Recycled fiber pulping lines face unique challenges due to the high content of contaminants such as plastics, stickies, sand, and undispersed fibers. An improperly designed screening system can lead to unstable operation, excessive rejects, frequent downtime, and poor paper quality. Therefore, designing an efficient and reliable screening system is a key step in recycled fiber processing.
Role of the Screening System
The primary functions of a screening system in recycled fiber pulping include:
- Removing coarse and fine contaminants
- Improving fiber dispersion and uniformity
- Protecting downstream equipment
- Providing stable pulp flow for subsequent processes
Coarse Screening: Inward Flow Pressure Screen
Inward flow coarse screens are typically installed in the early stage of recycled fiber pulping lines. Pulp flows from the outside of the screen basket to the inside, allowing large contaminants to remain outside the basket and be discharged as rejects. This design offers strong resistance to plugging and stable operation under high contaminant loads.
Fine Screening: Outward Upflow Pressure Screen
After coarse screening, the pulp enters the outward flow fine screens for detailed purification. In this configuration, pulp flows from the inside of the basket to the outside, achieving higher screening efficiency and better fiber dispersion. The upflow design further enhances the removal of light contaminants by utilizing buoyancy and gravity.
System Configuration Advantages
By combining inward flow coarse screens with outward upflow fine screens, recycled fiber pulping lines can achieve:
- Step-by-step contaminant removal
- Improved screening efficiency
- Stable system operation
- Reduced energy consumption and maintenance costs
An efficient screening system is the foundation of stable and high-quality recycled fiber pulping. Proper configuration of inward flow coarse screens and outward upflow fine screens ensures effective contaminant removal, operational stability, and consistent pulp quality, making it a proven solution for modern recycled fiber lines.
