Demulsifier is a chemical agent used to break the emulsion between oil and water. It is commonly applied in oilfields—both at the wellhead and in crude oil processing units. In marine oil spill response, demulsifiers are particularly useful for separating oil from seawater, allowing for faster and more effective cleanup of contaminated areas.

Demulsifier Application in Oily Water Separation

An emulsion is a colloidal system involving two immiscible liquids. The type of emulsion is typically classified based on the dispersed phase. In the case of oily water, the dispersed phase is oil, making it an oil-in-water emulsion.

As explained in our article Oily Water Treatment Using Oil Separator, emulsified oily water cannot be effectively treated through gravity-based separation alone, even with the assistance of coalescing media. Although emulsions can technically separate under gravity, the settling time required is often too long, making the process inefficient. Therefore, alternative methods are needed to effectively separate the oil phase.

There are several approaches to breaking emulsions, such as heat application using heater treaters and chemical injection using demulsifiers.

While heater treaters have been discussed in another article, this section focuses specifically on demulsifiers.

In summary, adding a demulsifier is a chemical separation process, as the demulsifier breaks the emulsion into two distinct phases—in this case, oil and water.

Demulsifiers work by reducing the interfacial tension between the oil and water phases. This enables the small dispersed oil or water droplets to coalesce into larger droplets, which can then be separated more easily and quickly.