Oil gas separation filter working principle
（1） Composition and characteristics of oil and gas mixture
Oil gas mixture is generally composed of lubricating oil and compressed gas. There are two forms of lubricating oil: one is liquid phase form; the other is gas phase form. This form of lubricating oil is mainly produced by the vaporization of liquid phase lubricating oil. It is affected by the pressure and temperature in the equipment, and the saturated vapor pressure of lubricating oil also affects the quantity of gas phase lubricating oil 。
Generally speaking, the higher the temperature and pressure in the equipment, the more gas-phase lubricating oil will be; otherwise, the lower the temperature and pressure, the more liquid-phase lubricating oil will be. Gas phase lubricating oil also has the characteristics of other gases, so it can not be separated by mechanical method, only by chemical method.
Therefore, in order to separate oil and gas, the first step is to change the gas-phase form of lubricating oil into the liquid-phase form of lubricating oil. Reducing temperature and pressure is the most common and effective method. In addition, it is also a common method to make the vapor pressure reach the saturation state and then change the gas-phase form into the liquid-phase form. Since the temperature or pressure of the equipment cannot be reduced to a very low level, the performance of the lubricating oil should be continuously improved in the actual production process. Synthetic oil or semi synthetic oil, which has a low steam pressure saturation, can be used to reduce the oil content in the exhaust gas.
Of course, in general, the content of gas phase lubricating oil is very small. In the operation of the equipment, it takes a certain time and pressure for the lubricating oil to change from liquid phase, but in the actual process, the pressure in the separation filter is not very high, and the separation process is also very short, so most of the oil-gas mixture is liquid-phase lubricating oil. Therefore, how to separate the liquid phase lubricating oil is the key content of the work.
In the form of liquid phase, the diameter of oil drops is generally 1 to 50 microns, and the smallest is only 0.01 microns, so the properties of different oil drops are different. Through the action of gravity, large oil drops can be precipitated to the point of separator, but small oil drops will be suspended in the gas and difficult to be separated.
（2） Methods of oil and gas separation
There are two ways to separate oil and gas in the case of oil injection rod compressor:
1. Affinity aggregation method
Affinity coalescence is to use special components to coalesce oil drops with smaller diameter into oil drops with larger diameter, and then separate them under the action of gravity. The main object of affinity coalescence method is to separate small oil droplets with diameter less than 1 μ m through two steps of filtration and coalescence. The original used in the separation process is a kind of porous filter material, which can filter the oil drops with larger diameter in the lubricating oil, and make the oil drops with smaller diameter coalesce on the fibers of the original material, and finally coalesce into the oil drops with larger diameter.
2. Mechanical collision method
The mechanical collision method is to use the weight of the oil drop itself to separate the large oil drop from the gas filled oil drop. The mechanical impact method is generally applicable to oil drops with rain diameter greater than 1 μ M. In the actual operation process, the collision between the obstacle and the oil drop is used to attach the oil drop to the surface of the obstacle, so as to achieve the purpose of separation. It must be noted that the mechanical collision method requires that the oil-gas mixture has a certain speed when hitting the obstacles. For example, the oil injection screw compressor, when the speed of the mixture reaches 3 meters per second, is the best. Too high or too low speed will reduce the accumulation of oil droplets.