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A mechanical separation process in a de-oiling hydrocyclone is described in which disperse oil droplets are separated from a continuous water phase. This separation process is influenced by droplet breakage and coalescence. Based on experimental data and simulation results in a stirred tank, a modified breakage model, which can be applied to droplet breakage in the de-oiling hydrocyclone, is developed. Then, a simulation model is developed coupling the numerical solution of the flow field in the hydrocyclone based on computational fluid dynamics (CFD) with population balances. The homogenous discrete method and the inhomogeneous discrete method are applied for solving the population balance model (PBM). The investigations show that the numerical results obtained by the simulation model coupled with the modified PBM using the inhomogeneous discrete method are in good accordance with experimental data under a high flow rate. According to this simulation model, the effect of three different inlet designs on the separation efficiency of the de-oiling hydrocyclone has been discussed. The results indicate that the separation efficiency of the de-oiling hydrocyclone can be improved with an appropriate inlet design. [ABSTRACT FROM AUTHOR]

Water-in-oil emulsion destabilization and separation in a batch gravity separator was investigated experimentally and by numerical modeling. A multiphase computational fluid dynamics (CFD) was used with a population balance model (PBM) to model separation behavior of crude oil emulsions. The inhomogeneous discrete method is used to solve the population balance equations. Closure kernels are applied to model droplet–droplet coalescence. To describe the increase in emulsion viscosity with water concentration, an emulsion viscosity model was selected that predicted emulsion stability and the denser emulsion layer forming above the coalescing interface, otherwise known as the dense packed zone or layer (DPZ). The results from a commercial CFD code are compared to experimental data of the water fraction vertical distribution measured by low-power ultrasound in the batch separator. The predicted time-dependent profiles of water fraction in the separator were found to be in good agreement with the experimental measurements for the range of water content from 6 to 50%. The model predicts the effect of water fraction on the separation kinetics and the evolution of the DPZ. Further studies are underway to apply the models to emulsions from different types of crude oils. [ABSTRACT FROM PUBLISHER]

In this article, emulsification process of liquid-liquid systems was presented, where the emulsification was conducted using ultrasound energy. Mathematical model describing coalescence and droplet breakage phenomena in the ultrasound field based on the model of Laso, Steiner, and Hartland was proposed. [ABSTRACT FROM AUTHOR]

The mathematical model presented in Part I of this article is compared to experimental data obtained from low-field NMR experiments on a heavy crude oil undergoing gravity separation with two different concentrations of a chemical demulsifier. Experimentally measured parameters are used in the model and include a) the water cut and drop size distribution of the emulsion (obtained directly from the NMR measurements), b) the densities and viscosities of the bulk liquids, and c) the interfacial tension; the results obtained from the model were used to analyze the experimental data in terms of these parameters. The model was formulated based on first-principle physical mechanisms, and thus, not only are the fitting parameters are kept to a minimum, good agreement between experiment and simulation results were obtained. The model reasonably predicts both sets of data for the different demulsifier concentrations with no change to the so-called fitting constants, but by the parameter that represents the magnitude of the interfacial force in the film drainage equations. Such a change in this physical parameter can be reasonably inferred by the action of the increased demulsifier concentration. Both the model and experimental NMR data indicate that the degree of poly-dispersity is a key factor in the rate of coalescence and subsequent rate of separation by sedimentation. This analysis illustrates the link between poly-dispersity and the coupling of coalescence and sedimentation rates; this is crucial for determining how different droplet size fractions will affect the overall efficiency of the separation and how physical properties of the fluids and phase interface can amplify or negate these phenomena. The separation model is a very helpful complement to the NMR technique as the model can output direct comparisons to the NMR data. [ABSTRACT FROM PUBLISHER]

A population balance model for the separation of emulsions in a batch gravity settler is presented. Within the context of the model development, possible methodologies were elucidated for incorporating a) the physical properties of the bulk liquids, b) the physical properties of the phase interface, and c) the presence and functioning of interfacially active compounds. The model presented explicitly accounts for interfacial coalescence and the deformation of the emulsion zone due to the dynamic growth of the resolved dispersed phase; interfacial coalescence is modeled in terms of physically meaningful film drainage models and an approach for incorporating the accumulated buoyancy force in the dense packed layer is also discussed. Hydrodynamically hindered sedimentation is also considered in the model. The model is well suited to predict experimental batch settling data, especially data obtained from low-frequency NMR measurements of emulsion destabilization. The model predicts the evolution of the volume fraction of the dispersed phase at any axial position and time in the separator. Furthermore, the model predicts the location of the resolved dispersed phase interface as a function of time. Additionally, for any axial position and time in the settler, the model predicts the evolution of the average number density of droplets, the average volume/radius of droplets, the standard deviation of the droplet volume/radius, and the rate of growth of the droplets. The model is compared directly with experimental data for crude oil separations in Part II of this article. [ABSTRACT FROM PUBLISHER]

A general model for suspension formulation that includes effects of particle breakage and clustering on suspension structure and resulting rheology is applied here to simulate agglomerate dispersion. The model employs the QMOM population balance to simulate variation of agglomerate size and structure in a system of complex geometry. As an example of such system a rotor-stator mixer is applied. Simulations are performed with the CFD code Fluent supplemented with UDFs for process kinetics, aggregate structure, and suspension rheology. A method of application of the population balance equation to describe evolution of fractal aggregates is presented and effects of application of either uniform or erosion daughter distribution are compared. [ABSTRACT FROM AUTHOR]

Theoretical aspects of shear flows of aggregated nanosuspensions are presented and applied to formulate appropriate models. Technological context of this work is related to formulation of stable suspensions of nanoparticles of specific rheological properties by breaking-up nanoparticle clusters in high shear devices. Accordingly the population balance modeling is applied with kinetics including effects of aggregation, breakage and restructuring of aggregates; effects of suspension rheology on the flow are included as well. Rheological model includes the effect of clustering of primary nanoparticles. Population balances are solved using QMOM that is linked to the CFD code. Results of numerical simulations are presented for laminar and turbulent flows. [ABSTRACT FROM AUTHOR]