(c)
Vapor recovery (light ends) unit (Figure 2-34).
Light gases are
produced by a number of refining processes including primary distillation,
cracking, catalytic reforming, and delayed coking. These gases are separated into
butane, pentane, propane, and ethane in the vapor recovery units.
The gasoline
produced by cracking and catalytic reforming holds these gases in solution and is
unstable. A series of small diameter distillation towers is used to accomplish the
vapor recovery process. The vapor recovery unit removes these dissolved gases and
so stabilizes the gasoline. The separated gases are piped from the vapor recovery
unit to either an alkylation or polymerization unit and the stabilized gasoline is
routed to the treating unit (Figure 2-29).
Major recognition features of vapor
recovery unit include:
Two or four tall, thin factionators arranged in a line
Absorber column (first tower) taller than others
Gas flare may be present.
Figure 2-34. Vapor Recovery Unit.
47 IT 0673
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