(74w) Optimizing Crude Oil Separations – a Study of Turbulence and Chemical Composition Influence on the Drop Size Distribution of Crude Oil in Maritime Conditions

Optimizing crude oil separations – a study of turbulence and chemical composition influence on the drop size distribution of crude oil in maritime conditions

Efficiency in the exploration of crude oil deposits is of great importance for the oil and gas industry. With the usage of large amounts of feed water in the process comes the need for fast and efficient separation processes for the liquid/liquid dispersion. The quality of the separation translates directly into costs for storage, transportation and subsequent processing. The dispersion is thermodynamically unstable and given time, the droplets will separate out to form two bulk liquid phases. The drop size distribution is the most relevant parameter for this type of separation process. Great efforts have been made to measure the size of liquid dispersed droplets. The utilized techniques can be divided into those that require samples to be withdrawn from the vessel or pipe, and those that can be applied in situ.

For deep sea analysis in-situ methods are preferential since they account of the significant impact of the present conditions on the size of the drops. Many investigations of droplet size distributions or a representable diameter like d₃₂ have focused on highly dilute dispersions, where it is assumed that coalescence can be eliminated. As this approach provides results with limited practical application, a measurement technology for high concentrations is necessary.  In comparison to chemical, pharmaceutical, and food manufacturing, the petroleum industry presents additional challenges, as the optical conditions of oil streams are much more complex then specialty and fine chemicals. Also the variation of fluid physical properties and process conditions is stronger. The understanding, prediction and control of the drop size in crude oil applications is rather challenging. A detailed description of the opposing phenomena, drop breakage and coalescence, is paramount for successful mathematical modeling. An additional difficulty in handling such dispersed systems is the probability of phase inversions (PI). In case of a spontaneous occurrence within a process, the consequences for product and equipment can be catastrophic [1]. On the contrary, it can be used for a more controlled handling of the described applications. Therefore a better understanding and modeling of this phenomenon is desirable.

This study reports on a turbulent liquid/liquid system using original North Sea crude oils and sea water was investigated. The operation parameters dispersed phase fraction, turbulence intensity and surfactant concentration have been varied systematically. The transient drop sizes as the unstable behavior of the water and organic phase have been observed using an in-situ microscope [2]. The drop size was measured using a fully automated image analysis tool [3].  These data give a reliable base to understand liquid-liquid separations better.

[1] Nienow, A. W., Adv. Colloid Interface Sci. 2004, 108, 95-103.

[2] Maaß, S., Wollny, S., Voigt, A., Kraume, M., Exp. Fluids 2011, 50, 259-269.

[3] Maaß, S., Rojahn, J., Hänsch, R., Kraume, M., Comput. Chem. Eng. 2012, 45: 27-37.