U.S. patent application number 15/082362 was filed with the patent office on 2016-07-21 for integrated hydrotreating and steam pyrolysis process including residual bypass for direct processing of a crude oil.
The applicant listed for this patent is SAUDI ARABIAN OIL COMPANY. Invention is credited to Ibrahim A. ABBA, Abdul Rahman Zafer AKHRAS, Abdennour BOURANE, Essam SAYED, Raheel SHAFI.
Application Number | 20160208180 15/082362 |
Document ID | / |
Family ID | 49113106 |
Filed Date | 2016-07-21 |
United States Patent
Application |
20160208180 |
Kind Code |
A1 |
SHAFI; Raheel ; et
al. |
July 21, 2016 |
INTEGRATED HYDROTREATING AND STEAM PYROLYSIS PROCESS INCLUDING
RESIDUAL BYPASS FOR DIRECT PROCESSING OF A CRUDE OIL
Abstract
A process is provided that is directed to a steam pyrolysis zone
integrated with a hydroprocessing zone including residual bypass to
permit direct processing of crude oil feedstocks to produce
petrochemicals including olefins and aromatics. The integrated
hydrotreating and steam pyrolysis process for the direct processing
of a crude oil to produce olefinic and aromatic petrochemicals
comprises separating the crude oil into light components and
components boiling in and above the residual oil range; charging
the light components and hydrogen to a hydroprocessing zone
operating under conditions effective to produce a hydroprocessed
effluent; thermally cracking the hydroprocessed effluent in the
presence of steam to produce a mixed product stream; separating the
mixed product stream; purifying hydrogen recovered from the mixed
product stream and recycling it to the hydroprocessing zone;
recovering olefins and aromatics from the separated mixed product
stream; and recovering a combined stream of pyrolysis fuel oil from
the separated mixed product stream and components boiling in and
above the residual oil range from step (a) as a fuel oil blend.
Inventors: |
SHAFI; Raheel; (Manama,
BH) ; BOURANE; Abdennour; (Ras Tanura, SA) ;
SAYED; Essam; (Dhahran, SA) ; ABBA; Ibrahim A.;
(Dhahran, SA) ; AKHRAS; Abdul Rahman Zafer;
(Dhahran, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAUDI ARABIAN OIL COMPANY |
Dhahran |
|
SA |
|
|
Family ID: |
49113106 |
Appl. No.: |
15/082362 |
Filed: |
March 28, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13865060 |
Apr 17, 2013 |
9296961 |
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15082362 |
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PCT/US13/23337 |
Jan 27, 2013 |
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13865060 |
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61790519 |
Mar 15, 2013 |
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61591816 |
Jan 27, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2300/4081 20130101;
C10G 9/36 20130101; C10G 69/06 20130101; C10G 45/00 20130101; C10G
2300/201 20130101; C10G 2300/308 20130101; C10G 2400/30 20130101;
C10G 2400/20 20130101 |
International
Class: |
C10G 69/06 20060101
C10G069/06 |
Claims
1. An integrated hydrotreating and steam pyrolysis process for the
direct processing of a crude oil to produce olefinic and aromatic
petrochemicals, the process comprising: a. separating the crude oil
into light components and components boiling in and above the
residual oil range; b. charging the light components and hydrogen
to a hydroprocessing zone operating under conditions effective to
produce a hydroprocessed effluent; c. thermally cracking
hydroprocessed effluent in the presence of steam to produce a mixed
product stream; d. separating the thermally cracked mixed product
stream; e. purifying hydrogen recovered in step (d) and recycling
it to step (b); f. recovering olefins and aromatics from the
separated mixed product stream; and g. recovering a combined stream
of pyrolysis fuel oil from the separated mixed product stream and
components boiling in and above the residual oil range from step
(a) as a fuel oil blend.
2. The integrated process of claim 1, further comprising separating
the hydroprocessing zone reactor effluents in a high pressure
separator to recover a gas portion that is cleaned and recycled to
the hydroprocessing zone as an additional source of hydrogen, and a
liquid portion, and separating the liquid portion from the high
pressure separator in a low pressure separator into a gas portion
and a liquid portion, wherein the liquid portion from the low
pressure separator is the hydroprocessed effluent subjected to
thermal cracking and the gas portion from the low pressure
separator is combined with the mixed product stream after the steam
pyrolysis zone and before separation in step (d).
3. The integrated process of claim 1 wherein the thermal cracking
step comprises heating hydroprocessed effluent in a convection
section of a steam pyrolysis zone, separating the heated
hydroprocessed effluent into a vapor fraction and a liquid
fraction, passing the vapor fraction to a pyrolysis section of a
steam pyrolysis zone, and discharging the liquid fraction.
4. The integrated process of claim 3 wherein the discharged liquid
fraction is blended with pyrolysis fuel oil recovered in step
(g).
5. The integrated process of claim 3 wherein separating the heated
hydroprocessed effluent into a vapor fraction and a liquid fraction
is with a vapor-liquid separation device based on physical and
mechanical separation.
6. The integrated process of claim 5 wherein the vapor-liquid
separation device includes a pre-rotational element having an entry
portion and a transition portion, the entry portion having an inlet
for receiving the flowing fluid mixture and a curvilinear conduit,
a controlled cyclonic section having an inlet adjoined to the
pre-rotational element through convergence of the curvilinear
conduit and the cyclonic section, a riser section at an upper end
of the cyclonic member through which vapors pass; and a liquid
collector/settling section through which liquid passes.
