Steam jet vacuum pump has a large volume of exhaust gas, a wide range of work, a simple structure, and no parts with relative motion. It is a widely used vacuum equipment and is mainly used in degassing, decolorization, drying, deodorization, distillation, refrigeration and transportation. In particular, it is non-selective for inhaled gases and shows superior advantages compared to mechanical vacuum pumps (oil pumps) in food production, petrochemicals, oil processing, polyester production, and the concentration of materials containing organic solvents. This article analyzes the influencing factors of the steam jet vacuum pump in order to provide reference for its wide application.
How Steam Jet Vacuum Pumps Work
A steam jet vacuum pump uses a gas dynamic principle that converts static pressure energy and kinetic energy when a fluid flows to form a vacuum. The water vapor with a certain pressure reaches the speed of sound when it passes through the Laval nozzle throat. When it reaches the diffuser of the nozzle, the static pressure can be converted into kinetic energy and reach supersonic speed. At the same time, a vacuum is formed at the outlet of the nozzle. The pumped gas is under pressure differential. It is pumped into the suction chamber, mixed with supersonic steam while entering the venturi tube, and then discharged at a subsonic speed from the venturi's diffusion tube, while the mixing gas is gradually reduced in velocity, the pressure is increased, and then discharged from the discharge port. discharge. If several jet pumps are used in series, a condenser is added between the pump and the pump to condense the steam and a higher degree of vacuum is obtained. The entire steam injection vacuum pump consists of several stages of pump body and condenser. The pump bodies at all levels are composed of nozzles, chambers and diffusers. The nozzles can be single or multiple. The nozzles are generally made of stainless steel. The suction chamber and diffuser can be made of stainless steel, cast iron and carbon steel. And other materials.
Main Factors Affecting Vacuum Pump Capacity
1. Research on working steam and its dryness
Both the low steam pressure and the pressure fluctuation have a great influence on the capacity of the vacuum pump. Therefore, the steam pressure should not be lower than the required working pressure, but the design of the vacuum pump used has been fixed. Increasing the steam pressure too much will not increase the suction volume and vacuum. degree. In addition, to ensure that the steam pressure supplied by the boiler is stable, it is best to use a boiler to provide steam to the steam jet pump so that the steam pressure does not fluctuate and the vacuum pump is stable.
The dryness of the steam also has a great influence on the performance of the vacuum pump. Among them, the water can cause vacuum fluctuations. If the water content is too high, even a vacuum cannot be pumped. Usually, a steam separator is added in front of the steam drum to obtain high dryness. Working steam, while effectively insulating the steam line. In order to obtain the best working efficiency, the working steam provided for jet vacuum pumps should be superheated steam at 5°C~10°C. In particular, the five-stage pump requires very high quality of steam. A trace amount of moisture may cause the ice plug of the nozzle to cause the vacuum level of the fifth-stage ejector to decrease or have no effect.
2. Research on requirements of circulating cooling water
The supply of cooling water is insufficient, the condenser will generate heat, the sound of the air flow will increase, the vacuum degree will drop rapidly, and even the steam will return to the exhaust pipe. For the inter-pipe cooling condenser, the water supply pressure should be 0.2 MPa, and the water supply should be slightly larger than the actual amount, so that the water fluctuations will be relatively stable. In addition, in order to avoid fluctuations in the vacuum caused by an unstable supply of water, it is preferable to use a separate circulating water system to supply water to the condenser of the vacuum pump.
If the cooling water temperature is too high, the capacity of the vacuum pump will drop, and sometimes even vacuum cannot be drawn. Generally, it does not exceed 32°C.
More vacuum pump information is available at China Vacuum Pump Trading Network (/).
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