U.S. patent application number 17/288179 was filed with the patent office on 2021-10-07 for method and reactor for conversion of hydrocarbons.
The applicant listed for this patent is SABIC Global Technologies B.V.. Invention is credited to Byeongjin Baek, Lei Chen, Istvan Lengyel, Sreekanth Pannala, Krishnan Sankaranarayanan, Vladimir Shtern, David West.
Application Number | 20210308650 17/288179 |
Document ID | / |
Family ID | 1000005851536 |
Filed Date | 2021-10-07 |
United States Patent
Application |
20210308650 |
Kind Code |
A1 |
Pannala; Sreekanth ; et
al. |
October 7, 2021 |
Method and Reactor for Conversion of Hydrocarbons
Abstract
A reactor (12, 128, 198) and method for the conversion of
hydrocarbon gases utilizes a reactor (12, 128, 198) having a unique
feed assembly (58, 136, 200) with an original vortex disk-like
inlet flow spaces (72, 74, 76, 80, 146, 148, 150, 152, 208, 216,
218), a converging-diverging vortex mixing chamber (116), and a
cylindrical reactor chamber (40). This design creates a small
combustion zone and an inwardly swirling fluid flow pattern of the
feed gases that passes through a converging conduit (48) with a
constricted neck portion (54). This provides conditions suitable
for efficient cracking of hydrocarbons, such as ethane, to form
olefins.
Inventors: |
Pannala; Sreekanth; (Sugar
Land, TX) ; Baek; Byeongjin; (Katy, TX) ;
Chen; Lei; (Sugar Land, TX) ; Shtern; Vladimir;
(Houston, TX) ; Lengyel; Istvan; (Sugar Land,
TX) ; West; David; (Bellaire, TX) ;
Sankaranarayanan; Krishnan; (Missouri City, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SABIC Global Technologies B.V. |
Bergen op Zoom |
|
NL |
|
|
Family ID: |
1000005851536 |
Appl. No.: |
17/288179 |
Filed: |
October 23, 2019 |
PCT Filed: |
October 23, 2019 |
PCT NO: |
PCT/US2019/057603 |
371 Date: |
April 23, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62749424 |
Oct 23, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 5/48 20130101; C10G
9/36 20130101; B01J 2219/00094 20130101; B01J 19/246 20130101; B01J
2219/0077 20130101 |
International
Class: |
B01J 19/24 20060101
B01J019/24; C07C 5/48 20060101 C07C005/48; C10G 9/36 20060101
C10G009/36 |
Claims
1. A reactor system for the conversion of hydrocarbons comprising:
a reactor vessel having a reactor wall that defines a reaction
chamber; a reactor inlet assembly having a converging conduit with
a circumferential wall that surrounds a central longitudinal axis
and extends from opposite upstream and downstream ends of the
converging conduit, the circumferential wall tapering in width from
the downstream and upstream ends to an annular constricted neck
portion located between the downstream and upstream ends of the
converging conduit, the downstream end of the converging conduit
being in fluid communication with the reaction chamber of the
reactor, the upstream end of the converging conduit forming an
inlet of the reactor inlet assembly; a feed assembly in fluid
communication with the inlet of the reactor inlet assembly, with
the central axis passing through the feed assembly, the feed
assembly comprising: a downstream feed assembly wall (60) that
extends circumferentially around and joins the upstream end of the
reactor inlet assembly, the downstream feed assembly wall being
oriented perpendicular or substantially perpendicular to the
central axis; an upstream feed assembly wall (62) that is axially
spaced upstream from the downstream feed assembly wall (60) along
the central axis and extends perpendicularly or substantially
perpendicular across the central axis; an upstream gas partition
wall (64) and a downstream gas partition wall (66) that are each
axially spaced between the downstream and upstream feed assembly
walls and are axially spaced from one another, the upstream gas
partition wall and the downstream gas partition wall or
circumferential portions thereof being oriented perpendicular or
substantially perpendicular to the central axis, at least one of
the upstream gas partition wall (64) and the downstream gas
partition wall (66) terminates at a position upstream from the
converging conduit to define a central opening (68, 70) that
surrounds the central axis of the converging conduit, an upstream
annular inlet flow space (72) being defined between the upstream
feed assembly wall (62) and the upstream partition wall (64), an
annular downstream inlet flow space (74) being defined between the
downstream feed assembly wall (60) and the downstream gas partition
wall (66), and an intermediate inlet flow space (76) defined
between the upstream gas partition wall (64) and the downstream gas
partition wall (66); wherein; said annular inlet flow spaces cause
introduced feeds to flow perpendicularly or substantially
perpendicular toward the central axis of the converging conduit in
an inwardly swirling fluid flow pattern within said flow spaces
about the central axis of the converging conduit; and wherein the
area extending from the central opening of the at least one of the
upstream and downstream partition walls to the inlet of the reactor
inlet assembly defines a central chamber of the feed assembly, with
hot combustion gases from at least one of the inlet flow spaces
being discharged into the central chamber, with the hydrocarbon
feed and heated combustion gases passing as swirling gases through
the converging conduit to the reaction chamber.
2. The reactor system of claim 1, wherein: at least one of the
annular inlet flow spaces is provided with circumferentially spaced
apart guide vanes oriented to facilitate the swirling fluid flow
within said at least one of the inlet flow spaces.
3. The reactor system of claim 2, wherein: the guide vanes are
movable to selected positions and tilting angles to provide
selected azimuthal-to-radial velocity ratios of fluids flowing
within the annular inlet flow spaces.
4. The reactor system of claim 2, wherein: the guide vanes are
configured as non-planar airfoils.
5. The reactor system of claim 1, wherein: the reactor wall is
cylindrical.
6. The reactor system of claim 1, wherein: the circumferential wall
of the converging conduit from the downstream end to the annular
constricted neck portion, and optionally an upstream portion of the
reactor wall of the reaction chamber that joins the circumferential
wall of the converging conduit, is configured as a smooth,
continuous wall that follows contour lines of an ellipsoidal cap or
spherical cap shape.
7. The reactor system of claim 1, wherein: the downstream gas
partition wall has an extended portion that is spaced from and
follows the contours of the circumferential wall of the converging
conduit of the reactor inlet assembly and terminates at a position
downstream of the annular constricted neck portion so that a
downstream inlet flow space is defined that discharges into an area
downstream from the constricted neck portion.
8. The reactor system of claim 1, wherein: at least one of A and B,
wherein: A is the intermediate annular gas inlet flow space is
divided by an intermediate gas partition wall having a central
opening that surrounds the central axis of the converging conduit
and divides the intermediate inlet flow space into upstream and
downstream intermediate annular inlet flow spaces that
constitute\inlet flow spaces for introducing a fuel gas feed and an
oxidizer feed; and B is the upstream annular gas inlet flow space
and the intermediate inlet flow space constitute inlet flow spaces
for introducing a fuel gas feed and an oxidizer feed.
9. The reactor system of claim 1, further comprising: a cooling gas
feed assembly in fluid communication with at least one of the
reaction chamber and the reactor inlet assembly, the cooling gas
feed assembly comprising: a pair of axially spaced apart cooling
gas feed assembly walls oriented perpendicular or substantially
perpendicular to the central axis, an annular cooling gas inlet
flow space being defined between the cooling gas feed assembly
walls and communicates with said at least one of the reaction
chamber and the reactor inlet assembly.
10. The reactor system of claim 9, wherein: the annular cooling gas
inlet flow space is provided with circumferentially spaced apart
guide vanes oriented to facilitate the swirling fluid flow within
said cooling gas inlet flow space.
11. A method of cracking hydrocarbons to cracked hydrocarbon
products, the method comprising: introducing a hydrocarbon feed
containing hydrocarbons to be cracked into a reactor system
comprising: a reactor vessel having a reactor wall that defines a
reaction chamber; a reactor inlet assembly having a converging
conduit with a circumferential wall that surrounds a central
longitudinal axis and extends from opposite upstream and downstream
ends of the converging conduit, the circumferential wall tapering
in width from the downstream and upstream ends to an annular
constricted neck portion located between the downstream and
upstream ends of the converging conduit, the downstream end of the
converging conduit being in fluid communication with the reaction
chamber of the reactor, the upstream end of the converging conduit
forming an inlet of the reactor inlet assembly; a feed assembly in
fluid communication with the inlet of the reactor inlet assembly,
with the central axis passing through the feed assembly, the feed
assembly comprising: a downstream feed assembly wall that extends
circumferentially around and joins the upstream end of the reactor
inlet assembly, the downstream feed assembly wall being oriented
perpendicular or substantially perpendicular to the central axis;
an upstream feed assembly wall that is axially spaced upstream from
the downstream feed assembly wall along the central axis and
extends perpendicularly or substantially perpendicularly across the
central axis; an upstream gas partition wall and a downstream gas
partition wall that are each axially spaced between the downstream
and upstream feed assembly walls and are axially spaced from one
another, the upstream gas partition wall and the downstream gas
partition wall or circumferential portions thereof being oriented
perpendicular or substantially perpendicular to the central axis,
at least one of the upstream gas partition wall (64) and downstream
gas partition wall terminates at a position upstream from the
converging conduit to define a central opening that surrounds the
central axis of the converging conduit, an upstream annular inlet
flow space being defined between the upstream feed assembly wall
and the upstream partition wall, a downstream annular inlet flow
space being defined between the downstream feed assembly wall and
the downstream gas partition wall, and an intermediate inlet flow
space defined between the upstream gas partition wall and the
downstream gas partition wall; wherein; said annular inlet flow
spaces causes introduced feeds to flow perpendicularly or
substantially perpendicularly toward the central axis of the
converging conduit in an inwardly swirling fluid flow pattern
within said flow spaces about the central axis of the converging
conduit; and wherein the area extending from the central opening of
the at least one upstream and downstream partition walls to the
inlet of the reactor inlet assembly defines a central chamber of
the feed assembly; and wherein a cracking feed of the hydrocarbon
feed to be cracked is introduced into a first inlet flow space and
a fuel gas feed and an oxidizer feed is introduced into adjacent
second and third inlet flow spaces so that the feeds pass through
said flow spaces perpendicularly or substantially perpendicularly
toward the central axis of the converging conduit in an inwardly
swirling fluid flow pattern within said flow spaces flowing about
the central axis of the converging conduit, the fuel gas feed and
oxidizer feed combusting in the central chamber to form hot
combustion gases, the hot combustion gases and cracking feed being
discharged into the central chamber and/or reaction chamber so that
the hot combustion gases and cracking feed are mixed together and
form a swirling, heated gas mixture; allowing the heated gas
mixture to react within the reaction chamber of the reactor vessel
under reaction conditions suitable for hydrocarbon cracking, with
at least a portion of the cracking feed of the gas mixture being
converted to cracked hydrocarbon products; and removing a cracked
hydrocarbon product from the reaction chamber of the reactor
vessel.
12. The method of claim 11, wherein: the oxidizer feed comprises an
oxygen-containing gas (O.sub.2) and the fuel gas feed comprises
hydrogen-containing gas of at least one of hydrogen gas (H.sub.2)
and methane (CH.sub.4), the oxygen-containing gas being introduced
into one of the first and second annular fuel gas inlet flow spaces
and the hydrogen-containing gas being introduced into the
other.
13. The method of claim 12, wherein: the hydrogen-containing gas is
introduced into the feed assembly to provide an excess of hydrogen
that is from 1 to 5 times that required for combustion of the fuel
gas feed.
