Advances in Water Treatment and Enviromental Management

Chapter 16COLLECTION EFFICIENCY OFLIQUID/LIQUID HYDROCYCLONESJ Woillez (Centre d’Etudes et de Recherches de Grenoble,France)SUMMARYWhen reduction of weight and size of oily water treatement installations is needed, liquid/liquid hydrocyclones can be used instead of settlers. An analytical model is proposed for theprediction of the collection efficiency of hydrocyclones adapted to the treatment of lightdispersions. This model is derived from flow velocity measurements in a cylindricalhydrocyclone using LDA and from modelling of the effects of turbulence. Agreement withexperimental data obtained with oil in water dispersions is good.NOMENCLATUREa : Acceleration (m/s2)b : Correction factorc : Light dispersion concentration (kg/m3)d : Oil droplet diameter (m): Mean inlet droplet diameter (m)D : Cyclone main diameter (m)E : Cyclone efficiencyf : Friction factorK : Swirl decay parameter (m-1)L : Cyclone length (m)n : Exponent of vortex lawni : Number of droplet of diameter diQ : Main flow rate (m3/s)q : Extraction flow rate (m3/s)r : Radial distance from cyclone axis (m)R0 : Cyclone main radius (m)Re : Droplet Reynolds numbert0 : Unitary shear stress at the wall (N/m2)U : Axial flow velocity (m/s)V : Tangential velocity (m/s)V0 : Tangential velocity at the wall (m/s)Ve : Inlet velocity (m/s)Vs : Tangential velocity at the end of the separation chamber (m/s)W : Droplet migration velocity (m/s)x : Axial distance along cyclone axis (m)µ : Water viscosity (Kg/m.s))δ : Water density (Kg/m3)∆δ : Density difference between light and heavy liquid (kg/m3)© 1991 Elsevier Science Publishers Ltd, EnglandWater Treatment- Proceedings of the 1st International Conference, pp. 165–172165