Meet demulsifiers

Demulsifier is a surfactant that destroys emulsion. Demulsifiers mainly destroy the emulsion by partially replacing the stabilizing membrane. used as a dehydrating agent, it can remove the water from crude oil and heavy oil to make the water content meet the requirements; It can reduce the viscosity of crude oil and prevent the well from being blocked. It is obtained by the polymerization of fatty alcohols, propylene oxide, and ethylene oxide. It is easily soluble in water, light yellow or milky white viscous liquid. Soapy smell. Freezing point 25~40°C. Hydroxyl ≤ 60 mg potassium hydroxide/g. , the aqueous solution is milky white.

Brief Introduction

In the flotation process, sometimes in order to improve the dispersion and flotation effect of the agent (such as the collector), it is necessary to add an emulsifier first and emulsify the agent. Some beneficiation agents themselves are easy to emulsify, and the emulsification foam in the slurry will affect the subsequent process, resulting in concentrate overflow loss or tailings wastewater pollution of rivers. For this reason, in the above cases, it is necessary to add demulsifier for treatment. When using demulsifier, the pH value of the emulsion should be adjusted first, and the pH value should generally be adjusted to the range of 1~10 for strong alkali and strong acid emulsions. In the wastewater treatment of oily emulsions in petroleum, chemical, wool spinning and mechanical processing industries, in addition to physical demulsification methods (such as heating method, membrane separation method, electric field demulsification method), demulsifiers are also commonly used for chemical treatment. Commonly used demulsifiers are highly dispersible mixtures of multiple components. Demulsification of oil-in-water emulsions usually uses inorganic substances with cations such as H+, Al3+, Fe3+ and other cations as demulsifiers, such as inorganic acid, iron sulfate, etc. For demulsification of water-in-oil emulsions, anionic and nonionic surfactants or mixtures of the two are generally used as demulsifiers.
Because some solids are insoluble in water, when one or several of these solids exist in large quantities in aqueous solution, under the agitation of hydraulic or external power, these solids can exist in the water in an emulsified state and form an emulsion. Theoretically, this system is unstable, but if there are some surfactants (soil particles, etc.), the emulsification state is very serious, and even the two phases are difficult to separate, typically in the oil-water mixture in oil-water separation and the water-oil mixture in sewage treatment, in these two phases to form a relatively stable water-in-oil or water-in-water structure, the theoretical basis of which is the “double electric layer structure”.
In this case, some agents are put in to destroy the stable electric double layer structure and stabilize the emulsification system, so as to achieve the purpose of two-phase separation. These agents used to destroy the emulsification effect are called demulsifiers.

