Filter aids are used for suspensions that prove hard to be filtered. Such systems often contain impurities that tend to block the filter medium, e.g., gelatinous particles. One widespread mode of filter-aid usage is called body filtration. In this mode, a precoat layer, composed of filter-aid particles, is first built on the filter medium. Subsequently, filter aids, called body feed, are constantly dosed to the suspension. The body feed creates a permeable filter cake, leading to a reduced pressure drop and, therefore, less energy consumption. Appropriately choosing the body-feed concentration is decisive for a successful filtration operation.
To address this issue, a new mechanistic model for filter-aid filtration is used to determine the optimal body feed concentration. The model is based on continuum mechanics and considers the mechanisms of surface and depth filtration; filter cakes are assumed to be incompressible. In a first step, the model is simplified so that only surface filtration is taken into account and an analytical solution for the optimal body feed that minimizes energy consumption is shown. Secondly, the full model is used for computational optimization; again, the body-feed concentration for minimal energy consumption is determined. It is found that...
Session: L13 - Process Optimization
Day: 15 March 2018
Time: 10:45 - 12:00 h