Why is the oil-water separation filtration so effective II?

Oil-water separation has a wide range of applications in environmental protection, manufacturing, agriculture, and petroleum and petrochemical fields, and the oil-water filter element provides a stable guarantee for filtering effect and efficient operation.

The research on oil-water separation technology includes two aspects: removing water from oil and removing oil from water. The former is widely used in the field of petrochemicals, while the latter is mainly used in the field of environmental protection. It is a technology for removing pollutants from sewage and removing organic liquids from oily sewage (usually the oil content in sewage is less than 1%). The filter cotton in the filter is fixed by a metal mesh and separates oil and water by the following method. The biggest benefit is protecting the environment.

Processing process

In terms of oil removal in water, there are six ways to deal with it, depending on the different particle sizes of the water in the continuous phase of the oil.

1. Gravity sedimentation separation method

Gravity sedimentation separation method is the most basic separation method for oil-water separation. This method utilizes the difference in density between the continuous phase and the dispersed phase in the oil-water mixture and the principle that oil and water are immiscible. The emulsion to be separated is left to stand for a long time to achieve the purpose of phase separation between the oil phase and the water phase. This method can remove free water and most of the free water in the oil. The sedimentation rate of water droplets is related to the average particle size of the water droplets, the density difference between the oil and water phases, and the dynamic viscosity of the continuous phase oil. Increasing the particle size of the water droplets, increasing the density difference between the oil and water phases, and reducing the viscosity of the oil can increase the sedimentation rate of the water droplets. Gravity sedimentation method has the advantages of low energy consumption and low cost, so it has become the preferred method for preliminary separation of oil and water.

2. Centrifugal separation method

Centrifugal separation method is a method developed on the basis of gravity sedimentation. According to Stokes' law of gravity sedimentation, in order to improve the separation efficiency, it is necessary to increase the dispersed phase particle size, increase the gravity, increase the density difference between the two phases, and reduce the viscosity of the continuous phase. Applying an electric field in the separation equipment can increase the particle size, and increasing the equipment temperature can reduce the viscosity of the continuous phase. However, these two aspects increase energy consumption and cost. Therefore, in order to improve efficiency, centrifugal separation is used to increase gravity.

Ordinary gravity sedimentation method is separated under the gravity of 9.8m/s2, while centrifugal separation can increase the gravity to 100-1000 times, which greatly improves the separation efficiency of oil and water. Centrifugal separation method has the advantages of simple structure, low cost, convenient and flexible installation, and low maintenance cost. However, it is easy to increase the emulsified water in the oil due to the large shear force during use, which affects the subsequent separation. In addition, the separation versatility of different oil products is not strong, and the equipment and filter elements need to be replaced frequently.

3. Vacuum separation method

The vacuum separation method is a method of separating oil and water based on the difference in volatility between the oil phase and the water phase in the oil-water mixture. In a sealed environment, a certain vacuum is formed on the surface of the liquid, and measures are taken to make the number of molecules leaving the liquid surface and entering the liquid equal per unit of time. At this time, a dynamic balance between volatilization and dissolution is formed. By vacuuming and other methods, the pressure in the closed space is reduced to below the saturated vapor pressure of water at that temperature. At this time, the water in the oil will vaporize and separate from the oil, achieving the purpose of oil-water separation.

The vacuum separation method has a high separation efficiency and can separate free water, emulsified water, and dissolved water with high efficiency on a large scale. However, the application of the vacuum separation method consumes a large amount of heat energy, which increases energy consumption and is not conducive to cost savings. At the same time, the frequent heating of oil shortens the service life of the oil.

4. Electrostatic Coagulation Method

The equipment used in the electrostatic coalescence method is an electrocoagulation dehydrator, in which electrocoagulation and gravity sedimentation are carried out simultaneously. It can be applied to a variety of oil products to be separated, and the demand for demulsifiers is also relatively small. It has the advantages of high dehydration efficiency, large processing capacity, fast speed, and cleanliness. However, when treating oil products with high water content, it is difficult to establish a stable electric field between the electrodes. Therefore, the electrocoagulation method is mostly used in conjunction with other dehydration methods.

5. Adsorption separation method

The adsorption separation method is a physical method. According to the oil-water separation principle and droplet wetting theory, the oil-water separation adsorption materials are mainly divided into super-hydrophobic and super-oleophilic materials, materials with super-hydrophobic and oleophilic properties, and stimulation-responsive oil-water separation materials. When the oil-water mixture passes through the material, the super-hydrophobic and super-oleophilic properties determine that the oil can pass through, while the water is intercepted by the filter material, thus achieving oil-water separation. There are three main types of optional substrates for this material, namely inorganic materials, polymer materials, and fiber materials. It has super-hydrophobic and super-oleophilic properties and can achieve efficient separation of emulsified water in oil products. The separation efficiency is above 99.99%, and the membrane flux is high, reaching 10⁵L/(m²·h·bar).

Fiber materials have the advantages of low cost, biodegradability, and wide sources. They have good separation effects on oil-water mixtures without emulsified water, can be recycled, and still have good separation performance in corrosive environments. A certain degree of roughness is constructed on the surface of the material by self-assembly, making the material hydrophobic, and having good separation performance for oil products containing emulsified water, which can be recycled.

6. Ultrasonic separation method

Ultrasonic waves refer to sound waves with a frequency higher than 20,000 Hz. They have the advantages of good directionality, strong reflection ability, and energy concentration. The application of ultrasonic waves in oil-water separation mainly utilizes its ability to demulsify oil-water emulsions. This method uses a lot of demulsifiers, which causes pollution to the oil and the environment. The ultrasonic demulsification method is a new demulsification method that can be used alone to demulsify emulsions. When used in conjunction with chemical demulsifiers the effect is remarkable.