U.S. patent application number 14/603511 was filed with the patent office on 2016-07-28 for gas distributor for heat exchange and/or mass transfer column.
This patent application is currently assigned to Technip Process Technology, Inc.. The applicant listed for this patent is Technip Process Technology, Inc.. Invention is credited to Kenneth Jack Fewel, JR., Kenneth Edward Krug, Sabah Kurukchi.
Application Number | 20160216051 14/603511 |
Document ID | / |
Family ID | 56417791 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160216051 |
Kind Code |
A1 |
Kurukchi; Sabah ; et
al. |
July 28, 2016 |
GAS DISTRIBUTOR FOR HEAT EXCHANGE AND/OR MASS TRANSFER COLUMN
Abstract
The present invention relates to a device that conditions high
entrance velocity, superheated feed gas, which include some high
boiling components, for example, asphaltenes and poly-nuclear
aromatics that tend to coke upon condensation and exposure to the
superheated feed gas temperature. Also included in superheated feed
gas are solid catalyst fines, from a single or multiple feed
nozzles to a quiescent flow regime for uniform distribution of the
gases, to a contact device within the Main Fractionator (MF)
column.
Inventors: |
Kurukchi; Sabah; (Houston,
TX) ; Krug; Kenneth Edward; (Houston, TX) ;
Fewel, JR.; Kenneth Jack; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Technip Process Technology, Inc. |
Houston |
TX |
US |
|
|
Assignee: |
Technip Process Technology,
Inc.
Houston
TX
|
Family ID: |
56417791 |
Appl. No.: |
14/603511 |
Filed: |
January 23, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 3/32 20130101; F28C
1/02 20130101; F28F 25/08 20130101; B01F 3/04078 20130101; B01D
3/008 20130101; F28F 25/10 20130101; B01F 3/04496 20130101; C10G
11/18 20130101; B01D 3/18 20130101; B01F 3/04468 20130101 |
International
Class: |
F28F 25/10 20060101
F28F025/10; B01F 15/02 20060101 B01F015/02; F28F 25/08 20060101
F28F025/08; B01D 3/32 20060101 B01D003/32; B01F 3/04 20060101
B01F003/04 |
Claims
1. A gas distributor for a heat exchange and/or mass transfer
column, said gas distributor located within said column and
comprising at least one feed gas inlet nozzle extending through a
shell wall of the column substantially perpendicular to the
longitudinal axis of said column for directing a feed gas
perpendicularly to a substantially vertical interior segmented
cylindrical deflector wall comprising at least one opening to an
annular interior open area within the gas distributor, a bottom
section that extends the interior cylindrical deflector wall and
conforms to the contour of the shell wall, said bottom section
comprising a bottom section opening to a column sump within the
column, and a generally horizontal ceiling above the feed gas inlet
nozzle between the interior cylindrical deflector wall and the
shell wall to define a generally circumferential gas flow channel
formed between the shell wall and the interior cylindrical
deflector wall, said ceiling comprising at least one opening.
2. The gas distributor of claim 1, wherein the column is a main
fractionator column.
3. The gas distributor of claim 1, wherein the bottom section is
cone shape and conforms to the contour of the shell wall of the
column.
4. The gas distributor of claim 1, wherein the column further
comprises packing and/or trays above the gas distributor.
5-6. (canceled)
7. The gas distributor of claim 1, wherein the ceiling comprises at
least one ceiling section.
8. The gas distributor of claim 7, wherein at least one ceiling
section is a flat plate with at least one perforation and/or
chimney.
9. The gas distributor of claim 8, wherein at least one chimney has
a high hat.
10. The gas distributor of claim 7, wherein the ceiling section
comprises rods spaced at least about 1 inch apart.
11. The gas distributor of claim 7, wherein the ceiling section is
corrugated with at least one perforation and/or chimney.
12. The gas distributor of claim 1, wherein there is a plurality of
openings between ceiling and the interior cylindrical deflector
wall and the ceiling and the shell wall.
13. The gas distributor of claim 7, wherein the ceiling section is
at least one selected from the group consisting of a flat plate
with at least one perforation and/or chimney, a section comprising
rods spaced at least about 1 inch apart, and a corrugated ceiling
section with at least one perforation and/or chimney.
14. The gas distributor of claim 1, wherein the opening is a vent
window.
15. The gas distributor of claim 1, wherein the bottom section
further comprises at least one overflow opening.
16. The gas distributor of claim 1, wherein segmented interior
cylindrical deflector wall segments are sized to fit through a
manway.
17. The gas distributor of claim 7, wherein the ceiling sections
are sized to fit through a manway.
18. The gas distributor of claim 1, wherein the bottom section
comprises bottom section segments.
19. (canceled)
20. The gas distributor of claim 1, further comprising a drain pipe
in fluid connection with the bottom section opening.
21. A method of improving feed gas distribution and reducing coke
formation in a heat exchange and/or mass transfer column,
comprising the step of delivering a high velocity superheated feed
gas to the gas distributor of claim 1.
22. A method for distributing feed gas in a heat exchange and/or
mass transfer column, said method comprising the steps of:
delivering a superheated feed gas through a feed gas inlet nozzle
that extends through a shell wall of the column into a generally
circumferential gas flow channel formed between the shell wall, an
interior cylindrical deflector wall having a bottom section and at
least one opening to an annular interior open area within the
column, and a ceiling above the inlet nozzle between the shell wall
and the interior cylindrical deflector wall, said ceiling having a
plurality of openings; cooling the superheated feed gas by
contacting the gas with a counter current flow of liquid as the
liquid passes through the plurality of openings in the ceiling and
into the circumferential gas flow channel; wetting the interior
cylindrical deflector wall and an interior side of the shell wall
that forms the circumferential gas flow channel with the counter
current flow of liquid after the liquid has passed through the
plurality of ceiling openings; and venting the superheated feed gas
to an area above the ceiling and the annular interior area within
the column through the at least one opening of the interior
cylindrical deflector wall and the plurality of openings in the
ceiling to provide a substantially uniform distribution of the
superheated feed gas within the column.
23. The method of claim 22, wherein the feed gas inlet nozzle
enters the column through the shell wall and is substantially
perpendicular to the longitudinal axis of the column.
24. The method of claim 22, wherein the feed gas flow rate increase
from about 500,000 Kg/h. upon entering the gas flow channel to
about 1,200,000 Kg/h upon leaving the plurality of openings in the
ceiling and the at least one opening of the interior cylindrical
deflector wall.
25. The method of claim 22, wherein the feed gas temperature
decreases from about 560.degree. C. upon entering the gas flow
channel to about 420.degree. C. upon leaving the plurality of
openings in the ceiling and the at least one opening of the
interior cylindrical deflector wall.
26. The method of claim 22, wherein there is a plurality of opening
between ceiling and the interior cylindrical deflector wall and the
ceiling and the shell wall.
27. The method of claim 22, wherein the bottom section extends the
interior cylindrical deflector wall and conforms to the contour of
the shell wall of the column.
28. The method of claim 22, wherein the bottom section is cone
shape.
