4.4.4. Influents / effluents scheme
The following schemes represent simply what enters and what goes out the battery limit
during normal operations.
48
Figure B-4-5: Influents/effluents scheme for C
3
selective hydrogenation during normal
operations
Figure B-4-6: Influents/effluents scheme for C
4
selective hydrogenation during normal
operations
Figure B-4-7: Influents/effluents scheme for gasoline hydrogenation during normal
operations
Gasoline
hydrogenation
H
2
Gasoline product
Fugitive emissions
Gas relieves
Off-gas
C
4
selective
hydrogenation
H
2
Hydrogenated C
4
cut
Fugitive emissions
Gas relieves
C
3
selective
hydrogenation
H
2
Hydrogenated C
3
cut
Fugitive emissions
Gas relieves
Raw C
3
cut
Raw C
4
cut
Recycle C
4
cut
Reflux drum purge gas
Reflux drum water draw-off
Raw pyrolysis
gasoline
49
4.5. Intermittent operations
4.5.1. Catalyst reduction / reactivation / hot hydrogen stripping
Catalyst reduction
Before the first use of the catalyst, and after regenerations, the catalyst is in the oxide form,
which is inactive. It has to be reduced with hydrogen to recover its active form. The reduction
reaction is the following:
MeO + H
2
→ Me + H
2
O
(Me corresponds here to the metal used as catalyst, for instance palladium Pd)
The flow of dry reduction gas through the catalyst allows the elimination of the water
contained in the catalyst.
Catalyst reactivation / hot hydrogen stripping
Reactivation is hot hydrogen stripping used when the catalyst is deactivated by free water
carry-over. These two operations are similar to reduction except the operating temperature.
Figure B-4-8: Influents/effluents scheme for C
3
selective hydrogenation during catalyst
reduction or reactivation
Figure B-4-9 Influents/effluents scheme for C
4
selective hydrogenation during catalyst
reduction, reactivation or stripping
C
4
selective
hydrogenation
Catalyst reduction
/ reactivation /
stripping
Gas (H
2
(25%)
+ N
2
(75%))
Gas with presence
of HC and H
2
O
C
3
selective
hydrogenation
Catalyst reduction
/ reactivation
Reduction /
reactivation
gas
Reduction /
reactivation gas
with presence of
HC and H
2
O
|