Effect of hydrophobically modified partially hydrolyzed polyacrylamide on the dehydration of W/O emulsion under the combination of demulsifier and <scp>DC</scp> electric field

Abstract Combing demulsifier and electric field can accelerate the phase separation in water‐in‐crude oil emulsions. However, the effect of hydrophobically modified partially hydrolyzed polyacrylamide (HMHPAM) on the separation efficiency of combination of demulsifier and electric field has not been studied. In this paper, the effects of three types of HMHPAM containing cationic, anionic, and nonionic hydrophobic monomers (abbreviated as P(AM‐AANa‐N)Cn, P(AM‐AANa‐S)Cn, and P(AM‐AANa‐O)Cn, respectively) on the demulsification result and interface behaviour (including dynamic interfacial tension and elastic properties of oil–water interface) of demulsifier D1–DC electric field combination were studied. The demulsification experiment results showed that as the concentration of HMHPAM in water increased and the length of hydrophobic chains in hydrophobic monomers increased, dehydration rate of D1–DC electric field combination decreased, the negative effect of P(AM‐AANa‐N)Cn on dehydration rate of D1–DC electric field combination was the largest. In particular, when the water contained 500 mg/L P (AM‐AANa‐N)‐C12, the dehydration rate decreased by 40%. Interface behaviour experiment results showed that the presence of HMHPAM (also known as polyelectrolyte) in water was helpful for the interfacial tension reduction, then was beneficial for the deformation ability of water droplet in oil under combination of demulsifier and DC electric field, thereby facilitating water droplet collisions. However, the presence of HMHPAM had a negative effect on change of elastic properties of oil–water interface and weakened the coalescence ability of water droplets after collision, resulting in a decrease in the dehydration rate of demulsification experiments.