Effect of residence time and energy dissipation on drop size distribution for the dispersion of oil in water using KMS and SMX+ static mixer

tThe Planar Laser Induced Fluorescence technique was used to determine the drop size dis-tribution of oil dispersed in water at the inlet and outlet of two static mixer geometries(KMS and Sulzer SMX+) equipped with either 6 or 12 elements. A mineral oil (Lytol®), threetimes more viscous than the water continuous phase, was used as the dispersed phase. Theoil flow rate was kept constant through all experiments forcing the drop detachment fromthe secondary inlet. The L–L system was very dilute (˜0.05–0.0007% v/v O/W) to avoid coales-cence phenomena. The flowrate of the continuous phase (water) was altered giving values ofReynolds number from 2000 to 12,000, covering high transitional and turbulent flow regimes.Increasing the flow rate of the continuous phase, the detached oil drops from the secondaryinlet decreased in size as expected. However, same drops after flowing a length of 0.4 m ofan empty pipe reached a constant size. To investigate a wider range of energy dissipationand residence time, the presence of static mixers has been investigated. Pressure drops,hence energy consumed, were measured to compare the different set ups and drop sizedistributions. The results show that by increasing the flow rate, the drop size decreased upto a critical point, beyond which oil droplet size reduction became inefficient. The collecteddata were then used to derive a methodology to identify the optimal flow conditions andchoice of static mixer device to achieve best drop size reduction with less energy per unitmass