Talk about crude oil demulsifier

The mechanism of crude oil demulsifier is phase transfer and reverse deformation mechanism. The addition of a demulsifier results in a phase transition, i.e., a surfactant of the opposite type of emulsion to that formed by the emulsifier (reverse demulsifier). This kind of demulsifier reacts with the water-repellent emulsifier to form a complex, so that the emulsifier loses its emulsifying property. Mechanism of collision breaking interfacial film. Under the condition of heating or stirring, the demulsifier has many opportunities to collide with the interface film of the emulsion, or adsorb on the interface film, or exclude some of the surface active substances to break the interface film, so that its stability is greatly reduced, and flocculation, agglomeration and demulsification occur.

Crude oil emulsions often appear in the production and refining of oil products. The main crude oils in the world are produced in the form of an emulsion. An emulsion consists of at least two immiscible liquids. One of them is a very fine dispersion, such as a droplet about 1mm in diameter, suspended on another liquid.

One of these liquids is usually water, and the other is often oil. The oil may be very finely dispersed in the water. In this case, the emulsion is an oil-in-water type. Water is called the continuous phase, while oil is called the dispersed phase. On the contrary, if the oil is a continuous phase and the water is a dispersed phase, the emulsion is called water-in-oil. Most crude oil emulsions fall into this category.

Just as water molecules attract each other, so do oil molecules. But there is a repulsive force between the individual water and oil molecules. Repulsive forces act at the interface between oil and water. The surface tension reduces this interface area to a minimum. So, water droplets in a water-in-oil emulsion are spherical. In addition, individual water droplets tend to form aggregates whose total area is smaller than that of all droplets combined. Therefore, an emulsion consisting of pure water and pure oil is unstable. The dispersed phase tends to agglutinate, and the two separated layers thus form repulsive forces at the interface, such as through the accumulation of specialty chemicals at the interface to reduce surface tension. Technically, many situations exploit this effect by adding well-known emulsifiers to produce stable emulsions. Any substance that acts as a stabilizer in this way must have a chemical composition that enables it to interact with both water and oil molecules at the same time, that is, it should contain a hydrophilic group and a hydrophobic group, and the crude oil emulsion is stabilized by the natural substances contained in the oil. These substances usually contain polar groups such as carboxylic or phenolic groups. They may exist as a solution or as a colloidal dispersion. The particular effect is attached to the ends. In this case, the vast majority of the particles are dispersed in the oil phase and accumulate at the oil-water interface, where they are arranged side by side with polar groups pointing towards the water. So you end up with a physically stable interface layer. A solid envelope like a microlayer or a paraffin crystal. Coated in the interface layer with results commonly recognized by the naked eye. This mechanism explains the aging of crude oil emulsions and the fact that they are difficult to break down.

In recent years, the research on demulsification mechanism of crude oil emulsions mainly focuses on the detailed investigation of droplet coalescence process and the influence of demulsifier on interfacial rheological properties. However, due to the complex effects of demulsifier on emulsions, there is no unified conclusion on the mechanism of demulsifier, although a lot of research work has been done in this field.

The following are currently recognized demulsification mechanisms: ③ solubilization mechanism. The use of demulsifier one or a few molecules can form micelles, this polymer wire group or micelle can dissolve emulsifier molecules, causing emulsified crude oil demulsification. ④ Mechanism of folding and deformation. The results of microscopic observation show that the W/O emulsion has two or more layers of water, and between the two layers of water is an oil ring. Under the action of heating stirring and demulsifier, the inner layers of the droplet are connected to each other, so that the droplet condenses and demulsifies.

In addition, there are some researches on demulsification mechanism of O/W type emulsified crude oil system in China. It is considered that the ideal demulsifier must have the following conditions: strong surface activity; Good wettability; Adequate flocculation capacity; Good coalescence effect.

There are many kinds of demulsifiers, which can be divided into cationic demulsifiers, anionic demulsifiers, non-ionic demulsifiers and two ionic demulsifiers according to the classification of surfactants. Anionic demulsifiers include carboxylate, sulfonate and polyoxyethylene fatty sulfate, etc., which have the disadvantages of large dosage, poor effect and easy to be affected by electrolytes. Cationic demulsifiers are mainly quaternary ammonium salts, which have obvious effect on thin oil, but are not suitable for heavy oil and aging oil. The non-ionic types are mainly block polyethers with amines as initiators, block polyethers with alcohols as initiators, alkyl phenolic resin block polyethers, phenolamine aldehyde resin block polyethers, silicon-containing demulsifiers, ultra high molecular weight demulsifiers, polyphosphates, modified products of block polyethers and imidazoline crude oil demulsifiers.