Crude pyrolysis char from waste tire pyrolysis comes out of the reactor as a very broad mixture of lumps, agglomerates and fine powder. Before entering the main grinding system (ACM classifier mill, fluidized bed jet mill or other ultrafine mill), it goes through pre‑crushing, magnetic separation and screening to reach a controlled feed size. The target feed size varies depending on mill type.
Standard Feed Size for ACM / Classifier Mill (Most Common rCB Line)
For commercial ACM air classifier mills, the pre‑treated pyrolysis char feed is normally controlled to ≤ 2–5 mm.
- Most of the feed mass is fine porous agglomerates in hundreds of microns (roughly 100–500 μm), mixed with small hard char lumps up to 2–5 mm.
- This size range is optimized for the high‑speed hammer impact zone. Lumps larger than 5 mm will reduce grinding efficiency, cause rotor overload and increase liner wear.
Feed Size for Fluidized Bed Opposed Jet Mill
Jet mills have stricter feed requirements, because oversized chunks disrupt fluidization and abrade nozzles.
Typical feed size: ≤ 1–2 mm, with majority below 1 mm.
Large lumps cannot form stable fluidized particle beds, so secondary fine crushing is required before jet milling.
Raw Reactor Char (Before Pre‑Crushing)
Directly from pyrolysis reactor, raw char can contain lumps up to 20–50 mm, with a wide PSD from coarse chunks down to fine dust. This raw char cannot be fed directly into the main mill. Pre‑crushing and sieving is mandatory to break down large blocks and remove oversize debris.
Important Note: PSD vs Lump Size
When we talk about feed size entering the rCB grinder, we refer to maximum lump dimension, not the primary particle size.
The porous char agglomerates already have nanoscale primary carbon black spheres bonded together; the grinding system’s job is de‑agglomeration, not breaking the original carbon nanoparticles.
Why Feed Size Control Matters
- Equipment protection: Pre‑crushing removes large hard lumps and, paired with magnetic separation, prevents steel fragments from entering the mill.
- Stable feeding: Uniform feed size maintains consistent material bed and air flow, stabilizing particle‑size output.
- Energy efficiency: Feeding oversized material increases power consumption and shortens service life of rotors, liners or jet nozzles.
Quick Reference Table
| Mill Type | Typical Max Feed Size | Dominant Feed Fraction |
|---|---|---|
| ACM Air Classifier Mill | ≤ 2–5 mm | 100–500 μm agglomerates |
| Fluidized Bed Opposed Jet Mill | ≤ 1–2 mm | <1 mm porous agglomerates |
| Raw char out of pyrolysis reactor | 20–50 mm lumps | Very broad PSD |
The standard feed entering an rCB ACM classifier mill is limited to 2–5 mm maximum lump size, with most material as porous agglomerates of hundreds of microns. For fluidized bed jet milling, feed must be finer, capped at 1–2 mm. Raw pyrolysis char with large lumps requires pre‑crushing and screening before it can be fed into any ultrafine grinding circuit.
