Jet vacuum pump is a momentum transfer pump that utilizes the pressure drop of the Venturi effect to generate a high-speed jet that delivers gas to the outlet. It is divided into water jet vacuum pump, steam jet vacuum pump, steam water series jet vacuum pump, and steam water combination jet vacuum pump. Jet vacuum pumps are increasingly being used in various processes of chemical operations due to their wide vacuum range, ability to directly extract condensable gases such as water vapor and granular media, simple structure, easy operation, minimal maintenance of non operating components, and energy-saving and consumption reducing advantages. The working principles of various jet vacuum pumps are introduced below.

(1) Working principle and structural diagram of water jet vacuum pump

The equipment composition of the water jet vacuum pump is shown in its structural diagram. Its working principle is that the water in the circulating water tank generates a certain pressure and flow rate after being pumped by the circulating water pump. The water with a certain pressure and flow rate enters the collection chamber of the water jet injector, and is sprayed by multiple Laval nozzles on the orifice plate, forming a high-speed jet that creates a vacuum in the mixing chamber of the injector. The pumped medium enters the mixing chamber of the injector under the action of vacuum, and is fully mixed with the high-speed water flow in the mixing chamber. After being slowed down and pressurized by the Venturi tube, it is discharged into the circulating water tank. Non condensable gases precipitate, and condensable vapor overflows from the overflow port of the water tank. This process is repeated. Its advantage is the low position complete machine type, which has a higher vacuum degree than the water ring vacuum pump. It can replace the W-type reciprocating vacuum pump by eliminating the pre condenser, saving one-time equipment investment and operating costs.

(2) Working principle and structural diagram of steam water series jet vacuum pump

Connect one or more stages of steam jet vacuum pump in front of the injector of the water jet vacuum pump, namely the steam water series jet vacuum pump. Its structure is shown in the steam water series jet vacuum pump. Its working principle is: saturated or superheated steam of a certain pressure is reduced in pressure and increased in speed through a Laval nozzle before entering the mixing chamber of the steam injector, creating a vacuum in the mixing chamber. The pumped medium is sucked into the mixing chamber and mixed with the working steam. The mixed fluid passes through a diffusion tube, with a decrease in velocity and an increase in pressure, until it reaches the suction inlet pressure of the next stage and is discharged into the next stage steam jet pump or water jet pump. It is a low-level complete machine type with relatively high vacuum degree, which can replace water ring Roots unit and rotary blade Roots unit to directly extract condensable gases. However, its ability to extract non condensable gases in high vacuum is limited.

(3) The working principle and process flowchart of the new steam jet vacuum pump

The new steam jet vacuum pump is composed of one or more steam jet pumps and a condenser. Saturated or superheated steam with a certain pressure is depressurized and accelerated through a Laval nozzle before entering the mixing chamber of the steam jet injector, creating a vacuum in the mixing chamber. The pumped medium is sucked into the mixing chamber and mixed with the working steam. The mixed fluid passes through a diffusion tube, with a decrease in velocity and an increase in pressure until it reaches the suction inlet pressure of the next stage before being discharged into the next stage steam jet injector. After the mixed fluid discharged from the steam jet in front of the condenser enters the condenser, the condensable vapor is cooled into liquid and discharged outside the condenser with the cooling water (see the process flow diagram of the new steam jet vacuum pump). It can be installed at any height and is suitable for suctioning media that are mostly condensable.