Vacuum pumps are commonly used in chemical production
Some processes in chemical production are often required to be carried out under atmospheric pressure. A vacuum pump is a mechanical device for obtaining absolute pressure below atmospheric pressure. There are many types of vacuum pumps, and the types of vacuum pumps commonly used in chemical plants are introduced as follows.
Reciprocating vacuum pump:
The working principle of reciprocating vacuum pump is basically the same as that of reciprocating compressor, and its structure is not much different. When the required vacuum degree is high, the compression ratio is large, and the residual gas in the residual gap has a great influence, so the vacuum system must be small. In order to reduce the influence of the balance gap, the balance air channel is set between the left and right ends of the vacuum pump cylinder. At the end of the piston exhaust, the balance air duct is connected for a very short time, allowing the residual gas in the clearance to flow from one side of the piston to the other side, thereby reducing its pressure.
Water ring vacuum pump:
There is an eccentric impeller in the circular shell and a certain amount of water in the pump. When the rotor rotates, due to the action of centrifugal force, water is thrown to the shell wall to form a water ring. The water ring ACTS as a seal, closing the gap between the blades into many small Chambers of different sizes. The rotor rotates to the right and the sealed chamber expands gradually. The gas is inhaled from the suction port on the right. As the rotor rotates to the left, the volume of the chamber shrinks gradually and the gas is discharged from the left vent.
The vacuum degree formed by water ring vacuum pumpis limited by water temperature and can reach 83.4x103Pa. The pump can also be used as a blower, and the pressure (surface pressure) produced shall not exceed 98.07x103Pa.
The water ring vacuum system is simple, compact, easy to manufacture, easy to maintain, and has a long service life because the rotating part has no mechanical friction.
The water ring vacuum pump is suitable for conveying corrosive or explosive gases. The disadvantage is low efficiency, generally 30~50%.
Water injection vacuum pump:
If the working fluid of jet pump is water, it is called water jet pump. If it is steam, it is called steam jet pump.
The pressure of the single-stage steam jet pump can reach 0.01MPa. If the pressure of the single-stage steam jet pump is to reach a higher vacuum degree, the multi-stage jet system can be adopted.
The advantages of spray vacuum pump are wide range of working pressure, large amount of gas extraction, simple structure. The disadvantage is low efficiency.