Breast Breaking Mechanism

Due to the complexity of the composition of oil, reservoir water and the natural emulsifiers contained in it, it is extremely difficult to study the physicochemical processes that occur at the oil-water interface, so the demulsification process and demulsification mechanism of chemical demulsifiers are still being studied, but both demulsifiers and emulsifiers are surfactants, and the effects of the two are diametrically opposite. The demulsification mechanism of various demulsifiers is summarized as follows:
Surfactant action. Demulsifiers have high-efficiency surfactants, and demulsifiers have higher activity than emulsifiers.
Some literature suggests that the activity of demulsifier should be 100~1000 times greater than that of emulsifier, so that the demulsifier can quickly disperse through the outer phase of the emulsion to the oil-water interface, replace or neutralize the emulsifier, reduce the interfacial tension and interfacial film strength of the emulsified water droplets, and make the W/O emulsion very unstable. The interface film is very easy to rupture under the action of external force, so that the water in the inner phase of the emulsion particles breaks through the interface film and enters the outer phase, so that the oil and water are separated. This can not only destroy the crude oil emulsion that has formed,
It can also prevent further emulsification of the oil-water mixture, reduce the viscosity of the oil-water mixture and accelerate the separation of oil-water. However, practice shows that there is no law that the higher the activity of demulsifier, the stronger the demulsifier ability.
Reversed-phase emulsification. Crude oil emulsion is formed under the action of water-repellent emulsifiers in crude oil, commonly known as W/O type emulsion
liquids, such as naphthenic acid, asphaltene, etc. The use of hydrophilic demulsifier can convert the emulsion into O/W emulsion, and the oil and water can be separated by the conversion of the emulsification process and the instability of the O/W emulsion. When the demulsifier promotes the transformation of water in oil to form an oil-in-water emulsion, the water is easy to collide and accumulate into large droplets on the outside and settle out.
“wetting” and “osmosising” effects. Demulsifiers can dissolve natural emulsifiers such as gelatin, asphaltene, and solid powder adsorbed at the interface between oil and water, preventing the interface film composed of natural emulsifiers from hindering the coalescence of water droplets. For example, solid particles such as clay, iron sulfide, and drilling mud are hydrophilic, and demulsifiers can pull these solid emulsifiers from the oil-water interface into water droplets. asphaltene and high melting point wax crystals are lipophilic, and demulsifiers can allow them to leave the oil-water interface and enter the crude oil. In this way, it is conducive to the merging of water droplets when they collide and achieve the purpose of water droplet sinking. (4) Antiionic action. Because the water droplets in the dispersed phase in the crude oil emulsion are always negatively charged, and some positive ions are adsorbed on their own surface, the dispersed phase is often positively charged, because the charges are the same, and the water droplets in the dispersed phase repel each other, making it difficult for the water droplets to merge. If an ionic demulsifier is added to crude oil, ions with opposite polarity are adsorbed on the surface of the water droplets and neutralize the positive charge, so that the electrostatic repulsion of the water droplets is weakened, the interface membrane protected by the same electricity is destroyed, and the water droplets merge and settle out of the oil.
Although the demulsification mechanism of demulsifier is not perfect, two conclusions can be drawn from long-term practice: (1) the molecular weight of demulsifier is greater than that of natural emulsifier to effectively demulsify; (2) If the demulsifier is used as an emulsifier for oil-water mixtures, it will produce a reversed-phase emulsion, that is, an O/W emulsion.

Main Uses:

Demulsifier is a surfactant substance, which can destroy the structure of emulsified liquids to achieve the purpose of separating the phases in the emulsion. Crude oil demulsification refers to the chemical action of demulsifier to separate the oil and water in the emulsified oil-water mixture to achieve the purpose of crude oil dehydration to ensure the water content standard of crude oil export.

Classification of Demulsifiers
According to the current use of demulsifiers, demulsifiers can be divided into two categories: water-soluble demulsifiers and oil-soluble demulsifiers.
Demulsifier is a type of surfactant, the demulsifier molecule is composed of lipophilic and hydrophilic groups, and the lipophilic part is composed of hydrocarbon groups, especially long-chain hydrocarbon groups. The hydrophilic part is composed of ionic or non-ionic hydrophilic groups. There are many types of demulsifiers, which can be divided into cationic, anionic, non-ionic, and two-type demulsifiers according to the classification method of surfactants.
1.The hydrophilic group formed by the anionic demulsifier dissolved in water is a negatively charged ion group, which is divided into the following according to its hydrophilic group:
Carboxylic acids, sulfonic acids, sulfates and phosphates. Anionic demulsifiers include carboxylates, sulfonates and polyoxyethylene fat sulfate salts, which have the disadvantages of large dosage, poor effect, and easy to be affected by electrolytes and reduce efficiency.
2.The hydrophilic group formed by the cationic demulsifier dissolved in water is a positively charged particle group, and the hydrophilic group is mainly basic nitrogen atoms, but also phosphorus, sulfur, iodine, etc. Cationic demulsifiers mainly include quaternary ammonium salts, which have obvious effects on general crude oil, but are not suitable for heavy oil and aging oil.
3.The non-ionic demulsifier does not dissociate after dissolving in water, so it does not have an electric charge. The nonionic types mainly include block polyether with amines as the starting agent, block polyether with alcohols as the starting agent, alkyl phenolic resin block polyether, phenolic aldehyde resin block polyether, silicon-containing demulsifier, ultra-high relative molecular weight demulsifier, polyphosphate, modified products of block polyether, and amphoteric ionic demulsifier represented by imidazoline crude oil demulsifier.
4.The two types of demulsifiers can generate positive and negative ions after being dissolved in water. It is cationic in acidic solution and anion in alkaline solution.
At present, the commonly used non-ionic demulsifiers in oilfields are mainly as follows:

