Hydrocarbon Processing - March 2022 - 39

Petrochemical Technology
calibration. For hydrogenated heavy oil, the product advantages
of a DTFB reactor are low olefin content in gasoline and high
RON. Additionally, with special catalysts and a flexible switch
of the reactor operation mode, it can produce more propylene.
Advances in processing paraffin-base heavy oil. With the
development of special catalysts and new DTFB engineering
technology, the adaptability of a DTFB in processing paraffinbase
heavy oil has been greatly improved. For a clean gasoline
production program, compared with an early DTFB, the olefin
content of gasoline can be reduced from 35% to less than 20%,
while RON increases.
Using a petrochemical company that is processing paraffinbase
heavy oil as an example, the changes in gasoline properties
before revamp (adopting a conventional riser) and after revamp
(adopting a DTFB) are shown in FIG. 9. It can be clearly seen
that the olefin content of gasoline produced is ~30% and RON
is ~90 when the conventional riser is used and the equilibrium
catalyst activity is 70 (the unit consumption of fresh catalyst is
1.6 kg/t of heavy oil). After revamp into the DTFB, the olefin
content of gasoline can be reduced to < 20%, the olefin content
of the gasoline is 23%-25% and RON is 90.5-91.1 after the operation
mode adjustment.
At this time, the unit consumption of fresh catalyst is only
0.5 kg/t of heavy oil. This is because the second reaction zone
of the DTFB has the characteristics of high catalyst density and
long reaction time, which strengthen the hydride ion transfer
reaction. From the reaction mechanism, the hydride ion transfer
reaction is the elementary reaction of the hydrogen transfer
reaction and the bimolecular cracking reaction. Therefore,
strengthening the hydride ion transfer reaction will inevitably
increase the hydrogen transfer reaction and the bimolecular
cracking reaction rate simultaneously. This strengthens the
conversion of small molecular olefins into isoparaffins; on the
other hand, it strengthens the bimolecular cracking reaction
between small molecular olefins in gasoline and large molecular
saturated hydrocarbons in diesel and slurry, which reduces
the yield of diesel and slurry. Finally, gasoline yield increases
and gasoline olefin content decreases.
Advances in processing high-proportion intermediatebase
vacuum resid (VR). A DTFB allows a wide adaptability
of raw materials and can even break through the bottleneck of the
selection of catalytic cracking raw materials to realize the longterm
safe and stable operation with high-mixing ratio and highcarbon
residue raw materials. With the newly developed catalyst
rich in intracrystalline mesoporous Y-type molecular sieve, the
gasoline yield reaches 44.6% when the catalytic cracking raw material
contains 46.6% intermediate-base VR (TABLE 4).
The coke produced by this unit can use the newly-developed
10 MPa-grade steam generation technology to make full use of
the characteristics of heavy oil catalytic cracking of a large steam
production load and high thermal energy. This can increase the
steam pressure of waste heat boilers and external heat extractors
to high pressure levels (10 MPa). Therefore, 280 t/hr of
high-pressure steam produced by the heavy oil catalytic cracking
unit with an annual capacity of 2.8 MMtpy will be sent to
the steam turbine unit (25 MW) for power generation through
the system pipe network. After the stable operation of the highTABLE
4. Overview of DTFB for processing heavy oil
with high residue content
Company
Feedstock
Density (20°C)/(kg·m-3
CCR, %
Hydrogen content, %
Product distribution, %
Dry gas
LPG
Gasoline
Diesel
Slurry
Coke
Loss
)
JM
939.1
6.55
11.91
3.62
20.34
44.6
13.75
5.69
11.8
0.21
pressure steam system, the company's power center changed.
Two 130-t/hr circulating fluidized bed (CFB) coal-fired power
boilers were shut down, and the catalytic cracking unit became
the company's new power center.
Takeaway. A DTFB is a multi-flow single-vessel fluidized bed
that is organically composed of a transport bed, a fast fluidized
bed and a turbulent fluidized bed. It has the characteristics of
multi-flow and multi-temperature zones, and has developed
into an open reactor engineering platform that is suitable for
processing various types of distillate oil or heavy oil with high
residue content. On this platform, a series of new technologies,
such as a catalytic cracking technology for producing ultra-low
olefin gasoline and a catalytic cracking technology for producing
more propylene and marine fuel oil components, have been
developed, injecting new vitality into catalytic cracking technology
development.
LITERATURE CITED
1
2
He M., " The development of catalytic cracking catalysts: Acidic property related
catalytic performance, " Catalysis Today, April 2002.
Xu Y., " Study on the effect of hydrogen transfer reaction on olefin conversion, "
Petroleum Processing and Petrochemicals, Research Institute of Petroleum
Processing, Beijing, China, 2002.
3
XU, Y.-H., J.-H. Gong, J.-S. Zhang, et al., " Experimental study on 'two-reaction
zone' concept connected with MIP process, " ACTA PETROLEI SINICA,
Research Institute of Petroleum Processing, Beijing, China, 2004.
4
XU, Y.-H., J.-S. Zhang, J.-G. Ma, et al., " Controllability of cracking reaction in
MIP process, " ACTA PETROLEI SINICA, Research Institute of Petroleum
Processing, Beijing, China, 2004.
Complete literature cited available online at www.HydrocarbonProcessing.com.
XIN WANG is a Senior Engineer at Sinopec's Research Institute
of Petroleum Processing. He is engaged in the research of
catalytic cracking processes, and has more than 60 patents.
YOUHAO XU is the Chief Expert of Sinopec. Dr. Xu is the
inventor of the proprietary DTFB. He has more than 200 patents
and has published 110 papers.
Hydrocarbon Processing | MARCH 2022 39
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