Demulsibilitet

Demulsibilitet, or demulsibility, is the ease with which an oil–water emulsion can break and separate into distinct oil and water phases. It is a key property in many industries, especially in petroleum production, refining and lubrication, where stable water-in-oil emulsions can hinder processing, reduce separation efficiency and promote corrosion.

In practice, demulsibility describes how readily water can be removed from an oil under controlled conditions. It is often quantified with standardized demulsibility tests that mix a sample of oil with water or brine at a specified temperature and agitation, then allow the mixture to settle for a set time. The remaining water in the oil (or the amount of water that has separated) is used to express the demulsibility. A common expression is the Demulsibility Number (DN); lower DN values indicate better demulsibility, meaning water separates more easily.

Factors that influence demulsibility include the oil’s composition (notably resins, asphaltenes and acids), salinity and hardness of the water, temperature, aging and contaminants, and the presence of surface-active substances. Additives such as demulsifiers are often used to improve separation by reducing interfacial tension and promoting coalescence of water droplets. Heating can also enhance demulsibility by lowering oil viscosity and accelerating separation.

Applications and implications vary by context. In crude oil handling and pipeline operation, good demulsibility supports efficient water removal and reduces corrosion risk. In lubricants and fuels, adequate demulsibility helps prevent water accumulation in systems and supports reliable operation.