1.SP type demulsifier
The main component of SP demulsifier is polyoxyethylene polyoxypropylene octadecyl ether, and the theoretical structural formula is
R(PO)x(EO)y(PO)zH, where EO-polyoxyethylene; PO-polyoxypropylene; R-fatty alcohols; x, y, z-aggregation degree. SP type demulsifier has a yellowish paste-like substance in appearance, with an HLB value of 10~12, and is soluble in water. SP non-ionic demulsifier has a good demulsification effect on paraffin-based crude oil. Its hydrophobic part is composed of carbon-12~18 hydrocarbon chains, and its hydrophilic group is hydrophilic through the interaction of hydroxyl groups (-OH) and ether groups (-O-) with water in the molecule to achieve the purpose of hydrophilicity. Because the hydrophilicity of hydroxyl and ether groups is weak, only one or two hydroxyl or ether groups cannot pull the hydrophobic group of carbon-12~18 hydrocarbon chains into the water
There must be multiple such hydrophilic groups to achieve the purpose of water solubility. The larger the molecular weight of the nonionic demulsifier, the longer the molecular chain, the more hydroxyl and ether groups it contains, the greater its tensile force, and the stronger the demulsification ability of crude oil emulsion. Another reason why SP type demulsifiers are suitable for paraffin-based crude oil is that paraffin-based crude oil contains no or very little colloidal and asphaltene, less lipophilic surfactant substances, and less relative density. For gelatinous and asphaltene content with high (or water content greater than 2 0 % ) of raw oil, the demulsification ability of SP type demulsifier is weak because the molecular structure is single, there is no branched chain structure and aroma structure.
2.AP type demulsifier
AP demulsifier is a polyoxyethylene polyoxypropylene polyethylene polyethylene polyethylene polyethylene with polyethylene polyamine as the initiator, which is a multi-branched nonionic surfactant, with the molecular structural formula D(PO)x(EO)y(PO)z H, where the formula: EO-polyoxyethylene; PO-polyoxypropylene; R-fatty alcohols; D- Polyethylene polyamine: x, y, z- degree of polymerization.
AP structure demulsifier is used for demulsification of paraffin-based crude oil emulsion, the effect is better than SP type demulsifier, it is more suitable for crude oil demulsification with a moisture content of raw oil higher than 20%, and can achieve the effect of rapid demulsification under low temperature conditions. For example, if SP type demulsifier settles and demulsifies within 55~60°C and 2h, AP type demulsifier only needs to settle and demulsify within 45~50°C and 1.5h. This is due to the structural characteristics of AP type demulsifier molecules. The initiator polyethylene polyamine determines the structure of the molecule: the molecular chain is long and the branched chain is long, and the hydrophilic ability is higher than that of SP demulsifier with a single molecular structure. When the crude oil emulsion is demulsified, the molecules of AP demulsifier can quickly penetrate into the oil-water interface film, which occupies more surface area than the upright monolayer arrangement of SP demulsifier molecules, so the dosage is small and the demulsification effect is obvious. At present, this type of demulsifier is the best non-ionic demulsifier used in Daqing Oilfield.
3.AE demulsifier
AE demulsifier is a polyoxyethylene polyoxypropylene polyethylene polyethylene polyethylene with polyethylene polyamine as the initiator, which is a multi-branch nonionic surfactant. Compared with AP demulsifiers, AE demulsifiers are a two-stage polymer with small molecules and short branched chains. The molecular structure formula is: D(PO)x(EO)yH, in the formula: EO-polyoxyethylene: PO-polyoxypropylene: D-polyethylene polyamine; x, y – degree of aggregation. Although there are great differences in molecular physiognomy between AE and AP demulsifiers, the molecular composition is the same, but there are differences in the amount of monomers and the order of polymerization.
(1) When the two nonionic demulsifiers are designed and synthesized, the amount of material used at the head and tail is different, and the length of the polymeric molecules produced is also different.
