Removal of fine-grained and thin filter cakes by a counter-current backwash treatment

In industrial solid/liquid separation, the removal of fine particles (≤ 10 μm) in a suspension with a low solids content (0.01-1 v/v %) is a challenging and demanding task. This application takes place in a wide array of industrial production such as metal processing and treatment industries. In order to achieve the required purity, different types of filters like candle and leaf filter can be used. In Figure 1, the commonly used candle filters are shown inside the vessel (a), during filtration (b), and cake removal (c). In respect of the field of applications, the procedure of removal has revealed that there is potential for improvement in pressure difference and amount of backwash reflux. These process variables highly depend on the material properties like cohesion within the filter cake and adhesion of the filter cake onto the filter media. In order to guarantee the removal of the filter cake, the applied removal force has to be larger than the adhesive forces. Furthermore, to remove the filter cake in large fragments, the removal force has to be lower than the cohesive force. These two effects also depend on porosity, pH-value, and further properties; they can be reflected by and measured as shear and tensile strength of the filter cake. ... mehrCurrently, the amount of backwash reflux is oversized and leads to an operating point below the optimum. Hence, research must be carried out how to improve the backwash treatment in respect of the process conditions in an economic and process-technical context. This presentation comprises a state-of-the-art review of the current backwash filters and differentiate between the various physical principles of cleaning process. Moreover, the project and experimental facility will be presented, followed by first results.