7. The integrated process of claim 1, wherein step (d) comprises
compressing the thermally cracked mixed product stream with plural
compression stages; subjecting the compressed thermally cracked
mixed product stream to caustic treatment to produce a thermally
cracked mixed product stream with a reduced content of hydrogen
sulfide and carbon dioxide; compressing the thermally cracked mixed
product stream with a reduced content of hydrogen sulfide and
carbon dioxide; dehydrating the compressed thermally cracked mixed
product stream with a reduced content of hydrogen sulfide and
carbon dioxide; recovering hydrogen from the dehydrated compressed
thermally cracked mixed product stream with a reduced content of
hydrogen sulfide and carbon dioxide; and obtaining olefins and
aromatics as in step (e) and pyrolysis fuel oil as in step (f) from
the remainder of the dehydrated compressed thermally cracked mixed
product stream with a reduced content of hydrogen sulfide and
carbon dioxide; and step (e) comprises purifying recovered hydrogen
from the dehydrated compressed thermally cracked mixed product
stream with a reduced content of hydrogen sulfide and carbon
dioxide for recycle to the hydroprocessing zone.
8. The integrated process of claim 7, wherein recovering hydrogen
from the dehydrated compressed thermally cracked mixed product
stream with a reduced content of hydrogen sulfide and carbon
dioxide further comprises separately recovering methane for use as
fuel for burners and/or heaters in the thermal cracking step.
9. The integrated process of claim 1, further comprising separating
the hydroprocessed effluent into a heavy fraction and a light
fraction in a hydroprocessed effluent separation zone, wherein the
light fraction is the thermal cracking feed used in step (c), and
blending the heavy fraction with the combined stream of step
(g).
10. The integrated process of claim 9, wherein the hydroprocessed
effluent separation zone is a flash separation apparatus.
11. The integrated process of claim 9, wherein the hydroprocessed
effluent separation zone is a physical or mechanical apparatus for
separation of vapors and liquids.
12. The integrated process of claim 9, wherein the hydroprocessed
effluent separation zone comprises a flash vessel having at it
inlet a vapor-liquid separation device including a pre-rotational
element having an entry portion and a transition portion, the entry
portion having an inlet for receiving the flowing fluid mixture and
a curvilinear conduit, a controlled cyclonic section having an
inlet adjoined to the pre-rotational element through convergence of
the curvilinear conduit and the cyclonic section, and a riser
section at an upper end of the cyclonic member through which the
light fraction passes, wherein a bottom portion of the flash vessel
serves as a collection and settling zone for the heavy fraction
prior to passage of all or a portion of said heavy fraction.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 13/865,060 filed on Apr. 17, 2013,
which
[0002] claims the benefit of priority under 35 USC .sctn.119(e) to
U.S. Provisional Patent Application No. 61/790,519 filed Mar. 15,
2013, and
[0003] is a Continuation-in-Part under 35 USC .sctn.365(c) of PCT
Patent Application No. PCT/US13/23337 filed Jan. 27, 2013, which
claims the benefit of priority under 35 USC .sctn.119(e) to U.S.
Provisional Patent Application No. 61/591,816 filed Jan. 27, 2012,
all of which are incorporated herein by reference in their
entireties.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The present invention relates to an integrated hydrotreating
and steam pyrolysis process for direct processing of a crude oil to
produce petrochemicals such as olefins and aromatics.
[0006] 2. Description of Related Art
[0007] The lower olefins (i.e., ethylene, propylene, butylene and
butadiene) and aromatics (i.e., benzene, toluene and xylene) are
basic intermediates which are widely used in the petrochemical and
chemical industries. Thermal cracking, or steam pyrolysis, is a
major type of process for forming these materials, typically in the
presence of steam, and in the absence of oxygen. Feedstocks for
steam pyrolysis can include petroleum gases and distillates such as
naphtha, kerosene and gas oil. The availability of these feedstocks
is usually limited and requires costly and energy-intensive process
steps in a crude oil refinery.
[0008] Studies have been conducted using heavy hydrocarbons as a
feedstock for steam pyrolysis reactors. A major drawback in
conventional heavy hydrocarbon pyrolysis operations is coke
formation. For example, a steam cracking process for heavy liquid
hydrocarbons is disclosed in U.S. Pat. No. 4,217,204 in which a
mist of molten salt is introduced into a steam cracking reaction
zone in an effort to minimize coke formation. In one example using
Arabian light crude oil having a Conradson carbon residue of 3.1%
by weight, the cracking apparatus was able to continue operating
for 624 hours in the presence of molten salt. In a comparative
example without the addition of molten salt, the steam cracking
reactor became clogged and inoperable after just 5 hours because of
the formation of coke in the reactor.
[0009] In addition, the yields and distributions of olefins and
aromatics using heavy hydrocarbons as a feedstock for a steam
pyrolysis reactor are different than those using light hydrocarbon
feedstocks. Heavy hydrocarbons have a higher content of aromatics
than light hydrocarbons, as indicated by a higher Bureau of Mines
Correlation Index (BMCI). BMCI is a measurement of aromaticity of a
feedstock and is calculated as follows:
BMCI=87552/VAPB+473.5*(sp. gr.)-456.8 (1) [0010] where: [0011]
VAPB=Volume Average Boiling Point in degrees Rankine and [0012] sp.
gr.=specific gravity of the feedstock.
[0013] As the BMCI decreases, ethylene yields are expected to
increase. Therefore, highly paraffinic or low aromatic feeds are
usually preferred for steam pyrolysis to obtain higher yields of
desired olefins and to avoid higher undesirable products and coke
formation in the reactor coil section.
[0014] The absolute coke formation rates in a steam cracker have
been reported by Cai et al., "Coke Formation in Steam Crackers for
Ethylene Production," Chem. Eng. & Proc., vol. 41, (2002),
199-214. In general, the absolute coke formation rates are in the
ascending order of olefins>aromatics>paraffins, wherein
olefins represent heavy olefins
[0015] To be able to respond to the growing demand of these
petrochemicals, other type of feeds which can be made available in
larger quantities, such as raw crude oil, are attractive to
producers. Using crude oil feeds will minimize or eliminate the
likelihood of the refinery being a bottleneck in the production of
these petrochemicals.
