Hydrocarbon Processing - June 2021 - 44

Catalysts
To be successful in such a challenging environment,
it is of paramount importance to
develop strong partnerships between refiners
and technology suppliers to ensure maximum
conversion, product slate flexibility and unit
availability, driving to the most profitable operations
needed to stay competitive. This article
describes a successful case of how a robust
combination of operating expertise, state-ofthe-art
hardware and novel catalyst technologies
have enabled AOR's RFCCU to achieve
the facility's ambitious conversion objectives
while processing one of the most challenging
feedstocks found worldwide.
FIG. 2. Boiling point distribution of residue vs. typical FCC gasoils (left), and an
asphaltene molecule (right).
Industry
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
FIG. 3. Industry Ecat benchmark of [Fe+Na] (wt%) content.
Property
Content in feed, wt% FF
V, mg/kg
Ni, mg/kg
Fe, mg/kg
Na, mg/kg
Ca, mg/kg
Feed S. G.
Feed concarbon, wt%
Distillation 10%, °C
Distillation 30%, °C
Distillation 90%, °C
TABLE 1. Atyrau RFCCU feedstock typical properties
VGO Atm residue
<35
0.1
>53
11
0.18
22
4.1
0.87
0.86
0.1
319
371
474
20
95
28
9.37
0.92
5.5
394
481
KMG Atyrau RFCCU
Residue conversion challenges. Residual
streams from atmospheric or vacuum distillation
fractionators are characterized as having a
heavier nature than traditional gasoils used in FCCUs due to the
presence of high molecular-weight polynuclear aromatic rings-
such as resins or asphaltenes-which then result in a higher
boiling point distribution, between 500°C-700°C (FIG. 2).
Residue streams possess high density and aromaticity, in addition
to much higher Conradson carbon residue, as compared
to vacuum gasoil (VGO). It is commonly accepted that the conditions
in the FCCU do not allow the ring-opening cracking of
aromatic rings; therefore, increasing density and/or aromaticity
directly results in loss of feed conversion. The high CCR presence
is believed to convert to coke within 30%-90%, depending
on the feed nature, which heavily impacts the heat balance in
FCC operations, as seen with higher regenerator temperature,
lower cat/oil (C/O) ratio and reduced conversion.
Residue feeds also contain high levels of contaminants. The
Coker gasoil
~5
<0.03
<0.04
0.13
<0.17
<0.25
0.89
0.11
350
387
463
mospheric/vacuum residues) into lighter, more valuable products
such as transportation fuels and petrochemical feedstocks.1
Almost every option under consideration involves upgrading residue
type feedstock through an FCCU to compete under current
market conditions. Considering future demand for refined products,
slow-to-flat growth is projected for transportation fuels over
the next decade, developing in parallel with the high-margins opportunities
available in the petrochemicals market.
44 JUNE 2021 | HydrocarbonProcessing.com
high metal " complexes " typical of residues like nickel (Ni) or
vanadium (V) accelerate poisoning of conventional catalysts.
Ni deposits on the catalyst surface present a strong dehydrogenation
activity to form undesired hydrogen and coke precursors
if not inhibited properly. Unlike Ni, the V complexes
destroy the zeolite Y portion in the cracking catalyst and lower
activity due to the formation of vanadic acid. Further, its mobility
characteristics allow it to move from one catalyst particle
to another catalyst particle, extending its destructive impact
to multiple catalyst particles. V is most detrimental when the
FCCU is operated in full burn mode.2
trap dramatically reduces the FCCU's ability to destroy the active
components of FCC catalyst and, therefore, maintain high
inherent cracking activity.
In addition, other metals can be present, such as iron (Fe)
or sodium (Na), which remarkably enhance the detrimental
impact of V on the catalyst activity when processing heavy
residue feedstock. Fe and Na tolerances are crucial factors for
Atyrau's FCCU, as it presents the highest Ecat [Fe+Na] among
81 FCCUs benchmarked in the industry (FIG. 3).
Typical feedstock properties of AOR's RFCCU are shown
in TABLE 1. Besides the mentioned extreme [Fe+Na] levels, the
residue fraction has very high Ni, V and calcium (Ca) levels,
along with a Conradson carbon content exceeding 5.5 wt%
and a 30% distillation point > 480ºC. This very challenging
residual stream is fed into the unit well above 50 wt% of the
Therefore, an effective V
Ecat [Fe + Na], wt%
http://www.HydrocarbonProcessing.com
Hydrocarbon Processing - June 2021

Table of Contents for the Digital Edition of Hydrocarbon Processing - June 2021
