Crude oil dehydration

Crude oil extracted from wells generally contains a certain amount of water, and high water content in crude oil leads to waste in storage and transportation, requires additional equipment, and increases energy consumption. The water present in crude oil often contains salts, which accelerate the corrosion of equipment, containers, and pipelines； During the external refining of oil, when water is heated together with crude oil, it vaporizes rapidly and expands, causing pressure to rise. This can disrupt the normal operation of the refinery and affect product quality; in severe cases, explosions may even occur. Therefore, before transporting crude oil externally, dehydration is required to ensure that the water content does not exceed 0.5%. Crude oil dehydration methods The dehydration process of crude oil consists of two stages: demulsification and sedimentation. The breakdown of an emulsion is known as demulsification; it refers to the process in which the oil-water interface within the emulsion, whose membrane is formed by the action of emulsifiers, is destroyed by external factors such as chemical, electrical, or thermal influences, leading to the collision and coalescence of the water droplets in the dispersed phase. After demulsification, water remains in a free state suspended in the oil; through further collisions, it forms larger water droplets that sink to the bottom due to gravity – this is sedimentation. 　　Methods of dehydration include: (1) heating ； (2) Chemical demulsification ； (3) Electroaggregation ； (4) Gravity settling. To improve the dehydration effect, these methods are often used in combination in oil fields. 　　1. Thermochemical dehydration Thermochemical dehydration of crude oil involves heating the water-containing crude oil to a certain temperature, and adding a small amount of surfactant (known as demulsifier) to the crude oil emulsion in order to break down its emulsified state and facilitate the separation of oil from water. The location where the demulsifier is added must not only ensure optimal performance of the agent but also take ease of management into account. It is generally best to add it at the oil well head, as this can fundamentally prevent the formation of water-in-oil emulsions (in oil fields, this is referred to as \"additive injection at the well head for demulsification inside the pipes\"). Adding chemicals at the wellhead takes advantage of the mixing in the transportation pipelines to ensure that the demulsifier is evenly dispersed in the crude oil, thereby achieving good comprehensive effects such as demulsification, drag reduction, and wax prevention. 　　The thermochemical dehydration process is simple, low-cost, and highly effective, and has been widely used at home and abroad over the past few decades. However, using solely thermochemical dehydration to reduce the water content in crude oil to acceptable levels is often uneconomical. 　　2. Gravity settling dehydration After demulsification, the oily crude oil needs to be separated from free water and impurities. In the sedimentation tank, oil and water are separated primarily through the washing action of the lower water layer caused by the density difference between oil and water, as well as the sedimentation of water droplets in the upper crude oil; this process is often referred to as primary dehydration in oil fields. Since the 1980s, China has developed various coalescing bed dehydrators (which utilize hydrophilic and lipophobic solid materials to create different types of coalescing beds, based on the differing affinities of oil and water for solid substances), which are used for initial dehydration and improve its efficiency. 　　3. Electrical dehydration Electrical dehydration is the best method for thoroughly removing water from crude oil with low water content. In oilfield electrical dehydration, it is often used as the final step in the crude oil dehydration process. In an electrodehydrator, the crude oil emulsion is subjected to a high-voltage direct or alternating current electric field, which weakens the strength of the interfacial films surrounding the water droplets. This causes the droplets to collide and merge, forming larger droplets that settle out of the crude oil. Water containing electrolytes is a good conductor of electricity. Oil-in-water emulsions are prone to electrical breakdown when subjected to a strong electric field, which prevents the dehydrator from functioning properly; therefore, electrical dehydrators can only handle oil-in-water emulsions with low water content. 　　To ensure effective dehydration, heating is generally used to reduce the viscosity of the crude oil entering the electrodehydrator. Most of the mineral salts in crude oil are dissolved in water, and most crude oil loses its salts as it is dehydrated. 　　Currently, \"two-stage dehydration\" (thermochemical dehydration and electrochemical dehydration) is widely used in oil fields to achieve satisfactory dehydration levels. In the first stage of dehydration, the water content is reduced to around 30%; in the second stage, it is brought down to below 0.5%, which meets the requirements for crude oil output, with the oil content in the separated water also being no higher than 0.5%.

The analysis is excellent; the detailed points are ① dehydration using chemical demulsifiers； ②Chemical dosing at the wellhead and pipeline demulsification ； ③Gravity settling dehydration ； ④Dehydration using centrifugal force ； ⑤Using a hydrophilic solid surface to coarsen and dehydrate emulsified water ； ⑥electrodehydration

Currently, a high-speed flow dehydrator is also under development for the direct dehydration of crude oil with a water content as high as 90%; its internal electrodes are covered with insulating material, eliminating the risk of breakdown. I wonder if it was successful?