Vacuum Jets/ Ejectors
A vacuum jet and ejector extend the operating range of process vacuum systems that is beyond what can be achieved by liquid ring vacuum pump-based systems alone. Utilizing the venturi principle, the motive fluid of the jet or ejector entrains the process stream (non-condensables and condensables) discharging either into a condenser or the liquid ring vacuum pump.
The motive fluid is either atmospheric air or pressurized steam. Steam is useful as it is condensable. The backing pump size stays small by removing the condensed steam from the process. However, the cost of steam utility may be a cause for a different motive fluid source. As an alternative, we utilize atmospheric air to compress the process to a higher absolute pressure. Because we use atmospheric air, there is no added utility cost. However, because we will still be operating under a vacuum, any non-condensable introduced into the process will expand. This causes the backing vacuum pump to increase in size. The analysis of the vacuum pump is against the added utility of a steam jet. This process determines which route is best suited to the application.
Advantages of vacuum ejectors and jets include the following:
- No moving parts
- Low cost
- Reduces load on other stages of compression (as a result, helps pull a deeper vacuum)