29. A method comprising the step of using the gas distributor of
claim 1 to perform steps: i) delivering a superheated feed gas
through a feed gas inlet nozzle that extends through a shell wall
of the column into a generally circumferential gas flow channel
formed between the shell wall, an interior cylindrical deflector
wall having a bottom section and at least one opening to an annular
interior open area within the column, and a ceiling above the inlet
nozzle between the shell wall and the interior cylindrical
deflector wall, said ceiling having a plurality of openings; ii)
cooling the superheated feed gas by contacting the gas with a
counter current flow of liquid as the liquid passes through the
plurality of openings in the ceiling and into the circumferential
gas flow channel; iii) wetting the interior cylindrical deflector
wall and an interior side of the shell wall that forms the
circumferential gas flow channel with the counter current flow of
liquid after the liquid has passed through the plurality of ceiling
openings; and iv) venting the superheated feed gas to an area above
the ceiling and the annular interior area within the column through
the at least one opening of the interior cylindrical deflector wail
and the plurality of openings in the ceiling to provide a
substantially uniform distribution of the superheated feed gas
within the column.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to a gas distributor
of "F-Flute" design that provides uniform gas flow in a heat
exchange and/or mass transfer column, and specifically to a gas
distributor that provides uniform gas flow to the trays or packing
of a Main Fractionator (MF) column in a fluid catalytic cracking
unit (FCCU) facility.
BACKGROUND
[0002] Providing uniform vapor distribution in high capacity
fractionation towers is one of the most challenging aspects of
designing a high performance column. Conventional devices within
the industry have attempted to evenly distribute the inlet feed gas
to the section directly above the feed nozzle in MF columns. For
example, the Vapor Horn and the Schoepentoeter, are proprietary
vapor inlet horn and vane type inlet devices, respectively, which
introduce gas/liquid mixtures into a vessel or column. However,
these devices proved to be problematic because as the feed gas
cools inside both devices, the heaviest components, e.g.,
asphaltenes, start condensing and deposit or stick to the cool
surfaces of the apparatus. With further and continuous contact of
the hot feed gas there is stripping of the lighter material from
the deposit, as well as stripping of hydrogen atoms from the
polymerized asphaltenes causing it to turn to coke. With time, the
coke deposit grows to significant size and caused interference with
the flow of gas and, as a result, the devices have to be taken out
of the MF columns.
[0003] Typical prior art devices that have tried to address the
problem of ensuring good mixing and even distribution are disclosed
in the following: U.S. Pat. No. 8,286,952 to Lee et al. discloses a
vapor distributor for gas-liquid contacting column; U.S. Pat. No.
8,025,718 to Kooijman et al. discloses a Fluid Inlet Device; U.S.
Pat. No. 7,744,067 to Kurukchi et al. discloses a three phase vapor
distributor; U.S. Pat. No. 7,459,001 to Christiansen et al.
discloses a vane diffuser; U.S. Pat. No. 7,281,702 to Jacobs et al.
discloses methods and an apparatus for mixing and distributing
fluids; U.S. Pat. No. 7,104,529 to Laird et al. describes a vapor
distributor apparatus, the vapor horn of which includes a series of
vanes the sizes of which increase with distance from the inlet
nozzle of the vapor distributor; U.S. Pat. No. 6,997,445 discloses
a method and device for introducing a liquid-vapor mixture into a
radial feed cylindrical fractionating column; U.S. Pat. No.
6,948,705 to Lee et al. describes a gas-liquid contacting apparatus
in which a gas stream, for example steam, is fed into a column via
an annular vapor horn; U.S. Pat. No. 6,889,961 to Laird et al.
described a modified vapor distributor with baffles in the lower
intermediate transitional section to reduce swirling of the feed
and thereby improve distribution; U.S. Pat. No. 6,889,962 to Laird
et al. disclosed an annular inlet vapor horn that circulates the
inlet feed so as to de-entrain any liquid droplets while providing
for more even distribution of the inlet flow across the column;
U.S. Pat. No. 6,309,553 to Lanting et al. discloses a phase
separator having multiple separation units, upflow reactor
apparatus, and methods for phase separation; U.S. Pat. No.
6,341,765 to Moser discloses a method for the infeed of a fluid
into an apparatus; U.S. Pat. No. 5,632,933 to Yeoman et al.
describes an annular bi-directional gas flow device having a
plurality of outlets at an inner wall of the housing and a series
of flow directing vanes for distribution of an inlet vapor stream
across the breadth of a column; U.S. Pat. No. 5,605,654 to Hsieh et
al. disclosing a vapor distributor having an annular housing with a
series of ports for feeding the vapor stream in a distributed
manner; U.S. Pat. No. 5,558,818 to Gohara et al. discloses a wet
flue gas scrubber having an evenly distributed flue gas inlet; U.S.
Pat. No. 5,632,933 to Yeoman discloses a method and apparatus for
vapor distribution in mass transfer and heat exchange columns; U.S.
Pat. No. 5,106,544 to Lee et al., which describe a combination of
an inlet horn having a 360 degree annular housing with directional
flow vanes; U.S. Pat. No. 4,435,196 to Pielkenrood discloses a
multiphase separator for treating mixtures of immiscible gaseous,
liquid and/or solid components, comprising a gas-tight and
pressure-proof tank; U.S. Pat. No. 3,651,619 to Miura discloses an
apparatus for the purification of gas; and U.S. Pat. No. 3,348,364
to Henby discloses a gas scrubber with a liquid separator.
[0004] Some other prior art devices that have tried to address the
above-referenced problems include the following: U.S. Published
Application 2005/0146062 to Laird et al. discloses a method and
apparatus for facilitating uniform vapor distribution in mass
transfer and heat exchange columns; U.S. Published Application
2005/0029686 to Laird et al. discloses a fluid stream feed device
for a mass transfer column; and U.S. Published Application
2003/0188851 to Laird et al. discloses a method and apparatus for
uniform distribution in mass transfer and heat exchange
columns.
[0005] Additional prior art references in this regard include:
McPherson, L. J.: "Causes of FCC Reactor Coke Deposits Identified";
O&GJ, Sep. 10, 1984, pp 1 39; NPRA Question and Answer Session,
1986, (Transcripts) Heavy Oil Processing, Question 12, pp 45;
Lieberman, N. P.: "Shot Coke: its origins and prevention":
O&GJ, Jul. 8, 1985. pp 45; Christopher Dean et. al. "FCC
Reactor Vapor Line Coking," Petroleum Technology Quarterly Autumn
2003; Christopher Dean et. al. "Process Equipment Specification and
Selection," Petroleum Technology Quarterly Autumn 2004; Hanson D.
W. et. al. "De-Entrainment and Washing of Flash-Zone Vapor in Heavy
Oil Fractionators," HCP, July 1999, 55-60; Scott W. Golden et. al.
"Correcting Design Errors can Prevent Coking in Main
Fractionators," Oil & Gas J. Nov. 21, 1994, 72-82; Dana G.
Laird. "Benefit of Revamping a Main Fractionator," Petroleum
Technology Quarterly; Winter 2005. David Hunt et. al.; "Minimizing
FCC Slurry Exchanger Fouling," Petroleum Technology Quarterly
Winter 2008; Mark Pilling et. al.; "Entrainment Issues in vacuum
Column Flash Zones," Petroleum Technology Quarterly; Winter
2010.
[0006] It is worth noting that in the majority of devices utilizing
a vapor horn the inlet flow is unidirectional with a cyclonic
effect on the vapor feed. In these types of devices, baffles or
vanes are used to redirect or disrupt the circular flow of the
inlet stream.
