Determinação da viscosidade de misturas assimétricas em alta pressão usando regras de mistura

Abstract

The knowledge of transport properties of mixtures at different pressures and temperatures is important in design, operation, control and optimization of industrial process. In these processes, often, the fluid system is a binary or multicomponent mixture of hydrocarbons such as petroleum fluids. The experimental properties of mixtures, specially, the dynamic viscosity as a function the temperature and pressure, can provide valuable information about the fluid behavior at different compositions and are useful in developing models and correlations and in the characterization of complex mixtures. Several mixing rules have been proposed in the literature for calculating viscosity of mixtures. These mixing rules predict mixture behavior mainly at atmospheric pressure using pure component properties. However, in several important applications it is necessary to estimate the viscosity of blends at high pressures. In this work, were evaluate the performance of several commonly used mixing models like Refutas, Factor Mixing and Index Mixing, Grunberg and Nissan, Kendall-Monroe and Eyring as well as linear Molar Additivity, using experimental viscosity data of mixtures at high pressures. Initially, the absolute viscosities for the highly asymmetric mixture of cyclohexane and n-hexadecane were measured in the temperature range of (318.15 to 413.15) K and pressures up to 62.053 MPa and for this system, a satisfactorily model is proposed for calculating of pure components viscosities for given temperature and pressure. Also, viscosity data of thirty mixtures, whose components differ in molecular shape, size or flexibility, were selected and were modeled employing mixing. The mixture viscosities were estimated by all the mixing rules using experimental viscosity of pure components measured at the same temperature and pressure. At high pressures, Refutas, Factor Mixing and Index Mixing showed the best results for all systems studied. For very asymmetric systems, Refutas, Factor Mixing and Index Mixing can be used