Fundamental Research on Deep Bed Filtration of Metals

摘要

Increasing demands on metal quality have led to the fact that filtration is a standard operation in aluminium foundries. Ceramic foam filters and classical deep bed filters are commonly used. By now, there is no theoretical platform describing deep bed filtration mode comprehensively. Working conditions for filters are only based on empirical data. The aim of this work is to describe mechanisms that occur inside ceramic foam filters in general. Two types of water models are used to achieve this: a full-scale model of an actual filtration box and a one-channel model that simulates one channel in a ceramic foam filter. For comparison also a deep bed filter is tested. Especially flow velocity is crucial for the performance of a filter since this parameter allows particles to be deposited and retained inside the filter but also causes detachment of particles. Furthermore it is found that at flow velocities, which are applied in practical use, there are already turbulent conditions predominant in large parts of the filter. In these areas particles may not be deposited and already detached particles can be washed out. Even singular perturbations like vibrations or uneven metal flow can cause particle detachment. Optimal and even flow conditions are therefore required for high filtration efficiency.