[0007] As such, it would represent an advancement in the state of
the art and resolve a long felt need in the art if a gas
distributor device that could cool the high velocity superheated
feed gas to the MF column and distribute it evenly to the bottom of
the slurry packed section without fouling and coke deposition
inside the feed distributor device.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a gas distributor for a
heat exchange and/or mass transfer column. The gas distributor is
located within the column and comprises at least one feed gas inlet
nozzle extending through a shell wall of the column for directing a
feed gas to a substantially vertical interior cylindrical deflector
wall comprising at least one opening to an annular interior open
area within the gas distributor. The gas distributor further
contains a bottom section that extends the interior cylindrical
deflector wall and conforms to the contour of the shell wall. The
bottom section comprises an opening to a column sump within the
column, and there is a generally horizontal ceiling above the feed
gas inlet nozzle between the interior cylindrical deflector wall
and the column shell that defines a generally circumferential gas
flow channel formed between the shell wall and the interior
cylindrical deflector wall, said ceiling comprises at least one
opening.
[0009] Additionally, the present invention is directed to a method
for distributing feed gas in a heat exchange and/or mass transfer
column. The method comprising the steps of: delivering a
superheated feed gas through a feed gas inlet nozzle that extends
through a shell wall of the column into a generally circumferential
gas flow channel formed between the shell wall, an interior
cylindrical deflector wall having a bottom section and at least one
opening to an annular interior open area within the column, and a
ceiling above the inlet nozzle between the shell wall and the
interior cylindrical deflector wall said ceiling having a plurality
of openings; cooling the superheated feed gas by contacting the gas
with a counter current flow of liquid as the liquid passes through
the plurality of openings in the ceiling and into the
circumferential gas flow channel; wetting the interior cylindrical
deflector wall and an interior side of the shell wall that forms
the circumferential gas flow channel with the counter current flow
of liquid after the liquid has passed through the plurality of
ceiling openings; and venting the superheated feed gas to an area
above the ceiling and the annular interior area within the column
through the at least one opening of the interior cylindrical
deflector wall and the plurality of openings in the ceiling to
provide a substantially uniform distribution of the superheated
feed gas within the column.
[0010] The claimed gas distributor is of a simple design and easily
may be installed in a column to provide uniform horizontal and
vertical distribution of gas entering the column. The presently
claimed F-Flute gas distributor advantageously provides for:
cooling of the superheated reactor multiphase feed gas inside the
F-Flute gas distributor by intimate contact with the showering
slurry liquid from the F-Flute gas distributor ceiling; immediate
reduction of the feed gas temperature to reduce the possibility of
high skin temperature of the main fractionator shell above its
design temperature; the F-Flute gas distributor reduces the
distance required between the feed nozzle and the slurry packed
section by about 2.5 meters or more, and a shorter overall tower
T-T length; using the F-Flute gas distributor in revamps is a cost
effective alternative to increasing the size of both the feed
nozzle and refractory lined gas transfer line; the fully wetted
F-Flute gas distributor internals prevent dry hot spots that cause
coke deposition and growth; the elimination of gas maldistribution
to the slurry packed section, helps to distribute the liquid over
the packing more evenly and results in more effective heat transfer
in the slurry section, which results in shorter required slurry
packed section length; and even gas distribution in the slurry
packed section reduces entrainment of slurry liquid to the oil wash
section, and may eliminate the need for the oil wash section all
together.
BRIEF DESCRIPTION OF THE DRAWING
[0011] The patent application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawings will be provided by the Office upon
request and payment of the necessary fee.
[0012] FIG. 1A is a cross-section view of an embodiment of the
claimed gas distributor having an F-Flute design depicted generally
within a column for heat exchange and/or mass transfer.
[0013] FIG. 1B is an isometric 3D view of the F-Flute gas
distributor and displays an embodiment of the invention having
perforated flat plate ceiling sections and perforated flat plate
with chimneys and high hats ceiling sections, as well as the
interior cylindrical deflector wall segments, vent windows, and the
bottom section that extends the interior cylindrical deflector
wall.
[0014] FIG. 1C is a 3D view of the perforated flat plate with
chimneys and high hats ceiling section of an embodiment of the
claimed F-Flute gas distributor.
[0015] FIG. 2A is a 3D view of the rod-plate ceiling section of an
embodiment of the claimed F-Flute gas distributor.
[0016] FIG. 2B is an isometric 3D view of the F-Flute gas
distributor and displays an embodiment of the invention having
rod-plate ceiling sections, as well as the interior cylindrical
deflector wall segments, vent windows, and the bottom section that
extends the interior cylindrical deflector wall.
[0017] FIG. 3A is a 3D view of the perforated flat-plate ceiling
section of an embodiment of the claimed F-Flute gas
distributor.
[0018] FIG. 3B is an isometric 3D view of the F-Flute gas
distributor and displays an embodiment of the invention having
perforated flat-plate ceiling sections, as well as the interior
cylindrical deflector wall segments, vent windows, and the bottom
section that extends the interior cylindrical deflector wall.
[0019] FIG. 4A is a 3D view of the perforated corrugated plate
ceiling section of an embodiment of the claimed F-Flute gas
distributor.
[0020] FIG. 4B is an isometric 3D view of the F-Flute gas
distributor and displays an embodiment of the invention having
perforated corrugated plate ceiling sections, as well as the
interior cylindrical deflector wall segments, vent windows, and the
bottom section that extends the interior cylindrical deflector
wall.
[0021] FIG. 5 is a graphic representation of the superheated feed
gas and slurry liquid temperature (C..degree.) and the superheated
feed gas and liquid flow rate in kg/hr at the packing inlet, gas
distributor outlet (i.e., flute outlet), and gas distributor inlet
(i.e., flute inlet).
[0022] FIG. 6 is a graphic representation of the cost ratio for
revamping three different size main fractionator towers, i.e., a
37KBPD system, a 90KBPD system, and 125KBPD system with twin ducts,
with the presently claimed F-Flute gas distributor.
[0023] FIG. 7 illustrates a color computational fluid dynamics
simulation of gas distribution velocity magnitude contours in the
cross section of a main fractionator column below the packing
entrance without an embodiment of the claimed F-Flute gas
distributor.
[0024] FIG. 8 illustrates a color computational fluid dynamics
simulation of gas distribution velocity magnitude contours in the
cross section of a main fractionator column below the packing
entrance with an embodiment of the claimed F-Flute gas
distributor.
[0025] FIG. 9 illustrates a color computational fluid dynamics
simulation of gas distribution vertical velocity magnitude contours
in the cross section of a main fractionator below the packing
entrance without an embodiment of the claimed F-Flute gas
distributor.
[0026] FIG. 10 illustrates a color computational fluid dynamics
simulation of gas distribution vertical velocity magnitude contours
in the cross section of a main fractionator below the packing
entrance with an embodiment of the claimed F-Flute gas
distributor.
[0027] FIG. 11 illustrates a color computational fluid dynamics
simulation of gas distribution velocity magnitude contours with an
embodiment of the claimed F-Flute gas distributor at feed gas inlet
nozzle level.
[0028] FIG. 12 is a cross-section view the claimed gas distributor
having an F-Flute design with exemplary dimensions in millimeters
and marking indicating high high liquid level (HHLL), high liquid
level (HLL), and low liquid level (LLL) positions.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The present claimed invention is directed to a gas
distributor for use in a heat exchange and/or mass transfer column
that evenly distributes gas from a feed gas stream about the
interior of the column. In particular, the present invention
relates to a gas distributor that conditions a high-entrance
velocity superheated feed gas stream, so that the gas from the feed
gas stream is evenly distributed within the inner periphery of the
column.