14. The method of claim 11, wherein: the cracking feed comprises at
least one of ethane, liquefied petroleum gas, butane, naphtha,
natural gas, light gas oils, and heavy gas oils, the cracking feed
optionally being premixed with steam.
15. The method of claim 11, wherein: at least one of hydrogen gas
(H.sub.2), methane, and carbon oxides are separated from the
removed cracked hydrocarbon product and recycled to the feed
assembly.
16. The method of claim 11, wherein: the azimuthal-to-radial
velocity ratio of each of the feeds and the oxygen gas feed stream
within the annular flow spaces is from 0 to .infin..
17. The method of claim 11, wherein: at least one of the annular
inlet flow spaces is provided with circumferentially spaced apart
guide vanes oriented to facilitate the spiraling fluid flow within
said at least one of the inlet flow spaces.
18. The method of claim 11, wherein: the reactor system further
comprises a cooling gas feed assembly in fluid communication with
at least one of the reaction chamber and the reactor inlet
assembly, the cooling gas feed assembly comprising a pair of
axially spaced apart cooling gas feed assembly walls oriented
perpendicular or substantially perpendicular to the central axis,
an annular cooling gas inlet flow space being defined between the
cooling gas feed assembly walls that communicates with said at
least one of the reaction chamber and the reactor inlet assembly
where cooling gases from the cooling gas feed assembly are
introduced.
19. The method of claim 11, wherein: the residence time of the gas
mixture within the reactor system is 50 milliseconds or less.
20. The method of claim 11, wherein: the reaction conditions
include at least one of temperature of from 900.degree. C. to
1300.degree. C. and a pressure of from 0 kPa (g) to 10,000 kPa (g)
at an outlet of the reactor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national stage application under 35
U.S.C. .sctn. 371 of International PCT Application No.
PCT/US2019/057603, filed Oct. 23, 2019, which claims the benefit of
U.S. Provisional Application No. 62/749,424, filed Oct. 23, 2018,
each of which is incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] The invention relates to conversion methods for converting a
variety of hydrocarbons to produce more valuable products and the
reactor designs for such conversion.
BACKGROUND
[0003] A single-stage combustion pyrolysis method to produce
acetylene was developed by BASF, which is described in U.S. Pat.
No. 5,789,644. This process has been commercialized at a 50 KTA
scale using multiple reactors in Germany and the U.S. In this
process, natural gas serves for the hydrocarbon feed and pure
oxygen serves as the oxidant to generate heat, which is critical
for acetylene production. The two streams are premixed in a
diffuser, and the premixed fuel rich gas is burnt using a burner
block through partial oxidation. A major disadvantage of such a
design is the flashback risks of the premixed flame under various
feedstock and operating conditions, as well as the plurality of
burners used, which increases the total cost of operation,
difficulties in heat control, and low carbon yield toward olefin
product. Furthermore, while acetylene used to be the building block
for chemicals, over the last six to seven decades olefins have
become the building blocks of the chemical industries and there is
a desire to directly produce olefins rather than the indirect
hydrogenation route using acetylene.
[0004] Conventional steam crackers are the industry go-to reactors
to break long-chain hydrocarbons and modify smaller alkanes (i.e.,
naphtha, butane, ethane) into smaller molecules and olefins, such
as ethylene and propylene. In such crackers, heavy gases such as
naphtha, liquefied petroleum gas (LPG), propane, butane, and ethane
are fed into a furnace with steam and converted into smaller
olefins. Steam is added to the process to increase the selectivity
to olefins with reasonable conversion. Typically, this process
operates at high temperatures (i.e., from 750.degree. C. to
900.degree. C.) and has residence times of around 100 to 500
milliseconds. This process has been optimized over the last five
decades but there are still significant disadvantages. These
include heat losses and complexity associated with separate
exothermic (combustion in the furnace) and endothermic steps
(cracking in the process tubes). The presence of inert compounds in
the combustion and process side also affects the overall
efficiency. Metallurgical limitations of the reactors also limit
the temperatures that can be used. Ideally, higher temperatures
with shorter contact times result in better selectivity and
conversion to smaller olefins. Plugging from coking also occurs in
these conventional processes, which can increase the capital cost
and operational expenses. This also prevents cracking certain
heavier feeds. There is also a lack of feedstock flexibility, as
commercial crackers are typically optimized for only a certain type
of feedstock. Typically, these crackers also operate at process
pressures less than 200 kPa and that increases the capital cost of
the downstream operations.
[0005] The proposed invention addresses many of the shortcomings of
these conventional reactors.
SUMMARY
[0006] A reactor system for the conversion of hydrocarbons
comprises a reactor vessel having a reactor wall that defines a
reaction chamber. The reactor system includes a reactor inlet
assembly that has a converging conduit with a circumferential wall
that surrounds a central longitudinal axis and extends from
opposite upstream and downstream ends of the converging conduit.
The circumferential wall tapers in width from the downstream and
upstream ends to an annular constricted neck portion located
between the downstream and upstream ends of the converging conduit.
The downstream end of the converging conduit is in fluid
communication with the reaction chamber of the reactor. The
upstream end of the converging conduit forms an inlet of the
reactor inlet assembly.
[0007] A feed assembly of the reactor system is in fluid
communication with the inlet of the reactor inlet assembly, with
the central axis passing through the feed assembly. The feed
assembly comprises a downstream feed assembly wall extending
circumferentially around and joining the upstream end of the
reactor inlet assembly, the downstream feed assembly wall being
oriented perpendicular or substantially perpendicular to the
central axis. An upstream feed assembly wall is axially spaced
upstream from the downstream feed assembly wall along the central
axis and extends perpendicularly or substantially perpendicularly
across the central axis. An upstream gas partition wall and a
downstream gas partition wall are each axially spaced between the
downstream and upstream feed assembly walls and are axially spaced
from one another. The upstream gas partition wall and the
downstream gas partition wall or circumferential portions thereof
are oriented perpendicular or substantially perpendicular to the
central axis. At least one of the upstream gas partition wall and
downstream gas partition wall terminates at a position upstream
from the converging conduit to define a central opening that
surrounds the central axis of the converging conduit. An upstream
annular inlet flow space is defined between the upstream feed
assembly wall and the upstream partition wall. A downstream annular
inlet flow space is defined between the downstream feed assembly
wall and the downstream gas partition wall.
[0008] The annular inlet flow spaces cause introduced feeds to flow
perpendicularly to the central axis of the converging conduit in an
inwardly swirling fluid flow pattern within said flow spaces about
the central axis of the converging conduit.
[0009] The area extending from the central opening of the at least
one of the upstream and downstream partition walls to the inlet of
the reactor inlet assembly defines a central chamber of the feed
assembly, with heated combustion gases from at least one of the
inlet flow spaces being discharged into the central chamber. The
hydrocarbon feed and heated combustion gases passing as swirling
gases through the converging conduit to the reaction chamber.
[0010] In particular embodiments, at least one of the annular inlet
flow spaces is provided with circumferentially spaced apart guide
vanes oriented to facilitate the swirling fluid flow within said at
least one of the inlet flow spaces. The guide vanes may be movable
to selected positions and tilting angles to provide selected
azimuthal-to-radial velocity ratios of fluids flowing within the
annular inlet flow spaces. In some embodiments, the guide vanes are
configured as non-planar airfoils.
[0011] In certain instances, the reactor wall is cylindrical. The
circumferential wall of the converging conduit from the downstream
end to the annular constricted neck portion, and optionally an
upstream portion of the reactor wall of the reaction chamber that
joins the circumferential wall of the converging conduit, may be
configured as a smooth, continuous wall that follows contour lines
of an ellipsoidal cap or spherical cap shape. The interior of the
reactor wall may be a refractory material.
[0012] In some embodiments, the downstream gas partition wall has
an extended portion that is spaced from and follows the contours of
the circumferential wall of the converging conduit of the reactor
inlet assembly and terminates at a position downstream of the
annular constricted neck portion so that a downstream inlet flow
space is defined that discharges into an area downstream from the
constricted neck portion.
[0013] In some applications, the intermediate annular gas inlet
flow space is divided by an intermediate gas partition wall having
a central opening that surrounds the central axis of the converging
conduit and divides the intermediate inlet flow space into upstream
and downstream intermediate annular inlet flow spaces that
constitute inlet flow spaces for introducing a fuel gas feed and an
oxidizer feed. In others, the upstream annular gas inlet flow space
and the intermediate inlet flow space constitute inlet flow spaces
for introducing a fuel gas feed and an oxidizer feed.
[0014] In certain embodiments, a cooling gas feed assembly is in
fluid communication with at least one of the reaction chamber and
the reactor inlet assembly. The cooling gas feed assembly includes
a pair of axially spaced apart cooling gas feed assembly walls
oriented perpendicular or substantially perpendicular to the
central axis. An annular cooling gas inlet flow space is defined
between the cooling gas feed assembly walls and communicates with
said at least one of the reaction chamber and the reactor inlet
assembly. The annular cooling gas inlet flow space may be provided
with circumferentially spaced apart guide vanes oriented to
facilitate the swirling fluid flow within the cooling gas inlet
flow space.
[0015] In a method of cracking hydrocarbons to cracked hydrocarbon
products, a hydrocarbon feed containing hydrocarbons to be cracked
is introduced into a reactor system. The reactor system comprises a
reactor vessel having a reactor wall that defines a reaction
chamber. A reactor inlet assembly has a converging conduit with a
circumferential wall that surrounds a central longitudinal axis and
extends from opposite upstream and downstream ends of the
converging conduit. The circumferential wall tapers in width from
the downstream and upstream ends to an annular constricted neck
portion located between the downstream and upstream ends of the
converging conduit. The downstream end of the converging conduit is
in fluid communication with the reaction chamber of the reactor.
The upstream end of the converging conduit forms an inlet of the
reactor inlet assembly.
[0016] The reactor system used in the method further includes a
feed assembly in fluid communication with the inlet of the reactor
inlet assembly, with the central axis passing through the feed
assembly. The feed assembly includes a downstream feed assembly
wall that extends circumferentially around and joins the upstream
end of the reactor inlet assembly. The downstream feed assembly
wall is oriented perpendicular or substantial perpendicular to the
central axis. The feed assembly also includes an upstream feed
assembly wall that is axially spaced upstream from the downstream
feed assembly wall along the central axis and extends
perpendicularly or substantially perpendicularly across the central
axis. An upstream gas partition wall and a downstream gas partition
wall are each axially spaced between the downstream and upstream
feed assembly walls and are axially spaced from one another. The
upstream gas partition wall and the downstream gas partition wall
or circumferential portions thereof are oriented perpendicular or
substantially perpendicular to the central axis. At least one of
the upstream gas partition wall and downstream gas partition wall
terminates at a position upstream from the converging conduit to
define a central opening that surrounds the central axis of the
converging conduit. An upstream annular inlet flow space is defined
between the upstream feed assembly wall and the upstream partition
wall. A downstream annular inlet flow space is defined between the
downstream feed assembly wall and the downstream gas partition
wall. An intermediate inlet flow space is defined between the
upstream gas partition wall and the downstream gas partition
wall.
[0017] The annular inlet flow spaces cause introduced feeds to flow
perpendicularly or substantially perpendicularly toward the central
axis of the converging conduit in an inwardly swirling fluid flow
pattern within said flow spaces about the central axis of the
converging conduit. The area extending from the central opening of
the at least one upstream and downstream partition walls to the
inlet of the reactor inlet assembly defines a central chamber of
the feed assembly.
