How does demulsifier break oil and water？

Demulsifiers are used in oil fields to separate the crude oil from the water and salt that are produced along with it.  Crude oil is often mixed with water and salt in the form of an emulsion, which is a stable mixture of two or more liquids that do not normally mix.  Demulsifiers are chemicals that break the emulsion by destabilizing the bonds between the oil and water molecules, allowing them to separate into different phases.  This process improves the quality and quantity of the crude oil, and also reduces the corrosion and environmental problems caused by the water and salt.

Due to the increasing demand for crude oil and its derivatives, as well as the need to improve the quality and efficiency of oil production and processing, demulsifiers are widely used in various oil fields.

According to some web search results, the global demulsifier market size was valued at around USD 2.3 billion in 2020 and is expected to grow at a compound annual growth rate (CAGR) of over 4% from 2021 to 2028  The major factors driving the market growth are the increasing oil and gas production, especially in offshore and unconventional sources, the expansion of petroleum refineries, the growing demand for lubricants and oil-based power plants,  and the rising need for sludge oil treatment.

How does demulsifier break oil and water？Emulsion is a stable mixture of two or more immiscible liquids, such as oil and water, that are held together by natural surfactants that form a thin film around the dispersed droplets.  Demulsifier is a chemical additive that can disrupt the emulsion by weakening or destroying the interfacial film, allowing the droplets to coalesce and separate into different phases. Demulsifiers are usually added to the crude oil before it enters the separation equipment, such as heaters, separators, or coalescers. The type and dosage of demulsifiers depend on various factors, such as the composition of the crude oil, the temperature and pressure of the system, the retention time of the emulsion, and the desired quality of the separated oil and water.

There are different types and mechanisms of demulsifier, depending on the composition and characteristics of the emulsion. Demulsifier products are usually classified into four main categories: oil-soluble, water-soluble.

Oil-soluble demulsifier is a type of demulsifier that is soluble in oil and insoluble in water.  It is used to break water-in-oil emulsions, where water droplets are dispersed in an oil phase

Oil-soluble demulsifier works by attaching to the water droplets and weakening the interfacial film that stabilizes the emulsion.  The interfacial film is composed of natural surfactants that are present in the crude oil, such as asphaltenes, resins, and naphthenic acids.  These surfactants form a thin layer around the water droplets and prevent them from coalescing and separating from the oil phase.

Oil-soluble demulsifier is typically based on organic polymers, such as polyalkylphenols, polyalkylamines, polyalkylamides, polyalkylethers, etc. These polymers have both hydrophobic and hydrophilic groups in their molecular structure.  The hydrophobic groups are compatible with the oil phase and the hydrophilic groups are attracted to the water droplets.  When oil-soluble demulsifier is added to the emulsion, it migrates to the oil-water interface and adsorbs onto the water droplets.  The hydrophilic groups of the demulsifier compete with the natural surfactants for the interfacial area and displace them from the interfacial film.  This reduces the interfacial tension and viscosity of the emulsion, making it easier for the water droplets to coalesce and form larger droplets that move to the oil-water interface

Water-soluble demulsifier is a type of demulsifier that is soluble in water and insoluble in oil.  It is used to break oil-in-water emulsions, where oil droplets are dispersed in a water phase.

Water-soluble demulsifier works by attaching to the oil droplets and weakening the interfacial film that stabilizes the emulsion.  The interfacial film is composed of natural surfactants that are present in the crude oil, such as asphaltenes, resins, and naphthenic acids.  These surfactants form a thin layer around the oil droplets and prevent them from coalescing and separating from the water phase.

Water-soluble demulsifier is typically based on inorganic salts, such as aluminum sulfate, ferric chloride, calcium chloride, etc.  These salts have high ionic strength and can reduce the electrostatic repulsion between the oil droplets, making them more prone to coalescence.  They can also react with the natural surfactants and form insoluble complexes that can be removed from the interfacial film.  This reduces the interfacial tension and viscosity of the emulsion, making it easier for the oil droplets to coalesce and form larger droplets that move to the water-oil interface.

The effectiveness of demulsifier depends on various factors, such as the type and dosage of demulsifier, the composition and characteristics of crude oil, the temperature and pressure of the system, the retention time of the emulsion, and the desired quality of separated oil and water.  Different types of crude oil may require different types of demulsifier to achieve optimal results.  The dosage of demulsifier should be optimized to avoid overdosing or underdosing, which can affect the separation efficiency and cost.  The temperature and pressure of the system can affect the solubility and dispersibility of demulsifier in the oil or water phase, as well as the viscosity and stability of the emulsion.  The retention time of the emulsion is the time required for the demulsifier to act on the emulsion and achieve sufficient separation.  The quality of separated oil and water is measured by parameters such as basic sediment and water (BS&W), salt content, oil content, etc
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