Removal of Inclusions from Molten Aluminium by Flotation in a Stirred Reactor: A Mathematical Model and a Computer Simulation

摘要

Inclusions removal by flotation in mechanically agitated vessels is widelynused in liquid aluminium treatments. Originating from different sources (oxidenskins, refractory or recycling wastes), inclusions may have disastrous repercussions,nsuch as physical properties alterations of the final products or difficultiesnduring forging processes.nWith the aim of both a better understanding of the physical processes acting duringnflotation and the optimization of the refining process, a mathematical modelling ofnthe behaviour of the inclusions population has been set up. Agglomeration, flotationnand settling of inclusions are considered here. The model is divided in twonsteps: a 3D calculation of the biphasic liquid aluminium/bubbles fluid flow basednon an Euler/Lagrange approach and a population balance. The population balancenis performed with the assumption of a perfectly stirred reactor, and the calculationnof agglomeration and flotation rates relies on mean values of fluid flow propertiesnprovided by the CFD simulation. Kruis & Kusters’ model is employed for thencalculation of the agglomeration rate and Kostoglou’s model is used for the flotationnrate. The fixed pivot method of Kumar & Ramkrishna is employed for thenresolution of the population balance equation.nA laboratory scaled flotation vessel is modeled and results of a simulation arenpresented.