Enhancement Of Water-oil Separation By Electrocoalescence (original) (raw)

2014, Qatar Foundation Annual Research Conference Proceedings Volume 2014 Issue 1

Dispersed water droplets in organic liquids are commonl y encountered in the oil, chemical and biochemical industries. A t ypical example is the separation of dispersed water drops in cr ude oil, in order to prevent catal yst fouling, viscosit y and volume increase, and to meet qualit y specifications of the cr ude oil. Water drops can be removed from a continuous oil phase by various techniques, such as chemical demulsification, gravit y or centrifugal separation, pH adjustment, filtration, heat treatment, membrane separation and electrostatic-enhanced coalescence. Compared to other methods, electrical demulsification is considered to be superior in terms of energ y efficienc y. The electrostatic effects arise from the much higher values of dielectric permittivit y and conductivit y of water in comparison to oil. However, the mechanism of electrocoalescence is still not full y understood and most of the conventional electro-separators are rather bulky. There is, therefore, a compelling need to optimiz e the design and operation of these separators by means of a better fundamental understanding of the under l ying physics. This study aims at investigating the coalescence behaviour of water droplets in sunflower oil when the aqueous phase is present in the form of a chain of droplets. Chains easil y form in an emulsion, since droplets tend to align themsel ves with the direction of the electric field. A pair of ladder-wise electrodes was implemented to set up an electric field almost parallel to the flow direction of the droplets. This design ensures that adjacent droplets in a chain experience the maximum attractive force and does not significantl y disturb the hydrodynamics of the continuous phase. The effect of the electric field strength, frequenc y and waveform on the process performance has been investigated. Both constant and pulsed dc fields have been applied to the dispersion. S inusoidal, sawtooth and square waves have been employed as pulsed dc waveforms. Droplet siz e distributions at the outlet of the device were measured by image anal ysis. The outcomes of the research suggest that it is possible to find a combination of electrical field intensit y, frequenc y and waveform to maximiz e the separation efficienc y.