Study of Hydrodynamics and Mass Transfer of Oil Emulsion in a Pilot Scale Sieve Tray Column

Abstract

A study of primary and secondary treat ed liquid petroleum wastes in a pilot sieve tray column has been undertak en. The literature related to this type of extractor and the relevant phenomena of droplet break-up and coalescence, drop size and drop mass transfer have been reviewed. The method of treatment in local re fineries has been investigated and it is observed that the primary and sec ondary processes are quite efficient, but the tertiary process leaves some of th e oil in he effluent and this is why the treated water is not recycled and re used. The treated waste/oil water is pumped into ponds for evaporation leav ing the oil and other less volatile components as a residue which have a ne gative impact on the environment. The system of oil in water is not a normal solute-solvent system, and to make it so the mixture has been em ulsified with a surfactant producing a partially water miscible emulsion. E xperiments were carried out with non- mass transfer to determine the operating column hydrodynamics such as flooding. At 85% of flooding, mass transfer experiments were performed and the effects of drop size, drop size distribution and dispersed phase holdup volume at variable agitation speeds on the column performance have been investigated. The concentration profile has been measured and the overall experimental mass transfer coefficien ts were calculated from the mean driving force using Simpson's rule. It is observed that drop size, drop size distribution and mass transfer coeffi cients were strongly dependent on the speed of agitation. As the oil droplets were composed of emulsified oil in water and the oil itself is completely immiscible in water, the direction of mass transfer was from the emulsified droplets to th e dispersed phase. This condition coupled with high solubility of oil in n-hexane made the extraction process very efficient and an almost oil-free water could be obtained and recycled. 5 This work is also mainly intended to compare the experimental mass transfer coefficients with those pr edicted by the models formulated by Angelo et al and Rose et al. It is found that the data fitted very well when correlated by the model formulated by Angelo et al, therefore it is recommended for mass transfer pred iction in agitated columns such as sieve trays.