Debottlenecking Delta Coke Limited FCC Operations
Martin Evans, Bart de Graaf, Paul Diddams
Johnson Matthey Process Technologies
214 Bourne Blvd, Savannah, GA USA
E-mail: [email protected]
Abstract
Many FCC units are run hard up against regenerator temperature, air rate or wet gas
compressor constraints. Decreasing the delta coke on the catalyst provides a way to relieve
these constraints, allowing refiners to run higher rates of heavier feeds, which has a
significant positive impact on FCC profitability.
FCC Process licensors are well aware of these incentives, and offer a variety of hardware
solutions to help reduce delta coke. FCC catalyst suppliers also offer lower activity and
lower delta coke catalysts, well suited for running high levels of residue feed. Lower catalyst
activity is typically compensated for by higher catalyst addition rates.
Rare earth oxides, titanates and various other metals traps have also been used for many
years to reduce contaminant delta coke in high Vanadium applications. These materials
have been used as trapping agents mainly because of their compatibility with FCC catalyst
manufacturing routes. This allows them to be easily incorporated into the main catalyst
particle.
Using a separate particle trapping approach allows more effective metal trapping
components to be used, since compatibility with the binding system of FCC catalyst is no
longer a limitation. More effective irreversible trapping of contaminant metals such as
vanadium can be achieved using mixed alkaline metal oxides, such as hydrotalcite like
materials. The stronger the interaction of contaminant metal with the metal trap, the larger
the benefits for the FCC operation. The subsequent reduction in delta coke and gas yield is
an effective way to relieve FCC operating constraints, allowing refiners to run heavier feed to
the FCC.
This paper shows commercial data demonstrating the high affinity of such separate particle
additives for contaminant metals. Data is presented from five different FCC operations
where separate particle metal traps were used to relieve delta coke constraints. In each
case different strategies were used to take advantage of the reduction in delta coke and gas
make. In addition to presenting this commercial data, tentative mechanisms will be
presented to explain how these additional benefits were achieved.
It is interesting to note that in addition to residue feed FCC applications, separate particle
metal traps are also becoming popular with refiners operating with lower levels of
contaminant metals. These additives are not just vanadium traps – their unique ability to
decrease delta coke and dry gas is becoming applicable to a broader range of FCC
operations.