Page 377 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Ejectors and Mechanical Vacuum Systems 345

I STEAM SUCTION SUPERSONIC SUBSONIC
NOZZLE CHAMBER DIFFUSOR THROAT DIFFUSOR

Steam & Air Diuhorge

A B E F G

VELOCITY
----+--,.1--r---t----:�-t--------=""j,-------,._=:--------t Moch I= 1000 Ip,
I
I
I
---+--+-+-- ..... ---+---------+------+--------� Operating
Steam Pressure
' PRESSURE
' \
Steam & Air Discharge
\
' '
'
' \
steam only - ···· air only -- steam and air mixture
Figure 6-1. Basic ejector components and diagram of energy conversion in nozzle and diffuser. By permission, Ingersoll-Rand Co.

suction nozzle or vapor inlet, passing into the suction 8. Installation costs are relatively low when compared
chamber. Here the air or other mixture is entrained by to mechanical vacuum pumps. Space requirements
and into the high velocity steam. This new mixture enters are small.
the upper (or inlet) portion of the diffuser, passes 9. Simple operation.
through the diffuser throat (center narrow portion) and
exits through the outlet end of the diffuser. In the dif- Ejectors are rather versatile when applied to a wide
fuser the velocity head of the mixture is converted back to variety of processing movement, compression, mixing,
a pressure which is higher than the air-mixture suction, etc., operations. A brief listing of some useful functions
but considerably less than the inlet steam pressure. are (By permission [30]):

Features • Pumping and Lifting Liquids
Using steam as the motive fluid
Ejectors have the following features that make them Steam jet syphons
good choices for continuously producing economical vac- Steam jet exhausters
uum conditions: Single-stage vacuum pumps
Using air as the motive fluid
1. They handle wet, dry, or corrosive vapor mixtures. Air jet syphons
Air jet exhausters
2. They develop any reasonable vacuum needed for
industrial operations. Using liquids as the motive fluid
Water jet eductors
3. AJl sizes are available to match any small or large Water jet exhausters
capacity requirements.
• Heating Liquids (by Direct Contact)
4. Their efficiencies are reasonable to good.
Tank type heaters
5. They have no moving parts, hence, maintenance is Stearn jet healers
low and operation is fairly constant when corrosion
is not z factor. Pipeline type heaters
Steam jet heaters
6. Quiet operation. Steam jet heaters (large capacity)
7. Stable operation within design range. Steam jet syphons