Study Of Ultrasonic Demulsification And Dehydration Of Refinery Waste Oil

The recovery waste oil collected from various workshops of petroleum refinery is composed of multifarious oils. It has complicated qualities and high water content, usually greater than 10%. The hydrous waste oil contains more colloid, asphaltene and impurities, its emulsify ability is powerful and aged degree is severely. The impurities of waste oil are come from mud of well, demulsifier of crude oil and swage treatment agent (flocculating agent, coagulating agent, scale inhibitor, corrosion inhibitor, bactericide, caustic soda) et al. Most of these impurities are electrolyte, which are the primary reason that destroy electric field, so we cannot use electric method to dehydrate like crude oil. At the same time, the components of waste oil are complicated, its stability is good, so it is difficult to dehydration. Usually it is treated at high temperature and be sold when the water content is less than 10% There are many factors affect waste oil emulsion breaking by ultrasound. On the one hand it is affected by ultrasonic factors such as ultrasonic intensity, frequency, treatment time and so on, on the other hand it is affected by waste oil natures such as viscosity, composition, density and so on. This paper emphasizes on the effect of controllable factors including ultrasonic intensity, treatment time, temperature, demulsifier dosage on waste oil emulsion breaking by ultrasound. The research result shows that the water content reduces with the increase of ultrasonic intensity at begin, and it begins to increase sharply when the ultrasonic intensity reaches cavitation threshold. The water content of waste oil after ultrasound action reduces with the increase of treatment time, but when treatment time comes to a certain time, it does not change any more or increases instead. In addition the water content after ultrasound action declines with the increase of sedimentation time, temperature and demulsifier dosage, but demulsifier dosage has a critical agglomeration concentration, the water content of waste oil increases when demulsifier dosage exceeds critical agglomeration concentration. Ultrasound dehydration technology parameters which suit the waste oil of yang-zi petroleum refinery are found through orthotropic test. The optimum conditions for waste oil dehydration in reverberation field are: the acoustic intensity 1.168W/cm2, frequency 40kHz, treatment time 15min,demulsifying agent dosage375ppm, dehydration temperature70oC, settling time 4hrï¼›the optimum conditions for waste oil dehydration in standing wave field are: the acoustic intensity 0.66W/cm2, frequency 10kHz, treatment time 5min,demulsifying agent dosage 375ppm, dehydration temperature 70oC, settling time 4hr, the water content of waste oil is under 0.2% (v%) in experiment...