Filter aids are used for systems that prove hard to filter. Such systems often contain impurities which tend to block the filter medium, e.g. substances that differ widely in their properties or 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. On the one hand, too little body feed leads to a pronounced clogging of the filter cake and, therefore, high pressure drop as well as energy consumption. On the other hand, too much body feed causes rapid cake growth which also results in increased pressure drop and energy consumption. Between these two factors the optimum is to be determined.
In this contribution, 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 the optimum body feed dosage is calculated analytically so that energy consumption is minimal . 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