Oil aerated flocs formation assisted by a flocculant for heavy oil produced water treatment

Air flotation cyclone is a potentially efficient method to improve the treatment efficiency of heavy oil produced water in offshore fields. For its practical application, it is of great significance to develop a flocculant that can flocculate air bubbles and oil droplets together to form oil aerated flocs. In this paper, a novel flocculant capable of rapidly forming oil aerated flocs was prepared and the formation conditions and mechanism of oil aerated flocs were investigated. Firstly, copolymer (PDAMPE-NH) was synthesized by free radical solution copolymerization of N-(3-dimethylaminopropyl) methacrylamide (DPM), diallylamine (DAA) and block polyether macromonomer (PEP) as the monomers . Then, the molecular weight of PDAMPE-NH was increased by using polyethylene glycol diacrylate (PEG-DA) as a chain extender. Finally, the target flocculant DA was obtained by protonating the tertiary amine group in the copolymer with formic acid . The protonated tertiary amine group in DA can capture oil droplets, and the polyether group in DA can capture air bubbles. When the DA dosage was 500 mg/L and bubble size was in range of 20 μm to100 μm, the oil aerated flocs were formed, and the oil content of heavy oil produced water reduced from 7250 mg/L to less than 100 mg/L within 90 s. Microscopic observation found that there were three stages for oil aerated flocs formation and the formation of oil-coated bubbles was the key step. The reported results can provide a reference for the fast treatment of heavy oil produced water in offshore fields.