Drop Breakage And Size Distribution Of Crude Oil-Water Dispersions In Turbulent Flow Field

Drop breakage and size distribution of crude oil-water dispersions in stirred tank is studied by theory analysis and experimental research. With the increase of temperature the crude oil viscosity decrease sharply and interfacial tension increase mildly. Drop distribution and Sauter mean diameter at different impeller speeds at every experimental temperature are measured. The effects of impeller speed and dispersed phase viscosity on drop breakage process and drop size distribution are analyzed. The Sauter mean diameter is found to decrease with the increasing of impeller speed and increase with the increasing of dispersed phase viscosity. The maximum stable drop diameter is in proportion to Sauter mean diameter. Meanwhile, a theory based on Voigt model in which the viscosity of the disperse phase is accounted for are applied for calculating the maximum stable drop diameter of the crude oil-water dispersions. The maximum stable drop diameters calculated based on the Voigt model agree with the experimental ones well.The population balance equation (PBE) model is proposed to predict the Sauter mean diameter. Mostly researcher neglected the effect of dispersed phase viscosity on drop breakage process and the models they built only apply for the dispersions with low viscous dispersed phase. For practicality of highly viscous dispersed phase with such as crude oil is in engineering field, in this paper a breakage rate include dispersed phase viscosity is proposed and a new PBE model are developed, hi this new model, viscous stress of dispersed phase as well as interfacial tension restrains the deformation of drops. The Sauter mean diameters are calculated by this new PBE model. The results are compared with the experimental date in this research well as well as with the experimental data in other literatures.It should be noted that at low temperature the crude oil as dispersed phase in this study shows obvious thixotropy. As the breakage time is very short compared with the time in which the viscosity approaches equilibrium one, the initial viscosity is considered to be constant in the droplet breakage process. The calculated data agree with the experimental ones well.