Modelling of 75- and 250-mm hydrocyclones and exploration of novel designs using computational fluid dynamics.

摘要

The hydrocyclone is widely used in the chemical and mineral industries. The success of hydrocyclones is that it can separate immiscible liquids, remove solids suspended from a slurry, thicken slurries, separate particles by specific gravity and classify particles by size. In this work, the application of hydrocyclone in the mineral industry is studied.; The computational fluid dynamics (CFD) modeling is applied on predicting the flow split, air-core dimensions, and size classification. This model is intended to be a useful tool in studying dimensions and, more importantly, alternate geometries for the design of hydrocyclones. The air-core dimension is the key parameter in the model to predict the mass split between the underflow and overflow. In turn, the mass split influences the prediction of the size classification curve.; Three models, the renormalization group kappa-&egr; model, the Reynolds stress model, and the large eddy simulation model, are compared for the predictions of air-core dimension, mass split, velocity fluctuations, and axial and tangential velocities. The large eddy simulation model, which produces some detailed features of the turbulence, is clearly closer in predicting the experimental data than the other two. It is shown that particle tracking done with the velocity field obtained from the large eddy simulation model accurately predicts the experimental size-classification curve for different slurry concentrations. Furthermore, the large eddy simulation model captures the changes in the dynamics of the flow when the geometry is modified.; The LES model was validated with experimental data on 75- and 250-mm diameter hydrocyclones. Such validation shows that LES model is capable of capturing the turbulent momentum transfer within hydrocyclones. Twenty-six different validation cases are presented for the 75-mm hydrocyclone and 5 for the 250-mm hydrocyclone.; The modification of the standard geometry was explored, leading to six variants of the basic design. Of the six, two designs seem to have improved the hydrocyclone performance. This thesis paves the way for studying alternate hydrocyclone geometries readily using LES based CFD.; The work presented in this thesis was limited by available computing power. A single simulation took three weeks for the 75-mm hydrocyclone and five weeks for the 250-mm hydrocyclone. Had this computational time not been so great, typical industrial hydrocyclones of 625-mm could have been studied in detail.