U.S. patent application number 10/013832 was filed with the patent office on 2002-08-15 for two-stage riser catalytic cracking process.
This patent application is currently assigned to PetroChina Company Limited and University of Petroleum (East China). Invention is credited to Du, Feng, Duan, Aijun, Han, Zhongxiang, Li, Chunyi, Li, Zheng, Ma, An, Niu, Genlin, Shang, Honghong, Sun, Yudong, Yang, Chaohe, Zhang, Jianfang.
Application Number | 20020108887 10/013832 |
Document ID | / |
Family ID | 4595996 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020108887 |
Kind Code |
A1 |
Zhang, Jianfang ; et
al. |
August 15, 2002 |
Two-stage riser catalytic cracking process
Abstract
This invention relates to a new two-stage riser catalytic
cracking process, particularly to an improvement of the
conventional riser reactor and reaction-regeneration system by
application of a two-stage riser reactor to fulfill the aims of the
concatenation of oil-vapor, catalyst in relays as result in
shortening reaction time and increasing average performance of the
catalyst.
Inventors: |
Zhang, Jianfang; (Dongying
City, CN) ; Shang, Honghong; (Dongying City, CN)
; Yang, Chaohe; (Dongying City, CN) ; Ma, An;
(Dongying City, CN) ; Niu, Genlin; (Dongying City,
CN) ; Du, Feng; (Dongying City, CN) ; Sun,
Yudong; (Dongying City, CN) ; Li, Zheng;
(Dongying City, CN) ; Li, Chunyi; (Dongying City,
CN) ; Han, Zhongxiang; (Dongying City, CN) ;
Duan, Aijun; (Dongying City, CN) |
Correspondence
Address: |
STERNE, KESSLER, GOLDSTEIN & FOX PLLC
1100 NEW YORK AVENUE, N.W., SUITE 600
WASHINGTON
DC
20005-3934
US
|
Assignee: |
PetroChina Company Limited and
University of Petroleum (East China)
|
Family ID: |
4595996 |
Appl. No.: |
10/013832 |
Filed: |
December 13, 2001 |
Current U.S.
Class: |
208/113 ;
208/120.01 |
Current CPC
Class: |
C10G 11/18 20130101 |
Class at
Publication: |
208/113 ;
208/120.01 |
International
Class: |
C10G 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2000 |
CN |
00134054.9 |
Claims
What is claimed is:
1. A catalytic cracking process, comprising the steps of: (a) high
temperature catalyst coming from a regenerator entering into the
bottom of the first stage riser (6) to contact with the feedstock
(15), which then is vaporized and begins to react; (b) separating
the partially coked catalyst, which is to be regenerated, from
oil-vapor in an intermediate separator (4); (c) recycling the
partially coked catalyst to a regenerator (2) to complete the first
cycle after the catalyst is stripped in a striping section (5) in
which the entrained oil-vapor is separate; (d) oil-vapor from the
intermediate separator (4) entering the second stage riser (7) to
contact with the hot catalyst coming from an external heat absorber
(3); (e) oil-vapor carrying the catalyst flowing upwards and
performing catalytic cracking reactions continuously; and (f) then,
the mixture of oil-vapor and catalyst entering a settler (1) to
separate, and the oil-vapor out of the settler (1) going into a
fractionation system while the catalyst returns to the regenerator
(2) after being stripped, which completes the second cycle of the
catalyst.
2. The catalytic cracking process according to claim 1, wherein
oil-vapor coming from the first stage of riser (6) also can be
separated through the intermediate separator (4) and the other
separators into gasoline, diesel oil, liquefied petroleum gas and
heavy oil; then one or several of them will enter the second stage
of riser to perform reactions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND
DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to a new two-stage riser catalytic
cracking process, particularly to an improvement of the
conventional riser reactor and reaction-regeneration system. It
uses a two-stage riser reactor to fulfill the aims of the
concatenation of oil-vapor, catalyst in relays as result in
shortening reaction time and increasing average performance of the
catalyst.
[0005] 2. Background Art
[0006] In the petroleum processing industry, the catalytic cracking
technology is one of the most important processes. In the prior
arts of current catalytic cracking, till today, it follows the
early riser reactor and reaction-regeneration system. All the riser
reactors are very long, mostly 30.about.36 meters. And some of them
are even more than 40 m. In the riser reaction-regeneration system,
preheated feedstock enters a riser reactor through the feed nozzle.
