and chilling, the emulsion passes to the settler located above the contactors for acid
separation. The acid phase is recycled by gravity to the contactor impeller. The
hydrocarbon phase (effluent) is routed through the tube side of the contactor heat
exchanger and allowed to flash to provide refrigeration.
The heat of reaction is removed by chilling the emulsion on the shell side of the
contactor heat exchanger by partially vaporizing settler effluent on the tube side.
Refrigerant vapor is separated from the effluent liquid in a flash drum, compressed,
and condensed. A portion of the condensed refrigerant is routed to a depropanizer.
The balance of the refrigeration and depropanizer bottoms is flash cooled and
returned to the reactors.
Feed Pretreatment
Feed treatment usually consists of de-ethanizing and Merox treating the FCC
olefins. Some refiners have added selective hydrogenation process (SHP) units to
saturate dienes and reduce acid consumption. Feeds are generally not dried.
Effluent Treating
The hydrocarbon effluent containing alkylate and excess isobutane is warmed by
chilling recycle isobutane and treated to remove traces of entrained acid and ester
D
E
I
S
O
B
U
T
A
N
I
Z
E
R
Propane
Compressor
Refrigerant
Refrigerant
Flash
Effluent
Flash
Effluent
Settler
Acid Recycle
STRATCO Contactors
Coalescer
Acid to
Contactors
Alkaline
Water
Wash
n-Butane
Acid
Wash
Acid
Mixed
Butanes
Alkylate
D
E
B
U
T
A
N
I
Z
E
R
D
E
P
R
O
P
A
N
I
Z
E
R
FCC
Olefins
Recycle
i-Butane
Fig. 5 STRATCO
R effluent refrigerated alkylation process
Alkylation in Petroleum Processing
449