In the vacuum evaporation process on the market, the vacuum pump is often used for the concentration of traditional Chinese medicine, the synthesis of Western medic ine and the washing of Western medicine. The commonly used vacuum pump type is water ring vacuum pump. In order to understand the specific role of water ring vacuum pump in the vacuum evaporation process, we need to understand the two concepts of vacuum evaporation and vacuum evaporation process, as well as why the vacuum pump is needed in the vacuum evaporation process, and by the way, analyze the principle of vacuum evaporation. With these questions, follow the EVP water ring vacuum pump manufacturer to understand it.
It is an important technology to form various films by vacuum evaporation.
The essence of vacuum evaporation distillation:
1. In essence, it is a heat transfer phase change process;
2. The evaporation process is endothermic vaporization;
3. The condensation process is exothermic liquefaction;
4. The purpose of vacuum pumping is to remove the non condensable and non condensable saturated steam;
5. Only the composition of the medium and the saturated vapor pressure at evaporation temperature determine the vacuum degree of the vacuum pump;
6. The only factors that determine the pumping speed of vacuum pump are the amount of leakage air, the amount of non condensable nitrogen and the temperature of condensation separation.
Vacuum evaporation process is a process of heating solid materials in a high vacuum environment, sublimating or evaporating them and depositing them on a specific substrate to obtain thin films. In microelectronics, vacuum evaporation technology is mainly used to make active components, contact of devices and their metal interconnection, film resistor with high precision and low temperature coefficient, insulation medium and electrode of film capacitor, etc.
In the vacuum evaporation process, the secondary steam of the final effect is usually condensed in the mixed condenser. In order to automatically discharge the cooling water under vacuum, the installation height of condenser is generally higher than 10m. The vacuum degree of the evaporator is determined by the condensation temperature of the secondary steam. As the dissolved gas in the solution is released by heating, the evaporator and pipeline also have air leakage. In order to maintain the vacuum, it is necessary to use a water ring vacuum pump (see fluid conveying machinery) to continuously remove these non condensable gases.
The principle of vacuum evaporation is a physical process. The evaporation rate of the solvent in the solution is related to the external resistance. Under vacuum condition, the boiling point of the solution decreases, so does the resistance of the solvent molecules escaping from the liquid surface. At the same time, the difference between the negative pressure caused by the inner space of the evaporator and the pressure at the bottom of the evaporator is used as the power to make the solution circulate automatically, so as to improve the evaporation speed. That is to say, the characteristics of vacuum evaporation are: the boiling point of the solution is reduced under low pressure, and a large amount of water is evaporated with less steam.
Vacuum pump is used to pump vacuum, or water jet vacuum pump is used to replace liquid ring vacuum pump to pump vacuum. Water with a certain pressure is input into the water chamber of jet pump through water pump. Then, water flows through symmetrical and evenly arranged nozzles to form a water beam with a high flow rate. After a certain distance, each water beam is gathered on the center line of throat pipe. Due to the Adsorption, forming negative pressure around it, plays the role of suction vacuum. The high vacuum can be obtained by the interaction of water and air, the impact of vortex entrainment and mixed compression, and then through a long tail pipe suction.
Therefore, in the vacuum condition, when the solution is heated by the heat exchanger, it enters the evaporator from the pipe on the upper part of the heat exchanger. The solution in the evaporator takes away the heat due to the evaporation water, which makes the temperature drop. The cool solution flows into the heat exchanger from the bottom of the evaporator. The solution entering the evaporator circulates in the evaporator and heat exchanger, evaporating a large amount of water. Part of the acid mist is entrained by the evaporated water vapor, which affects the water discharge quality. Before the water vapor enters the condenser, it is necessary to separate and catch the acid mist through the mist separator. The separated water vapor is brought to the condenser with vacuum to condense into water, and then flows into the water seal tank towel for circulation or discharge.