[0018] In the method, a cracking feed of the hydrocarbon feed to be
cracked is introduced into a first inlet flow space and a fuel gas
feed and an oxidizer feed are introduced into adjacent second and
third inlet flow spaces so that the feeds pass through said flow
spaces perpendicularly or substantially perpendicularly toward the
central axis of the converging conduit in an inwardly swirling
fluid flow pattern within said flow spaces flowing about the
central axis of the converging conduit. The order of fuel feed and
oxidizer feed may be altered in some applications. The fuel gas
feed and oxidizer feed combust in the central chamber to form
heated combustion gases. The hot combustion gases and cracking feed
are discharged into the central chamber and/or reaction chamber so
that the heated combustion gases and cracking feed are mixed
together and form a swirling, heated gas mixture.
[0019] The heated gas mixture is allowed to react within the
reaction chamber of the reactor vessel under reaction conditions
suitable for hydrocarbon cracking, with at least a portion of the
cracking feed of the gas mixture being converted to cracked
hydrocarbon products. Cracked hydrocarbon product is removed from
the reaction chamber of the reactor vessel.
[0020] In particular embodiments, the fuel gas feed, which may
comprise a hydrogen-containing gas of at least one of hydrogen gas
(H.sub.2) and methane (CH.sub.4), is introduced into one of the
first and second annular fuel gas inlet flow spaces. An oxidizer
feed, which comprises an oxygen-containing gas, is introduced into
the other of the first and second annular fuel gas inlet flow
spaces.
[0021] The hydrogen-containing gas may be introduced into the feed
assembly to provide an excess of hydrogen that is from 1 to 5 times
that required for cracking the hydrocarbon feed
[0022] The cracking feed may include at least one of ethane,
liquefied petroleum gas, butane, naphtha, natural gas, light gas
oils, and heavy gas oils, the cracking feed optionally being
premixed with steam.
[0023] At least one of hydrogen gas (H.sub.2), methane, and carbon
oxides or combinations thereof may be separated from the removed
cracked hydrocarbon product and recycled to the feed assembly.
[0024] The azimuthal-to-radial velocity ratio of each of the feeds
and the oxygen gas feed stream within the annular flow spaces may
be from 0 to co, more particularly from 0 to 30.
[0025] Each of the feeds may each be introduced into the respective
annular flow spaces in the same rotational direction. In certain
applications, at least one of the annular inlet flow spaces is
provided with circumferentially spaced apart guide vanes oriented
to facilitate the spiraling fluid flow within said at least one of
the inlet flow spaces. The guide vanes may be movable to selected
positions and tilting angles to provided selected
azimuthal-to-radial velocity ratios of the fluid flow within said
at least one of the inlet flow spaces.
[0026] In some embodiments, the reactor wall is cylindrical. The
circumferential wall of the converging conduit from the downstream
end to the annular constricted neck portion, and optionally an
upstream portion of the reactor wall of the reaction chamber that
joins the circumferential wall of the converging conduit, may be
configured as a smooth, continuous wall that follows contour lines
of an ellipsoidal cap or spherical cap shape. The interior of the
reactor wall may be a refractory material.
[0027] The residence time of the gas mixture within the reactor
system is 50 milliseconds or less in certain instances. The
reaction conditions may include a temperature of from 900.degree.
C. to 1300.degree. C. and a pressure of from 0 kPa (g) to 10,000
kPa (g) at an outlet of the reactor.
[0028] In certain embodiments of the method, the reactor system
further comprises a cooling gas feed assembly in fluid
communication with at least one of the reaction chamber and the
reactor inlet assembly. The cooling gas feed assembly comprises a
pair of axially spaced apart cooling gas feed assembly walls
oriented perpendicular or substantially perpendicular to the
central axis. An annular cooling gas inlet flow space is defined
between the cooling gas feed assembly walls that communicates with
said at least one of the reaction chamber and the reactor inlet
assembly where cooling gases from the cooling gas feed assembly are
introduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] For a more complete understanding of the embodiments
described herein, and the advantages thereof, reference is now made
to the following descriptions taken in conjunction with the
accompanying figures, in which:
[0030] FIG. 1 is a process flow diagram of a cracking system for
cracking of hydrocarbons into cracked hydrocarbon products in
accordance with particular embodiments of the invention;
[0031] FIG. 2 is a schematic representation of a reactor system for
cracking shown in cross section and constructed in accordance with
particular embodiments of the invention;
[0032] FIG. 3 is perspective view of a lower or upstream portion of
the reactor system of FIG. 2, showing a reactor inlet assembly and
reactor feed assembly constructed in accordance with particular
embodiments of the invention;
[0033] FIG. 4 is schematic showing the angle of guide vanes of the
reactor feed assembly of the reactor of FIG. 2 relative to a
central longitudinal axis of the reactor;
[0034] FIG. 5 is a schematic of the cracking reactor system of FIG.
2 showing gas flows within the reactor;
[0035] FIG. 6 is schematic representation of an alternate
embodiment of a reactor system for cracking hydrocarbons shown in
cross section and constructed in accordance with particular
embodiments of the invention;
[0036] FIG. 7 is a perspective view of an airfoil for use in the
reactor feed assemblies described herein;
[0037] FIG. 8 is a top plan view of the airfoil of FIG. 7;
[0038] FIG. 9 is a schematic diagram of the three different arcs
used in forming the airfoil of FIG. 7;
[0039] FIG. 10 is a diagram showing a pair of airfoils as arranged
in a circular pattern to demonstrate the configuration and location
of the circumferentially spaced airfoils as they may be used with
those reactor feed assemblies described herein;
[0040] FIG. 11 is schematic representation of another embodiment of
a reactor system for cracking hydrocarbons shown in cross section
and constructed in accordance with particular embodiments of the
invention;
[0041] FIG. 12 is a representation of the cracking reactor geometry
and axial velocity distribution of gas flow in a lab scale reactor
unit model of Example 1;
[0042] FIG. 13 is a representation of the cracking reactor geometry
and swirl velocity distribution of gas flow in a lab scale reactor
unit model of Example 1;
[0043] FIG. 14 is a representation of the meridional flow pattern
(stream function contours) in the lab scale reactor unit of Example
1;
[0044] FIG. 15 is a representation of the cracking reactor geometry
and mass fraction distribution for ethane cracking feed of the lab
scale reactor unit of Example 1;
[0045] FIG. 16 is a representation of the cracking reactor geometry
and the temperature distribution of the lab scale reactor unit of
Example 1;
[0046] FIG. 17 is a representation of the cracking reactor geometry
and mass fraction distribution for hydrogen gas (H.sub.2) of the
lab scale reactor unit of Example 1;
[0047] FIG. 18 is a representation of the cracking reactor geometry
and mass fraction distribution for oxygen gas (O.sub.2) of the lab
scale reactor unit of Example 1;
[0048] FIG. 19 is a representation of the cracking reactor geometry
and mass fraction distribution for steam (H.sub.2O) of the lab
scale reactor unit of Example 1;
[0049] FIG. 20 is a representation of the cracking reactor geometry
and mass fraction distribution for atomic oxygen (O) of the lab
scale reactor unit of Example 1;
[0050] FIG. 21 is a representation of the cracking reactor geometry
and mass fraction distribution for the cracked product ethylene of
the lab scale reactor unit of Example 1;
[0051] FIG. 22 is a representation of the cracking reactor geometry
and mass fraction distribution for the cracked product acetylene of
the lab scale reactor unit of Example 1;
[0052] FIG. 23 is a representation of the cracking reactor geometry
and mass fraction distribution for the cracked product propylene of
the lab scale reactor unit of Example 1; and
[0053] FIG. 24 is a representation of the cracking reactor geometry
and mass fraction distribution for carbon monoxide (CO) of the lab
scale reactor unit of Example 1
DETAILED DESCRIPTION
[0054] In the present disclosure, a novel system is utilized that
converts hydrocarbons to higher value products, such as olefins, by
utilizing high centrifugal forces generated by swirling flow in a
unique reactor configuration to create and control a reacting flow
environment that maximizes the production of desirable olefins with
very high productivity (cracking). This is achieved by utilizing
annular highly swirled jets of feed gases where hydrogen (or other
fuels such as natural gas, recycled syngas, etc.) and oxygen gases
are mainly used to generate the heat required for cracking of
hydrocarbons. The cracking reactor used is similar to the pyrolysis
reactor described in U.S. Patent Application No. 62/639,577 and
International Publication No. WO2019/173570A1, each of which is
incorporated by reference herein for all purposes. U.S. Patent
Application No. 62/639,577 and International Publication No.
WO2019/173570A1 each describe a reactor that can be used in the
pyrolysis conversion of hydrocarbon gases. This type of reactor may
be referred to as an ANJEVOC (ANnular JEt VOrtex Chamber) reactor.
The ANJEVOC reactor described herein, while similar to that
described in U.S. Patent Application No. 62/639,577 and
International Publication No. WO2019/173570A1, is used for cracking
and therefore is configured differently. Such reactor may be
referred to as the ANJEVOC-C (ANnular JEt VOrtex Chamber--Cracking)
reactor.
[0055] Referring to FIG. 1, a flow schematic of a hydrocarbon
conversion system 10 is shown for the conversion of hydrocarbons to
higher value products, such as olefins. The system 10 includes an
ANJEVOC-C cracking reactor 12, which is described in more detail
later on. A cracking feed 14 is fed to the reactor 12 as a separate
stream. The cracking feed 14 can include hydrocarbons such as
ethane, liquefied petroleum gas (LPG), butane, naphtha, natural
gas, light gas oils, and/or heavy gas oils. The cracking feed
stream 14 may be preheated prior to being introduced into the
reactor 12. In particular applications, the feed stream 14 may be
heated to a temperature of from 25.degree. C. to 500.degree. C. to
improve conversion efficiency or vaporize heavier liquid
hydrocarbons either externally or within the reactor
[0056] It should be noted in the description, if a numerical value,
concentration or range is presented, each numerical value should be
read once as modified by the term "about" (unless already expressly
so modified), and then read again as not so modified unless
otherwise indicated in context. Also, in the description, it should
be understood that an amount range listed or described as being
useful, suitable, or the like, is intended that any and every value
within the range, including the end points, is to be considered as
having been stated. For example, "a range of from 1 to 10" is to be
read as indicating each and every possible number along the
continuum between about 1 and about 10. Thus, even if specific
points within the range, or even no point within the range, are
explicitly identified or referred to, it is to be understood that
the inventor appreciates and understands that any and all points
within the range are to be considered to have been specified, and
that inventor possesses the entire range and all points within the
range.
[0057] An oxygen-containing gas feed 16 for combustion of a
hydrogen-rich fuel gas feed 18 is also fed to the reactor 12 as a
separate stream. The oxygen-gas feed 16 may be a concentrated
oxygen-gas feed, wherein a majority of the feed (i.e., >50 mol
%) is composed of oxygen gas (O.sub.2). In many instances, the
oxygen-containing gas will be a high-purity oxygen-containing gas
feed composed of O.sub.2 in an amount of from 20 mol % to 100 mol %
of the oxygen gas feed stream. This may be that provided from an
air separation unit (not shown) used for separating oxygen gas from
air or other oxygen-gas source. Air may also be used as the
oxygen-containing gas. In cases where air is used as the
oxygen-containing gas, or cases where there are large amounts of
impurities (e.g., N.sub.2) in the oxygen-containing gas feed,
separation of such impurities from the product may be necessary
downstream.
[0058] A steam or water (H.sub.2O) feed is also feed to the reactor
12 as separate steam feed stream 20. The cracking feed 14, fuel 18,
and/or oxygen-gas feed 16 may also be premixed with steam in
certain embodiments. In some instances, the separate steam feed
stream 20 may be eliminated where sufficient steam is provided and
mixed with the feeds 14 and/or 16.
