Oil-water mixing is commonly applied in chemical, oil, pharmaceutical, food and cosmetic industries to increase the interfacial area, i.a., available for mass transfer. Ideally, the oil-in-water (o/w) or water-in-oil (w/o) emulsion characteristics (mostly droplet size distribution (DSD) and the representative characteristic diameter: Sauter mean diameter, d32) are carefully controlled during these processes. The liquid-liquid mixing process is often followed by a separation process, e.g., for material recovery or contaminant reduction. A convenient, simple and often applied method is gravity separator which only utilizes density differences between phases. The separation performance of the gravity separator is largely determined by the feeding conditions (such as feeding total flow rates, feeding oil volume ratios, feeding droplet sizes, and feeding temperatures, etc.). This work aims to investigate the influence of feeding conditions on the separation performance of a continuous gravity separator.
This study is carried out in a continuous gravity separator setup, and Figure 1 shows the schematic drawing of the system. Two different methods are used to generate and control the water-oil dispersions including static mixer (orifice plates) and stirred tank. Endoscope system is applied to analyze the feeding droplet size. Separation process is observed through a transparent glass separator and separation performance is determined with the help of introducing a secondary separator with coalescence aids.
CFD numerical work
Many efforts have been made numerically to study the separation processes in a continuous gravity separator. However, simulation of the dense packed zone and coalescence in the gravity separator remains challenging. This work tries to give a thorough description of these two phenomena in the gravity separator by using Simcenter STAR-CCM+.