High-pressure viscosity measurements of orange oil saturated with CO2

FORTUNATTI MONTOYA, M.; HEGEL, P. E.; PEREDA, S.

Cordoba

Conferencia; VI Iberoamerican Conference on Supercritical Fluids; 2023

Universidad Nacional de Córdoba

Thermophysical properties play an important role in the design of packed columns. In particular, the viscosity of the liquid phase determines the hydraulic behavior of the column and controls the mass transfer phenomena that govern the separation process. It is well known that the height of the theoretical stage in the supercritical CO2 fractionation of oily substrates is highly dependent on the viscosity of the saturated liquid phase. Predicting the viscosity of liquid mixtures, based on pure compound properties, is a complex challenge. Furthermore, supercritical extraction processes involve mixing a liquid substrate and supercritical CO2, which further increases the complexity of accurately modeling this property. Despite this, it is a common practice to assume an ideal solution behavior to estimate the properties of the raffinate phase in the column, even though it may deviate substantially from the actual mixing property. Additionally, it is worth noting that viscosity is highly sensitive to the CO2 concentration in the saturated phase.In this work, we demonstrate the development of a high-pressure viscosimeter for saturated liquid mixtures under high pressure for the purpose of supercritical process engineering design. A high-pressure falling weight viscometer is used to measure the viscosity of saturated liquid mixtures of orange oil + CO2 at different temperatures (293 K to 333 K) and saturated pressures (20 bar to 95 bar). This technique has been employed by various authors to measure the viscosity at high-pressure conditions of different oily substrates + CO2 systems. In particular, we investigate the viscosity behavior of orange oil saturated with CO2 (0 - 62 molar % of CO2 in the liquid phase).Results show the operating temperature influences the viscosity of both the pure oil and the CO2-saturated oily substrate. It has been observed that the effect of temperature is more pronounced in the variability of the viscosity of the pure oil compared to the analysis of the orange oil + CO2 saturated mixture. Additionally, the viscosity of the liquid mixture decreases with increasing CO2 concentration at a given operating temperature. This effect is remarkably noticeable at the lowest temperature studied (293 K). The new viscosity data is properly correlated using a modified version of the Litovitz equation.