Characterising the floc size distribution of flowing pulp suspensions:: from fibre flocculation to sheet formation

The floc size distribution of pulp suspensions flowing in a flat channel is determined by image analysis (binary morphology). Among tested statistical distributions, the Weibull distribution is the best descriptor for floc size distribution, over a wide range of papermaking conditions: hardwood/softwood mixtures with consistency ranging from 3.5 to 9.5 g/L and estimated shearing level ranging from 240 to 960 s(-1). Results are analysed in terms of shape and scale factor of the model distribution and floc coverage in the image. Then, the corresponding sheet formation index is calculated, using the Farnood et al floc layering model at various inspection sizes. It is shown that the relationship between the flocculation index and the calculated sheet formation index is not expected to be linear.