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up and recycle diluent from separators, enters the reactor top and flows downwards through
two beds of the same catalyst. Reactions occur in mixed phase (mainly liquid).
Main reactions happening are:
- Hydrogenation of diolefins.
- Hydrogenation of alkenyl aromatics (hydrogenation of the linear side chain).
- Isomerization of olefins.
- Hydrogenation of olefins
- Thermal and catalytic polymerization of unstable compounds.
The two last reactions must be avoided.
After being cooled, reactor effluent is sent to hot separator. Vapor from the separator, which
contains light hydrocarbons, is partially condensed and sent to cold separator. Vapor from the
cold separator is sent to second stage reaction section as hydrogen make-up. Liquid effluents
from hot and cold separators are mixed together. Part of this liquid is recycled, the remaining
is sent to the second stage reaction section.
Second stage reaction section
The feed coming from the first stage reaction section is mixed with the recycle gas. The
mixture is heated before entering the second reactor top and flows downward through two
types of catalysts: the first one to finish hydrogenation, the second one for desulphurization.
Main desirable reactions occurring are:
- Hydrogenation of olefins.
- Hydrogenation of sulphur compounds.
After consecutive cooling, reactor effluent enters a separator in which the vapour phase is
partly purged, partly recycled, and the liquid phase is partly recycled, partly fed to stabilizer
column.
Stabilization section
The purpose of this column is to eliminate light components such as hydrogen and hydrogen
sulphide dissolved in the gasoline.
The stabilizer overhead is condensed and sent in a reflux drum where vapour and liquids
phases are separated. Vapour phase is routed to sour gas and decanted water is sent to battery
limit.
The column bottom stream constitutes the final product. This desulphurized product is cooled
down and routed to battery limit.
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