Hydrocarbon Processing - December 2022 - 57

Refinery-Petrochemical Integration
propylene can be produced by β-scission.
Higher temperatures in the RTC
reactor. The pre-lift gas transports regenerated
high-temperature catalysts to the
bottom of the RTC reactor to mix with preheated
feedstocks. Although DCC is an endothermic
process, the high concentration
of catalysts in the reactor can provide sufficient
heat capacity for endothermic cracking.
Correspondingly, the temperature
gradient from the bottom to the top of the
RTC reactor axis does not change much.
The entire reactor is kept at high temperatures,
which is beneficial to strengthen
β-scission to produce propylene and suppress
hydrogen transfer in DCC.
More efficient contact between catalysts
and reactants. Catalytic cracking is a
volume expansion process. If the diameter
of the reactor remains unchanged, the gas
flow velocity gradually increases from the
bottom to the top. Severe boundary effects
can occur at high central gas velocities.
The RTC reactor adopts a special configuration,
by which the gas flow velocity along
the axial direction of the reactor keeps
relatively uniform. Part of the catalyst is
refluxed from the boundary to the center
of the reactor, enabling more efficient contact
between catalysts and reactants.
A longer stable operation period.
The rear end of the DCC reactor is a
dense-phase bed. The outlet oil gas may
diffuse into the whole disengager and
eventually form coke. The coke thus
formed can easily settle and clog the spent
catalyst valve, causing the DCC unit to
shut down. In contrast, the outlet of the
RTC reactor can be directly connected
to an enclosed cyclone to prevent oil gas
from diffusing into the disengager to form
coke. Therefore, RTC has a longer stable
operation period vs. DCC.
Commercial application of RTC technology.
In November 2019, SINOPEC
Anqing Co. converted its DCC unit to
RTC technology, replacing the original
combined reactor of a riser + dense-phase
bed with a specially configured fast-fluidized
bed. During nearly 2.5 yr of smooth
operation, test
TABLE 2. A comparison between
RTC and DCC in terms of product
distribution and gasoline properties
Process
Ratio of hydrotreated
residue in the feed, wt%
Feeds
Density (20°C, kg × m-3
CCR, wt%
)
Product distribution, wt%
Dry gas
LPG
Gasoline
Light cycle oil
Slurry
Coke
Loss
Propylene yield, %
Ethylene yield, %
Ratio of ethylene
in dry gas, wt%
Ratio of propylene
in LPG, wt%
RON
DCC
52.67
916
2.65
9.59
30.77
28.43
15.8
6.35
8.83
0.23
13.71
3.51
36.6
44.56
97.6
RTC
50.22
910.6
2.11
9.35
34.47
26.99
14.91
5.83
8.27
0.18
16.27
4
42.79
47.2
98
VGO blends. Compared with DCC, RTC
technology showed an increased ethylene
yield of 0.49%, an increased propylene
yield of 2.56% and a decreased coke yield
of 0.56%. In addition, the mass ratios of
ethylene in dry gas, propylene in LPG and
the research octane number (RON) of
gasoline were improved.
Economic benefits of RTC technology.
At the time of this publication, this RTC
technology has been licensed to three refineries
with a total processing capacity of
12 MMtpy. Another unit, with a processing
capacity of 3 MMtpy, will be commissioned
in May 2023, and three additional
units will be commissioned in 2024. Based
on a comprehensive evaluation of product
production, product quality and energy
consumption, the incremental profit margin
of the RTC technology is $11.94/t of
feedstocks vs. DCC technology.
runs (including varying
feedstocks and operating modes) were
carried out. All tests have demonstrated
an increasing light olefin selectivity and
a decreasing coke selectivity for the RTC
technology. TABLE 2 details a comparison
of the performance of RTC and DCC
when treating hydrotreated residue and
Follow-up development of RTC technology.
The RTC technology is characterized
by the application of a specially
configured fast-fluidized bed to intensify
β-scission to convert heavy and inferior
feedstocks into light olefins. In the further
development of RTC technology,
FIG. 3. The RTC reactor, consisting of a
specially configured fast-fluidized bed.
its feedstock will be expanded to light
raw materials such as crude oil, naphtha
and diesel, among others. According to
industry forecasts, ethylene demand will
continue to increase over the next decade.
Therefore, it is necessary to increase ethylene
yield from the existing 5% to more
than 10%, while maintaining an appropriate
propylene yield.
NOTES
a SINOPEC RIPP's DCCpro
technology
1
residue-to-chemicals
REFERENCES
Lee, R., " Petrochemicals-The growth area that
refiners will need, " Asian Petrochemical Industry
Conference, Taipei, May 2019.
Complete literature cited available online at
www.HydrocarbonProcessing.com.
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