Aerodynamic characterisation of fluffed pulp for ozone delignification at high consistency

The aerodynamic specific surface area (ASSA) of fluffed pulps was measured and used to characterise the state of aggregation or fluffiness of these pulps. The development of ASSA of a pulp in a high shear blender depended on fluffing time, pulp type and Kappa number. The development of ASSA reached a maximum within 20 seconds of fluffing. The presence of lignin in fibres appeared to improve the development of ASSA during fluffing. The development of ASSA also depended on pulp type. Fluffed E. globulus kraft pulps had a higher ASSA than fluffed E. nitens kraft pulps when subjected to the same fluffing time. Inadequate pulp fluffing before ozone bleaching at high consistency could lead to a highly non-uniform bleaching effect.