[0059] Cracked reaction products 22 are removed from the reactor 12
where they may be cooled by quenching in a quenching unit 24, such
as a water-droplet-spray quench vessel, or other suitable gas
quench devices. The cracked products 22 will typically be a mixture
of hydrogen gas, steam, oxygenates, some heavies (>C4), some
aromatics, and product olefins.
[0060] The quenched cracked reaction products 26 may be delivered
to a separation unit 28, where the product gases are separated to
form a product stream 30 containing product olefins, such as
ethylene (C.sub.2H.sub.4), propylene (C.sub.3H.sub.6), and others,
and a separated gas stream 32.
[0061] The separated gas stream 32 is removed from the separator 28
and will typically contain hydrogen gas (H.sub.2), with minor
amounts of methane (CH.sub.4), and carbon oxides of CO and
CO.sub.2. In certain applications, CO.sub.2 can be separated before
separating other gases so that recycled gas stream 32 may contain
only H.sub.2, CH.sub.4, and CO. Because dehydrogenation occurs
during the cracking reaction, enough hydrogen is typically
generated so that it can be used as a fuel gas for generating heat
for the cracking reaction in reactor 12. Thus, the gas stream 32
may be recycled and fed as the hydrogen-rich fuel feed 18. In some
cases, enough fuel gas (e.g., H.sub.2) is recycled during the
cracking reaction so that no additional fuel is needed in addition
to that supplied by the recycle stream 32. In other cases, however,
additional fuel feed 34 of a hydrogen-rich or natural gas feed may
be used for the fuel feed 18, such as an initial fuel feed during
reactor startup, or that is combined with the recycle stream 32 to
form the fuel feed 18 when an insufficient amount of hydrogen is
available in the recycle stream 32 for combustion reaction
heat.
[0062] Based upon the type of cracking feed, the operational
conditions of the reactor 12 may vary. In a typical cracking
reaction using the ANJEVOC-C reactor, the oxygen feed 16 is
typically used with excess hydrogen or fuel gas so that all the
oxygen is consumed. Usually, the amount of hydrogen will be 1 or 2
to 4 times the stoichiometric amount needed for combustion with
oxygen. In some cases, hydrogen is sub-stoichiometric (below 1) to
allow for additional exothermic reactions in the mixing zone. The
oxygen feed 16 may provide an oxygen equivalent-to-fuel mole ratio
of from 0.125 to 0.50. Furthermore, the ratio between the crack
feed to hydrogen fuel will typically range from 1.0 to 15 based on
mass depending on the hydrocarbon feed. The residence time within
the reactor 12 may range from 50 milliseconds or less, more
particularly from 20 milliseconds or less. As will be discussed in
more detail later on, recirculation zone temperature within the
reactor will typically range from 1000.degree. C. to 1300.degree.
C. The pressure at the reactor outlet may vary. A suitable pressure
at the reactor outlet may range from 0 kPa (g) to 10,000 kPa (g),
more particularly from 0 kPa (g) to 1,000 kPa (g).
[0063] It should be noted that while the system 10 of FIG. 1 shows
single units for the various process steps, each unit could be
composed of one or more units that may operate in conjunction with
one another, such as parallel or sequentially, to carry out the
various process steps described.
[0064] Referring to FIG. 2, an elevational cross-sectional
schematic representation of the cracking reactor system 12 for
cracking of hydrocarbons, such as ethane, LPG, butane, naphtha,
natural gas, light gas oils, heavy gas oils, or a combination of
these hydrocarbons, is shown. The reactor 12 constitutes an
ANJEVOC-C reactor and includes a reactor vessel 36 having a reactor
wall 38 that defines an interior reaction chamber 40. The reactor
wall 38 may have a cylindrical configuration with a constant
diameter along all or a portion of its length, which may constitute
a majority of its length. In most instances, the reactor 12 is
oriented vertically so that the cylindrical reactor wall 38 is
oriented in an upright orientation. The reactor can have other
orientations (e.g., horizontal, sloped, or downward), however,
because the process is controlled by the centrifugal force, which
exceeds the gravitational force by several orders of magnitude. The
reactor vessel 36 may be configured to provide a length to diameter
ratio (L/D) of at least 2. In particular applications, the L/D
ratio may range from 2-10, more particularly from 2-5.
[0065] The reactor vessel 36 may be formed from steel. In certain
embodiments, a cooling jacket can be provided around the reactor
vessel, wherein a second steel wall 42 is positioned around and
spaced from the inner reactor wall 38 and a cooling fluid, such as
water may be circulated through the jacket formed between the walls
38, 42. In other embodiments, the reactor wall 38 may be formed
from one or more layers of refractory material that line the
interior of an outer steel wall to reduce heat loss and sustain the
high temperatures of the reactor 12. As will be described later on,
because of the unique design and operation of the reactor 12, the
reactor wall 38 is cooled internally by the high-velocity near-wall
gas flow pushed by centrifugal forces against the reactor wall 38
so that in some applications no exterior cooling jacket is
required. This also allows refractory materials to be used for the
interior of the reactor wall 38. Refractory materials (without
cooling) typically cannot be used with conventional cracking
reactors with pure oxygen due to the higher temperatures (e.g.,
from 2000.degree. C. to 2800.degree. C.) encountered.
[0066] An outlet 44 is provided at the upper or downstream end of
the reactor vessel 36 for removing or discharging cracked products
from the reaction chamber 40. Although the outlet 44 is shown
located at the upper end of the reactor vessel 36, in other
embodiments it may be located at the lower end of the reactor
vessel 36, so that the flow through the reactor is in the opposite
direction (i.e., from top to bottom). The outlet diameter can be
same as the diameter of the reactor wall 38 or the outlet diameter
may be reduced to accelerate the flow before quenching and
collection downstream.
[0067] The reactor 12 includes a reactor inlet assembly 46 that is
coupled or joined to the lower or upstream end of the reactor wall
38 of the reactor vessel 36. The inlet assembly 46 has a converging
conduit 48 with a circumferential wall 50 that surrounds a central
longitudinal axis 52 of the reactor. Where the reactor 12 is
oriented vertically, the central axis 52 will also be oriented
vertically as well and will be concentric with or parallel to a
central vertical axis of the reactor vessel 36. In the embodiment
shown, the axis 52 is concentric with and aligned with the central
longitudinal axis of the reactor vessel 36. The circumferential
wall 50 extends from opposite upstream and downstream ends of the
converging conduit 48. As used herein, the terms "upstream" and
"downstream" or similar expressions with respect to describing
various components of the reactor system 12 shall refer to the
position of the component with respect to the direction of overall
fluid flow through the reactor 12 along the central axis 52. As can
be seen in FIG. 2, the circumferential wall 50 smoothly tapers in
width or diameter from the downstream and upstream ends to an
annular constricted neck portion 54 located between the downstream
and upstream ends of the converging conduit 48. The interior of the
circumferential wall 50 may have a circular perpendicular
transverse cross section (with respect to the axis 52) along its
length. The circumferential wall 50 defines an interior flow path
of the inlet assembly 46 with the constricted neck portion 54
forming a converging-diverging streamlined nozzle of the inlet
assembly 46. The nozzle geometry of the neck portion 54 is
configured based upon the theory relating to swirling conical jets
of a viscous incompressible fluid.
[0068] The circumferential wall 50 of the converging conduit 48
from the downstream end where it joins reactor wall 38 to the
annular constricted neck portion 54 may, in some embodiments, be
configured as a smooth, continuous concave wall having an
ellipsoidal cap or spherical cap shape or configuration. Likewise,
the upstream portion of the reactor wall 38 of the reaction chamber
40 that joins the circumferential wall 50 of the converging conduit
48 may also be configured as a smooth, continuous concave wall that
follow contour lines of an ellipsoidal cap or spherical cap shape
or configuration.
[0069] The downstream end of the converging conduit 48 joins the
reactor wall 38 around its perimeter so that the converging conduit
48 is in fluid communication with the reactor chamber 40 of the
cracking reactor vessel 36. The upstream end of the converging
conduit 48 forms a reactor inlet 56 of the reactor vessel 36.
[0070] A reactor feed assembly 58 is provided with the reactor 12.
The reactor feed assembly 58 is in fluid communication with the
reactor inlet 56 of the inlet assembly 46, with the central axis 52
passing through the reactor feed assembly 58. The feed assembly 58
includes a downstream feed assembly wall 60 that extends
circumferentially around and joins the upstream end of the reactor
inlet 56. The feed assembly wall 60 or circumferential portions
thereof are oriented perpendicularly or substantially
perpendicularly (i.e., <5 degrees from perpendicular about its
circumference as it extends radially from the central axis) to the
central axis 52.
[0071] Axially spaced upstream from the downstream wall 60 along
the central axis 52 is an upstream feed assembly wall 62. The
upstream wall 62 or circumferential portions thereof are oriented
perpendicular to or substantially perpendicularly (i.e., <5
degrees from perpendicular about its circumference as it extends
radially from the central axis) to the central axis 52 and extends
across the central axis 52.
[0072] An upstream gas partition wall 64 and a downstream gas
partition wall 66 are axially spaced between the downstream and
upstream feed assembly walls 60, 62 and are axially spaced from one
another, with the upstream wall 64 being positioned upstream from
the downstream partition wall 66. The partition walls 64, 66 or
circumferential portions thereof are also each oriented
perpendicularly to or substantially perpendicularly (i.e., <5
degrees from perpendicular about its circumference as it extends
radially from the central axis) to the central axis 52. The inner
ends of the partition walls 64, 66 terminate at a position below
the converging conduit 48 to define a central opening 68, 70,
respectively, that surrounds the central axis 52 and is concentric
with the converging conduit 48. The central openings 68, 70 each
have a circular configuration. Other shapes for the central
openings 68, 70 (e.g., oval) may also be used provided such
configuration facilitates the swirling of gases to provide the
required flow patterns described herein. This shape may also
correspond to the cross-sectional shape of the circumferential wall
50 of the converging conduit 48. In most applications, however, the
central openings 68, 70 will be circular in shape. The central
openings 68, 70 may have a diameter or width that is the same or
slightly different than the diameter or width of the constricted
neck 54 of the converging conduit 48 at its narrowest point.
[0073] The upstream partition wall 64 defines an annular gas flow
space 72 located between the upstream feed assembly wall 62 and the
upstream side of the upstream partition wall 64. In the embodiment
shown, the flow space 72 constitutes an upstream annular
hydrocarbon cracking feed inlet flow space. Likewise, an annular
gas flow space 74 is defined by the downstream side of the
downstream partition wall 66 and the downstream feed assembly wall
60. In the embodiment shown, the flow space 74 constitutes an
annular steam or water inlet flow space.
[0074] A further annular flow space 76 is defined between the
upstream side of the downstream gas partition wall 66 and the
downstream side of the upstream gas partition wall 64. An
intermediate partition wall 78 is axially spaced between the
downstream gas partition wall 66 and the upstream gas partition
wall 64 to define downstream and upstream intermediate annular gas
inlet flow spaces 80, 82. The intermediate partition wall 78 or
circumferential portions thereof is also oriented perpendicularly
to or substantially perpendicularly (i.e., <5 degrees from
perpendicular about its circumference as it extends radially from
the central axis) to the central axis 52. In the embodiment shown,
the intermediate partition wall constitutes a fuel gas partition
wall that defines the flow spaces 80, 82, which constitute first
and second annular fuel gas inlet flow spaces. The inner end of the
intermediate partition wall 78 terminates to define a central
opening 84 that surrounds the central axis 52 of the converging
conduit 48, and wherein the periphery of the central opening 84 of
the fuel gas partition wall 78 is spaced radially outward a
distance from the central openings 68, 70 of the upstream gas
partition wall 64 and the downstream gas partition wall 66, as is
shown. The area spaced radially inward from the central opening 84
of the intermediate partition wall 78 between the upstream and
downstream gas partition walls 64, 66 defines an annular combustion
zone 86. The size of the central opening 84 can vary to fit the
radial extent of combustion zone 86.