It comes into contact with the high-temperature catalyst coming out
of a regenerator and was vaporized. Then reactions happen. The
oil-vapor carrying catalyst flows along the riser upwards at an
average linear velocity of about 10 m/s. It reacts while it flows,
which takes about 3 seconds. During the reaction procedure, coke is
generated and deposits on the surface and the active center of
catalyst so that the activity and selectivity of catalyst drop
rapidly. For this reason, the coked catalyst must be separated from
the oil-vapor in time. And it should enter the regenerator to be
regenerated for recycling application, which forms a circuit of
catalyst. The oil-vapor enters a distillation system to separate
into products. The slurry oil, which is not converted into light
fractions (generally called recycle oil) after the reaction, enters
the riser reactor again. It is the basic process of the catalytic
cracking reaction-regeneration system. Due to the especial
characteristics of heavy oil, varieties of difficulties are brought
into the catalytic cracking processing. In recent years, the
development of the catalytic cracking technology was focused mainly
on the RFCC technology. In the prior art, lots of revamps have been
made before or after the riser reactor and achieved certain
positive effects. The following are some examples of main new
technologies and their functions:
[0007] One example is the atomization technology of heavy feed
(nozzle). It improves the contact state between feedstock and
catalyst and to enhance the yield of light oil.
[0008] A second example is the gas-solid high-speed separation
technology at the outlet of risers to separate the gas-solid
quickly to reduce the over cracking reaction.
[0009] A third example is the high-efficiency multi-stage stripping
technology of spent catalyst. This technology increases stripping
effects, reduce the yield of coke and increase the yield of light
oil.
[0010] A fourth example is the two-stage high-efficiency
regeneration technology. The technology enhances the burning of
coke, reduce coke content on regenerated catalyst and maintain the
activity of catalyst.
[0011] A fifth example is the reaction termination technology. This
technology shortens the reaction time, reduce the harmful secondary
reactions and enhance the yield of light oil.
[0012] A sixth example is the multi-position of the feedstock
injection technology. It treats different feedstock with different
characteristics and optimizes the reaction process.
[0013] A seventh example is the millisecond catalytic cracking
technology. It also shortens the reaction time and decreases the
detrimental secondary reactions. (But it is still in R & D
phase.)
[0014] An eighth example is the down flowed riser technology which
is now still in R & D phase.
[0015] In the prior arts , except that the last two items involved
the changing of the riser reactor, those improvements didn't change
the general structure of the current riser reactor.
[0016] The most major disadvantage of the current riser reactor is
that the riser is too long, which leads to an overlong reaction
time of about 3 seconds. It has been proved that the current
catalyst activity at the outlet of the riser is only about 1/3 of
the initial activity. After only one second's the reaction, the
catalyst activity declines by 50%. Obviously, the activity and
selectivity of catalyst has dropped to a fairly low level in the
second half of the riser reactor so that catalysis is weakened and
the thermal cracking reactions and detrimental secondary reactions
are promoted. This kind of situation not only limits the
enhancement of the single-pass conversion of the feedstock, but
also makes the content of olefin in FCC gasoline very high
(45.about.60%) which cannot meet the new requirements of gasoline
standard.
BRIEF SUMMARY OF THE INVENTION
[0017] The aim of this invention is to avoid the shortcomings of
the above-mentioned technologies and to provide a new two-stage
riser catalytic cracking process. It adopts a two-stage riser
reactor and a double-loop reaction-regeneration system to realize
the concatenation of oil-vapor, the relay of catalyst, shortened
reaction time and increased average performance of catalyst. The
invention is characterized by application of a two-stage riser
reactor and a double-loop catalyst regeneration system. It makes
the process a brand new one with the concatenation of oil-vapor in
two-stage riser and the relay of catalyst along two routes.