(2) The molecule of AP type demulsifier is two-stage, with polyethylene polyamine as the initiator, polymerization with polyoxyethylene and polyoxypropylene to form a block copolymer: the molecule of AE type demulsifier is two-stage, with polyethylene polyamine as the initiator, polymerization with polyoxyethylene and polyoxypropylene to form a two-stage copolymer, so the molecule of the designed AP type demulsifier should be longer than that of AE type demulsifier.
AE type is a two-stage multi-branch structure crude oil demulsifier, which is also suitable for demulsification of asphaltene crude oil emulsions. The more lipophilic surfactant content in asphalt-based crude oil, the stronger the viscosity, the smaller the difference in oil-water density, and it is not easy to demulsify. The demulsification speed of using AE type demulsifier is fast, and at the same time, AE type demulsifier is a better anti-wax and viscosity reducer. Due to the multi-branched structure of its molecules, it is very easy to form a tiny network, so that the paraffin single crystals formed in crude oil fall into these networks, hindering the free movement of paraffin single crystals and cannot be connected to each other, forming a paraffin network structure, reducing the viscosity and freezing point of crude oil, preventing wax crystals from coalescing, so as to achieve the purpose of wax prevention.
4.AR type demulsifier
AR type demulsifier is a new oil-soluble non-ionic demulsifier composed of alkyl phenolic resin (AR resin) polymerized with polyoxyethylene and polyoxypropylene, with an HLB value of about 4~8 and a demulsification temperature as low as 35~45°C. The molecular formula is:
AR(PO)x(EO)y H, where EO-polyoxyethylene; PO-polyoxypropylene; AR-resin; x, y, z-degree of aggregation. In the process of synthesizing demulsifiers, AR resins not only play the role of initiators, but also enter the molecules of demulsifiers to become lipophiles. The characteristics of AR type demulsifier are that the molecules are not large, and there is a good dissolution, diffusion and permeation effect when the freezing point of crude oil is higher than 5 °C, which promotes the flocculation and coalescing of emulsified water droplets, and can remove more than 80% of the water in the crude oil with a moisture content of 50%~70% within 45 minutes below 45 °C, which is incomparable to SP type and AP type demulsifiers.
General principles for choosing demulsifiers
Demulsifiers eliminate the factors that stabilize the original emulsion, resulting in aggregation, coalescing, delamination and demulsification of the emulsion. The main reason for the stability of emulsion is that the emulsifier forms an interface film with a certain mechanical strength or space obstruction that acts as an emulsifier. Therefore, the main function of demulsifier is to eliminate the effective effect of emulsifier, and the selection of demulsifier should be selected according to the characteristics of emulsifier.
The basic principles for choosing demulsifiers are as follows:
Solid powder emulsifier stable emulsion can choose a good wetting agent of solid powder as a demulsifier to make the powder completely wetted into the aqueous or oil phase.
From these principles, it can be seen that some emulsifiers and demulsifiers often have no clear boundary, depending on the specific system. Of course, there are also some surfactants that are only suitable for demulsifiers for a certain type of emulsion, and can not be used as demulsifiers or emulsifiers for other systems.
It has good surface activity and can replace the emulsifier in the emulsion from the interface. Emulsifiers are surface active
otherwise, an adsorption film cannot be formed at the interface, and this adsorption is a spontaneous process. Therefore, demulsifiers must also have strong interfacial adsorption capacity to replace emulsifiers.
The interface film formed by the demulsifier at the interface of oil and water should not be firm, and it is easy to rupture under external conditions or when the droplets collide, so that the droplets are prone to coalescence.
Ionic emulsifiers can make droplets charged and stable, and ionic demulsifiers with opposite charges can neutralize the surface charge of droplets.
Nonionic or polymer demulsifiers with relatively large molecular weights are dissolved in the continuous phase, which can cause droplets to aggregate due to bridging, and then coalesce, stratify and demulsify.