[0030] The claimed gas distributor is particularly efficient at
avoiding coke formation when the boiling point components of FCCU
reactor products are cooled very close to their dew point. These
products can condense where there are cold spots, or some reaction
product components can polymerize to form large molecules that
become non-volatile at feed gas inlet temperatures. Cold spots can
be attributed to inadequate insulation, or high heat loss near
fittings such as flanges, which facilitate condensation. If these
deposited liquids have sufficient residence time on the solid
surfaces of the vessel, coke begins to accumulate on the inside of
the transfer line and on the vessel walls. Once coke is formed,
additional coke has a surface where it grows more easily.
[0031] Naphthenes in the feedstock to the FCC reactor are not
efficiently cracked by the FCC catalyst, so they are carried with
the hot reactor effluent gas to the MF column. FCC catalyst
formulations in recent years have resulted in greater usage of high
hydrogen-transfer reaction catalysts and operate at higher reactor
temperature that favor the production of more olefins and in
conjunction with heavier aromatic feeds, tend to produce higher
boiling-point polynuclear aromatics (PNAs), which are more likely
to condense at the point of entry to the MF column. Once these PNAs
condense on solid surfaces inside the column, they easily form
coke. High rare earth zeolite FCC catalyst tends to form aromatics
from naphthenes as a result of secondary hydrogen transfer
reactions. These aromatics can undergo further thermal reactions to
form coke.
[0032] Coke formation has been described by the following two
independent mechanisms: (i) "Asphaltic Coke" is formed as
solutizing oils are thermally cracked and the remaining large
asphaltene and resin molecules precipitate out to form a solid
structure (coke) without much change in form; and (ii) "Thermal
Coke" is produced by cross-linking of aromatic rings.
[0033] The first condensed droplets from the superheated reactor
feed gas stream to the gas distributor are likely to be heavy oil
rich in asphaltenes and resins. If this material reaches a rough
metal surface in a low velocity area of the MF column, the long
residence time there may allow the solvent oils to slowly evaporate
and form coke by precipitation. Once coke deposits, it becomes an
ideal site for more condensed droplets to deposit on its rough
surface and cause growth of a coke site.
[0034] There are two basic principles for minimizing coke formation
that are utilized in the present invention, the first is to avoid
dead spots by preventing heat losses from bare metal surface, and
the second is to keep solid surfaces wetted. In the instant
invention, reactor effluent (i.e., superheated feed gas to the gas
distributor) enters the main column and is cooled through direct
contact with cold slurry pumparound. The MF column uses packing,
shed (baffle), or disc and donut trays to contact the two streams,
i.e., gas from the feed gas stream and slurry liquid. The
packing/trays work by creating a sheet of liquid that the hot gas
must pass through. Ideally, the gas and liquid are uniformly
distributed. However, in practice, this uniform gas and liquid
distribution does not occur. Liquid and gas distribution is
generally poor, hence the packing, shed or disc and donut trays
flood well below their rated capacities.
[0035] Due to maldistribution of the liquid and gas of the prior
art devices, in some instances, more than 50% of the MF column
inlet nozzle is blocked with coke raising gas velocity to well over
70 m/sec, which is double the design velocity. Therefore, more gas
flows up the column 180 degrees from the inlet nozzle, i.e., areas
in the column directly opposite the feed nozzle, which can cause
localized flooding of the packing or shed (baffle) trays in the
high gas velocity region. Assuming initial liquid distribution to
the top packing/tray is uniform, gas temperatures leaving the
packing/trays are higher at 180 degrees from the inlet nozzle due
to gas maldistribution. Columns fitted with thermocouples located
in the gas space above the packing/trays, which are oriented
directly above and at 180 degrees from the inlet nozzle, have
temperature differences up to 50.degree. C. Once the packing trays
flood, cold slurry is entrained into the wash oil trays located
directly above the slurry section packing. As a result, the
pressure drop across the wash oil trays increases, further
impacting unit pressure balance.
[0036] The above-mentioned gas and liquid maldistribution in the
slurry section above the feed gas inlet is resolved with the
presently claimed F-Flute gas distributor. The instant gas
distributor provides more uniform flow entering the slurry
pumparound bed, withstands the high temperature erosive
environment, and resists damage and coking.
[0037] Both conventional tangential distributors (e.g., Vapor
Horns, Vane Inlet Devices, and V-Baffles) and radial flow multivane
distributors (e.g., Schoepentoeter) have proven not to work in FCCU
main fractionators due to coking, erosion, or both. Poorly designed
distributors have coked to the point that gas flow was obstructed,
resulting in premature shutdowns.
[0038] The inventors note the staggered pipe plate distributor is a
gas distributor that can roughly distribute the gas while remaining
coke free throughout the run. The staggered pipe plate distributor
comprises staggered pipe placed on an oval shaped ring placed in
the column at an angle to the direction of gas upflow above the
feed nozzle where the feed gas and slurry liquid from the packed
slurry section flow through the distributor counter currently. The
success of the distributor in combating coking is due to the
immediate and continuous washing action of the asphaltene droplets
condensing on the distributor pipes by the flowing slurry liquid.
However, this distributor provides limited improvement of gas
distribution to the packed section above.
[0039] If the slurry pumparound section is designed properly, there
will be very little entrainment and no need to have a wash section.
However, when there is high entrainment, the correct solution is to
fix the slurry pumparound section to reduce the entrainment. Thus,
the wash oil section serves no purpose and can be eliminated.
[0040] There are two main mechanisms that contribute to wash oil
section coking. The first is entrainment of slurry pumparound
liquid into the wash oil section, and the second is local hot areas
on the wash oil tray. In some cases, both occur at the same time,
causing rapid coke formation and ultimately an unscheduled
shutdown.
[0041] When slurry pumparound liquid becomes entrained with the gas
from the pumparound section and cannot drain because the wash oil
trays are heavily loaded, or blowing (i.e., high gas rate and low
liquid rate) is occurring, coke is formed. Entrainment alone is not
the problem, as the entrained liquid must be subjected to prolonged
residence time and relatively high localized temperatures.
Moreover, local temperatures can be very high at the same time that
liquid flow rates are extremely low, thereby creating ideal
conditions for coke to form.
[0042] Prior art devices, such as the Vapor Horn and the
Schoepentoeter have not been successful in evenly distributing the
feed gas stream to the section directly above the feed gas inlet
nozzle in MF column. This is because as the feed gas stream cools
inside these devices and the heaviest components, which included
asphaltenes, start condensing and deposit/stick on the cool
surfaces of the devices. By continuous contact with the hot feed
gas, there is stripping of the lighter material from the deposit.
Additionally, stripping of hydrogen atoms from the polymerized
asphaltenes causes it to turn to coke. With time, the coke deposits
grow to a significant size and cause interference with the flow of
gas. As a result, the devices have to be removed from the MF
columns.
[0043] In order to increase the efficiency of the heat exchange and
mass transfer taking place between the gas of the feed gas stream
and slurry liquid, it is important that the gas be uniformly
distributed across the horizontal cross-section of the column,
particularly at the lower gas-liquid interface where the gas enters
the packing. When the feed gas stream is introduced from a feed gas
inlet nozzle into the column below the packing without a gas
distributor, the momentum of the gas can prevent the desired
horizontal distribution of the gas prior to its entry into the
packing.