[0016] While the steam pyrolysis process is well developed and
suitable for its intended purposes, the choice of feedstocks has
been very limited.
SUMMARY OF THE INVENTION
[0017] The system and process herein provides a steam pyrolysis
zone integrated with a hydroprocessing zone including residual
bypass to permit direct processing of crude oil feedstocks to
produce petrochemicals including olefins and aromatics.
[0018] The integrated hydrotreating and steam pyrolysis process for
the direct processing of a crude oil to produce olefinic and
aromatic petrochemicals comprises separating the crude oil into
light components and heavy components; charging the light
components and hydrogen to a hydroprocessing zone operating under
conditions effective to produce a hydroprocessed effluent having a
reduced content of contaminants, an increased paraffinicity,
reduced Bureau of Mines Correlation Index, and an increased
American Petroleum Institute gravity; thermally cracking the
hydroprocessed effluent in the presence of steam to produce a mixed
product stream; separating the mixed product stream; purifying
hydrogen recovered from the mixed product stream and recycling it
to the hydroprocessing zone; recovering olefins and aromatics from
the separated mixed product stream; and recovering a combined
stream of pyrolysis fuel oil from the separated mixed product
stream and heavy components from step (a) as a fuel oil blend.
[0019] As used herein, the term "crude oil" is to be understood to
include whole crude oil from conventional sources, including crude
oil that has undergone some pre-treatment. The term crude oil will
also be understood to include that which has been subjected to
water-oil separation; and/or gas-oil separation; and/or desalting;
and/or stabilization.
[0020] Other aspects, embodiments, and advantages of the process of
the present invention are discussed in detail below. Moreover, it
is to be understood that both the foregoing information and the
following detailed description are merely illustrative examples of
various aspects and embodiments, and are intended to provide an
overview or framework for understanding the nature and character of
the claimed features and embodiments. The accompanying drawings are
illustrative and are provided to further the understanding of the
various aspects and embodiments of the process of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will be described in further detail below and
with reference to the attached drawings where:
[0022] FIG. 1 is a process flow diagram of an embodiment of an
integrated process described herein;
[0023] FIGS. 2A-2C are schematic illustrations in perspective, top
and side views of a vapor-liquid separation device used in certain
embodiments of the integrated process described herein; and
[0024] FIGS. 3A-3C are schematic illustrations in section, enlarged
section and top section views of a vapor-liquid separation device
in a flash vessel used in certain embodiments of the integrated
process described herein.
DETAILED DESCRIPTION OF THE INVENTION
[0025] A flow diagram including an integrated hydroprocessing and
steam pyrolysis process and system including residual bypass is
shown in FIG. 1. The integrated system generally includes a feed
separation zone, a selective hydroprocessing zone, a steam
pyrolysis zone and a product separation zone.
[0026] Feed separation zone 20 includes an inlet for receiving a
feedstock stream 1, an outlet for discharging a rejected portion 22
and an outlet for discharging a remaining hydrocarbon portion 2.
The cut point in separation zone 20 can be set so that it is
compatible with the residue fuel oil blend, e.g., about 540.degree.
C. Separation zone 20 can be a single stage separation device such
a flash separator
[0027] In additional embodiments separation zone 20 can include, or
consists essentially of (i.e., operate in the absence of a flash
zone), a cyclonic phase separation device, or other separation
device based on physical or mechanical separation of vapors and
liquids. One example of a vapor-liquid separation device is
illustrated by, and with reference to, FIGS. 2A-2C. A similar
arrangement of a vapor-liquid separation device is also described
in U.S. Patent Publication Number 2011/0247500 which is
incorporated by reference in its entirety herein. In embodiments in
which the separation zone includes or consist essentially of a
separation device based on physical or mechanical separation of
vapors and liquids, the cut point can be adjusted based on
vaporization temperature and the fluid velocity of the material
entering the device.
[0028] Selective hydroprocessing zone includes a hydroprocessing
reaction zone 4 having an inlet for receiving a mixture 3 of
hydrocarbon portion 21 and hydrogen 2 recycled from the steam
pyrolysis product stream and make-up hydrogen as necessary.
Hydroprocessing reaction zone 4 further includes an outlet for
discharging a hydroprocessed effluent 5.
[0029] Reactor effluents 5 from the hydroprocessing reactor(s) are
cooled in a heat exchanger (not shown) and sent to a high pressure
separator 6. The separator tops 7 are cleaned in an amine unit 12
and a resulting hydrogen rich gas stream 13 is passed to a
recycling compressor 14 to be used as a recycle gas 15 in the
hydroprocessing reactor. A bottoms stream 8 from the high pressure
separator 6, which is in a substantially liquid phase, is cooled
and introduced to a low pressure cold separator 9 in which it is
separated into a gas stream 11 and a liquid stream 10. Gases from
low pressure cold separator include hydrogen, H.sub.2S, NH.sub.3
and any light hydrocarbons such as C.sub.1-C.sub.4 hydrocarbons.
Typically these gases are sent for further processing such as flare
processing or fuel gas processing. According to certain embodiments
herein, hydrogen is recovered by combining stream gas stream 11,
which includes hydrogen, H.sub.2S, NH.sub.3 and any light
hydrocarbons such as C.sub.1-C.sub.4 hydrocarbons, with steam
cracker products 44. All or a portion of liquid stream 10 serves as
the feed to the steam pyrolysis zone 30
[0030] Steam pyrolysis zone 30 generally comprises a convection
section 32 and a pyrolysis section 34 that can operate based on
steam pyrolysis unit operations known in the art, i.e., charging
the thermal cracking feed to the convection section in the presence
of steam. In addition, in certain optional embodiments as described
herein (as indicated with dashed lines in FIG. 1), a vapor-liquid
separation section 36 is included between sections 32 and 34.
