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For oil-water separation, the oil-water separator is commonly used. The oil-water separator is also called an oil-water separator. Its main principle is to separate oil and water by using the different specific gravity of oil and water, filtering, settling, floating and other methods.
In addition, we classified and summarized several scientific and effective oil-water separation methods:
Using the difference in oil-water density, the high-speed rotating oil-water mixture produces different centrifugal forces, thus separating oil from water. Because the centrifugal equipment can reach a very high rotational speed and generate centrifugal force up to hundreds of times of gravity acceleration, the centrifugal equipment can completely separate the oil and water, and only needs a short residence time and a small equipment volume. Because centrifugal equipment has moving parts, it is difficult to maintain daily, so it is only used in laboratory analysis equipment and places that need to reduce the floor space.
Hydrocyclone, the main equipment room that works on the principle of centrifugal separation, is used to physically separate liquid as a continuous phase from solid particles, liquid droplets, or bubbles as a dispersed phase. The greater the density difference between the dispersed phase and the continuous phase, the easier it is to separate the two phases.
According to the different affinities of oil and water to solid substances, hydrophilic and oleophobic solid substances are commonly used to make various evaporation devices. Solid substances used for oil-water separator element should have good wettability. Materials suitable for this requirement are: ceramics, wood chips, fiber materials, walnut shells, etc. For example, the ceramsite evaporator in Dagang Oilfield uses ceramsite as filler. When the oil-water mixture flows through the ceramsite layer, it is forced to constantly change the velocity and direction, which increases the probability of collision and coalescence of water droplets and makes small droplets coalesce and settle quickly.
Air floatation is a method of purifying water by forming tiny bubbles in water and floating flocs to the liquid surface. The condition is that bubbles attached to oil droplets can form oil-gas particles. Because the appearance of bubbles increases the density difference between water and particles, and the diameter of particles is larger than that of crude oil droplets, the rising speed can be obviously increased by replacing the oil density with the density between particles. That is, when one bubble (or multiple bubbles) is attached to one oil drop, the vertical rising speed can be increased, so that oil drops with a diameter much smaller than 50μm can be removed.
Because the relative densities of oil, gas and water are different, the oil-water mixture with certain components will form a certain proportion of the oil, gas and water phase when the system is in equilibrium at a certain pressure and temperature. When the relatively light components are in laminar flow, the heavier liquid droplets settle according to the motion law of the Stokes formula, and the gravity settling separation equipment is designed according to this basic principle. According to Stokes's formula, the sedimentation rate is directly proportional to the square of water radius in oil, the density difference between water and oil, and the inverse ratio to the viscosity of the oil. By increasing the water density, enlarging the oil-water density difference and reducing the oil viscosity, the settling separation speed can be increased, thus improving the separation efficiency.
As the final means of oil-water treatment, electric evaporation is widely used in oil fields and refineries. Its principle is that the emulsion is placed in a high-voltage AC or DC electric field. As the electric field acts on water droplets, it weakens the interfacial film strength of the emulsion, promotes the collision and merger of water droplets, and finally aggregates into water droplets with larger particle size, which are separated from crude oil. When treating crude oil emulsion with high water content by electro-evaporation, electric breakdown will occur and the necessary electric field strength between electrodes cannot be established. Therefore, electro-desorption can not be used independently, and can only be used as the subsequent process of other treatment methods.
