Hydrocarbon Processing - December 2022 - 55

RefineryPetrochemical
Integration
D.
CAO, China Petroleum and Chemical Corp.,
Beijing, China; Q. MA, SINOPEC Anqing Co., Anhui,
China; J. GONG, J. ZHANG, Z. ZHANG, X. WEI,
X. CHANG and J. ZHU, SINOPEC Research Institute
of Petroleum Processing, Beijing, China; and
L. WU, SINOPEC Engineering Inc., Beijing, China
A novel deep catalytic cracking technology
for residue-to-chemicals processes
Over the past two decades, annual global
demands for refined products and basic
petrochemicals have increased by approximately
1.3% and 3.5%, respectively. Many
refiners around the world are focusing on
improving their operations to co-produce
petrochemical feedstocks as demand for
refined products is forecast to decline. The
production of basic petrochemicals accounted
for 14 MMbpd of global crude oil
demand in 2018 and is forecast to increase
to 20 MMbpd by 2050, accounting for approximately
50% of the expected growth
in oil demand. In addition, global demand
for ethylene and propylene is forecast to
increase from 270 MMtpy in 2018 to 385
MMtpy in 2030.
Fluid catalytic cracking (FCC) has
become the second major propylene production
technology after steam cracking,
showing high flexibility in feedstocks and
product distribution. FCC units (FCCUs)
typically use vacuum distillation products,
namely vacuum gasoil (VGO) and vacuum
residue as feedstocks. Deep catalytic
cracking (DCC) is an FCC process that
uses proprietary catalysts to selectively
crack various heavy feedstocks to light
olefins. The process was developed by the
co-authors' company and has been commercially
proven since 1990 through more
than 10 installed units. The DCC process
is like the traditional FCC process, with the
modified reactor consisting of a riser and a
fluidized dense bed. The dense bed at the
end of the riser results in longer residence
times at high catalyst/oil ratios, favoring
secondary cracking of primary intermediates,
which is believed to increase propylene
production at the expense of gasoline
yield. It is noteworthy that DCC has poor
adaptability to feedstocks. The density of
feedstocks is generally not more than 0.92
g/cm3
, and the hydrogen content is not
less than 12.6 wt%. As the quality of the
feedstocks tends to be heavier, the application
of DCC technology is greatly limited.
Analysis of the DCC reactor. For a
long time, research on the DCC reactor
(FIG. 1) has been neglected. The proprietary
catalyst-consisting primarily of
ZSM-5-has a short residence time in the
riser, which is insufficient to convert heavy
oil to light olefins. Therefore, the combination
of a riser and an additional fluidized
dense bed is generally considered to
be a good choice for DCC focused on enhancing
olefin production. Nevertheless,
this combination of reactors has several
disadvantages, which are discussed below.
The regenerated catalysts are transported
to the bottom of the riser for
contact with feedstocks. The feedstock
then undergoes evaporation and catalytic
cracking. Since the riser operates in the dilute
phase bed, not all feed molecules can
effectively contact the catalysts. Those
heavy oil molecules that are not in contact
with the regenerated catalysts may underFIG.
1. The configuration of the DCC reactor,
consisting of a riser and a fluidized dense bed.
Hydrocarbon Processing | DECEMBER 2022 55
Hydrocarbon Processing - December 2022

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