Vapor-liquid separation section 36, through which the heated steam
cracking feed from convection section 32 passes, and is fractioned,
can be a flash separation device, a separation device based on
physical or mechanical separation of vapors and liquids or a
combination including at least one of these types of devices. In
additional embodiments, a vapor-liquid separation zone 18 is
included upstream of sections 32, either in combination with a
vapor-liquid separation zone 36 or in the absence of a vapor-liquid
separation zone 36. Stream 10a is fractioned in separation zone 18,
which can be a flash separation device, a separation device based
on physical or mechanical separation of vapors and liquids or a
combination including at least one of these types of devices.
[0031] Useful vapor-liquid separation devices are illustrated by,
and with reference to FIGS. 2A-2C and 3A-3C. Similar arrangements
of a vapor-liquid separation devices are described in U.S. Patent
Publication Number 2011/0247500 which is herein incorporated by
reference in its entirety. In this device vapor and liquid flow
through in a cyclonic geometry whereby the device operates
isothermally and at very low residence time. In general vapor is
swirled in a circular pattern to create forces where heavier
droplets and liquid are captured and channeled through to a liquid
outlet as liquid residue, for instance, which is added to a
pyrolysis fuel oil blend, and vapor is channeled through a vapor
outlet as the charge 37 to the pyrolysis section 34. In embodiments
in which a vapor-liquid separation device 36 is provided, residue
38 is discharged and the vapor is the charge 37 to the pyrolysis
section 34. In embodiments in which a vapor-liquid separation
device 18 is provided, residue 19 is discharged and the vapor is
the charge 10 to the convection section 32. The vaporization
temperature and fluid velocity are varied to adjust the approximate
temperature cutoff point, for instance in certain embodiments
compatible with the residue fuel oil blend, e.g., about 540.degree.
C.
[0032] Rejected residuals derived from streams 19 and/or 38 have
been subjected to the selective hydroprocessing zone and contain a
reduced amount of heteroatom compounds including sulfur-containing,
nitrogen-containing and metal compounds as compared to the initial
feed. This facilitates further processing of these blends, or
renders them useful as low sulfur, low nitrogen heavy fuel
blends.
[0033] A quenching zone 40 includes an inlet in fluid communication
with the outlet of steam pyrolysis zone 30 for receiving mixed
product stream 39, an inlet for admitting a quenching solution 42,
an outlet for discharging the quenched mixed product stream 44 and
an outlet for discharging quenching solution 46.
[0034] In general, an intermediate quenched mixed product stream 44
is converted into intermediate product stream 65 and hydrogen 62,
which is purified in the present process and used as recycle
hydrogen stream 2 in the hydroprocessing reaction zone 4.
Intermediate product stream 65 is generally fractioned into
end-products and residue in separation zone 70, which can be one or
multiple separation units such as plural fractionation towers
including de-ethanizer, de-propanizer and de-butanizer towers, for
example as is known to one of ordinary skill in the art. For
example, suitable apparatus are described in "Ethylene," Ullmann's
Encyclopedia of Industrial Chemistry, Volume 12, Pages 531-581, in
particular FIG. 24, FIG. 25 and FIG. 26, which is incorporated
herein by reference.
[0035] In general product separation zone 70 includes an inlet in
fluid communication with the product stream 65 and plural product
outlets 73-78, including an outlet 78 for discharging methane, an
outlet 77 for discharging ethylene, an outlet 76 for discharging
propylene, an outlet 75 for discharging butadiene, an outlet 74 for
discharging mixed butylenes, and an outlet 73 for discharging
pyrolysis gasoline. Additionally an outlet is provided for
discharging pyrolysis fuel oil 71. The rejected portion 22 from the
feed separation zone 20 and optionally the rejected portion 38 from
vapor-liquid separation section 36 are combined with pyrolysis fuel
oil 71 and the mixed stream can be withdrawn as a pyrolysis fuel
oil blend 72, e.g., a low sulfur fuel oil blend to be further
processed in an off-site refinery or used as fuel for optional
power generation zone 120. Note that while six product outlets are
shown, fewer or more can be provided depending, for instance, on
the arrangement of separation units employed and the yield and
distribution requirements.
[0036] An optional power generation zone 120 can be provided,
includes an inlet for receiving fuel oil 72 and an outlet for
discharging a remaining portion, e.g., a hydrogen deficient
sub-standard quality feedstock. An optional fuel gas
desulfurization zone 120 includes an inlet for receiving the
remaining portion from the power generation zone 110, and an outlet
for discharging a desulfurized fuel gas.
[0037] In an embodiment of a process employing the arrangement
shown in FIG. 1, a crude oil feedstock 1 is introduced into the
feed separation zone 20 to produce a rejected portion 22 and a
remaining hydrocarbon fraction 21. The hydrocarbon fraction 21 is
mixed with an effective amount of hydrogen 2 and 15 (and if
necessary a source of make-up hydrogen) to form a combined stream 3
and the admixture 3 is charged to the inlet of selective
hydroprocessing reaction zone 4 at a temperature in the range of
from 300.degree. C. to 450.degree. C. In certain embodiments,
hydroprocessing reaction zone 4 includes one or more unit
operations as described in commonly owned United States Patent
Publication Number 2011/0083996 and in PCT Patent Application
Publication Numbers WO2010/009077, WO2010/009082, WO2010/009089 and
WO2009/073436, all of which are incorporated by reference herein in
their entireties. For instance, a hydroprocessing zone can include
one or more beds containing an effective amount of
hydrodemetallization catalyst, and one or more beds containing an
effective amount of hydroprocessing catalyst having
hydrodearomatization, hydrodenitrogenation, hydrodesulfurization
and/or hydrocracking functions. In additional embodiments
hydroprocessing zone 200 includes more than two catalyst beds. In
further embodiments hydroprocessing reaction zone 4 includes plural
reaction vessels each containing one or more catalyst beds, e.g.,
of different function.