[0075] This configuration provides flow passages through which
hydrocarbon gas feed to be cracked, steam, oxygen gas, and
hydrogen-rich fuel for providing combustion heat can each be
separately introduced and passed through the flow spaces 72, 74,
80, 82, respectively, perpendicularly or substantially
perpendicular to the central axis 52 of the converging conduit 48.
In some instances, the lowermost or upstream flow space 72 will
constitute a hydrocarbon cracking feed inlet flow space. The steam
feed may be introduced into the uppermost or upstream annular steam
inlet flow space 74. In other instances, the hydrocarbon cracking
feed may be introduced into the uppermost or downstream flow space
74 and the steam feed may be introduced into the lowermost or
upstream flow space 72. A fuel gas feed comprised of an
hydrogen-rich gas feed may be introduced into one of the first and
second adjacent annular fuel gas inlet flow spaces 80, 82, with an
oxidizer or oxygen-containing gas feed being introduced into the
other of the flow spaces 80, 82. The downstream flow space 80 may
be used for delivering the oxidizer or oxygen-containing gas and
the upstream flow space 82 will be used for delivering the
hydrogen-rich fuel gas. In other instances, these may be reversed
or altered in other sequences.
[0076] The flow passages 72, 74, 80, 82 are configured so that the
different feeds pass through flow spaces perpendicularly or
substantially perpendicularly to the central axis 52 of the
converging conduit 48 in an inwardly swirling fluid flow pattern
within said flow spaces so that the feeds flow about the central
axis 52 of the converging conduit 48. The fuel gas and oxidizer
feeds combust primarily in the small combustion zone 86 between the
upstream and downstream partition walls 64, 66 within the central
opening 84 of the fuel gas partition wall 78.
[0077] The walls 60, 62, 64, 66, and 78 forming the different flow
spaces 72, 74, 80, 82 may be parallel to one another in many cases,
but may be non-parallel to one another in certain cases. The walls
60, 62, 64, 66, and 78 are axially spaced apart to provide the
desired volume and flow characteristics for the gases flowing
through them. This may be based upon the desired flow rates or
linear velocities of each of the feed gases and their relative
amounts. For instance, the relative volume of oxygen gas needed for
the combustion is typically smaller than that of the hydrogen-rich
fuel gas needed for the combustion. Therefore, the partition wall
78 may be spaced closer to the downstream partition wall 66 so that
the flow space 82 for the hydrogen fuel is larger to accommodate
the greater flow of fuel gas. The particular spacing may depend on
fuel gas and oxidizer combination, the desired volume for
combustion, and cracking feeds.
[0078] Annular gas manifolds 88, 90, 92, 94 may be provided around
the outer periphery of the flow spaces 72, 74, 80, 82,
respectively. The gas manifold 88 is fluidly coupled to a cracking
feed source, such as cracking feed 14 of FIG. 1. The manifold 90 is
fluidly coupled to a steam source, such as the steam feed 20 of
FIG. 1. The manifold 92 is fluidly coupled to an
oxygen-containing-gas source, such as the oxygen gas feed 16 of
FIG. 1. And the manifold 92 is fluidly coupled to a hydrogen-rich
or fuel feed source, such as the fuel feed 18 of FIG. 1. The
manifolds 88, 90, 92, 94 are provided with the reactor feed
assembly 58 to facilitate introduction of feed gases into the flow
spaces 72, 74, 80, 82.
[0079] Gas inlets 96, 98, 100, 102 from the manifolds 88, 90, 92,
94, respectively, may be directed tangentially into the flow spaces
72, 74, 80, 82 so that the gases are not directed only radially
toward the central axis 52 from the inlets 96, 98, 100, 102, but
instead are directed mostly tangentially around the central axis 52
to provide an inwardly swirling flow pattern. As shown in FIG. 2,
each flow space 72, 74, 80, 82 may have one or more tangential
inlets, such as the inlets 96A and 96B, 98A and 98B, 100A and 100B,
and 102A and 102B. Furthermore, the walls 60, 62, 64, 66, and 78
forming the different flow spaces of the feed assembly 58 keep the
gases introduced from the manifolds 88, 90, 92, 94 from flowing
axially along the central axis 52 while they are contained within
the flow spaces 72, 74, 80, 82. The manifolds 88, 90, 92, 94 can be
configured as standard manifolds (e.g., snail-like) as may be
typically used in vortex devices.
[0080] Referring to FIG. 3, one or more or all of the flow spaces
72, 74, 80, 82 may be provided with a plurality of
circumferentially spaced guide vanes 104, 106, 108, 110 (e.g., 10
to 60 guide vanes). Each guide vane 104, 106, 108, 110 may be a
planar member that is oriented in a plane that is parallel to the
central axis 52 and extends between the walls 60, 62, 64, 66, and
78. The guide vanes 104, 106, 108, 110 may be circumferentially
spaced an equal distance from one another. In certain embodiments,
the guide vanes 104, 106, 108, 110 may be fixed in place, with the
upper and lower side edges of the guide vanes being joined along
their lengths or a portion of their lengths to the walls 60, 62,
64, 66, and 78 so that there are no air gaps between the side edges
of the vanes 104, 106, 108, 110 and the walls 60, 62, 64, 66, and
78. In other embodiments, however, the guide vanes are movable. In
such cases, the upper and lower side edges of the vanes 104, 106,
108, 110 may be closely spaced from the walls 60, 62, 64, 66, and
78 to provide a small clearance to allow such movement but that
minimizes air gaps where gases may pass through. Seals may also be
used to effectively close these spaces or clearances while allowing
movement. In other instances, the vanes 104, 106, 108, 110 may be
oriented so that the plane of the vane is in a non-parallel or
slanted orientation relative to the central axis 52. In such cases,
the side edges may be fixed to the walls 60, 62, 64, 66, and 78 or
remain closely spaced from walls 60, 62, 64, 66, and 78 to minimize
air gaps for gasses to pass through. In certain applications, the
guide vanes 104, 106, 108, 110 may be configured as airfoils, such
as National Advisory Committee for Aeronautics (NACA) airfoil
shapes, as described in E. N. Jacobs, K. E. Ward, & R. M.
Pinkerton, NACA Report No. 460, "The characteristics of 78 related
airfoil sections from tests in the variable-density wind tunnel"
(NACA, 1933). The guide vanes may have curved surfaces, which may
be oriented with the width being parallel or non-parallel to the
axis 52, to provide desired flow characteristics, such as reduced
drag and pressure drop. An example of a suitable airfoil design for
the vane is discussed later in more detail.
[0081] The guide vanes 104, 106, 108, 110 are provided adjacent to
the outer perimeter of the flow spaces 72, 74, 80, 82 and are
spaced in an annular or circular ring pattern near the manifold
inlets 96, 98, 100, 102, respectively, although they may be
provided in an annular pattern at other positions located radially
inward or further within the interior of the flow spaces 72, 74,
80, 82, or one or more additional annular sets of guide vanes may
be located radially inward from those located along the outer
periphery to facilitate inwardly swirling fluid flow.
[0082] Feed gases from the manifolds 88, 90, 92, 94 are delivered
nearly tangentially to the outer perimeter of the flow spaces 72,
74, 80, 82, where the guide vanes 104, 106, 108, 110 further
facilitate directing the gas flow in an inwardly swirling or
spiraling fluid flow pattern within the flow spaces 72, 74, 80, 82.
In other embodiments, the guide vanes 104, 106, 108, 110 may impart
the full tangential flow of the introduced gases in cases where the
gas from inlets 96, 98, 100, 102 may be directed radially toward
the central axis 52. In such cases the guide vanes 104, 106, 108,
110 prevent flow directly toward the central axis 52 and direct the
flowing gases tangentially to provide the inwardly swirling or
spiraling fluid flow pattern.
[0083] The guide vanes 104, 106, 108, 110 of each flow space 72,
74, 80, 82 may be mounted on actuators (not shown) so that they can
be selectively movable to various positions to provide a selected
inwardly spiraling flow pattern. The guide vanes 104, 106, 108, 110
may be pivotal about an axis that is parallel to the central axis
52 so that the vanes 104, 106, 108, 110 may be moved to various
positions.
[0084] The orientation of the vanes 104, 106, 108, 110, as well as
the orientation of the tangential inlets 96, 98, 100, 102 may be
seen in FIG. 4. As shown, the line 112 represents the angle of
orientation of the vanes 104, 106, 108, 110 and/or inlets 96, 98,
100, 102 with respect to the radial line 114 extending radially
from the central axis 52. Angle A is the angle between the
tangential line 112 and the radial line 114. For non-planar vanes,
such as airfoils, the line 112 may correspond to or represent a
chord line passing through the leading edge and trailing edge of
the vane or airfoil. In particular embodiments, the angle A may
range from 50.degree. to 90.degree., more typically from 60.degree.
to 85.degree.. Thus, the vanes 104, 106, 108, 110 may be
permanently oriented at an angle A within this range or may be
movable to various angular orientations within this range. In most
cases, each of the vanes 104, 106, 108, 110 within the annular
pattern will be set at the same angle A and when actuated will move
in unison or close to unison to the same angle A to provide the
desired swirling fluid flow characteristics. The angle(s) of
orientation A of the vanes 104, 106, 108, 110 and/or inlets 96, 98,
100, 102 of the different flow passages may be the same or
different than the angle(s) of orientation of the vanes or inlets
of the others.
[0085] In most cases, the tangential gas inlets 96, 98, 100, 102
and/or the guide vanes 104, 106, 108, 110 will be oriented to
provide swirling or spiraling fluid jet flow that is in the same
rotational direction about the axis 52, i.e., clockwise or
counter-clockwise. Thus, gases within each of the flow spaces will
flow clockwise or counterclockwise about the axis 52.
[0086] Referring again to FIG. 2, the area extending from the
central openings 68, 70 of the partition walls 62, 70,
respectively, to the reactor inlet 56 define a central mixing
chamber 116. It is here that heated combustion gases from the flow
space 76, hydrocarbon cracking feed from the upstream hydrocarbon
feed inlet flow space 72, and steam from flow space 74 are
discharged into the central chamber 116 so that hydrocarbon
cracking feed, steam and heated combustion gases are mixed together
and form a swirling gas mixture within the chamber 116. This
swirling gas mixture then passes through the converging conduit 48
and into the reaction chamber 40 of the reactor vessel 36.
[0087] Because the oxygen-containing gas and hydrogen-rich fuel gas
are introduced separately from one another into the flow spaces 80,
82, respectively, and not as mixture, this eliminates safety issues
that would otherwise occur if these gases were premixed prior to
their introduction into the feed assembly 58. Furthermore, the
combustion reaction takes place very rapidly wherein most of the
combustion occurs within a very small space within the combustion
zone 86 where the two streams of oxygen-containing gas and
hydrogen-rich fuel gas from the flow spaces 80, 82 are mixed
immediately adjacent to the central opening 84 and prior to
entering the chamber 116. The combustible mixture can be ignited
through spark or chemicals or pilot flame through bottom surface or
side surfaces of the reactor as the suction from the strong
swirling flow (that mimics a tornado) will transport the hot gases
from the ignition device to the combustion zone 86 to initiate the
ignition.
