Page 91 - Fluid Catalytic Cracking Handbook

68 Fluid Catalytic Cracking Handbook

desalter and carry over salts with the desalted crude. Slop can be
fed to the coker or FCC main fractionator with the same result,
« Purchased FCC feedstock can be exposed to salt water as ballast,
* The me of atomizing steam and/or water that contain sodium. Just
about every refiner practices some type of feed atomization using
either steam or water. The steam or water can contain varying
amounts of sodium depending on the quality of water treatment
used in the refinery.

Another problem associated with sodium appears in the form of
sodium chloride. Chlorides tend to reactivate aged metals by redis-
tributing the metals on the equilibrium catalyst and allowing them to
cause more damage.

Other Metals
Iron is usually present in FCC feed as tramp iron and is not cata-
lytically active. Tramp iron refers to various corrosion by-products
from upstream processing and handling.
Copper is as active as nickel, but the feed contains much less of it.

Summary
The metals in the FCC feed have many deleterious effects. Nickel
causes excess hydrogen production, forcing eventual loss in the con-
version or thruput. Both vanadium and sodium destroy catalyst struc-
ture, causing losses in activity and selectivity. Solving the undesirable
effects of metal poisoning involves several approaches:
* Increasing the makeup rate of fresh catalyst
* Employing some type of metal passivation
* Adding good quality equilibrium catalysts to flush the metals
* Employing demetalization technology to remove metals from the
equilibrium catalyst
Both demetalization and passivation technology are addressed in
Chapter 3.

The typical refinery laboratory is not equipped to conduct PONA
and other chemical analyses of the FCC feed on a routine basis.