water in oil emulsion blog
Susanna Laurén Dec 8, ’20 > 3 min

Demulsification of oil-water emulsions

Demulsification is a process where emulsions are broken down, most typically by the addition of chemicals. Demulsification is especially important in oil industry where stable oil-water emulsions are formed during oil production.

Demulsification is especially important in oil industry

Emulsion stability is often discussed in various industries such as food and cosmetics. But as important as the stability of the emulsions is for those products, the possibility to destabilize the emulsion can be such as essential.

During oil production, very stable water-in-oil (W/O) emulsions are formed. These emulsions are stabilized by the naturally occurring ingredients in oil, such as asphaltenes and resins. These molecules behave as surfactants and adsorb at the oil-water interface, preventing coalescence of water droplets and making the emulsions extremely difficult to break. 

In oil production, the emulsions are problematic as the high water content will cause problems in the refinery through pipeline corrosion. The water needs to thus be removed prior transportation to the refinery.  

In oil-water demulsification process, the following points are important

  • Rate of the speed at which the separation process takes place
  • Amount of water left in the crude oil after separation
  • Quality of the separated water for disposal

These factors dictate the time it takes to destabilize the emulsion as well as the quality of both, the produced crude oil as well as the wastewater.

Demulsifiers are used to destabilize emulsions

The stability of the emulsion arises from the formation of the interfacial film at oil-water interface. To separate the emulsion, this film needs to rapture for the coalescence of the droplets to happen. In oil industry, chemical demulsifiers are used to help in this process.

Demulsifier is a surfactant used to break the oil-water emulsions. Typically, water-soluble demulsifiers are used to destabilize oil-in-water emulsions and oil-soluble demulsifiers are used to break water-in-oil emulsions. To break the emulsions, the water droplets should flocculate and eventually coalescence to form two separate phases, i.e. oil and water. For destabilization to happen the demulsifier must adsorb to the interface, remove, and break up the asphaltene aggregates.  Also, they should reduce the interfacial tension between the oil and water phases to facilitate the droplet coalescence.

To hear more about the emulsion stability and how it can be studied through interfacial rheology, listen to the pod through the link below.

Podcast  Episode: Interfacial Rheology  Listen

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