[0088] Referring to FIG. 2, in operation, a cracking feed is
introduced from manifold 88 to tangential inlets 96A, 96B into flow
space 72. The cracking feed may be ethane, LPG, butane, naphtha,
natural gas, light gas oils, heavy gas oils, or their combinations.
While these cracking feed materials are typically introduced as
gases, in some instances they may be introduced as liquids. Once
introduced as liquids they are rapidly vaporized within the
reactor. This may be beneficial in that light and heavy gas oils,
for example, are typically vaporized outside the reactor in
conventional cracking systems. Such exterior vaporization creates
coking issues, however. By injecting them directly into the reactor
in liquid form, these issues are avoided. The cracking feed will
typically be denser than the combustion products. This is a result
of both the high molecular weight of the cracking feed and its
density at the selected temperature of the cracking feed. The
denser gas/liquids move outward while the lighter combustion
products move inward due to very high centrifugal acceleration
(100,000-1M g forces). The denser hydrocarbons rapidly mix into the
peripheral combustion products at very high temperature due to high
swirl.
[0089] A hydrogen-containing fuel gas is introduced from manifold
94 to tangential inlets 102A, 102B into flow space 82. The
hydrogen-containing fuel gas may be hydrogen gas (H.sub.2) and/or
methane (CH.sub.4). In certain embodiments where a combination of
hydrogen gas and methane are used, the methane may be present in
the fuel gas in an amount of from 20 mol %, 15 mol %, 10 mol %, 5
mol % or less. Greater amounts of methane may impact the desired
selectivity. In other embodiments, however, greater amounts of
methane may be used, including 100% methane for the fuel gas.
Natural gas may also be used as the fuel gas.
[0090] The hydrogen-containing fuel gas may be a hydrogen-gas-rich
stream composed primarily of hydrogen gas, which may be a recycled
stream such as the recycle stream 32 (FIG. 1) or additional
hydrogen gas, such as the stream 34. The hydrogen-gas-rich stream
may contain other components such as methane, CO, steam, inert
gases, and CO.sub.2. Other hydrocarbons can also be used as the
fuel gas in certain embodiments and applications. Additionally,
small amounts of N.sub.2 can also be present. Sulfur can also be
present in the fuel gas or other feed streams. If sulfur is
present, additional separation upstream or downstream may be
required. The reactor and process are sufficiently robust to
accommodate the presence of sulfur, particularly since no catalyst
is used. The ratio between the crack feed to hydrogen-containing
fuel will typically range from 1 to 15, more particularly from 1 to
10, based on mass.
[0091] An oxidizer or oxygen-containing gas, which may be a
concentrated or pure oxygen gas, such as from an air separation
unit (not shown), is introduced as the oxidizer feed through
manifold 92 through inlets 100A, 100B into the flow space 80.
Having the oxygen-containing gas introduced through flow space 80
spaces it further from the cracking gas introduced through flow
space 72 to eliminate or minimize any combustion of the introduced
cracking gas. In certain applications, the mole ratio of
H.sub.2/O.sub.2 may range from 2 to 9, more particularly from 2 to
5, and still more particularly from 2 to 4. The oxygen feed may
provide an oxygen equivalent-to-fuel mole ratio of from 0.2 to 1.0.
An excess of hydrogen also helps to scavenge free radicals (e.g.,
O, OOH, OH) formed that would otherwise react with the cracking
feed. In some cases, a mole ratio of H.sub.2/O.sub.2 may be less
than 2 to compensate for other fuel gases or to have excess O.sub.2
in the mixing region to release heat to counter endothermic
cracking reactions.
[0092] Steam or water is introduced through manifold 90 and through
inlets 98A, 98B into the flow space 74. Steam is introduced
upstream of the other feeds and is used to cool the walls of the
converging conduit 48 and reactor 12. The introduced steam also
facilitates reducing the reaction temperatures within the reactor
12. Steam may also be pre-mixed with the various feeds, such as
with the cracking gas feed, fuel gas, and/or oxygen-containing
feed. Steam may be used in a mass ratio of steam-to-fuel of from
greater than 0 to 10.0, more particularly from 0 to 2.0, in certain
applications.
[0093] FIG. 5 shows a schematic diagram of the reactor 12 with the
individual flows of the different feeds. These individual flows are
schematically represented by dashed lines. In actual practice, all
of the oxygen gas and at least a portion of the hydrogen-containing
fuel gas are combusted to form heated combustion products that are
almost entirely mixed with the other feeds prior to exiting the
converging conduit 48 and entering the reaction chamber 40. Thus,
while the individual feeds are schematically shown by the dashed
lines, the gases flowing into the reaction chamber 40 constitutes a
gas mixture. With the high centrifugal force of the swirling gases,
the denser gases (e.g., cracking feed) flow closer to the reactor
wall, while the hotter combustion products tend to flow through the
center of the reactor. The device geometry and the swirling
gas-mixture from chamber 116 results in a back flow of the gas
mixture as represented by dashed lines 118. This mixture flows
upstream and radially inward from the thin, outer annular mixed gas
flow layers 120, 122, circulating within the reaction chamber 40 to
form recirculation zone 124. Internal cooling of the walls occurs
due to the high swirling steam delivered through flow space 74 in
FIG. 2. Additional cooling (if necessary) occurs by a water jacket
located between walls 38 and 42 in FIG. 2.
[0094] The gas feed streams may be introduced to provide different
flow velocities to provide the Kelvin-Helmholtz instability for
enhanced mixing. The flow velocities may range from 10 m/s to 500
m/s, more particularly from 100 m/s to 400 m/s. The reactor may be
operated at from 0 kPa (g) or 100 kPa (g) to 1,000 kPa (g), 2,000
kPa (g) or as much as 10,000 kPa (g), with a gas residence time
within the reactor of from 50 milliseconds or less, more
particularly from 20 milliseconds or less, and still more
particularly from 10 microseconds to 20 milliseconds. In particular
embodiments, the residence time may range from 20, 19, 18, 17, 16,
15, 14, 13, 12, 11, or 10 milliseconds or less, with 10
microseconds being the approximate lowest residence time.
[0095] The reaction temperature within the reactor and
recirculation zone 124 may range from 900.degree. C. to
1300.degree. C. In particular embodiments, the temperature within
the reactor and recirculation zone 124 may range from 1000.degree.
C. to 1300.degree. C., more particularly from 1200.degree. C. to
1250.degree. C. In some embodiments, the reactor temperature is
higher than what is achieved in conventional cracking reactors,
such as tube furnace reactors, which typically operate at
800.degree. C. to 900.degree. C. As discussed earlier, this is due
to the temperature limitations of the metallic materials used for
such conventional reactors. In the present case, the swirling gas
mixture facilitates keeping the walls of the reactor much cooler
than in such conventional reactors. The use of such higher
temperatures also allows a shorter residence or contact times
shorter contact times resulting in better selectivity and
conversion without formation of unwanted products. Operating
temperatures for the reactor may be selected to avoid excess
production of such unwanted compounds, such as acetylene.
[0096] The gases are introduced and flow through the flow spaces
72, 74, 80, 82 so that the axial velocity (i.e., relative to the
axis 52) is zero prior to being discharged into the mixing chamber
116. The tangential inlets 96, 98, 100, 102 and/or the orientation
of the guide vanes 104, 106, 108, 110 may be set for each flow
space 72, 74, 80, 82 so that a selected azimuthal-to-radial
velocity for each of the feed streams that flow through the flow
spaces 72, 74, 80, 82 is achieved. With respect to the
azimuthal-to-radial velocity, in particular embodiments, this may
range from 0 to 30 or more, more particularly from 0, 1, or 2 to 3,
4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
22, 23, 24, 25, 26, 27, 28, 29, or 30. In some applications the
azimuthal-to-radial velocity may range from 0 to 5, more
particularly from 2 to 4. The particular azimuthal-to-radial ratio
may vary depending upon the particular reactor configuration and
composition of the various streams, however. This is more
intimately related to the mixing times and reaction times depending
on the flow rates, composition of the fuel and feedstocks used for
cracking.
[0097] Cracked hydrocarbon products produced in the reactor are
removed from the reactor vessel 36 through outlet 44, where they
may be quenched and further processed and recycled, as discussed
with respect to the process steps previously described for FIG.
1.
[0098] In a variation of the reactor described, additional cracking
feed gas can be introduced as a secondary feed stream at an
intermediate position along the length of reactor vessel 36, such
as at inlet 126 (FIG. 2). One or more such inlets 124 may be
provided at various locations and in the reactor vessel 36, which
may be circumferentially and longitudinally spaced apart. The
inlets 126 may be oriented or configured so that gases are
introduced tangentially, as well, to facilitate swirling fluid
flow, similar to that delivered from the inlets of the feed
assembly 58. Feed assemblies provided on the reactor vessel 36
similar to the feed assembly 58 may be used for the introduction of
such cracking feed gas so that the cracking feed is introduced as a
swirling fluid flow.
[0099] In some embodiments, a plurality of reactor inlet assemblies
and corresponding feed assemblies can be provided in a single
reactor while maintaining the high performance.
[0100] Referring to FIG. 6, an alternate embodiment of a reactor
128 is shown. The reactor 128 is similar to reactor 12, previously
described, with similar components labeled with the same referenced
numerals. The reactor 128 includes a reactor feed assembly 130,
which is similar to the feed assembly 58 previously described with
some differences with respect to the partition walls located
between the downstream feed assembly wall 60 and the upstream feed
assembly wall 62.
[0101] As shown in FIG. 6, the feed assembly 130 has an upstream
gas partition wall 132 and a downstream gas partition wall 134 that
are axially spaced between the downstream and upstream feed
assembly walls 60, 62. An intermediate partition wall 136 is
axially spaced between the upstream gas partition wall 132 and the
downstream gas partition wall 134, with the partition walls 132,
134, 136 being axially spaced from one another. The partition walls
132, 134, 136 or circumferential portions thereof are also each
oriented perpendicularly to or substantially perpendicularly (i.e.,
<5 degrees from perpendicular about its circumference as it
extends radially from the central axis) to the central axis 52.
Each of the partition walls 132, 134, 136 terminates at their inner
ends at a position below or upstream of the converging conduit 48
to define central openings 138, 140, 142, respectively, that
surrounds the central axis 52 and are concentric with the
converging conduit 48. The central openings 138, 140, 142 each have
a circular configuration. Other shapes for the central openings
138, 140, 142 (e.g., oval) may also be used provided such
configuration facilitates the swirling of gases to provide the
required flow patterns described herein. This shape may also
correspond to the cross-sectional shape of the circumferential wall
50 of the converging conduit 48. In most applications, however, the
central openings 138, 140, 142 will be circular in shape. The
central openings 138, 140, 142 may have a diameter or width that is
the same or slightly different than the diameter or width of the
constricted neck 54 of the converging conduit 48 at its narrowest
point.
[0102] In the reactor 128, the central opening 138 of the upstream
partition wall 132 may have a periphery that is spaced radially
outward a distance from the central opening 142 of the intermediate
partition wall 136, as is shown. The area spaced radially inward
from the central opening 142 of the intermediate partition wall 136
between the upstream feed assembly wall 62 and the intermediate
partition wall 136 defines an annular combustion zone 144. The size
of the central opening 138 can vary to fit the radial extent of
combustion zone 144.
