Double layer characteristics of droplets dispersed with Na2CO3 in EMSF that is applied to dehydration of Shale oil

Shale oil is highly mineralized by salt ions, which makes it difficult to demulsify and dehydrate. The synergistic electromagnetic field (EMSF) is a more efficient method than AC electric field (ACEF) to enhance Shale oil dehydration. However, the critical coalescence conditions and transformation mechanism of droplets dispersed with electrolyte ions in EMSF still lack research. Herein, a series of Na2CO3-dispersed droplets with different ionic strengths were prepared, and the critical coalescence electric intensity (Ec) of the droplets under ACEF and EMSF were compared. Micro high-speed experiments revealed that Ec of droplets under EMSF is higher. Under the action of both EMSF and ACEF, Ec decreases with the increase of ionic strength Is. An ion enrichment theory is proposed to explain the relationship between ion strength and potential energy. This study provides technical guidance for the performance regulation of EMSF-based equipment to enhance oil-water separation, the allowable optimal voltage should be higher than that of the electrostatic coalescer, and the adjustment range is 3.81 %–5.88 %.