[0044] Additionally, for optimum operation of the packed slurry
section in main fractionator columns an even distribution of liquid
films and gas flow through the packing is required. While the role
of proper liquid distribution was never disputed, prior art devices
have neglected the initial distribution of gas within the column.
The importance of the initial gas distribution within the column
has become more evident as large column diameters with short bottom
sections and packing with lower pressure drop are considered. Thus,
the instant F-Flute gas distribution system introduces, for
example, the superheated FCC reactor gas (i.e., a superheated feed
gas stream) into the column and distributes it evenly over the
entire cross section of the column.
[0045] To achieve this, the velocity of the feed gas stream needs
to be reduced over a short distance between the feed gas inlet
nozzle and the packing and/or tray section above. At the same time,
the feed gas inlet nozzle should not unduly block the column cross
section or lead to excessive pressure drops. For economic reasons,
a minimum distance between the nozzle and the packing/trays is
desired, thus an efficient gas distributor device is highly
desirable.
[0046] The presently claimed gas distributor provides a solution to
the problems of the prior art devices. The gas distributor is for a
heat exchange and/or mass transfer column. The F-Flute design
provides even distribution of a superheated feed gas stream
utilizing an open internal shell column having a generally vertical
center axis. At least one feed gas inlet nozzle extends through the
column shell wall and directs the superheated feed gas stream
towards a generally annular vertical interior cylindrical
deflecting wall that is spaced radially inwardly from the feed gas
inlet nozzle, so that the feed gas travels in a circumferential
direction. The gas distributor further comprises a ceiling and a
bottom extending between the internal deflecting wall and the
column shell to substantially close the top and extend the bottom
of the distributor in a cylindrical or cone shape bottom section to
the column sump. Thus, the F-Flute gas distributor prevents direct
feed gas bypassing to the packed section above.
[0047] The claimed gas distributor has an "F-Flute" design that
cools the feed gas stream by contacting it with a counter-current
flow of slurry liquid from the column slurry section above the gas
distributor. As such, the slurry liquid is partly vaporize upon
contact with the feed gas stream causing the feed gas stream to
cool. The down-flowing slurry liquid "washes" and disengages the
solid catalyst fines if present in the feed gas stream.
[0048] The cooled gas of the feed gas stream leaves the F-Flute gas
distributor through both vent windows in the circumferential
interior cylindrical deflector wall and gas openings in the ceiling
of the F-Flute gas distributor. The ceiling (i.e., roof) of the
F-Flute gas distributor occupies the space between the top of the
substantially vertical circumferential interior cylindrical
deflector wall and the interior wall of the column shell. As such,
the ceiling defines the top of a feed gas flow channel and
separates the feed gas flow channel from interior full cross
section open area above the F-Flute gas distributor within the
column. The slurry liquid from the packed section above the
interior full cross section open area partly collects on top of the
ceiling to a level of about 25 mm to about 50 mm depending on the
type of ceiling. By various means, as more fully described herein
below, the slurry liquid cascades over or "showers" down through
the feed gas stream in the feed gas flow channel.
[0049] According to an embodiment of the invention, the F-Flute gas
distributor ceiling comprises perforated flat plate sections, or
segments made of flat metal sheet containing a plurality of about 1
inch to about 1.5 inch perforations, i.e., holes, distributed
evenly over the flat plate section. The sections or segments are
designed to be fitted or connected together to form a ceiling
between the generally annular circumferential interior cylindrical
deflector wall and the interior side of the column shell wall. The
sections forming the ceiling, for example, can be welded to a
circumferential rim. The perforated flat plate sections or segments
allow both the cooled gas of the feed gas stream and slurry liquid
to flow through perforations (holes), with a reduction in the
amount of slurry liquid that collects on the top of the ceiling.
Specifically, the holes in the ceiling allow the gas and slurry
liquid to alternatively pass through the same perforation and
provides a quick washing effect. Any coke particles formed that
otherwise would be carried with the gas are picked up by the
contacting liquid and washed downward with the flowing slurry
liquid. In this regard, the plurality of holes in the ceiling
distribute the downwardly flowing slurry liquid in a shower type
fashion and create a large surface contact area of liquid to
enhance the heat/mass transfer interaction with the upwardly
flowing gas of the feed gas stream. Using perforated flat plate
sections reduces or minimizes the liquid hold up on the roof
[0050] In another embodiment of the invention, the F-Flute gas
distributor ceiling in addition to a plurality of holes may
comprise gas chimneys that allow the cooled gas from feed gas
inside the feed gas flow channel to enter the interior full cross
section open area of the column above the gas distributor and below
the packing tray slurry section. The chimneys in the ceiling are
surrounded by the plurality of ceiling holes and the slurry liquid
from the slurry packed section collects on the top of the ceiling,
as the slurry liquid passes through the plurality of holes to
shower the feed gas stream.
[0051] According to another embodiment of the invention, the
F-Flute gas distributor ceiling can be provided with rod-plate
sections or segments comprising staggered rods spaced at least
about one inch apart and welded to a circumferential rim. The
rod-plate sections allow both gas and slurry liquid to flow through
the spacing between the staggered rods. This design forces the
up-flowing gas to intimately contact the down-flowing slurry
liquid, thus giving rise to froth formation on the top of the
rod-plate sections, but with a minimum amount of slurry liquid
collecting or holding up on top of the rods.
[0052] Yet, according to another embodiment of the invention, the
F-Flute gas distributor ceiling comprises perforated corrugated
plate sections or segments made of a perforated corrugated sheet
metal welded to a circumferential rim. The perforations (i.e.,
holes) on the corrugated plate allow both gas and slurry liquid to
alternatively pass through. Further, the corrugated sheet provides
increased surface and open area (i.e., more holes) for both the gas
and liquid to pass through the ceiling. Furthermore, the corrugated
sheet minimizes the liquid collecting or holding up on the
roof.
[0053] The invention further contemplates combinations of the
aforementioned ceiling designs, for example, perforated corrugated
plate sections with perforated flat plate sections and rod-plate
sections, in addition to the chimneys. Further, the present
invention differs from prior art gas distribution devices in that
the presently claimed F-Flute gas distributor is constructed with
metal surfaces that are extremely smooth and/or polished, as well
as providing surfaces that are fully wetted with the slurry liquid
to prevent coke deposition.
[0054] The F-Flute gas distributor produces a not seen before
uniform and even distribution of the gas to the slurry packed
section above the distributor. The advantages of the presently
claimed F-Flute gas distributor can be more fully appreciated by
the following description of the Figures presented herein.
[0055] FIG. 1A depicts one embodiment of the present invention. In
FIG. 1A, the F-Flute gas distributor 10 is depicted generally
within a column 1 for heat exchange and/or mass transfer. The
column 1 can be any type of column for heat exchange and/or mass
transfer, including but not limited to, main fractionators,
distillation, absorption, stripping, quench oil and/or quench water
towers, decoking towers and superfractionators. The column 1 can be
of any desired shape, including, but not limited to circular, oval,
square, rectangular or other polygonal cross section. The column 1
of FIG. 1A is an open internal shell and having a generally
vertical center axis and generally annular shape. The F-Flute
distributor 10 can be designed to accommodate any shape of any heat
transfer and/or mass transfer column.
[0056] In FIG. 1A a feed gas flow channel 14 is formed between the
interior of the shell wall 15 of the column 1, the interior
cylindrical deflector wall 12, and ceiling 11. The F-Flute gas
distributor 10 further comprises a bottom section 13 that can be
cone shape to accommodate the contour of the column shell wall 15.
