In cake forming filtration of suspensions, we are interested in having a reliable selection, design and optimization of the selected filter equipment with minimal experimental effort. The lack of reliable and user-friendly theory-based analysis of filtration data leads to unsystematic experimental procedure in laboratory scale. This leaves no possibility to judge the experimental results and do data correction in order to get reliable filtration efficiency parameters. Furthermore, the empirical approach for the characterization of the suspensions with regard to the filtration behavior in pilot-scale tests is time consuming and uneconomical. This is due to the relatively many unsystematic tests.

The determination of the filtration parameters using a novel and theory-based laboratory experimental approach, which enables to get maximal information from minimal number of tests, will be discussed. Questions like, which experimental settings are necessary, how test results can be plotted and analyzed based on practical equations, and how correct filtration parameters can be determined even with simple apparatuses, will be answered. Emphasis will be given to the correct determination of the filtration efficiency parameters: cake permeability (p_c0), cake compressibility (n_c), filter medium resistance (Rm₀) and filter medium compressibility (m_c).

Three methods (equations) for analyzing cake forming filtration data will be presented and discussed: The integral, the “general” integral and the differential cake formation equation...

With: p_c0, n_c, R_m0, m_c the parameters for the characterization of the filtration efficiency of a given suspension. The specific filter medium resistance h_ce is determined from the absolute filter medium resistance as follows: h_ce=p_c*R_m. It will be explained, why is important to use the h_ce-parameter and why with practical accuracy a constant value can be used. The above three filtration test data analysis methods will be compared by demonstrating representative examples of laboratory filtration tests. important conclusions for the practical use of the above methods will be presented. It will be finally explained why the reliable determination of the above filtration parameters is a real challenge...