Page 68 - Chemical Process Equipment - Selection and Design

40 PROCESS CONTROL

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Figure 3.1. Optimized control of an ethylene tower (Skrokov (Ed.), Mini- and Microcomputer Control in Industrial Processes, Van
NostrandlReinhold, New York, 1980).

TYPICAL ETHYLENE SPECIFICATIONS
Ethylene 99.95% weight
Methane less than 500 ppm mol. %
FEED Ethane less than 500 ppm mol. %
Propylene (and heavier) less than 100 ppm mol. %
Acetylene less than 5 ppm mol. %
Carbon dioxide less than IO ppm mol. %
Total sulfur less than 5 ppm mol. '3%
Hydrogen sulfide less than I ppm mol. %
COMFRESCR Water less than 15 ppm mol. %
Oxygen less than 5 ppm mol. %
CAUSTIC DRYER Hydrogen less than I ppm mol. '3%
SCRUBBER Carbon monoxide less than 5 ppm mol. %
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PROPYLENE
PF(OWCT

METHYIACETY-
LENES 8 PROPY-
LENE REMOVAL RECYCLE
DEMETHANEER DEETHANER ETHYLENE
SPLITTER
DEPROPANIZER PROPYLENE
SPLITTER
Figure 3.2. Flowsketch of an olefins plant and specifications of the ethylene product. AR designates a composition analyzer
and controller (after Skrokov (Ed.), Mini- and Microcomputer Control in Industrial Processes, Van NostrandlReinhoZd,
New York, 1980).