Paperboard Food Contact Declarations and Recycled Fiber Traceability
Food contact safety for recycled board requires functional barrier proof and complete chain of custody documentation down to invoice line items.
De-Inking Flotation Cell
Pulp Separation
A de-inking flotation cell is a specialized mechanical vessel that separates printed ink particles from repulped paper slurry by injecting microbubbles into an aerated suspension. Hydrophobic ink agglomerates attach to rising gas bubbles while hydrophilic cellulosic fibres remain in the liquid phase. Air injection rates govern collision efficiency between mineral-coated ink specks and rising gas phases within the mixing chamber.
Surfactant chemistry lowers surface tension to facilitate selective attachment without degrading physical strength properties of recovered cellulose.
Reject Extraction
Separated contaminants migrate upward into a stable foam layer that overflows a weir at the vessel lip for continuous removal. Overflow consistency depends on stable froth density management rather than mechanical skimming intensity. Heavy mineral fillers and unbonded coatings occasionally settle toward the bottom cone for separate drainage through an automated purge valve.
Wash water sprays suppress premature foam collapse inside the collection trough to prevent settled ink particles from re-entering the cleaned stock slurry.
Yield Optimization
Minimizing fibre loss during flotation requires precise control over pulp consistency, reagent dosage and hydraulic retention time inside the recovery circuit. Excessive turbulence shears fragile ink agglomerates back into colloidal dimensions that evade bubble capture and lower final brightness targets. Secondary cleaning stages process primary rejects to recover valuable long fibres while discharging heavily pigmented sludge fractions to the wastewater treatment plant.
Optimized air-to-solid ratios maintain high brightness gains without increasing chemical consumption beyond economic limits for packaging paper production.