[0103] The upstream partition wall 132 is axially spaced between
the upstream feed assembly wall 62 and the intermediate partition
wall 136 to define flow spaces 146, 148 which constitute first and
second annular fuel gas inlet flow spaces. In the embodiment shown,
the flow space 146 constitutes an upstream annular fuel gas feed
inlet flow space and the flow space 148 constitutes a downstream
annular fuel gas feed inlet flow space. The fuel gas feed may be
comprised of an oxygen-containing fuel gas feed and a hydrogen-rich
fuel gas feed, as described previously, that are introduced into
the first and second annular fuel gas inlet flow spaces 146, 148,
as with reactor 12. In many applications, the flow space used for
the oxygen-containing will be spaced furthest from the hydrocarbon
cracking feed flow to prevent or minimize any combustion of the
cracking feed. Thus, in the embodiment shown, the oxygen-containing
gas would be introduced into flow space 146. Either of the
oxygen-containing or hydrogen-rich fuel gases introduced into flow
spaces 146, 148, or both, may be introduced with a steam cofeed. An
annular gas flow space 150 is defined by the downstream side of the
downstream partition wall 134 and the downstream feed assembly wall
60. In the embodiment shown, the flow space 150 may constitute an
annular hydrocarbon cracking feed inlet flow space or alternatively
a steam feed inlet flow space.
[0104] A further annular flow space 152 is also defined between the
upstream side of the downstream gas partition wall 134 and the
downstream side of the intermediate partition wall 136. The flow
space 152 may constitute an annular steam or water inlet flow space
or alternatively an annular hydrocarbon cracking feed inlet flow
space.
[0105] Where steam is cofeed with the fuel feeds, a separate steam
feed to the feed assembly 130 may be eliminated. In such cases, one
of the flow spaces 150, 152 may be eliminated by the removal of
either the partition walls 134, 136 and the intervening flow
space.
[0106] The flow passages 146, 148, 150, 152 are configured so that
the different feeds pass through flow spaces perpendicularly or
substantially perpendicularly to the central axis 52 of the
converging conduit 48 in an inwardly swirling fluid flow pattern
within said flow spaces so that the feeds flow about the central
axis 52 of the converging conduit 48. Guide vanes 104, 106, 108,
110 may also be used to facilitate swirling fluid flow. The fuel
gas feed from flow combusts primarily in the small combustion zone
144 between the inner end of partition wall 136 and upstream feed
assembly wall 62 within the central opening 138 of the upstream
partition wall 132.
[0107] In the embodiment of FIG. 6, the oxidizing gas nears
complete combustion in the combustion zone 144, located below the
cracking feed introduced into one of the flow passages 150, 152.
Therefore, the cracking gas meets only combustion products above
the zone 144. Additionally, the cold flow of the incoming cracking
gas in the flow passage 150 or 152 moderates the temperature of the
circumferential wall 50 of conduit 48 as it flows through the
reactor inlet 46 and also protects the reactor walls 38 from
overheating.
[0108] The reactor 128 also differs from the reactor 12 in that the
wall 42 (FIG. 2) for the cooling jacket is eliminated. To
facilitate cooling of the reactor 28 one or more cooling gas feed
assemblies 154, 156 are provided for introducing or injecting
cooling gases into the reactor 128. The cooling gases may be a
neutral or inert gas, such as steam, which may be at a temperature
sufficient to provide the desired cooling effect. This may include
steam at a temperature of from 100.degree. C. to 250.degree. C.
(e.g., 150.degree. C.). The cooling gas can also be hydrocarbon
cracking feed at a relatively lower temperature, for example from
25.degree. C. to 500.degree. C.
[0109] The cooling gas feed assemblies 154, 156 may be configured
similarly to the feed assemblies 58, 130 of the reactors 12 and 128
to provide a swirling flow of cooling gases as they are introduced
into the reactor 128. Each cooling gas feed assembly 154, 156 is
constructed from a pair of axially spaced apart cooling gas feed
assembly walls 158, 160 oriented perpendicular or substantially
perpendicular (i.e., <5 degrees from perpendicular about its
circumference as it extends radially from the central axis) to the
central axis 52.
[0110] An annular cooling gas inlet flow space 162 is defined
between the cooling gas feed assembly walls 158, 160 of each
cooling gas feed assembly 154, 156. In the embodiment shown, the
cooling gas feed assembly 154 constitutes a downstream cooling
assembly with the inlet flow space 162 communicating with a
circumferential opening or inlet 164 of the reactor wall 38 and the
reaction chamber 40. The position of the feed assembly 154 and
inlet 164 may be located at a position along the length of the
reactor wall 38 or cylindrical portions of the reactor wall 38
above the contoured, concave or tapered portion 166 and above the
reactor inlet assembly 46 and converging conduit 48.
[0111] The cooling gas feed assembly 156 constitutes an upstream
cooling assembly with the inlet flow space 162 communicating with a
circumferential opening or inlet 168 of the reactor wall 38 or
circumferential wall 50 along the contoured, concave or tapered
portion 166 where the reactor wall 38 and circumferential wall 50
of the converging conduit 48 meet.
[0112] Each of the annular flow spaces 162 of the cooling gas feed
assemblies 154, 156 may also be provided with a plurality of
circumferentially spaced guide vanes 170 to facilitate swirling
fluid flow within the cooling gas inlet flow spaces 162 of the feed
assemblies 154, 156. The guide vanes 170 may be constructed and
operate similarly to the guide vanes 104, 106, 108, 110, previously
described.
[0113] An annular cooling gas manifold 172 may be provided around
the outer periphery of the flow spaces 162 of each of the feed
assemblies 154, 156. The gas manifold 172 is fluidly coupled to a
cooling gas feed source, such as steam. Cooling gas inlets 174 of
the manifold 172 may be directed tangentially into the flow space
162 so that the cooling gases are not directed radially toward the
central axis 52, but instead are directed mostly tangentially
around the central axis 52 to provide an inwardly swirling flow
pattern. Furthermore, the walls 158, 160 forming the flow spaces
162 of the cooling gas feed assemblies 154, 156 keep the cooling
gases introduced from the manifold 172 from flowing axially along
the central axis 52 while they are contained within the flow spaces
162. The manifolds 172 can be configured as standard manifolds
(e.g., snail-like) as may be typically used in vortex devices.
[0114] The high swirl velocity and comparatively low temperature of
the injected cooling gases presses the cooling gases along the
sidewalls of the reactor. The cooling effect allows the elimination
of a cooling jacket and/or the use of refractory materials for the
reactor 128.
[0115] In certain embodiments, several cooling gas feed assemblies,
such as the feed assemblies 154, 156, may be provided as necessary
along the length of the reactor 128 to facilitate sufficient
cooling. Likewise, either one of the feed assemblies 154, 156 may
be eliminated in certain embodiments.
[0116] Referring to FIG. 7, a vane 176 that may be used for any one
or all of the feed assemblies 58, 136, 154, 156. The vane 176 is
non-planar and is configured as an airfoil. The vane 176 is
configured to reduce drag and includes a leading end 178 and
trailing end 180.
[0117] FIG. 8 shows a top plan view of the airfoil vane 176. A
chord or line 182 passing through the leading edge and trailing
edge of the vane 176 may correspond to the line 112 of FIG. 4. The
leading end 178 and trailing end 180 are joined by opposite
sidewalls 184, 186 that converge at the trailing end 180. The
transverse dimensions of the vane 176 may be uniform along the
height of the vane. In other embodiments, however, the transverse
dimensions may vary along the height of the vane. As shown in FIG.
9, the curved sidewalls of the airfoil 176 may be represented by
three arcs 188 190, and 192, which are shown exploded away from one
another. The arc 188 represents the leading end or leading end wall
or cap of the vane 176. The arc 190 constitutes a left arc
representing the left sidewall 184 that joins the leading arc 184
at one end and terminates at the other end at the trailing end 180
of the airfoil 176. The arc 192 constitutes a right arc
representing the right sidewall 186 that joins the leading arc 184
at one end and terminates at the other end at the trailing end 180
of the airfoil 176.
[0118] Referring to FIG. 10, a schematic showing a pair of airfoil
vanes 176A and 176B as they would be arranged within any one of the
flow spaces of the gas inlet feed assemblies as has been previously
described. As can be seen, the trailing ends 180 are arranged
around the perimeter of a circle 194 having a radius R, which
defines the inner boundary of the gas vanes 176. Points on the
vanes 176A, 176B can be determined by the polar coordinates r and
.PHI.. The points on the vanes 176A, 176B can also be presented by
the Cartesian coordinates x=rcos(.PHI.) and y=rsin(.PHI.).
[0119] To design the airfoil 176A, the arc of an ellipse having a
center 196 located at x.sub.e=0, and y.sub.e=R+b can be used. The
left arc 190 can be described by the equations
(x/a).sup.2+((y-y.sub.e)).sup.2=1, -a<x<0, and y<y.sub.e,
a=k.sub.1R, b=a/2. As an example, k.sub.1 can equal 0.85.
[0120] The right arc 192 is essentially the left arc 190 compressed
to the y axis. Here, the right arc 192 can be defined by
x.sub.R=k.sub.2x.sub.L where y.sub.R=y.sub.L. As an example,
k.sub.2 can equal 0.75. The equation describing the leading arc 188
is the upper half of a circle
((x-x.sub.c)/R.sub.2).sup.2+((y-y.sub.e)/R.sub.2).sup.2=1,
y>R+b, where x.sub.c=k.sub.1R(1+k.sub.2)/2 and
R.sub.2=k.sub.1R(1-k.sub.2)/2. These three arcs 188, 190, 192
together constitute the left guide vane 176A.
[0121] In order to represent the right vane 176B, each point for
the left vane 176A (i.e., x.sub.1, y.sub.1), its polar coordinates
r.sub.1=(x.sub.1.sup.2+y.sub.1).sup.1/2 and
.PHI..sub.1=acos(x.sub.1/r.sub.1) are calculated. Then the polar
angle, .PHI..sub.2=.PHI..sub.1-2.pi./N is calculated, where N is
the total number of circumferentially-spaced guide vanes within the
flow space. The Cartesian coordinates of the right vane 176B can be
calculated as x.sub.2=r.sub.1cos(.PHI..sub.2) and
y.sub.1sin(.PHI..sub.2).
[0122] The procedure of calculating the right vane 176B can be
repeated until all guide vanes are represented. The control
parameters R, N, k.sub.1, and k.sub.2 can be modified for specific
applications.
[0123] FIG. 11 shows another embodiment of a reactor 198 is shown.
The reactor 198 is similar to the reactors 12 and 128, previously
described, with similar components labeled with the same referenced
numerals. The reactor 198 includes a reactor feed assembly 200,
which is similar to the feed assemblies 58, 130 previously
described with some differences.
[0124] The feed assembly 200 has an upstream gas partition wall 202
and a downstream gas partition wall 204 that are axially spaced
between the downstream and upstream feed assembly walls 60, 62. An
upstream partition wall 202 is axially spaced between the upstream
gas feed assembly wall 62 and the downstream gas partition wall
204, with the partition walls 202 and 204 being axially spaced from
one another. The partition walls 202, 204 or circumferential
portions thereof are also each oriented perpendicularly to or
substantially perpendicularly (i.e., <5 degrees from
perpendicular about its circumference as it extends radially from
the central axis) to the central axis 52.
