Desalting and dewatering of crude oil in ultrasonic standing wave field

A standing wave field of ultrasound was established in the designed standing wave tube. The enhancement of ultrasound irradiation on desalting and dewatering process of LU-NING pipeline oil was studied. The results showed that the best conditions of the oil pretreatment was: adding 30 mg/L demulsifier, injecting 5% (v.) wash water, irradiating the crude oil 5 min by 10 kHz ultrasound (intensity 0.38 W/cm2, standing wave field), settling for 90 min. The final results of salt and water contents were 3.851 mg/L and 0.37%, respectively. The effect of standing wave field combined with demulsifier was better than that of the demulsifier only. High temperature (80 °C) in the process was better than low temperature. Salt balance study showed that the key of desalting was: the wash water and the oil should be mixed sufficiently to extract the salts into the water as more as possible, the water added in should be provided to be separated out. If one stage of desalting process could not achieve the norm, two stages of desalting process should be considered.