Study Of Hydrodynamics And Mass Transfer Of Oil Emulsion In A Pilot Scale Sieve Tray Column

Abstract

A study of primary and secondary treated liquid petroleum wastes in a pilot sieve tray column has been undertaken. 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 refineries has been investigated and it is observed that the primary and secondary processes are quite efficient, but the tertiary process leaves some of the oil in he effluent and this is why the treated water is not recycled and reused. The treated waste/oil water is pumped into ponds for evaporation leaving the oil and other less volatile components as a residue which have a negative 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 emulsified with a surfactant producing a partially water miscible emulsion. Experiments were carried out with nonmass 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 coefficients were calculated from the mean driving force using Simpson's rule. It is observed that drop size, drop size distribution and mass transfer coefficients 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 the 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.