Steam Ejector Basics.-1

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Northvale Korting Fluid Jet
Theory and Applications of Eductors
By
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.
Pumping



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
application.
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
high.
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
introduce
powders in
to liquid
stream
To make
lime
solution.
Eductor Benefits

No moving parts.
– Minimal Maintenance
– Use in restricted space
– Suitable for hazardous
zones


Can run with no
suction flow, or with
entrained solids.
Self Priming
– Ideal for intermittent
use

Available in virtually
all materials
– Carbon Steel
– Stainless
/316/304/Duplex
– PTFE lined pipe
– Poly Propylene
– UPVC
– ABS
– 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
motive
 Flow from bottom of tank could be of
benefit.

Eductor Uses


GAC/ Sand/Resin
removal.
Dilution
– Suction of concentrates
»
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Sulphuric Acid
Caustic
Brine
Citric Acid
Orthophosphoric acid
Anti foaming agent
Hypochlorite solution


Dissolved air flotation
Pumping
– Emptying pits and bunds


Tank mixing
System priming
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