The contribution of different fractions of fines to pulp drainage in mechanical pulps

The relevant contribution of fines, colloidal and dissolved materials to pu lp drainage were evaluated by various types of pulp with whole fines and co arse fines: the interactions among those components were investigated as we ll. It was found that drainage was impaired more by the presence of ultra-f ines than by the dissolved pulp components in the white water. The interact ions occurred between thermomechanical pul (TMP) coarse fines and ultra-hig h-yield sulphite pulp (UHYS) ultra-fines, which is a major cause of poor dr ainage. A physical mechanism in which sulphonated microgels adhere to the s urface of TMP fines, and cause interparticle repulsion and fines dispersion , is proposed.