Cfd Modelling of a Rapidorr 444 Clarifier: Recent Progress

Past Computational Fluid Dynamics(CFD) work on the Rapidorr 444 required a quantitative check of its accuracy. Factory tracer tests were used to validate the developed CFD model. Since the model was a function of its input, these parameters, particularly juice and mud densities were re-calculated over an entire season and average values used. In addition a new three-dimensional model of the Rapidorr clarifier was created offering improved accuracy and presentation of results but at the sacrifice of increased computation time. Hence this model was used sparingly. Possible structural modifications were tested and evaluated in terms of the diameter of the smallest particle that settled out and the change in juice residence time. A combination of a deflector baffle mounted directly in the path of the inlet flow and a baffle mounted on the scraper arms lead to a quantitative improvement in mud settling at the sacrifice of increased residence time. However, the residence time could be restored either by flow manipulation or further structural modification. The modifications also lead to improved robustness of the Rapidorr at low mud densities.