Vacuum tower steam ejector

When a steam ejector is in operation, its core principle relies on Bernoulli’s equation and the jet effect; it is capable of converting high-pressure steam into a high-speed jet stream, while creating negative pressure in the constricted section of the ejector. This negative pressure draws in the surrounding gases, such as the non-condensable gases and water vapor in the vacuum tower, mixing them with the high-speed steam; subsequently, as the velocity decreases and the pressure rises in the expansion section, the mixed gas is expelled, thereby achieving vacuuming inside the vacuum tower. If an excessive amount of steam is supplied to the injector, several scenarios are theoretically possible: 1. **If the nozzle design can handle it**: If the design of the injector permits a larger flow rate of steam, the additional steam will still be accelerated into a high-velocity stream, thereby generating a stronger negative pressure that can draw in more surrounding gas. In this case, the performance of the injector may be improved. 2. **Situations beyond the nozzle’s design capacity**: If the nozzle of the ejector is not designed to handle this increased steam flow, it may lead to one or both of the following situations: – **Inadequate fluid mixing**: An excessive amount of steam can affect the efficiency of fluid mixing inside the ejector, resulting in poor mixing. - **Rising back pressure**: A large amount of steam accumulating at the inlet of the ejector can lead to an increase in back pressure, that is, an increase in the pressure at the outlet of the ejector. This, in turn, reduces the ejector’s suction capacity and can result in a weaker decompression effect. In practice, injectors usually have a designed operating range; beyond this range, especially when there is an excess supply of steam, the efficiency of the injector decreases, and it can even lead to positive pressure issues, as you are concerned about. This is because the injector nozzle is unable to handle excessive steam, preventing the steam from being accelerated to the required speed at the inlet or nozzle, and thus losing its ability to generate negative pressure. In practical engineering applications, designers design injectors based on specific operating conditions and performance requirements to ensure that the injectors can function stably and effectively within the normal operating range. Excess steam needs to be controlled through means such as regulating valves in order to maintain the proper operation of the system. .

After entering the inlet of the steam ejector, the steam passes through steam nozzles (either single or multiple) before it can mix with the non-condensable gases from the vacuum tower at the ejector inlet; thereafter, it flows at high speed through the throat of the steam ejector and into the diffuser chamber. The steam nozzle has a much smaller diameter compared to the throat of a steam ejector. The situation you mentioned won’t happen.