Different Vacuum Pumps Used in Chemical Industry- Advantages and Disadvantages

  1. The common vacuum pumps in the chemical industry can be simply divided into variable volume vacuum pumps and jet vacuum pumps. Variable volume vacuum pumps use the periodic change of the pump chamber volume to complete suction and exhaust. The reciprocating vacuum pump, rotary vane vacuum pump, piston vacuum pump, liquid ring vacuum pump, roots vacuum pump are  variable volume vacuum pumps. The jet vacuum pump is a momentum transfer pump that uses the high-speed jet generated by the pressure drop of the Venturi effect to transport the gas to the outlet.

 

  1. Variable volume vacuum pump working principle, advantages and disadvantages

  • Reciprocating vacuum pump, rotary vane vacuum pump, piston vacuum pump and roots vacuum pump rely on the reciprocating motion or rotation of the piston to suction, compress and discharge the gas. Their advantage is that the vacuum degree of the new pump is relatively high, but the piston is a running part, so the wearing of the piston is unavoidable, and the working vacuum degree will continue to decrease with the increase of the number of inspections until it can not meet the production requirements. This type of pump has high working noise, high fuel consumption, and high failure rate, which are also its fatal disadvantages.

Generally, it is necessary to run a pump and the second pump as spare one, which increases equipment investment and operating costs. In addition, if this type of pump is used to pump condensable gases such as water vapor, it will emulsify the lubricating oil, so it can only be used to pump non-condensable (air) gases, and it cannot pump particulate media, which limits its scope of application.

 

  • The water ring vacuum pump is rotated by the eccentric rotor with multi-blade installed in the pump casing, and the water is thrown to the pump casing to form a water ring concentric with the pump casing. The gas is sucked in, compressed and discharged. Its advantage is that the pumping capacity is large in low vacuum, and condensable gases such as water vapor can be directly pumped.

Disadvantages:

The vacuum degree is low

It cannot pump granular media

The high-speed rotation of the rotor is not easy to do anti-corrosion treatment, so it cannot pump corrosive media.

 

  1. Jet vacuum pump working principle, advantages and disadvantages

The jet vacuum pump is a momentum transfer pump that uses the high-speed jet generated by the pressure drop of the Venturi effect to transport the gas to the outlet. It is divided into water jet vacuum pump, steam jet vacuum pump, gas-water series jet vacuum pump, gas-water combined jet vacuum pump.

 

Jet Vacuum Pump Advantages:

Jet vacuum pump has a wide range of vacuum degrees, and can directly suck condensable gases such as water vapor and granular media.

Simple structure

Easy operating

No running parts and less maintenance

Energy saving

 

  • The working principle of water jet vacuum pump

The water jet vacuum pump working principle is: the water in the circulating water tank generates a certain pressure and flow rate after the circulating water pump does work, certain pressure and flow rate enters the water collection chamber of the water ejector, and is ejected through multiple nozzles on the orifice plate. The formed high-speed jet makes the mixing chamber of the ejector vacuum, and the pumped medium enters the ejector for mixing under the action of vacuum. In the mixing chamber, it is fully mixed with the high-speed water flow, and the Venturi tube is decelerated and pressurized, and then discharged into the circulating water tank. Its advantage is that it has a higher vacuum degree than a water ring vacuum pump.

 

  • The working principle of steam-water series jet vacuum pump. One or more stages of steam jet vacuum pumps are connected in series in front of the ejector of the water jet vacuum pump, that is, the steam-water series jet vacuum pump.Its working principle is: the saturated or superheated steam of a certain pressure enters the mixing chamber of the steam ejector after decompressing and increasing the speed through the nozzle, so that the mixing chamber generates a vacuum, and the pumped medium is sucked into the mixing chamber and mixed with the working steam. After the fluid passes through the diffuser, the velocity drops and the pressure rises until it reaches the suction port pressure of the next stage and then is discharged into the next stage steam jet pump or water jet pump. It has relatively high vacuum degree, which can replace the water ring pump-roots vacuum system and the rotary vane pump-roots It directly pump condensable gas, but its pumping non-condensable gas in high vacuum is limited.

 

  • The working principle of new high-efficiency steam jet vacuum pump

The new high-efficiency steam jet vacuum pump is composed of a one-stage or multi-stage steam jet pump and a high-efficiency condenser. After the pressure is increased, it enters the mixing chamber of the steam ejector, so that the mixing chamber generates a vacuum, and the pumped medium is sucked into the mixing chamber and mixed with the working steam. After the first stage suction pressure is discharged into the next stage steam ejector. After the mixed fluid discharged from the steam ejector in front of the condenser enters the high-efficiency condenser, the condensable gas is cooled into liquid and the non-condensable gas is discharged out of the condenser together with the cooling water. It can be installed at any height, and the amount of non-condensable gas in the pumped medium is relatively small, most of which are condensable gas. Compared with traditional multi-stage steam jet vacuum pump, it can save more than 60% of the working steam.

 

  • The working principle of steam-water combined jet vacuum pump.

It is composed of a first-stage steam-water jet vacuum pump in series behind the first-stage condenser of the traditional steam jet pump. It overcomes the shortcomings of the steam jet vacuum pump and the water jet vacuum pump, and exerts their advantages. It can not only achieve a higher working vacuum, but also have a larger pumping capacity, saving working steam more than 50%, saving cooling water more than 30% compared with the traditional multi-stage steam jet vacuum pump. It does not need to equip a starting pump, and the evacuation time is short.

  • The advantages of multi-stage steam jet vacuum pump are simple structure, convenient use, stable and reliable operation. The disadvantage is that the steam consumption is large (high operating cost), and it must be installed at a height of 11 meters or higher, which is inconvenient for maintenance.

 

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