Category: Gravity Separation

Electrostatic Coalescers

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Coalescing of the small water drops dispersed in the crude can be accomplished by subjecting the water-in-oil emulsion to a high-voltage electrical field. When a non-conductive liquid (oil) containing a dispersed conductive liquid (water) is subjected to an electrostatic field, the conductive particles or droplets are caused to combine by one of three physical phenomena: …

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Coalescing Media

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It is possible to use a coalescing media to promote coalescence of the water droplets. These media provide large surface area upon which water droplets can collect. The most common coalescing media is wood shavings or excelsior, which is referred to as a “hay section.” The wood excelsior is tightly packed to create an obstruction …

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Water Droplet Size and Retention Time

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The droplet diameter is the most important single parameter to control to aid in water settling since this term is squared in the settling equation. A small increase in diameter will create a much larger increase in settling rate. It would be extremely rare to have laboratory data of droplet coalescence for a given system.  …

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Temperature Effects

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Adding heat to the incoming oil/water stream is the traditional method of separating the phases. The addition of heat reduces the viscosity of the oil phase allowing more rapid settling velocities in accordance with Equation 6-1. It also has the effect of dissolving the small crystals of paraffin and asphaltenes and thus neutralizing their effect …

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Viscosity

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Laboratory testing of a particular oil at various temperatures is the most reliable method of determining how an oil behaves. ASTM D 341 outlines a procedure where the viscosity is measured at two different temperatures and then either through a computation or special graph paper the viscosity at any other temperature can be obtained. Figure …

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Coalescence

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The process of coalescence in oil treating systems is time dependent. In dispersions of two immiscible liquids, immediate coalescence seldom occurs when two droplets collide. If the droplet pair is exposed to turbulent pressure fluctuations, and the kinetic energy of the oscillations induced in the coalescing droplet pair is larger than the energy of adhesion …

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Gravity Separation

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Most oil-treating equipment relies on gravity to separate water droplets from the oil continuous phase, because water droplets are heavier than the volume of oil they displace. However, gravity is resisted by a drag force caused by the droplets’ downward movement through the oil. When the two forces are equal, a constant velocity is reached, …

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