Carbopol as a model fluid for studying mixing of pulp fibre suspensions

The selection of operating conditions for a geometrically scaled 1:18 laboratory pulp stock chest in which aqueous carbopol solutions were chosen as the model fluid is detailed. These transparent solutions permit the use of optically based techniques to measure velocity profiles throughout the vessel and thus enable validation of computational models. To ensure that the carbopol solutions mix similarly to pulp fibre suspensions at the new scale it is necessary to select a mixing criterion for conservation. The dimensionless cavern size was chosen as the conserved quantity, although the implications of scaling based on other criteria were also examined. The fibre suspensions and carbopol solutions were modelled as Herschel–Bulkley fluids, based on laboratory measurements.