Method: Vary net vapor rate, make-up vapor (steam).
Process: Vacuum systems. Must always have vapor product.
Advantages: Easily added to systems after construction.
Control valve and piping small and relatively cheap.
Disadvantages: Increases steam use and hot well water make.
Increases cooling water load.
Application: Often added after-the-fact to vacuum systems
for improved control.
Variants: Air or other inert gases may be used to bleed
into the jet suction instead of steam.
Configuration notes: Using inert gas or air instead of
steam will add a larger inert gas load to the condenser and may
affect condenser operation. In multi-stage ejector systems, using
non-condensable gas (air or inert gas) will load up all ejectors
in the system. Steam will only load the ejector with the steam
injection directly upstream.
Operation: Added load moves the vacuum jet ejector along
its operating curve. The higher the load to the ejector, the higher
the ejector suction pressure.
Warnings: Wet steam may cause ejector erosion from water
droplets. Combination of electrical tracing, superheated steam,
local water knock-out before addition to system, or other measures
may be required to reduce erosion to allowable levels.
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