Stock Separation
Processing recycled pulp requires separating the mixed slurry into distinct fractions based on fibre length and flexibility. Through fiber fractionation, the stock passes through pressurized screen baskets with holes or slots that separate the long, sturdy chemical fibres from the short, weak hardwood or mechanical fibres. This separation divides the pulp into an accept stream containing the short fibres and a reject stream holding the long ones.
The boundary of this sorting process is defined by the slot width of the screen, which is matched to the specific grade of raw material.
Pulp Utilisation
Papermaking efficiency improves when each fibre fraction is directed to the most appropriate layer of a multi-ply sheet. The long-fibre fraction separated by fiber fractionation is ideal for the outer plies of packaging boards where tensile and bending stiffness are required, while the short-fibre fraction is routed to the core to provide bulk. This targeted distribution optimizes the raw material usage and reduces the dependence on virgin chemical pulp.
It allows mills to produce high-performance packaging from lower-cost recycled sources.
Refining Economy
Energy consumption in stock preparation is optimized by treating only the fibres that require development. Rather than refining the whole pulp mixture, the mill applies mechanical energy solely to the long-fibre fraction. This selective treatment prevents the short fibres from being over-refined and degraded.
