Steam Ejector Basics.-1

Northvale Korting Fluid Jet
Theory and Applications of Eductors
Patrick Belcher
Eductor Basics.-1
Pressurised liquid is fed, at normal pipeline
velocity, into the motive fluid connection. 1
Eductor Basics.-2
The motive fluid enters the nozzle and is sent into the
suction chamber as a high velocity, low pressure jet.
This generates a low pressure area in the chamber.
Eductor Basics.-3
The low pressure area entrains or draws in the
suction fluid.
Both streams are thoroughly mixed within the
turbulent area of the diffuser throat.
Eductor Basics.-4
In the outlet cone of the diffuser, the velocity of the mixed
stream is converted back to pressure energy
This enables the eductor to overcome a discharge head
which is higher than the suction head but lower than the
motive pressure.
Maximum lift 8mwg
Lift affected by
specific Gravity
Performance is
dependent on motive
water pressure and
flow rate.
Vacuum Producing
Liquid or gas
 Used for pump priming
 Vessel evacuation
 Fume Extraction
Aeration 1
Adds compressed air to water
Small bubbles promote solubility
Mixing throat increases intimacy between air
& fluid
Aeration 2
Uses atmospheric air.
Mixes tank contents
Aids flocculation
Mixing 1
Standard mixing
3:1 mixing
No. of nozzles and
orientation depending
on tank shape.
Dilution 1
Can dilute and lift at
the same time.
Control dilution using
suction valve.
Risk of backflow if
discharge pressure too
PTFE lined option
Dilution 2
Scheme for high dilution ratios.
Around the pump loop. Uses the pressure differential
between inlet & outlet of pump.
Does not create a permanent pressure loss in the pump
discharge line. Can be isolated when not required.
Additional mixing created by pump action.
Hopper Eductor
Used to
powders in
to liquid
To make
Eductor Benefits
No moving parts.
– Minimal Maintenance
– Use in restricted space
– Suitable for hazardous
Can run with no
suction flow, or with
entrained solids.
Self Priming
– Ideal for intermittent
Available in virtually
all materials
– Carbon Steel
– Stainless
– PTFE lined pipe
– Poly Propylene
– Hastelloy
Design Considerations.
High backpressure a problem => Backflow
to suction branch.
 Requires a high pressure drop - Typical
discharge pressure < 0.5 Motive pressure.
 Best designed for single motive operating
point. Adjust mixture by suction, not by
 Flow from bottom of tank could be of
Eductor Uses
GAC/ Sand/Resin
– Suction of concentrates
Sulphuric Acid
Citric Acid
Orthophosphoric acid
Anti foaming agent
Hypochlorite solution
Dissolved air flotation
– Emptying pits and bunds
Tank mixing
System priming
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