Grant: Collaborative Research and Development Grants

The focus of the present work is the study of separation or fractionation of different classes of non-Brownian particles in a yield stress fluid. The motivation for the present work stems from an interest in one particular particle suspension, i.e. papermaking fibre suspensions. Papermakers fractionate to allow targeted processing of the low quality fraction to improve product performance while minimizing the amount of processing and subsequent energy, chemicals and capital required. The pulp fractions can also be used to produce papers with radically different properties. There are essentially two industrially methods to fractionate pulp fibres in use today: pressure screens and hydrocyclones. The efficiency for fractionation in both hydrocyclones and pressure screens is known to be relatively low. The inherent separation potential is not realized because of the complexity of the flow within these devices. A stochastic element is introduced into the system through turbulence, the presence of boundaries, flocculation, and long range hydrodynamic interactions and these effects diminish the efficiency of the separation process. In previous work we proposed a new principle for fractionation by studying the motion of particles in a viscoplastic fluid. Here we show that fractionation can indeed proceed based on either length, diameter or density in a mechanistic fashion. In this proposed project, we will continue our line of research work and develop a continuous process, in collaboration with EKA, for the separation of papermaking fibre suspensions as well as other gels that contain papermaking fibres. The work will be mostly experimental and will be staffed by one PhD and 3 summer students.