(562f) Influence of Particle Size Distribution on the Separation Processes in Decanter Centrifuges

The mechanical fluid separation is widely applied in the processing industry. Almost all processes which are handling finely dispersed particles in the liquid use unit operations, such as the filtration, the thickening or the centrifugation, for the separation of both phases. Centrifuges generate high mass forces. This also allows to separate submicron particles. At this point, especially continuously working decanter centrifuges are widely applied. The screw conveyor system within the centrifuge permits the change in the process parameters in a wide range. The design of centrifuges is limited to simplified assumptions for the machine and the process parameters [1]. The calculation of the separation efficiency takes not into account the sediment build-up, real flow conditions or bulk transport.

We developed a 2D-model for the calculation of the separation efficiency within decanter centrifuges. The current model describes the behaviour of the apparatus by material and machine functions. The material functions consider the behaviour of the particulate system such as, sedimentation velocity distribution, sediment build-up and transport of the sediment. These material parameters are empirical parameters and measured in well-established laboratory equipment. The machine functions represent the time-dependent behaviour of the machine. The 2D-modelling approach can be used for a better prediction of the process behaviour of the machine. The model does not only considering the sedimentation of the particles, but also the whole behaviour of the centrifuge. The results of the numerical simulations are validated with different experiments. The investigations were performed with a lab decanter centrifuge.

The financial support of DFG (German Research Foundation) within the priority program SPP 1679 "Dynamic simulation of interconnected solids processes DYNSIM-FP" is gratefully acknowledged."

[1] M. Gleiss, H. Nirschl: Modeling Separation Processes in Decanter Centrifuges by Considering the Sediment Build-up, Chem. Eng. Technol. 2015, 38, No. 10, 1873-1882