Discrepancies in High Yield Pulp Mass Balance Calculations across Multi Ply Board Mills
High yield pulp mass balances fail when mills exclude white water solubles and moisture variation, exposing buyers to chain of custody audit liabilities.
Retention Aids
Wet End Flocculation
Papermaking stocks contain fine fibres and mineral filler particles that can pass through the forming fabric during drainage. Chemical additives known as retention aids bind these small materials to the larger wood fibres before the slurry reaches the wire. This reduces the solid load in the recycled water loop.
Polymer Reaction Mechanism
High molecular weight polymers act by forming bridges or electrostatic bonds between the negatively charged surfaces of the stock components. Anionic and cationic polymers are often applied in tandem as dual polymer systems to maximize the catch of fine particles. The performance of retention aids depends on the shear forces present in the headbox and the stock pumps, which can break the polymer chains.
When these chains are sheared, the efficiency of the flocculation decreases, requiring careful selection of the addition points.
Production Run Effect
Optimizing the addition of these polymers prevents the buildup of deposits on the machine fabric and improves the lifespan of the dewatering elements. If retention aids are over-dosed, they cause excessive flocculation which leads to poor paper formation and uneven sheet weight. If they are under-dosed, high concentrations of fillers escape into the water loop, increasing the risk of sheet breaks and drainage blockages.
Monitoring the white water consistency allows operators to balance the polymer dosage during the production run.