The reliable and optimal operation of Filter Centrifuges is in many cases a challenge. The reliable prediction of the centrifuge performance based on praxis oriented (half empirical) equations for the cake formation, cake washing and cake deliquoring step with minimal number of systematic tests is a great help for the proper centrifuge design, the optimal operation but also for the performance judgment and troubleshooting for filter centrifuges already in operation. Such mathematical models are the basis of the CENTRISTAR software. This novel program enables among others the simulation of the performance of Batch Filter centrifuges as well as the analysis of laboratory and pilot test data. Guided by the theory, the systematic experiments are reduced to a minimum, because only those tests are needed, which are necessary for the determination of the equations adaptation parameters (the so-called efficiency parameters).

The most important efficiency parameter is the cake permeability p_c (or the cake resistance r_c with r_c=1/p_c) because this parameter influences not only the cake formation step but also the optional steps of cake washing and cake deliquoring. The higher the p_c-value, the higher he centrifuge performance. The cake permeability p_c is not a constant parameter but depends on the centrifugal pressure (Dp_c) and the cake compressibility (n_c):..

In this paper, the influence of the cake compressibility on cake formation, cake washing and cake deliquoring in filter centrifuges will be presented. The cake compressibility n_c can have values from 0 to 1. A value of n_c=0 means a not compressible cake and n_c=1 means maximal cake compressibility. The prediction of the centrifuge performance for different rotational speeds (that means for different centrifugal pressures Dp_c) requires the calculation of the cake permeability p_c and this requires reliable values for the cake compressibility (see above equation). Besides the influence of the cake compressibility on the dry solids mass rate (q_ms), the cake moisture content (Rf) and the cycle time (t_c), the method for the determination of the cake compressibility via analysis of tests will be discussed. For a given application, by not considering the cake compressibility or by using wrong compressibility values means that any performance prediction for different rotational speeds will be not reliable. In fig. 1 a screenshot of the Tables & Charts module of the CENTRISTAR software shows for a given application how the cake compressibility can influence the cake moisture content, the specific dry solids rate and the cycle time. The higher the ...