Method: Vary net vapor rate, no make-up gas.
Process: Vacuum systems. Must always have vapor product. This is commonly referred to as a 'dry' or 'damp' system, depending on the application, because there is no condenser before the vacuum ejector.
Advantages: All ejector discharge available for recycle. Often gives the most stable operation.
Disadvantages: Difficult to implement in systems with the ejector directly attached to its condenser. Relatively large recycle line and control valve often required. Overhead product must be compatible with water.
Application: The best ejector pressure control system for ejectors that are not stable to zero load. Often, the most economical system for stable ejector control.
Variants: System often used without reflux return to the tower (external liquid feed or pumparound reflux generation).
Operation: Recycle gas moves the vacuum jet ejector along its operating curve. The higher the load to the ejector, the higher the ejector suction pressure.
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