A high velocity superheated feed gas 30 is introduced into the feed
gas flow channel 14 through at least one gas inlet nozzle 20 in a
direction generally perpendicular to the height of the column 1.
The superheated feed gas 30 flow travels through feed gas flow
channel 14 circumferentially along the generally cylindrical
exterior column shell wall 15 of column 1 due to centrifugal forces
and the high rate at which the superheated feed gas 30 is
introduced into the F-Flute gas distributor 10.
[0057] The interior cylindrical deflector wall 12 and ceiling 11 of
the F-Flute gas distributor 10 may be constructed of any high
temperature steel material suitable for the heat and/or mass
transfer processes that will not be susceptible to degradation from
high velocity superheated gas 30 flow of volatile chemicals,
liquids and solid particulates, as is well known to those skilled
in the art.
[0058] As shown in FIG. 1A, the superheated feed gas 30 flows
circumferentially around gas flow channel 14 within F-Flute gas
distributor 10. The superheated feed gas 30 from gas inlet nozzle
20 flows through gas flow channel 14 in which solids and liquids
are separated as the superheated gas is cooled. The gas of
superheated feed gas 30 is removed from the feed gas flow channel
14 by multiple means. The first means comprises vent windows 21
provided in the interior cylindrical deflector wall 12. The vent
windows 21 allow the cooled gas to exit the feed gas flow channel
14. In an embodiment of the invention, the number of vent windows
21 ranges from about 10 to about 30. The vent windows 21 can be any
size up to about 1 meter.times.0.6 meters. The gas exiting the feed
gas flow channel 14 via the vent window 21 flows into an interior
open area 23 formed by the cylindrical shape of the interior
cylindrical deflector wall 12 and annular construction of the
F-Flute gas distributor 10. The gas then proceeds upwardly to the
interior full cross section open area 25 of the column 1 as well as
the contact packing and/or trays 40 of the column 1 located above
the F-Flute gas distributor 10.
[0059] Additional means shown in FIG. 1A by which the gas from the
superheated feed gas 30 is separated and directed into the interior
full cross section open are 25 of the column 1 above the F-Flute
gas distributor 10 are located in the ceiling 11 of the F-Flute gas
distributor 10. According to one embodiment of the invention, the
ceiling 11 comprises chimneys 24 which allow the cooled gas from
the superheated feed gas 30 proceeds upwardly to the interior full
cross section open area 25 of column 1 and contact packing and/or
trays 40 of the column 1 located above the F-Flute gas distributor
10.
[0060] The chimneys 24 can be equipped with high hats 41 (see FIG.
1C) to regulate the rate at which gas from multiphase superheated
feed gas 30 is allowed to leave gas flow channel 14 through
chimneys 24. According to an embodiment of the invention, the
number of chimneys 24 ranges from about 1 to about 3 per meter of
length of the feed gas flow channel 14. The chimneys 24 have a
cross sectional area ranging from about 0.1 to about 0.4 m.sup.2
and the high hats 41 are constructed from about 100 mm to about 300
mm above the chimneys 24 and have a cross sectional area ranging
from about 0.1 to about 0.4 m.sup.2 or larger.
[0061] FIG. 1A displays the cone shape bottom section 13 of the
F-Flute gas distributor 10 which comprises a bottom section opening
16 and at least one overflow opening 27 that feeds into the column
sump 28 of the column 1 located directly below the F-Flute gas
distributor 10. The overflow openings 27 provide for drainage of
liquid that has been separated from the gas in and above the
interior open area 23 into the column sump 28. According to an
embodiment of the invention, the number of overflow openings 27
ranges from about 4 to about 6. The overflow openings 27 are sized
to accommodate all liquid showering or raining into the interior
open area 23 of the F-Flute gas distributor 10 and acting as an
overflow spillway in case the drain pipe 18 in fluid communication
with bottom section opening 16 becomes clogged. FIG. 1A further
displays marking indicating high high liquid level (HHLL), normal
liquid level (NLL), and low liquid level (LLL) positions.
[0062] FIG. 1B is an isometric 3D view of the F-Flute gas
distributor 10 outside of the column 1, including the ceiling 11,
which comprises ceiling sections 29A, and 29C (29B, 29D not shown
in FIG. 1B), the interior cylindrical deflector wall 12 comprised
of wall segments 12A connected together by conventional techniques
known to those of ordinary skill in the art in an annular fashion
to provide interior cylindrical deflector wall 12. FIG. 1B further
displays the cone shape bottom section 13 of the F-Flute gas
distributor 10. In an embodiment of the present invention, the
interior cylindrical deflector wall 12 comprises wall segments 12A
that are sized to provide widths that can pass through a given
manway. Vent windows 21 are located in several wall segments 12A
around the interior cylindrical deflector wall 12. Vent windows 21
can be cut into the wall segments 12A or into the interior
cylindrical deflector wall 12. When segments 12A are used to
provide the interior cylindrical deflector wall 12 they continue in
an annular fashion including vent windows 21 until they form the
interior open area 23 of the F-Flute gas distributor 10. The
segments 12A that make up the feed gas flow channel 14 are
generally uniform in size, i.e., height and width.
[0063] FIG. 1B shows the ceiling 11 comprising ceiling sections
29A, 29C that can comprise one or more of solid sheet metal (not
shown), a metal perforated flat plate section 29C, and perforated
flat plate section with chimneys and high hats 29A (see also FIG.
1C) that allow the gas to flow out of the F-Flute gas distributor
10 and into the interior full cross section open area 25 of the
column 1.
[0064] Each perforated flat plate section with chimneys and high
hats 29A as presented in FIG. 1C is furnished with at least two
chimneys 24 and a plurality of perforations, i.e., holes 42. The
holes 42 are drilled between the chimneys and sized to hold-up just
enough liquid to create a gas seal.
[0065] In FIG. 1A and FIG. 1B, the cone shape bottom section 13 of
the F-Flute gas distributor 10 is conically shaped to accommodate
the lower portion of column 1 and feeds into column sump 28.
Further, the cone shape bottom section 13 can comprise bottom
section segments 13A that are connected together and extend
interior cylindrical deflector wall 12 in a fashion that forms a
conical shape to the lower portion of the feed gas flow channel 14
while further accommodating the shape of the column 1. Although
bottom section 13 of the F-Flute gas distributor 10 is cone shaped,
as depicted as in FIGS. 1A and 1B, it is contemplated that any
shape required to accommodate the lower portion of the heat
exchange and/or mass transfer column and extend the interior
cylindrical deflector wall 12 to feed liquids and solid particles
to the column sump can be used. The segments of cone shape bottom
section 13 are sized to provide widths that can pass through a
manway.
[0066] The cone shaped bottom section 13 serves two purposes: to
prevent the gas from feed gas inlet nozzle 20 from bypassing the
F-Flute gas distributor 10 openings, i.e., the vent windows 21 and
chimneys 24; and to facilitate the draining of the drops to the
interior open area 23 of the F-Flute gas distributor 10 to the
column sump 28 without possibility of liquid entrainment. In other
words, the gas is separated from the drops falling outside the
F-Flute gas distributor. The cone shape follow the contour of the
tower swage section, allowing quick draining of liquid and help
prevent re-entrainment of liquid into the vapor stream.