[0038] Hydroprocessing reaction zone 4 operates under parameters
effective to hydrodemetallize, hydrodearomatize,
hydrodenitrogenate, hydrodesulfurize and/or hydrocrack the crude
oil feedstock. In certain embodiments, hydroprocessing is carried
out using the following conditions: operating temperature in the
range of from 300.degree. C. to 450.degree. C.; operating pressure
in the range of from 30 bars to 180 bars; and a liquid hour space
velocity in the range of from 0.1 h.sup.-1 to 10 h.sup.-1. Notably,
using crude oil as a feedstock in the hydroprocessing zone
advantages are demonstrated, for instance, as compared to the same
hydroprocessing unit operation employed for atmospheric residue.
For instance, at a start or run temperature in the range of
370.degree. C. to 375.degree. C. the deactivation rate is around
1.degree. C./month. In contrast, if residue were to be processed,
the deactivation rate would be closer to about 3.degree. C./month
to 4.degree. C./month. The treatment of atmospheric residue
typically employs pressure of around 200 bars whereas the present
process in which crude oil is treated can operate at a pressure as
low as 100 bars. Additionally to achieve the high level of
saturation required for the increase in the hydrogen content of the
feed, this process can be operated at a high throughput when
compared to atmospheric residue. The LHSV can be as high as 0.5
hr.sup.-1 while that for atmospheric residue is typically 0.25
hr.sup.-1. An unexpected finding is that the deactivation rate when
processing crude oil is going in the inverse direction from that
which is usually observed. Deactivation at low throughput (0.25
hr.sup.-1) is 4.2.degree. C./month and deactivation at higher
throughput (0.5 hr.sup.-1) is 2.0.degree. C./month. With every feed
which is considered in the industry, the opposite is observed. This
can be attributed to the washing effect of the catalyst.
[0039] Reactor effluents 5 from the hydroprocessing zone 4 are
cooled in an exchanger (not shown) and sent to a high pressure cold
or hot separator 6. Separator tops 7 are cleaned in an amine unit
12 and the resulting hydrogen rich gas stream 13 is passed to a
recycling compressor 14 to be used as a recycle gas 15 in the
hydroprocessing reaction zone 4. Separator bottoms 8 from the high
pressure separator 6, which are in a substantially liquid phase,
are cooled and then introduced to a low pressure cold separator 9.
Remaining gases, stream 11, including hydrogen, H.sub.2S, NH.sub.3
and any light hydrocarbons, which can include C.sub.1-C.sub.4
hydrocarbons, can be conventionally purged from the low pressure
cold separator and sent for further processing, such as flare
processing or fuel gas processing. In certain embodiments of the
present process, hydrogen is recovered by combining stream 11 (as
indicated by dashed lines) with the cracking gas, stream 44, from
the steam cracker products. The bottoms 10 from the low pressure
separator 9 are optionally sent to separation zone 20 or passed
directly to steam pyrolysis zone 30.
[0040] The hydroprocessed effluent 10a contains a reduced content
of contaminants (i.e., metals, sulfur and nitrogen), an increased
paraffinicity, reduced BMCI, and an increased American Petroleum
Institute (API) gravity.
[0041] The hydroprocessed effluent 10a is conveyed to the inlet of
a convection section 32 as feed 10 in the presence of an effective
amount of steam, e.g., admitted via a steam inlet. In additional
embodiments as described herein a separation zone 18 is
incorporated upstream of the convection section 32 whereby the feed
10 is the light portion of said pyrolysis feed. The steam cracking
feed can have, for instance, an initial boiling point corresponding
to that of the stream 10a and a final boiling point in the range of
about 370.degree. C. to about 600.degree. C.
[0042] The steam pyrolysis zone 30 operates under parameters
effective to crack effluent 10a or a light portion 10 thereof
derived from the optional separation zone 18, into desired
products, including ethylene, propylene, butadiene, mixed butenes
and pyrolysis gasoline. In the convection section 32 the mixture is
heated to a predetermined temperature, e.g., using one or more
waste heat streams or other suitable heating arrangement. The
heated mixture of the pyrolysis feedstream and steam is passed to
the pyrolysis section 34 to produce a mixed product stream 39. In
certain embodiments the heated mixture of from section 32 is passed
through a vapor-liquid separation section 36 in which a portion 38
is rejected as a fuel oil component suitable for blending with
pyrolysis fuel oil 71. In certain embodiments, steam cracking is
carried out using the following conditions: a temperature in the
range of from 400.degree. C. to 900.degree. C. in the convection
section and in the pyrolysis section; a steam-to-hydrocarbon ratio
in the convection section in the range of from 0.3:1 to 2:1
(wt.:wt.); and a residence time in the convection section and in
the pyrolysis section in the range of from 0.05 seconds to 2
seconds.
