Effects of flocculation and floc trapping on fibre treatment in low-consistency refining

Equations ale developed to describe the number of impacts and the force of each impact on fibres in low-consistency refining. The equations treat the application of mechanical work to the fibres as a floc capture process, cha racterized by the rate at which flocs are captured, and the area and thickn ess of the captured floc. The equations are compared with refining trials o n two radiata pine pulps that had been refined with an Escher-Wyss conical laboratory refiner at three consistencies and three values of specific edge lend. For these refining trials, it was found that rate of floc capture an d the area and thickness of the captured flocs was independent of consisten cy. The expression for the tensile force on fibres in contact with the bar edge was used to develop an index for-fibre shortening in refining. Literat ure data from refining three different softwood pulps and one hardwood pulp were used to show that the fibre-shortening index is strongly correlated w ith fibre length reduction in refining.