In many chemical enterprises, water, electricity, compressed air and other vacuum equipment are indispensable public facilities. Vacuum is usually used to remove air or water vapor to prevent interference with the process. Vacuum can also improve the efficiency of the reaction process and the recovery of important compounds.
In the vacuum state, the boiling point of the liquid decreases, which is very conducive to the treatment of thermal sensitive materials. In the vacuum state, the solid final product produced from the liquid is more uniform, and there are almost no holes caused by bubbles.
In addition, it is safer to handle and transfer corrosive compounds under vacuum.
Vacuum in chemical process of role
1. Remove oxygen and water vapor from the air (if these components are combined with process components, the chemical reaction will change);
2. Remove excess reactants or unnecessary by-products considering efficiency and yield;
3. Reduce the boiling point of the mixture during distillation;
4. Dry the material by removing the solvent;
5. Use differential pressure to transport materials.
Various methods of obtaining vacuum
The vacuum is generated by the vacuum pump. There are many types of vacuum pumps. In order to obtain low pressure and high pumping speed, multi-stage vacuum pumps can be connected in series and in parallel to form a vacuum system. However, all vacuum systems include a main pump or vacuum pump, called exhaust pump. According to different pumping methods, primary vacuum acquisition equipment is divided into the following categories:
1. Mechanically intercept the gas and transmit the inhaled gas from the suction port to the exhaust port, such as variable volume vacuum pump.
2. Momentum is transmitted through the ejector, and the pumped gas is taken away, such as steam jet pump and atmospheric ejector.
3. On the expanded surface, the gas is absorbed by porous media at low temperature, such as adsorption pump.
The first two vacuum pumps are widely used in the chemical industry, but the steam jet pump is rarely used because of its high energy consumption and pollution. The adsorption pump stores the pumped gas in the pump and cannot be directly discharged into the atmosphere, so it is not suitable for industrial application. With the more and more extensive application of vacuum in the field of chemical industry, it is more suitable to adopt a composite vacuum system, that is, a vacuum device composed of multiple vacuum pumps in series.
Due to the harsh working conditions and long working cycle of the chemical process, the vacuum pump must be reliable, durable and stable, and must also have the following characteristics:
1. Be able to handle the steam of various solvents without damaging the pump;
2. It will not pollute the process and environment;
3. Waste generated shall be minimized;
4. The vacuum pump shall be corrosion resistant.
5. Be able to handle flammable gas or steam;
6. Be able to suck in liquid without damaging the pump.