Reasonable feed particle size is the basic premise to guarantee stable milling efficiency, finished powder quality and equipment service life of recovered carbon black (rCB). Excess coarse materials easily cause roller and liner wear, blockage and uneven grinding; overly fine raw materials will lead to dust overflow, reduced classification accuracy and increased energy consumption. Different grinding equipment and downstream application scenarios correspond to matched ideal feed particle size ranges.
1. General Ideal Feed Particle Size Benchmark
For conventional rCB fine grinding and ultrafine grinding production line, the universal qualified feed particle size standard:
- Optimal feed size: 2 mm ~ 10 mm
- Maximum allowable particle size: ≤15 mm
- Prohibited oversized lump: Lump diameter over 20 mm is forbidden to feed directly
After pyrolysis, raw rCB often contains agglomerated blocks, rubber residues and impurities. It must be pre-crushed to reach the above range before entering formal milling process.
2. Ideal Particle Size Matching Different Grinding Equipment
| Grinding Equipment Type | Ideal Feed Particle Size | Adaptation Features |
| Ring roller mill / Raymond mill | 3 mm ~ 8 mm | Most mainstream model, stable grinding effect, suitable for conventional fineness production |
| Vertical roller mill | 5 mm ~ 10 mm | Large processing capacity, high requirement on uniform feeding size |
| Ultrafine impact mill | 2 mm ~ 5 mm | Fine feed required, used for high mesh ultrafine rCB powder |
| Batch small grinding equipment | 2 mm ~ 6 mm | Small output, strict control on oversized materials |
3. Feed Size Standard Divided by End Product Fineness
Adjust raw material particle size according to finished powder mesh requirement, to maximize grinding efficiency:
- Coarse grade rCB (300~800 mesh) Ideal feed size: 8 mm ~ 10 mm, properly larger feed particle size can improve unit output
- Medium fine grade rCB (800~1500 mesh) Ideal feed size: 4 mm ~ 8 mm, balanced grinding speed and powder uniformity
- Ultrafine grade rCB (1500~3000 mesh) Ideal feed size: 2 mm ~ 4 mm, fine and even feed to avoid incomplete grinding
4. Influence of Unqualified Feed Particle Size
4.1 Excess coarse feedstock
- Cause strong impact wear on grinding roller, ring plate and liner, shorten spare parts service cycle
- Material grinding incompletely, finished particle size uneven, poor product stability
- Easy to cause equipment jamming, frequent shutdown cleaning and production loss
4.2 Excess fine powdery feedstock
- Material slips in grinding cavity, insufficient rolling force, reduced grinding yield
- A large amount of fine dust enters classification system in advance, disturb particle grading
- Increase dust treatment pressure and raise production safety risk
5. Pre-treatment Process to Reach Ideal Particle Size
- Primary screening: Remove large foreign matters, metal impurities and oversized hard blocks
- Secondary crushing: Use jaw crusher or hammer crusher to crush agglomerated rCB blocks
- Secondary sieving: Screen crushed materials, return oversized materials back to crushing process
- Homogeneous feeding: Keep feed particle size stable within ideal range before conveying to mill
6. Field Inspection & Control Method
- Regular sieve inspection: Use standard sieves to detect particle size of feeding materials per shift
- Visual inspection: No obvious large hard blocks, rubber bulk and irregular impurities in feed
- Linkage adjustment: Adjust crusher gap timely if feed size deviates from standard
7. Core Summary
- The most widely applicable ideal feed particle size of rCB raw material is 2 mm ~ 10 mm
- Match specific particle size range according to grinding equipment and finished powder fineness
- Strictly control oversized materials through pre-crushing and screening, avoid abnormal wear and unstable quality
- Uniform and qualified feed size can effectively lift milling efficiency, reduce energy consumption and improve finished rCB performance