Page 379 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Ejectors and Mechanical Vacuum Systems 347

PIIESSURE AIR INLET
HGUlATIHG + j
SPINDLE
z
0
6 ..
:::,
"'

I
D!SCHAIGf DISCHARGE DISCHARGE DISCHARGE
STEAM JET JET COMPRESSOR JET SYPHON STEAM JET BLOWER
VACUUM PUMP AND BLAST NOZZLE

SUPERHEATED
STEAM INLET
I PIESSURI
WATfR

DISCHARGE
DESUPERHEATED
STEAM OUTLET
DESUPERHEAT ER LIQU!D MIXING EDUCTOR FUME SCRUBBER

Figure 6-2. Steam, air, gas, and liquid ejectors. By permission, Ketema, Schutte & Koerting Division.

sure. Single-stage units are usually not used for compression rosive vapors. Standard materials include cast iron, Mee-
ratios (ratio of absolute discharge to suction pressures) haniie, cast steel, stainless steel, Mone!®, Hastelloy®, tita-
greater than three [16]. This type of pressure increase for nium, Teflon®, Haveg®, rubber-lined steel, graphite-
low pressure steam is usually uneconomical when the final lined, polyvinyl chloride (PVC), fiberglass reinforced plas-
discharge pressure exceeds one-third of the high pressure tic (FRP), and bronze for the body and diffuser depend-
motive steam [ 16]. These units are usually limited to single- ing on the pressure and temperature rating. The nozzle is
stage installations based on steam economy. usually stainless steel or monel. Other materials of con-
struction include: porcelain, carbon, graphite, impreg-
Materials of Construction nated graphite, synthetic resins, glass, and special metals
of all types. lntercondensers and aftercondensers are
Because the ejector is basically simple in construction, sometimes made of these same materials and may include
it is available in many materials suitable for handling cor- random-packed surface-type, graphite or glass tubes, etc.