solution: Re-dry calcined coke and control air humidity of the system.
4. Fines accumulate inside shaping chamber
   Cause: Unstable negative pressure or blocked filter bags.
   Solution: Clean filter bags, inspect fans and stabilize negative pressure.

Separating ultra-fine particles from calcined coke during shaping uses a staged strategy: pre-fines removal by upstream ACM mill, built-in dynamic classification inside JCSM-V, adjustable fine extraction airflow and downstream secondary classification. The system extracts edge-generated ultra-fine debris online during spheroidization, instead of waiting until shaping completes. Operators tune classifier wheel speed and fine extraction airflow while keeping JCSM-V rotor at the minimum speed required for sphericity. This stabilizes D10, controls PSD span and BET, producing qualified near-spherical calcined coke precursors for artificial graphite anode.