Microbubbles preparation by partial vaporization of low boiling condensate for crude oil/water separation

Abstract

The poor adhesion of oil droplets and bubbles in the flotation process leads to inefficient separation of oil and water. In this paper, condensate bubbles were prepared by partial vaporization of low boiling point condensate to increase the oil removal effect. The purpose of partial vaporization was achieved by bringing emulsified condensate droplets into the produced water at different temperatures. The structure of the bubble is composed of condensate film wrapped around the gas core of the vaporized portion. The contact angle between condensate bubble and oil surface is >150°, which show great similarity-intermiscibility. The average bubble size prepared at 303 K - 318 K is 20 - 100 μm. The stability of bubbles decreased with an increase in temperature, the half-decay time decreased from 340 s to 110 s, and the zeta potential decreased from −31 mV to −12 mV. However, the gas hold-up of the bubbles first increased and then decreased with the increase in temperature, while the highest gas holdup was 21 % at 313 K. The rise of the condensate/water ratio (Rcon-wat) did not increase the stability of the bubbles, but the gas holdup increase. The condensate bubble flotation experiment found that at the optimum temperature 313 K, the oil removal efficiency of 1.5 % Rcon-wat can reach 85 %. In contrast, the oil removal efficiency of the dissolved air flotation experiment is <75 %. Otherwise, with a smaller amount of flocculant (ferric chloride), the oil removal efficiency of condensate bubble flotation can reach >95 %.