Answer: According to the different separation mechanisms, two different oil-gas separation methods are used in oil-injected screw air compressor units. One is called the mechanical method, that is, the collision method or cyclone separation method, which relies on the gravity of the oil droplets themselves and the centrifugal force to separate oil droplets with larger diameters from the gas. Actual tests show that for oil droplets with a diameter greater than 1μm, they can be effectively separated by mechanical methods. The other is the affinity coalescence method, which uses components made of special materials (generally called oil fine separators or separator cores) to make oil droplets with a diameter of less than 1μm first coalesce into oil droplets with larger diameters, and then separate them.
Nowadays, these two different oil-gas separation methods are generally used in oil-injected screw compressor units at the same time, that is, the mechanical method is used as a rough separation, and the affinity coalescence method is used as a fine separation.
Early mechanical methods generally used the collision method, that is, setting a certain obstacle in the flow direction of the oil-gas mixture. When the oil-gas mixture collides with the obstacle, the oil droplets in the mixture will gather on the surface of the obstacle and fall to the bottom of the separator under the action of gravity. When the collision method is used, the speed at which the oil-gas mixture hits the obstacle has a certain range, and its optimal value is related to the density of the gas and lubricating oil. Generally speaking, the optimal impact speed is about 3m/s.
Modern units generally use cyclone separation or a combination of the two methods for rough separation. This method is to set a cyclone channel in the oil-gas separator. When the oil-gas mixture enters the oil-gas separator, it first passes through the cyclone channel. Large oil droplets will be thrown onto the wall under the action of centrifugal force, and then fall to the bottom of the separator under the action of gravity.
When the oil-gas mixture is separated by mechanical method, about 99.7% of the oil will be separated, and the diameter of the oil droplets at this time is mostly below 1μm, and it can no longer be separated by mechanical method.
