Hydrocarbon Processing - December 2022 - 24

Catalysts
low-sulfur crude slate during
the pandemic to meet IMO
bunker fuel specifications
4. 2021-present: FCCU online
again; minimum UCO amount
required to feed the FCCU.
These four distinct modes of operation
selected (segmented data) vs.
a Base Case are visualized in FIGS. 6
and 7: ~320/65 m3
/hr.
/hr (fresh feedrate/
UCO recycle rate, hereafter). Minimum
UCO-flow requirement to the FCCU =
130 m3
Pre-pandemic: Base Case: ~320/
65 m3/hr; fresh feedrate at 320 m3
/hr
and UCO recycle rate at 65 m3/hr recycle;
UCO flow requirement to FCCU
at 130 m3
/hr.
* Case 1: ~350/25 m3
* Case 2: ~325/35 m3
/hr; to
maximize fresh feed intake
with the same UCO flow to
the FCCU (i.e., 130 m3
/hr)
/hr;
Reactor 2 replaced with a more
mid-distillate selective catalyst
with the same UCO flow to
the FCCU (i.e., 130 m3
/hr)
Pandemic:
* Case 3: ~200/150 m3
* Case 4: 200/150 m3
/hr; FCCU
down, maximize hydrocracking
conversion as UCO required
to feed the FCC is not needed
/hr; FCCU
/hr.
online with reduced UCO flow
to the FCCU at ~85 m3
The pre-pandemic mode of operaFIG.
6. Operational modes of four distinct cases running at different fresh feed and recycle rates
at different hydrocracking conversion levels vs. a Base Case.
tion maximized conversion by increasing
fresh feed intake while still meeting
the minimal UCO feed requirement.
Pre-pandemic, ART helped Preemraff to
replace a second-reactor catalyst earlier
than the planned turnaround. The company
advised the client to optimize the
temperature profile to make optimal use
of the more selective catalyst system in
Reactor 2, achieving additional mid-distillate
gain of > 4 wt% on a fresh feed basis.
During the pandemic, the FCCU was
temporarily shut down. The mode of operation
was to reduce fresh feed intake to
the minimum while maximizing conversion
and still meeting client obligations.
During the most recent cycle, which
occurred during the pandemic, performance
improved further by increasing
conversion, enabling the unit to increase
middle-distillate output by reducing fresh
feed intake and running low-sulfur North
Sea crudes. FIG. 7 shows that Case 3 runs
at the highest conversion around 90 vol%
with a mid-distillate gain of > 27 wt% on
a fresh feed basis vs. the Base Case when
the FCCU was down. Case 4 shows a
mid-distillate gain of ~9 wt% on a fresh
feed basis at a reduced conversion level
of 58 vol% when the FCCU was up again,
meeting the minimum UCO requirement
to feed the FCCU.
FIG. 7. Operational modes of four distinct cases running at different hydrocracking conversion
levels and mid-distillate gain vs. a Base Case.
24 DECEMBER 2022 | HydrocarbonProcessing.com
Operational challenges during the
pandemic. During the transition between
the different modes of operation,
proper heat management is required to
always keep sufficient heat in both the
first and second reactors to meet the

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Hydrocarbon Processing - December 2022

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