Systematization, description, and evaluation of imperfections in the displacement washing of filter cakes

The displacement washing of filter cakes is an established, cost-effective method for separating dissolved impurities or valuable substances from a filter cake. During this process, a washing liquid flows through the filter cake, displacing the mother liquor. This goal is to be achieved reliably and with the lowest possible effort (washing liquid, washing time, filter area).

The design and operation of displacement washing are generally based on well-defined laboratory tests (well-defined geometry, cake homogeneity, alignment, washing liquid application, filtrate discharge, etc.). In the actual process, however, these assumptions are only inadequately met. It remains unclear whether and to what extent these imperfections influence the course of the displacement washing and how this affects design, dimensioning, and operation. This is the starting point of the project. There is a need for a reliable transfer to real-world processes, which can be unpredictably dominated by imperfections.

The project focuses on imperfections in a) the filter cake, b) the contact area between the washing liquid and the filter cake, and c) the filtrate discharge. Due to the large number of possible imperfections, a prioritization will be carried out within a systematic variant study. These will be investigated using specially adapted laboratory nutsche filters (57 cm²) as well as theoretical models. Central to this approach is the reproducible creation and characterization of imperfections. The model calculations will be validated or revised based on the measurement results.

In the second step, selected scenarios will be investigated on an indexing belt filter (0.1 m²; from project 20687 N) to verify the transferability of the findings obtained thus far. The competitiveness of SMEs on the manufacturer, supplier, and user side is enhanced by these research findings. The design and operation of such processes can be executed faster, more securely, and in a cost-optimized manner.