The electric desalination unit is one of the indispensable devices in the refinery plant. The operation effect of the electric desalination unit will affect the long-term, safe and stable operation of the refinery production unit to a considerable extent. The function of crude oil electric desalination is to remove inorganic salts and water in crude oil. The method is to add a certain amount of demulsifier and water, dissolve the salt in water at a certain temperature, and separate oil and water under the action of an electric field, so as to achieve The purpose of crude oil desalination and dehydration. With the deterioration of crude oil properties at home and abroad, it is becoming more and more difficult to control the salt content of crude oil after desalination and the oil content in sewage by existing electrical desalination devices and processes. Electric desalination sewage accounts for about 3% of the total sewage in refineries, which is called electric desalination sewage.
Traditional Processing Technology
(1) Gravity separation
Gravity separation: Separation is carried out by using the density difference between oil and water and the incompatibility of oil and water. Sedimentation separation is carried out in grease traps or large tanks, and the common types are advection (API), parallel plate (PPI), corrugated plate (CPI) and so on. The technical equipment is simple in structure, easy to operate, and has stable oil removal effect. However, when the oil particle size is small, contains a large number of fine suspended particles, serious emulsification, heavy oil has a high specific gravity, and the density of dirty oil is very close to water, gravity sedimentation can only remove part of the floating oil. Oil, resulting in poor treatment effect, from the perspective of application, most of them can not meet the current environmental protection requirements, often lead to excessive oil content in the influent of sewage treatment plants, which seriously affects the discharge and reuse of sewage treatment plants.
(2) Hydrocyclone
A hydrocyclone, also known as a hydrocyclone, is a multiphase separation device that separates heterogeneous phase mixtures, and its structure is usually a combination of a cylinder and a cone. Due to the small particle size of oil and a large number of fine suspended particles of oil, the emulsification is serious, the specific gravity of heavy oil is high, and the density is close to that of sewage, resulting in poor separation effect (separation efficiency 50%~60%) and high oil content in effluent. In addition, the sewage has high salt content and high salinity, and the cyclone tube is easy to scale. In severe cases, the cyclone cannot work normally, which seriously affects the operation of the electric desalination device.
(3) Coalescing
There are two main mechanisms of coalescence, namely wetting coalescence and collision coalescence. The objects of coalescence treatment are mainly dispersed oil and non-surfactant-stabilized emulsified oil in oily sewage. The coalescence method increases the oil droplet size, makes the oil droplets float and separate faster, shortens the oil droplet residence time, and has strong impact resistance.
(4) Dissolved air flotation
Air flotation technology is to introduce a large number of highly dispersed micro-bubbles into the water to be treated, making them adhere to the particles (oil droplets, SS or flocs) suspended in the water as a carrier to form a floating body with an overall density less than that of water. Relying on the action of natural buoyancy, it floats to the surface of the water together to form scum and remove it to complete the water purification method of separating solids from solids, solids from liquids, and liquids from liquids. The air flotation method was first used in the mineral processing industry. Disadvantages: The residence time is long 15~40mim, the uniformity of the bubble diameter is 5-100um, and the slag scraper is used for mechanical slag discharge.
Excessive salt content of crude oil will not only increase the corrosion of equipment or pipelines during processing, transportation and storage of crude oil, but more importantly, for downstream refineries, if the salt content is too high, it cannot enter the refinery for direct processing and refining. Under normal circumstances, refineries must specify the salt content index of crude oil when buying crude oil. In the process of process design, according to the water content in the crude oil and the salt content in the water, it should be calculated to determine whether the salt content in the final crude oil is lower than the specified index. Make the salt content in the crude oil lower than the specified index. The desalination process mainly uses the principle that the salt in the crude oil is easily dissolved in the fresh water, and adopts the method of "washing" the salt-bearing crude oil with fresh water. Since the salts in the crude oil are soluble in water, most of the salts are removed during dehydration. The water content of crude oil is reduced, and the salt content is correspondingly reduced, and finally can meet the user's requirements. Theoretically, the lower the water content of the crude oil product, the lower the salt content; the lower the salt concentration in the water after washing, the lower the salt content. Therefore, the cleaner the dehydration of salt-bearing crude oil, the more washing, water and washing times, the lower the final crude oil salt content, but this will greatly increase the production cost. Generally, the most economical process plan will be considered to meet the needs of users. That's it.
Luoyang Zhengyuan Petrochemical Electric Desalination Technology
Pulse electric desalination technology is the advanced electric desalination technology of Luoyang Zhengyuan Petrochemical. It has the following characteristics.
(1) Efficiency
Good demulsification effect and high dehydration effect
Strong adaptability to crude oil with poor properties
(2) Energy saving
Reduce electric dehydration power consumption
Reduce the amount of demulsifier or do not use demulsifier
(3) Intelligence
The control system can automatically adjust, automatically increase or decrease the voltage, and the operation is more stable
(4) Environmental protection
Reduce drain oil
