Breakdown mechanism and application of high frequency pulsed electric field-demulsifier combination on water-in-oil emulsion

High-frequency pulse electric dehydration technology gradually replaced AC (alternating current) and DC (direct current) dehydration because of its technical advantages such as low energy consumption and no electric field collapse. In this paper, a high frequency pulsed electric field-demulsifier combined dehydration technology was proposed. The dehydration performance of high frequency pulsed electric field and the demulsification of high frequency pulsed electric field-demulsifier combined action were analyzed. The effects of pulse amplitude, pulse width ratio, pulse frequency and dehydration time on the dehydration rate of simulated emulsion under high frequency pulsed electric field were discussed, and the optimal electric dehydration parameters were selected. The results show that for the simulated FY crude oil emulsion with a water content of 25 %, the optimal dehydration conditions are pulse amplitude of 1320 V, frequency of 3.86 kHz, pulse width ratio of 75 %, demulsifier AR919 concentration of 60 mg/L, dehydration temperature of 55 °C, and dehydration time of 10 min. Through the study of microscopic water droplet breakdown, the breakdown mechanism of pulsed electric field was revealed: Accumulation by electrophoresis, Dipole coalescence, Accumulation by oscillating. The demulsifier reduced the optimal pulse frequency and pulse width ratio of the pulsed electric field to the demulsification and dehydration of the emulsion, but had no effect on the optimal pulse amplitude. At the same time, the advantages of high frequency pulse electric demulsification in saving energy were calculated. The results show that the dehydration performance of high frequency pulse electric field is much higher than that of AC and DC electric field, and the energy consumption is saved by more than 90 %. The field application also achieved good results.