[0067] According to an embodiment of the invention, the superheated
feed gas 30 is cooled as it circulates inside the F-Flute gas
distributor 10 feed gas flow channel 14 by the counter-current flow
of "drops" of the slurry liquid from the column slurry section
liquid falling from holes 42 in the ceiling sections. This effect
provides greater heat transfer inside the F-Flute gas distributor
10 when compared to a column that does not contain a gas
distributor because: (i) the velocity of the superheated feed gas
30 inside the F-Flute gas distributor 10 is higher than the
velocity of the gas in the column (this effect of increased
velocity of the superheated feed gas 30 past the slurry liquid
drops improves heat transfer rates); (ii) this higher velocity and
turbulence of the superheated feed gas 30 tends to aerodynamically
breakup the slurry liquid drops inside the F-Flute gas distributor
10, increasing their interfacial surface area for heat and mass
transfer; (iii) the F-Flute gas distributor 10 provides greater
wetted surface area for greater convective heat transfer; and (iv)
the F-Flute gas distributor 10 creates an even distribution of gas
to the packing, and prevents the segregation of liquid drops and
gas caused by the nozzle jetting into an empty tower. The
beneficial result of all these advantages is that the F-Flute gas
distributor increases the heat transfer rate from gas to the slurry
liquid drops and this allows a smaller length of tower/column for a
given amount of heat and mass transfer.
[0068] Alternatively, the present invention F-Flute gas
distributor's 10 ceiling 11 can be made up of rod-plate sections
29B as presented in FIG. 2A. The rod-plate section 29B as presented
in FIG. 2A comprises staggered rods 43 that are spaced at a minimum
of about 1 to about 11/2 inches apart and can be welded to a
circumferential rim. The staggered rods 43 can be positioned in one
or various combinations of patterns, e.g., herringbone, diagonal,
etc., as presented in FIG. 2B. The rod-plate sections 29B allow
both the gas and the slurry liquid to flow through the spacing
between the rods. This forces the up-flowing gas from feed gas flow
channel 14 to intimately contact the down-flowing slurry liquid,
thus giving rise to froth formation on top of the rod-plate
sections 29B. There is a small amount of slurry liquid hold up on
the staggered rods 43. However, the ceiling design of FIG. 2B
reduces the slurry liquid hold up on the ceiling section compared
to that of the perforated flat plate section with chimneys and high
hats presented in FIG. 1B.
[0069] FIG. 3A presents another alternative to the F-Flute gas
distributor 10, wherein the ceiling section comprises perforated
flat plate sections 29C. The perforated flat plate sections 29C are
perforated with holes 42. The perforated flat plate sections 29C
can be made of sheet metal and welded to a circumferential rim. The
holes 42 in the perforated flat plate section 29C allow both gas
and slurry liquid to alternatively pass through. The countercurrent
flow of gas and liquid alternatively through the same perforations
provide quick washing effect of any coke particles formed and
carried with the gas. The solid particles are picked up by the
contacting liquid and washed downward with the flowing slurry
liquid. The perforated flat sheet sections 29C, as presented in
FIG. 3B, are the simplest to construct and provide minimized liquid
hold up on the top of ceiling 11.
[0070] FIG. 3B is an isometric 3D view of the F-Flute gas
distributor 10 outside of the column 1, including the ceiling 11,
which comprises ceiling section 29C (29A, 29B, 29D not shown in
FIG. 3B), the interior cylindrical deflector wall 12 comprised of
wall segments 12A connected together by conventional techniques
known to those of ordinary skill in the art in an annular fashion
to provide interior cylindrical deflector wall 12. FIG. 3B further
displays the cone shape bottom section 13 of the F-Flute gas
distributor 10. the interior cylindrical deflector wall 12
comprises wall segments 12A, vent windows 21 are located in several
wall segments 12A around the interior cylindrical deflector wall
12. The segments 12A that make up the feed gas flow channel 14 are
generally uniform in size, i.e., height and width and allow gas to
enter the interior open area 23.
[0071] FIG. 4A presents yet another alternative type of F-Flute gas
distributor 10 ceiling 11 containing perforated corrugated plate
sections 29D. In FIG. 4A, the perforated corrugated plate sections
29D are made of sheet metal and can be welded to a circumferential
rim. The perforations (i.e., holes 42) on the corrugated plate
allow both gas and slurry liquid to alternatively pass through. The
perforated corrugated plate sections 29D corrugated sheet provides
increased effective area for both the gas and liquid to pass
through the roof. The countercurrent flow of gas and liquid
alternatively through the same corrugation holes provide quick
washing effect of any coke particles formed and carried with the
gas. Such particles are picked up by the contacting liquid and
washed downward with the flowing slurry liquid to the column sump
28. Also, the perforated corrugated plate sections 29D minimizes
the liquid hold up on the roof. This type of F-Flute gas
distributor 10 as presented in FIG. 4B, with perforated corrugated
plate sections 29D represent a preferred option for use in a main
fractionator column, as it offer the highest resistance to fouling
with coke.
[0072] The presently claimed F-Flute gas distributor 10 invention
can use of any combination of the afore described ceiling
sections.
[0073] FIG. 5 is a graphic representation of the superheated feed
gas and slurry liquid temperature (.degree. C.) and traffic (i.e.,
gas and liquid flow rate in kg/hr). The temperatures and flow rates
are measured from the F-Flute gas distributor's inlet area, i.e.,
the superheated feed gas at gas inlet nozzle of FIG. 1A to the
packing inlet. The simulated traffic and temperature of both slurry
liquid (which enters the column 1 through slurry liquid distributor
44 of FIG. 1A) and superheated gas stream into and out of the
F-Flute gas distributor. The graphic representation indicates that
the superheated feed gas enters the claimed F-Flute gas distributor
at a temperature of approximately 560 C..degree. and is immediately
quenched to approximately 420 C..degree. inside the F-flute gas
distributor's feed gas flow channel by evaporating the slurry
liquid. Thus, the mass flow of gas increases from approximately
from about 500,000 kg/hr to a maximum of approximately 1,600,000
kg/hr, and similarly the liquid rate increases and drops to
approximately 1,100,000 kg/hr from 1,550,000 kg/he to 450,000
kg/hr. The gas from the superheated gas feed leaves the F-Flute gas
distributor (flute outlet) at a rate of approximately 1,200,000
kg/hr and a temperature of approximately 410.degree. C.
[0074] FIG. 6 is a graphic representation of the cost ratio for
revamping three different size main fractionator towers with the
presently claimed F-Flute gas distribution of FIG. 1A. Conventional
revamping of existing main fractionator towers require replacing
the tower feed nozzle(s) and swaging a portion of the length of
refractory line transfer line leading to the feed nozzle, of a
length equivalent to 5-7 time the feed nozzle diameter, in
proportional cross sectional area to the ratio of the
revamp/original design capacity. This elaborate work can be avoided
by installing the claimed F-flute gas distributor, since it
provides an even distribution of the quenched superheated feed gas
under the packing above the feed nozzle. The cost advantage as
presented in FIG. 6 are significant using the claimed F-Flute gas
distributor compared with replacing the feed nozzle and swaging the
transfer line duct work, i.e., in a 37 thousand barrels per day
("KBPD") unit there is approximately 100% cost savings, in a 90
KBPD unit there is more than a 400% cost savings, and in a twin
duct 125 KBPD unit there is an approximate 400% cost savings.
[0075] To show the improved gas distribution of the claimed F-Flute
gas distributor of FIG. 1A, computational fluid dynamics (CFD)
simulations were prepared, the results of which are presented FIGS.