[0043] In certain embodiments, the vapor-liquid separation section
36 includes one or a plurality of vapor liquid separation devices
80 as shown in FIGS. 2A-2C. The vapor liquid separation device 80
is economical to operate and maintenance free since it does not
require power or chemical supplies. In general, device 80 comprises
three ports including an inlet port for receiving a vapor-liquid
mixture, a vapor outlet port and a liquid outlet port for
discharging and the collection of the separated vapor and liquid,
respectively. Device 80 operates based on a combination of
phenomena including conversion of the linear velocity of the
incoming mixture into a rotational velocity by the global flow
pre-rotational section, a controlled centrifugal effect to
pre-separate the vapor from liquid (residue), and a cyclonic effect
to promote separation of vapor from the liquid (residue). To attain
these effects, device 80 includes a pre-rotational section 88, a
controlled cyclonic vertical section 90 and a liquid
collector/settling section 92.
[0044] As shown in FIG. 2B, the pre-rotational section 88 includes
a controlled pre-rotational element between cross-section (S1) and
cross-section (S2), and a connection element to the controlled
cyclonic vertical section 90 and located between cross-section (S2)
and cross-section (S3). The vapor liquid mixture coming from inlet
32 having a diameter (D1) enters the apparatus tangentially at the
cross-section (S1). The area of the entry section (S1) for the
incoming flow is at least 10% of the area of the inlet 82 according
to the following equation:
.pi. * ( D 1 ) 2 4 ( 2 ) ##EQU00001##
[0045] The pre-rotational element 88 defines a curvilinear flow
path, and is characterized by constant, decreasing or increasing
cross-section from the inlet cross-section S1 to the outlet
cross-section S2. The ratio between outlet cross-section from
controlled pre-rotational element (S2) and the inlet cross-section
(S1) is in certain embodiments in the range of
0.7.ltoreq.S2/S1.ltoreq.1.4. The rotational velocity of the mixture
is dependent on the radius of curvature (R1) of the center-line of
the pre-rotational element 88 where the center-line is defined as a
curvilinear line joining all the center points of successive
cross-sectional surfaces of the pre-rotational element 88. In
certain embodiments the radius of curvature (R1) is in the range of
2.ltoreq.R1/D1.ltoreq.6 with opening angle in the range of
150.degree..ltoreq..alpha.R1.ltoreq.250.degree..
[0046] The cross-sectional shape at the inlet section S1, although
depicted as generally square, can be a rectangle, a rounded
rectangle, a circle, an oval, or other rectilinear, curvilinear or
a combination of the aforementioned shapes. In certain embodiments,
the shape of the cross-section along the curvilinear path of the
pre-rotational element 88 through which the fluid passes
progressively changes, for instance, from a generally square shape
to a rectangular shape. The progressively changing cross-section of
element 88 into a rectangular shape advantageously maximizes the
opening area, thus allowing the gas to separate from the liquid
mixture at an early stage and to attain a uniform velocity profile
and minimize shear stresses in the fluid flow.
[0047] The fluid flow from the controlled pre-rotational element 88
from cross-section (S2) passes section (S3) through the connection
element to the controlled cyclonic vertical section 90. The
connection element includes an opening region that is open and
connected to, or integral with, an inlet in the controlled cyclonic
vertical section 90. The fluid flow enters the controlled cyclonic
vertical section 90 at a high rotational velocity to generate the
cyclonic effect. The ratio between connection element outlet
cross-section (S3) and inlet cross-section (S2) in certain
embodiments is in the range of 2.ltoreq.S3/S1.ltoreq.5.
[0048] The mixture at a high rotational velocity enters the
cyclonic vertical section 90. Kinetic energy is decreased and the
vapor separates from the liquid under the cyclonic effect. Cyclones
form in the upper level 90a and the lower level 90b of the cyclonic
vertical section 90. In the upper level 90a, the mixture is
characterized by a high concentration of vapor, while in the lower
level 90b the mixture is characterized by a high concentration of
liquid.
[0049] In certain embodiments, the internal diameter D2 of the
cyclonic vertical section 90 is within the range of
2.ltoreq.D2/D1.ltoreq.5 and can be constant along its height, the
length (LU) of the upper portion 90a is in the range of
1.2.ltoreq.LU/D2.ltoreq.3, and the length (LL) of the lower portion
90b is in the range of 2.ltoreq.LL/D2.ltoreq.5.
[0050] The end of the cyclonic vertical section 90 proximate vapor
outlet 84 is connected to a partially open release riser and
connected to the pyrolysis section of the steam pyrolysis unit. The
diameter (DV) of the partially open release is in certain
embodiments in the range of 0.05.ltoreq.DV/D2.ltoreq.0.4.
[0051] Accordingly, in certain embodiments, and depending on the
properties of the incoming mixture, a large volume fraction of the
vapor therein exits device 80 from the outlet 84 through the
partially open release pipe with a diameter DV. The liquid phase
(e.g., residue) with a low or non-existent vapor concentration
exits through a bottom portion of the cyclonic vertical section 90
having a cross-sectional area S4, and is collected in the liquid
collector and settling pipe 92.
[0052] The connection area between the cyclonic vertical section 90
and the liquid collector and settling pipe 92 has an angle in
certain embodiment of 90.degree.. In certain embodiments the
internal diameter of the liquid collector and settling pipe 92 is
in the range of 2.ltoreq.D3/D1.ltoreq.4 and is constant across the
pipe length, and the length (LH) of the liquid collector and
settling pipe 92 is in the range of 1.2.ltoreq.LH/D3.ltoreq.5. The
liquid with low vapor volume fraction is removed from the apparatus
through pipe 86 having a diameter of DL, which in certain
embodiments is in the range of 0.05.ltoreq.DL/D3.ltoreq.0.4 and
located at the bottom or proximate the bottom of the settling
pipe.
[0053] In certain embodiments, a vapor-liquid separation device is
provided similar in operation and structure to device 80 without
the liquid collector and settling pipe return portion. For
instance, a vapor-liquid separation device 180 is used as inlet
portion of a flash vessel 179, as shown in FIGS. 3A-3C. In these
embodiments the bottom of the vessel 179 serves as a collection and
settling zone for the recovered liquid portion from device 180.
