Ultrasound-assisted desalination of crude oil: The influence of mixing extent, crude oil species, chemical demulsifier and operation variables

Coalescence of water droplets in crude oil has been effectively promoted by chemical demulsifiers integrated with ultrasound. Temporary images of water droplets in W/O emulsions were directly monitored using a metallurgical microscope. Water droplets achieved expansion of 118% at 40 min ultrasonic irradiation time under well mixing conditions. However, water droplets in heavy crude oil undergo less aggregation than those in light crude oil, due to resistance of mobility in highly viscous fluid. In the absence of chemical demulsifiers, water droplets enveloped by native surfactants appeared to aggregate arduously because of occurrence of interfacial tension gradients. Influential significance analyses have been executed by a factorial design method on operation variables, including acoustic power intensity, operation temperature, ultrasonic irradiation time and chemical demulsifier dosages. In this work, the outcomes indicate that the optimal operating conditions for desalination of crude oil assisted by ultrasound were as follows: acoustic power intensity = 300 W, operation temperature = 90℃, ultrasonic irradiation time = 75 min and chemical demulsifier dosages = 54 mg/L. Besides, it was found that the most influential importance of operation parameter was temperature, followed with acoustic power intensity, ultrasonic irradiation time and chemical demulsifier dosages.