A Computational Analysis of Multiphase Flow Cyclonic Separator for Clean Combustion in Power Plants

In this paper a numerical computation of the flow dynamics in a compact cyclonic separator (CCS) for multiphase mixtures is presented. The study is directed to power plants consumption requirements where fuel gas must be free of solid particulate. A finite volume approach has been employed with body-fitted coordinates in a 3-D solution of the CCS dynamics. The cylindrical geometry under study includes aspect ratios in the range 2.5<R<3.8 (where R = height/diameter). The CCS has three exits as follows: one on the top for gas; one on the bottom for low particle concentration liquid; and the last one tangentially located on the lower part of the CCS for high particle concentration liquid. The turbulence was resolved using a RNG model, while the interactions between each component of the flow were addressed using a mixture slip model. The three-phase liquid-gas-solid mixture considered was gasoil-propane-mineral coal particles with the composition in volume fraction of liquid to gas of 0.9 to 0.1 in addition to 109 kg/m³ of 40 microns coal particles as the disperse phase. The results indicate that reversible flow of liquid through the upper gas-outlet may be a function of the outlet pressure conditions. Also, velocity conditions of the income mixture flow at the inlet defined the residence time of the flow during the operation of the CCS, which affects the separation too. In this work density profiles are shown to indicate the regions of up flow for gas and liquid drag. The presence of a third phase in the form of solid particles affects the flow patterns in a CCS.