Multi phase numerical modelling of thickening and sedimentation
Phenomena that involve the settling of particulates in a host fluid are encountered in many practical systems which find applications in many areas of industry. A numerical model has been developed to simulate the settlement of non-flocculated particulate suspensions in batch sedimentation. The non-flocculated mode of the model is extended to predict the performance of a continuous gravity thickener. The various particle species within the particulate susepnsion are represented as separate phases with distinct concentrations and velocities. A multiphase representation of the settling process gives greater detail of the interactions present between the particulates. The build up of the sediment as well as a prediction of the compression point for flocculated suspensions, is modelled using a revised version of packing theory. The build up of floes in the free setting region is incorporated via population balances. Also, as well as the above theoretical work, experimental work has been undertaken to obtain data for non-flocculated suspensions. For batch sedimentation this data is in the form of density profiles and for the continuous thickener it is in the form of concentration profiles. The proposed model compares favourably with this experimental data and gives closer predictions than does a model representing the state of the art, at this point in time, for non-flocculated batch sedimentation.