[0018] In order to realize the above-mentioned aims of this
invention, the inventors carry out the brand new reaction
technology in the following steps: The high-temperature catalyst
coming from the regenerator (2) enters firstly into the bottom of
the first stage of riser (6), and contacts with the feed stock (15)
which is vaporized immediately. After about one second's reaction,
the mixture of oil-vapor and catalyst enter an intermediate
separator (4) to separate the partially coked catalyst. After being
stripped in the stripping section (5), the partially coked catalyst
flows into the regenerator (2) to complete the first cycle. The
oil-vapor coming from the intermediate separator (4) enters the
second stage riser (7) to contact with the hot catalyst from the
external heat absorber (3). The oil-vapor carrying the catalyst
flows upwards and performs catalytic cracking reactions
continuously. After reaction, the mixture of oil-vapor and catalyst
enter the settler (1) to separate. The oil-vapor flows out into the
fractionation system while the catalyst returns to the regenerator
(2) after it is stripped, which completes the second cycle of
catalyst.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0019] FIG. 1 is a schematic process flow chart of the present
process, wherein the reference numerals in the appended drawing are
described as follows: 1=Reaction settler; 2=Regenerator; 3=External
heat absorber; 4=Intermediate separator; 5=Stripping section;
6=First stage riser; 7=Second stage riser; 8=Outlet of the
oil-vapor; 9=Outlet of the flue gas; 10=Pre-lifting gas; 11=Lifting
medium of the catalyst; 12=Air for fluidizing the catalyst; 13
=demineralized water; 14=Saturated vapor; 15=Feedstock; 16=Air.
DETAILED DESCRIPTION OF THE INVENTION
[0020] In the reaction-regeneration system of two-stage riser
catalytic cracking process, the high-temperature catalyst coming
from the regenerator entered the bottom of the first stage riser
(6) to contact with the feedstock, which was vaporized and then
began to reaction. After about one second's reaction, the mixture
of oil-vapor and catalyst entered the intermediate separator (4) to
separate. After being stripped in the striping section (5), the
partially coked catalyst returned to the regenerator (2) to
complete the first cycle. The oil-vapor coming from the
intermediate separator (4) entered the second stage riser (7) to
contact with the hot catalyst coming from the external heat
absorber (3). The oil-vapor carrying the catalyst flows upwards and
performed catalytic cracking reactions continuously. After
reaction, it entered the settler (1) to separate with the coked
catalyst. The oil-vapor flew out into the fractionating system. At
the same time, the spent catalyst returned to the regenerator (2)
after it was stripped, which completed the second cycle.
[0021] In the present invention, the changes brought by the
two-stage riser reactor and the new reaction-regeneration system
result in the replacement of the partially coked catalyst, which is
separated from the reaction system between the two stages of the
riser reactor, by new regenerated catalyst during the second half
reaction. It fulfills the two-route cycle of the catalyst,
concatenation of the oil-vapor, catalyst in relays, and short
reaction time (the total reaction time being only 1/2.about.2/3 of
the conventional catalytic cracking one). So it enhances the
average performance of the catalyst in the riser reactor (average
activity and selectivity of the catalyst enhanced), strengthens and
improves the catalytic cracking reaction process.
[0022] The operating parameters of the two-stage riser FCC
technology are similar to those of the conventional one. The
reaction temperature is 470.about.540 degree centigrade; the ratio
of catalyst/oil is 4 to 9, and the total resident time of oil-vapor
is 1.about.2 seconds. According to the experimental data comparison
between the single stage riser reactor and a two-stage one, some
conclusions can be obtained as follows.
[0023] Firstly, the single-pass feedstock conversion is increased
by 8.about.10 percents under the identical yield of light oil.
[0024] Secondly, the yield of light oil is increased by 1.about.2
percents, the yield of liquid is increased by 6.about.8 percents,
the dry gas is reduced by somewhat, and the coke is increased by 2
percents when the feedstock conversion is 8.about.10 percents
higher than that of the single stage riser reactor.
[0025] Thirdly the quality of products is improved distinctly, and
the content of olefin in catalytic gasoline is reduced greatly.
Under proper conditions, it can be reduced by more than 15 percents
(if it is compared with the data of the fluorescence method, it
would be reduced by more, and the content of olefin is also
decreased by more.). The content of isoalkane in gasoline can be
increased by 6.about.7 percents (with the analytical data of the
chromatography). The content of aromatic hydrocarbon is increased
by 5 percents. And the octane number of the FCC gasoline is
increased by 1.about.2 units.
[0026] In comparison with the prior arts, the process of the
present invention is able to strengthen and improve the reaction
process of catalytic cracking of heavy oil, and also can increase
the single-pass feedstock conversion greatly. It can obtain a
better product distribution and enhance the yield of light oil and
improve the quality of FCC gasoline distinctly as evidenced by both
reducing the content of olefin and increasing the contents of
isomeric hydrocarbon and aromatic hydrocarbon. The present process
can also enhance the octane number. Thus, the new two-stage riser
catalytic cracking process described in this invention has a wide
range of application and introduction prospect.
* * * * *