Page 21 - Microsoft Word - Sulfo and Sulfa 1.doc

A direct expansion air chiller vessel cools the compressed air to a temperature of 7°C
(45°F). The chilled air is then dried in dual, automatic pulse-less desiccant-type air
dryers to a dew point of –80°C (–112°F). The lack of a pulse in the air stream is vital to
product quality. If the air pulses, there will be a momentary interruption in mole ratio
which results in a loss of product quality. The result is product with high free oil, dark
color and possibly other undesirable by-products. The dual air dryers are equipped with
11 individual bubble tight control valves. The control valves ensure absolutely no
interruption of process air when changing dryers and a smooth pressure transition when
the dryers switch to regeneration cycle. A cooling air blower supplies cool air to the
regenerated (off-line) air dryer to reduce the bed temperature to an acceptable level prior
to bringing the regenerated air dryer back on-line. This is important – if the dryer bed is
too hot, the process air dew point will be higher than desirable due to the increased
equilibrium concentration of water in the hot air exiting the dryer.

Figure 20. Air Supply System

VENT REGENERATION/
UTILITY AIR

AIR DRYER
SYSTEM PROCESS AIR

AIR VENT AIR
CWR
DRYER DRYER
COOLING
AIR BLOWER

FILTER
CWS
DIRECT EXPANSION
AIR CHILLER SYSTEM

CWS
MAIN PROCESS CWS CWR
AIR BLOWER CWR

REGENERATION/
UTILITY AIR
REGENERATION
AIR BLOWER

A regeneration/utility air blower supplies cooling air to the double pipe gas coolers used
in the gas plant. Hot air (200°C) leaving the low maintenance double pipe coolers

Page 20 of 36 © 1997 The Chemithon Corporation