Modelling fibre loss by entrainment during flotation of flocculated pulps

The loss of wood fibres and fines in the foam phase during flotation was modeled by assuming that fibres present as flocs would not fit in the interbubble spacing in the foam. Thus predicting the loss was reduced to predicting the fraction of fibres and fines that were not flocculated. Flocculated fibre suspensions were assumed to be a binary aqueous suspension of uniform flocs and unflocculated fibres and fines. The volume fraction of flocs, the solids concentration in the flocs, and the fraction of fines in the flocs were modeled using three empirical adjustable parameters. In an effort to account for the variation of flocculation behaviour with fibre type, the volume fraction of flocs was related to experimentally determined sedimentation behaviour of quiescent fibre suspensions. A variety of experimental entrainment behaviours were predicted by the model.