[0054] In general a vapor phase is discharged through the top 194
of the flash vessel 179 and the liquid phase is recovered from the
bottom 196 of the flash vessel 179. The vapor-liquid separation
device 180 is economical to operate and maintenance free since it
does not require power or chemical supplies. Device 180 comprises
three ports including an inlet port 182 for receiving a
vapor-liquid mixture, a vapor outlet port 184 for discharging
separated vapor and a liquid outlet port 186 for discharging
separated liquid. Device 180 operates based on a combination of
phenomena including conversion of the linear velocity of the
incoming mixture into a rotational velocity by the global flow
pre-rotational section, a controlled centrifugal effect to
pre-separate the vapor from liquid, and a cyclonic effect to
promote separation of vapor from the liquid. To attain these
effects, device 180 includes a pre-rotational section 188 and a
controlled cyclonic vertical section 190 having an upper portion
190a and a lower portion 190b. The vapor portion having low liquid
volume fraction is discharged through the vapor outlet port 184
having a diameter (DV). Upper portion 190a which is partially or
totally open and has an internal diameter (DII) in certain
embodiments in the range of 0.5<DV/DII<1.3. The liquid
portion with low vapor volume fraction is discharged from liquid
port 186 having an internal diameter (DL) in certain embodiments in
the range of 0.1<DL/DII<1.1. The liquid portion is collected
and discharged from the bottom of flash vessel 179.
[0055] In order to enhance and to control phase separation, heating
steam can be used in the vapor-liquid separation device 80 or 180,
particularly when used as a standalone apparatus or is integrated
within the inlet of a flash vessel.
[0056] While the various members are described separately and with
separate portions, it will be understood by one of ordinary skill
in the art that apparatus 80 and apparatus 180 can be formed as a
monolithic structure, e.g., it can be cast or molded, or it can be
assembled from separate parts, e.g., by welding or otherwise
attaching separate components together which may or may not
correspond precisely to the members and portions described
herein.
[0057] It will be appreciated that although various dimensions are
set forth as diameters, these values can also be equivalent
effective diameters in embodiments in which the components parts
are not cylindrical. Mixed product stream 39 is passed to the inlet
of quenching zone 40 with a quenching solution 42 (e.g., water
and/or pyrolysis fuel oil) introduced via a separate inlet to
produce an intermediate quenched mixed product stream 44 having a
reduced temperature, e.g., of about 300.degree. C., and spent
quenching solution 46 is discharged. The gas mixture effluent 39
from the cracker is typically a mixture of hydrogen, methane,
hydrocarbons, carbon dioxide and hydrogen sulfide. After cooling
with water or oil quench, mixture 44 is compressed in a multi-stage
compressor zone 51, typically in 4-6 stages to produce a compressed
gas mixture 52. The compressed gas mixture 52 is treated in a
caustic treatment unit 53 to produce a gas mixture 54 depleted of
hydrogen sulfide and carbon dioxide. The gas mixture 54 is further
compressed in a compressor zone 55, and the resulting cracked gas
56 typically undergoes a cryogenic treatment in unit 57 to be
dehydrated, and is further dried by use of molecular sieves.
[0058] The cold cracked gas stream 58 from unit 57 is passed to a
de-methanizer tower 59, from which an overhead stream 60 is
produced containing hydrogen and methane from the cracked gas
stream. The bottoms stream 65 from de-methanizer tower 59 is then
sent for further processing in product separation zone 70,
comprising fractionation towers including de-ethanizer,
de-propanizer and de-butanizer towers. Process configurations with
a different sequence of de-methanizer, de-ethanizer, de-propanizer
and de-butanizer can also be employed.
[0059] According to the processes herein, after separation from
methane at the de-methanizer tower 59 and hydrogen recovery in unit
61, hydrogen 62 having a purity of typically 80-95 vol % is
obtained. Recovery methods in unit 61 include cryogenic recovery
(e.g., at a temperature of about -157.degree. C.). Hydrogen stream
62 is then passed to a hydrogen purification unit 64, such as a
pressure swing adsorption (PSA) unit to obtain a hydrogen stream 2
having a purity of 99.9%+, or a membrane separation units to obtain
a hydrogen stream 2 with a purity of about 95%. The purified
hydrogen stream 2 is then recycled back to serve as a major portion
of the requisite hydrogen for the hydroprocessing zone. In
addition, a minor proportion can be utilized for the hydrogenation
reactions of acetylene, methylacetylene and propadienes (not
shown). In addition, according to the processes herein, methane
stream 63 can optionally be recycled to the steam cracker to be
used as fuel for burners and/or heaters.
[0060] The bottoms stream 65 from de-methanizer tower 59 is
conveyed to the inlet of product separation zone 70 to be separated
into methane, ethylene, propylene, butadiene, mixed butylenes and
pyrolysis gasoline discharged via outlets 78, 77, 76, 75, 74 and
73, respectively. Pyrolysis gasoline generally includes C5-C9
hydrocarbons, and benzene, toluene and xylenes can be extracted
from this cut. The rejected portion 22 from the feed separation
zone 100 and optionally the unvaporized heavy liquid fraction 38
from the vapor-liquid separation section 36 are combined with
pyrolysis fuel oil 71 (e.g., materials boiling at a temperature
higher than the boiling point of the lowest boiling C10 compound,
known as a "C10+" stream) from separation zone 70, and this is
withdrawn as a pyrolysis fuel oil blend 72, e.g., to be further
processed in an off-site refinery (not shown).
[0061] In certain optional embodiments, fuel oil 72 can be passed
to power generation zone 110 to generate power (e.g., one or more
steam turbines that can employ fuel oil 72 as a fuel source), and a
remaining portion is conveyed to a fuel gas desulfurization zone
120 to produce a desulfurized fuel gas.