[0125] As shown in FIG. 11, the downstream gas partition wall 204
differs from those previously described in that extending from the
downstream partition wall 204 is a curved annular extended wall
portion 206 that curves upward or downstream and is spaced from and
follows the contours of the circumferential wall 50 of the
converging conduit 48 of the reactor inlet assembly 46 and
terminates at a position downstream of the annular constricted neck
portion 54. The partition wall 204 with the extended curved portion
206 defines a downstream inlet flow space 208 located in the
annular space between the downstream feed assembly wall 60 and
circumferential wall 50 of the reactor inlet assembly 46 and the
partition wall 204 with the extended portion 206. A curved portion
210 of the downstream inlet flow space 208 discharges at a central
annular opening 212 that surrounds the central axis 52 into the
reactor chamber 40 downstream from the constricted neck portion
54.
[0126] The upstream partition wall 202 terminates at its inward end
at a position upstream from the converging conduit 48 and has a
central opening 214 that surrounds the central axis 52 and is
concentric with the converging conduit 48. The central opening 214
has a circular configuration. Other shapes for the central opening
214 (e.g., oval) may also be used provided such configuration
facilitates the swirling of gases to provide the required flow
patterns described herein. This shape may also correspond to the
cross-sectional shape of the circumferential wall 50 of the
converging conduit 48.
[0127] The upstream partition wall 202 is axially spaced between
the upstream feed assembly wall 62 and the downstream partition
wall 204 to define flow spaces 216, 218 which constitute first and
second annular fuel gas inlet flow spaces. In the embodiment shown,
the flow space 216 constitutes an upstream annular fuel gas feed
inlet flow space and the flow space 218 constitutes a downstream
annular fuel gas feed inlet flow space. The fuel gas feed may be
comprised of an oxygen-containing fuel gas feed and a hydrogen-rich
fuel gas feed, as have been described previously, that are
introduced into the first and second annular fuel gas inlet flow
spaces 216, 218. Either of the oxygen-containing or hydrogen-rich
fuel gases introduced into flow spaces 216, 218, or both, may be
introduced with a steam cofeed. In the embodiment shown, the flow
space 208 may constitute an annular hydrocarbon cracking feed inlet
flow space.
[0128] The flow passages 208, 216, 218 are configured so that the
different feeds initially pass through flow spaces perpendicularly
to the central axis 52 of the converging conduit 48 in an inwardly
swirling fluid flow pattern within said flow spaces so that the
feeds flow about the central axis 52 of the converging conduit 48.
Guide vanes 220, 223, 224 may be used to facilitate such swirling
flow.
[0129] In the case of the cracking gas introduced through flow
space 208, the cracking gas flows spirally upward through the
curved portion 210 of the flow space 208 and is discharged through
opening 212 into the reaction chamber.
[0130] The fuel gas feed from flow spaces 216, 218 combusts in the
central chamber 116. Because the downstream partition wall 204 has
an extended portion 206 that extends past the constricted neck
portion 54 and separates the combusting fuel gases within the
central chamber 116 where they are fully combusted or the
oxygen-containing gas is fully consumed there is no danger of the
introduced cracking gas being combusted. The introduced cracking
gas also facilitates cooling of the reactor walls.
[0131] The reactor designs described herein feature high conversion
of the cracking feed and higher selectivity for olefins than other
conventional cracking methods and at much higher pressures than
typically used. The reactors are relatively simple in
configuration, which can significantly reduce the capital and
operating costs. The high-swirling gas mixture provides stable and
compact combustion using non-premixed fuel gases (i.e.,
H.sub.2+O.sub.2) that are combusted within a small combustion zone
of the feed assembly. The reactor walls are cooled by the swirling
steam flow (or cooler feed) against the wall allowing for higher
temperatures in the reactor, requiring shorter residence times, so
that more desirable products (e.g., ethylene) are produced.
Maintaining lower reactor wall temperatures also allows refractory
materials to be used in place of metal materials and thus
minimizing heat loss.
[0132] Because the heated combustion gases are directly mixed with
cracking feed in the swirling gas mixture, there is direct gas-gas
heat transfer to carry out the cracking reactions. This differs
from conventional cracking reactors, such as tube furnaces, that
rely on non-direct heat transfer where heat is transferred through
the tube walls of the reactor from a separate heating source, such
as external combustion gases. Here the process is intensified in
that the exothermic step of providing heat from the combustion of
the fuel feed is immediately combined with the endothermic step of
cracking the cracking feed. Thus, energy losses due to heat
transfer through reactor walls and equipment, as with conventional
systems, are eliminated or minimized. The reactor can be scaled up
by increasing feeding rate and dimension scale up.
[0133] The following examples serve to further illustrate various
embodiments and applications.
EXAMPLES
Example 1
[0134] Computational Fluid Dynamics (CFD) simulations, using
commercial software available as the ANSYS FLUENT.RTM. software
product, were conducted for the optimal design of a cracking
reactor, as has been described herein, to verify its performance by
numerical experiments. The swirling fluid flow, heat transfer, and
detailed gas phase reactions were modeled in a two-dimensional
axisymmetric CFD framework using Reynolds Averaged Navier-Stokes
(RANS) approach using Reynolds Stress turbulence model. The modeled
base case ANJEVOC-C reactor had an inner diameter of about 6
inches. Ethane was used as the cracking feed. The feeds used were
72 kg/h ethane, 38 kg/h oxygen blending with 38 kg/h steam, 12 kg/h
hydrogen, and another 18 kg/h steam stream near the wall of the
reactor for wall protection. Based upon prior experience with
similar reactors, one can scale this reactor to use 3600 kg/h
ethane, 1800 kg/h oxygen blending with 1800 kg/h steam, 612 kg/h
hydrogen, and another 900 kg/h steam stream near the wall of the
reactor for wall protection.
[0135] FIGS. 12 and 13 show the cracking reactor geometry and axial
velocity and swirl velocity distribution in a lab scale unit model.
The darker areas of FIG. 6 indicate a high axial velocity while the
lighter areas indicate a low axial or negative (reverse flow)
velocity relative to the longitudinal axis. Together with the axial
velocity contour, arrows are presented on the same figure
indicating flow directions. At the feed assembly inlet, the axial
velocity was close to zero for each of the feeds, the radial and
the azimuthal velocity were uniform, and the azimuthal-to-radial
velocity ratio was 10 for all the inlet streams. This highly
swirling flow forms a recirculation region near the axis of the
reactor as described above with respect to recirculation zone 124
of FIG. 5. This can be seen by the lightest regions (reverse flow
region in reaction chamber near the axis in FIG. 12). The highest
axial flow regions were the darker areas along the converging
conduit and along the reactor walls.
[0136] FIG. 13 shows the swirl velocity, with the darker regions
representing higher swirl velocity and the lighter regions
representing lower swirl velocity. As can be seen, the swirl
velocity is greatest along the outer edges of the mixing chamber of
the feed assembly, with the greatest swirl velocity being along the
constricted neck portion of the converging conduit. The swirl
velocity is also high along the sidewalls of the reactor where it
joins the converging conduit.
[0137] FIG. 14 shows the stream function. The through-flow goes
near the reactor wall in the nozzle and the adjacent half of the
cylindrical parts. There the reversed flow near the axis and the
recirculation of mixed gases occurs between the axis and the wall.
The curves separating gray scales are streamlines.
[0138] FIG. 15 shows the mass fraction distribution of the ethane
(C.sub.2H.sub.6) cracking feed within the reactor system.
[0139] FIG. 16 shows the temperature profile of the reactor system.
As shown, the combustion occurs within the combustion zone,
corresponding to combustion zone 86 of the feed assembly 58 of FIG.
2, with the higher temperatures from the combustion gases being
located along the converging neck portion. Additionally, the steam
feed provides a thin cooler layer immediately adjacent to the
constricted neck portion. The temperature within the reactor itself
is uniformly maintained at approximately 1200.degree. C.
[0140] FIGS. 17, 18, and 19 show the mass fraction distribution of
the hydrogen gas, oxygen gas, and steam, respectively, within the
reactor system. As can be seen in FIG. 17, almost all of the feed
hydrogen is burned in the combustion zone. Hydrogen produced by
cracking is uniformly distributed in the cylindrical part of the
reactor. As can be seen in FIG. 18 all of the oxygen gas is
immediately consumed within the combustion zone of the feed
assembly, corresponding to combustion zone 86 of the feed assembly
58 of FIG. 2. As can be seen in FIG. 19, all the feed steam
introduced through the steam inlet flow space protects the nozzle
wall from overheating. All these components are uniformly
distributed in the cylindrical part.
[0141] FIG. 20 shows the mass fraction distribution of atomic
oxygen (O), which is produced and consumed within the combustion
zone and nearly absent with the reactor system.
[0142] FIGS. 21, 22, and 23 show the mass fraction distribution of
the cracked products of ethylene, acetylene, and propylene,
respectively, formed within the reactor system. FIG. 21 shows that
C.sub.2H.sub.4 is mostly produced in the nozzle and near the
reactor wall. FIG. 22 shows that C.sub.2H.sub.2 is mostly produced
in the nozzle. FIG. 23 shows that the cracking finishes around two
diameters axial distance downstream of the nozzle neck.
[0143] FIG. 24 shows the mass fraction distribution of the CO
within the reactor system. The CO is produced near the nozzle neck
because only 94% oxygen is burned within the combustion zone. The
remaining 6% of oxygen reacts with the hydrocarbons.
Example 2
[0144] Along with the CFD simulations, a reactor network model was
used with a detailed mechanism in order to examine the chemical
kinetics limit and the maximum performance metrics of this novel
design on varying feedstock. One simulation (Case 1) was conducted
with H.sub.2 as fuel and C.sub.2H.sub.6 as the cracking hydrocarbon
similar to the CFD simulation in EXAMPLE 1. A second simulation
(Case 2) was conducted with H.sub.2 as fuel and Naphtha (NP) as the
cracking hydrocarbon. A third simulation (Case 3) was also
conducted using CH.sub.4 as the fuel gas for naphtha cracking. The
results were compared to a conventional ethane cracker and a
conventional naphtha. The results are presented in Table 1
below:
TABLE-US-00001 TABLE 1 Case 1: Case 2: Case 3: ANJEVOC-C ANJEVOC-C
ANJEVOC-C *Ethane Fuel H.sub.2 = 100% *Naphtha Fuel H.sub.2 = 100%
Fuel CH.sub.4 = 100% Cracker Cracker gas: C.sub.2H.sub.6 Cracker4
Cracker gas: NP Cracker gas: NP Selectivity to 77.6 84 48 66 77
C.sub.2H.sub.4 & C.sub.2H.sub.2/ (83 from CFD) C.sub.3H.sub.6
(%) Conversion of 65 95 95 100 100 Crack Gas (%) (65 from CFD)
Total C2/C3 53 80 46 66 77 Olefin Yield/ (42 if CH.sub.4 is pass
(%) included) Temperature 840-860 1227 820~840 1243 1067 [.degree.
C.] Residence 100~600 ~5.sup. 100~600 ~4 ~15.sup. Time [ms]
The results show that the crack gas conversion and C.sub.2/C.sub.3
selectivity of ANJEVOC-C reactor are better than the conventional
ethane and naphtha steam cracker due to the direct mixing and heat
transfer, favorable operating temperature, and short residence
time.
[0145] While the invention has been shown in some of its forms, it
should be apparent to those skilled in the art that it is not so
limited, but is susceptible to various changes and modifications
without departing from the scope of the invention based on
experimental data or other optimizations considering the overall
economics of the process. Accordingly, it is appropriate that the
appended claims be construed broadly and in a manner consistent
with the scope of the invention.
* * * * *