Ejectors have chambers that convert pressure energy into velocity energy. Steam (or motive fluid) that acts as motive fluid is introduced into the chamber with an reducer type arrangement and followed immediately by reducer and expander arrangement. This arrangement increases the velocity of motive fluid as it enters the chamber. As the motive fluid exits the ejector the empty space left in the chamber is filled with the process fluid (liquid / vapor) and is carried out along with the motive fluid. Thisvis the basic phenomena that is known as the vacuum. Location of steam ejectors at the top of the systems is to ensure lesser energy consumption during the vacuum production. Any vapor will condense in the piping and will build a liquid head in the upstream of ejectors and will need more energy to create vacuum and subsequent process. Unless there is space created for the incoming material in the downstream of the vacuum production equipment, energy costs of vacuum production will be expensive. The location at top will allow lot of vertical space and time for the evacuation of material drawn out of the columns. Also the system under vacuum is ready to take in air in case of any leak. So it is better that the areas of possible leaks (under vacuum) to as minimum as possible. The system in the downstream of vacuum production equipment will be on highervpressure side and will not allow air ingress even if it leaks. So probably it is a combination of safety and energy optimization that governs the Ejectors location. The following paper is about understanding ejector system better.