[0062] Advantages of the system described with respect to FIG. 1
include improvements in hydroprocessing, in which the process can
be efficiently utilized to improve the hydrogen content of the
products. For example, the system described herein uses
hydrotreating catalyst having smaller pore size which contributes
to significantly more active hydrotreating reactions. In addition,
the overall hydrogen consumption of the hydrotreating zone is
significantly reduced. Hydrogen is not consumed for upgrading
unsaturated heavy residue, but rather is utilized for the fraction
undergoing pyrolysis reaction, e.g., fractions boiling below
540.degree. C. The heavier fraction, e.g., boiling above
540.degree. C., is used to generate power for the plant, while the
remaining portion is recovered as fuel oil.
[0063] In certain embodiments, selective hydroprocessing or
hydrotreating processes can increase the paraffin content (or
decrease the BMCI) of a feedstock by saturation followed by mild
hydrocracking of aromatics, especially polyaromatics. When
hydrotreating a crude oil, contaminants such as metals, sulfur and
nitrogen can be removed by passing the feedstock through a series
of layered catalysts that perform the catalytic functions of
demetallization, desulfurization and/or denitrogenation.
[0064] In one embodiment, the sequence of catalysts to perform
hydrodemetallization (HDM) and hydrodesulfurization (HDS) is as
follows:
[0065] A hydrodemetallization catalyst. The catalyst in the HDM
section are generally based on a gamma alumina support, with a
surface area of about 140-240 m.sup.2/g. This catalyst is best
described as having a very high pore volume, e.g., in excess of 1
cm.sup.3/g. The pore size itself is typically predominantly
macroporous. This is required to provide a large capacity for the
uptake of metals on the catalysts surface and optionally dopants.
Typically the active metals on the catalyst surface are sulfides of
Nickel and Molybdenum in the ratio Ni/Ni+Mo<0.15. The
concentration of Nickel is lower on the HDM catalyst than other
catalysts as some Nickel and Vanadium is anticipated to be
deposited from the feedstock itself during the removal, acting as
catalyst. The dopant used can be one or more of phosphorus (see,
e.g., United States Patent Publication Number US 2005/0211603 which
is incorporated by reference herein), boron, silicon and halogens.
The catalyst can be in the form of alumina extrudates or alumina
beads. In certain embodiments alumina beads are used to facilitate
un-loading of the catalyst HDM beds in the reactor as the metals
uptake will range between 30 to 100% at the top of the bed.
[0066] An intermediate catalyst can also be used to perform a
transition between the HDM and HDS function. It has intermediate
metals loadings and pore size distribution. The catalyst in the
HDM/HDS reactor is essentially alumina based support in the form of
extrudates, optionally at least one catalytic metal from group VI
(e.g., molybdenum and/or tungsten), and/or at least one catalytic
metals from group VIII (e.g., nickel and/or cobalt). The catalyst
also contains optionally at least one dopant selected from boron,
phosphorous, halogens and silicon. Physical properties include a
surface area of about 140-200 m.sup.2/g, a pore volume of at least
0.6 cm.sup.3/g and pores which are mesoporous and in the range of
12 to 50 nm.
[0067] The catalyst in the HDS section can include those having
gamma alumina based support materials, with typical surface area
towards the higher end of the HDM range, e.g. about ranging from
180-240 m.sup.2/g. This required higher surface for HDS results in
relatively smaller pore volume, e.g., lower than 1 cm.sup.3/g. The
catalyst contains at least one element from group VI, such as
molybdenum and at least one element from group VIII, such as
nickel. The catalyst also comprises at least one dopant selected
from boron, phosphorous, silicon and halogens. In certain
embodiments cobalt is used to provide relatively higher levels of
desulfurization. The metals loading for the active phase is higher
as the required activity is higher, such that the molar ratio of
Ni/Ni+Mo is in the range of from 0.1 to 0.3 and the (Co+Ni)/Mo
molar ratio is in the range of from 0.25 to 0.85.
[0068] A final catalyst (which could optionally replace the second
and third catalyst) is designed to perform hydrogenation of the
feedstock (rather than a primary function of hydrodesulfurization),
for instance as described in Appl. Catal. A General, 204 (2000)
251. The catalyst will be also promoted by Ni and the support will
be wide pore gamma alumina. Physical properties include a surface
area towards the higher end of the HDM range, e.g., 180-240
m.sup.2/g gr. This required higher surface for HDS results in
relatively smaller pore volume, e.g., lower than 1 cm.sup.3/g.
[0069] The method and system herein provides improvements over
known steam pyrolysis cracking processes:
[0070] use of crude oil as a feedstock to produce petrochemicals
such as olefins and aromatics;
[0071] the hydrogen content of the feed to the steam pyrolysis zone
is enriched for high yield of olefins;
[0072] coke precursors are significantly removed from the initial
whole crude oil which allows a decreased coke formation in the
radiant coil; and
[0073] additional impurities such as metals, sulfur and nitrogen
compounds are also significantly removed from the starting feed
which avoids post treatments of the final products.
[0074] In addition, hydrogen produced from the steam cracking zone
is recycled to the hydroprocessing zone to minimize the demand for
fresh hydrogen. In certain embodiments the integrated systems
described herein only require fresh hydrogen to initiate the
operation. Once the reaction reaches the equilibrium, the hydrogen
purification system can provide enough high purity hydrogen to
maintain the operation of the entire system.
[0075] The method and system of the present invention have been
described above and in the attached drawings; however,
modifications will be apparent to those of ordinary skill in the
art and the scope of protection for the invention is to be defined
by the claims that follow.
* * * * *