7-11. The computational fluid dynamics simulations of FIGS. 7-11
illustrate three dimensional gas distribution velocity magnitude
contours in the cross section of a main fractionator column. The
simulations presented in FIGS. 7-10 illustrate gas distribution in
the cross section of a main fractionator column 5 cm below the
packing entrance with and without an F-Flute gas distributor,
respectively. The feed gas inlet nozzle is positioned on the left
side of each Figure, i.e., FIGS. 7-11. The computational fluid
dynamics simulations were based on the claimed F-Flute gas
distributor having the dimensions in millimeters (mm), as presented
in FIG. 12. However, gas distribution can be improved for any size
vessel when the presently claimed F-Flute design gas distributor is
proportioned to accommodate the vessel.
[0076] FIG. 7 and FIG. 8 present CFD simulation models of gas
distribution velocity magnitude contours of gas distribution (i.e.,
gas distribution patterns) in the cross section of a main
fractionator column 5 cm below the packing entrance with and
without the claimed F-Flute gas distributor, respectively. The
comparison can be measured using peak to average velocity (PAV)
levels. For FIGS. 7 and 8 the PAV levels range in numerical value
from 0.00 to 8.38. The empty column, i.e., FIG. 7 absent the
F-Flute gas distributor, has a PAV magnitude of 8.38 times the
average velocity level. FIG. 7 displays prominent velocity
magnitude contours illustrated by large oval contours with high PAV
levels leaving the feed gas inlet nozzle and directed to the
opposite sides of the fractionator column. The large oval contours
are separated by a narrow velocity magnitude contour having a low
PAV level. The pattern of the velocity magnitude contours in FIG. 7
indicate an extremely uneven velocity distribution of gas within
the cross section of the column. However, the simulation of the
column with the claimed F-Flute gas distributor, i.e., FIG. 8, has
a PAV magnitude of 4.45 that is 47% lower than the empty column.
The substantially even velocity magnitude contours within the cross
section of the column presented in FIG. 8 are illustrated by the
uniformity of the contours displayed and the absence of high PAV
levels.
[0077] FIGS. 9 and 10 are CFD simulation models of vertical gas
distribution velocity magnitude contours (i.e., gas distribution
patterns) at 5 cm below the packing of the column. FIG. 9 indicates
the vertical gas distribution velocity magnitude contours for the
empty column, i.e., absent the claimed F-Flute gas distributor, and
FIG. 10 presents the vertical gas distribution velocity magnitude
contours for the column with the claimed F-Flute gas distributor
installed. The PAV levels range in numerical value from -0.50 to
2.81. The simulation of the empty column in FIG. 9 measures a PAV
vertical component at 2.8 times the average velocity level
illustrated by significant oval velocity magnitude contours having
high PAV levels leaving the feed gas inlet nozzle and directed to
the opposite sides of the fractionator column. These vertical
velocity magnitude contours indicate an extremely uneven velocity
distribution of gas below the packing of the column. The column in
FIG. 10 with the F-Flute gas distributor, however, measures a PAV
vertical component of 2.1 that is 25% lower than the empty column.
The simulation models clearly indicate that the claimed F-Flute gas
distributor improves the velocity uniformity, and thus improves gas
distribution to the packing area when installed.
[0078] FIG. 11 is a CFD simulation model illustrating superheated
feed gas velocity magnitude contours (i.e., gas distribution
patterns) inside an F-Flute gas distributor of the present claimed
invention at the feed gas inlet nozzle level. This simulation
clearly indicates uniform velocity magnitude contours over the
majority of the feed gas flow channel and interior open area of the
claimed F-Flute gas distributor.
[0079] Additionally, the claimed F-Flute gas distributor will
enhance heat and mass transfer by reducing the Sauter mean diameter
(SMD) of the droplet distribution. Estimates based on aerodynamic
breakup, indicate that the SMD of droplets inside the F-Flute gas
distributor will be 33% smaller than in a column without the
F-Flute gas distributor. This increases the interfacial surface
area between liquid and gas to increase heat and mass transfer.
[0080] The following Table 1 presents the estimated difference in
SMD and heat transfer with and without the F-Flute gas distributor
of FIG. 1A.
TABLE-US-00001 TABLE 1 Design SMD- mm Heat Transfer - Watt/.degree.
K Empty Colum 4.0 4.2 E 05 F-Flute gas distributor 10 2.7 5.5 E
05
[0081] The plurality of vent windows in the F-Flute gas distributor
are positioned throughout the interior cylindrical deflector and
the wall and chimneys positioned throughout the ceiling, allow for
the cooled separated superheated feed gas to exit the distributor
into the column's interior full cross section open area with
greatly slowed and uniform velocity for distribution to packing or
trays located within the column and above the F-Flute gas
distributor.
[0082] The walls of the F-Flute gas distributor, i.e., interior
cylindrical deflector wall, cone shape bottom section that extends
the interior cylindrical deflector wall and the interior side of
column shell wall, which comprises the exterior wall of the F-Flute
gas distributor, are entirely wetted with slurry liquid. The
interior cylindrical deflector wall, bottom section, and interior
side of column shell wall are completely wetted because the ceiling
is connected to the interior cylindrical deflector wall and the
interior side of column shell wall through a connection device,
such as, a dowel, circular rim, welded rod or bracket, and the
like, to include a plurality of openings so that the slurry liquid
can fall vertically down the interior cylindrical deflector wall,
bottom section, and interior side of column shell wall and keep
them wetted.
[0083] Any condensation of high boiling point components of the
super-heater feed gas components inside the F-Flute gas distributor
will occur in the liquid slurry phase and will immediately mix and
washed down with the flowing slurry liquid to the column sump of
the MF column. This will prevent the condensed droplets of the
superheated feed gas containing asphaltenes from sticking to the
solid wall surfaces and being exposed for lengthy periods to hot
superheated feed gas which is the main cause of coke particles
formation and their growth that caused failure of the prior art gas
distribution devices.
[0084] Additionally the expansion of the superheated feed gas from
the feed gas inlet nozzle together with the showering of the slurry
liquid from the ceiling sections inside the F-Flute gas distributor
provides a vehicle for the solid catalyst fines to separate out of
the superheated feed gas and be carried with the large flow of
slurry liquid down to the column sump without causing erosion
problems to the column walls and internals. If the solid catalyst
fines and coke particle are not efficiently separated from the
superheated feed gas at point of entry to the column and pass with
the superheated feed gas to the slurry packed section and deposit
on its packing, the column's efficiency to cool the feed gas is
reduced. Moreover, the column requires more frequent cleaning for
the removal of the solid catalyst fines and coke particle.
[0085] Further, the presently claimed F-Flute gas distributor has
been shown to decrease significantly the maximum local gas velocity
below the packing in the portion of the column situated above the
F-Flute gas distributor, i.e., cooled superheated feed gas in the
interior full cross section open area. This reduction in local gas
velocity results in a more uniform distribution of gas pressure and
ultimately a more efficient heat transfer in the slurry section as
well as better fractionation in the upper column sections. An even
distribution of the gas on the packing and trays is critical for
proper heat and mass transfer. Even distribution can be
accomplished for a higher degree of heat exchange and fractionation
through the use of the F-Flute gas distributor of the present
invention, which allows the conventionally designed capacity
profile of a given mass and/heat transfer column/MF column to be
exceeded well beyond its traditionally accepted limitations. This
results in higher capacity within the same column relative to
similar devices that do not employ the gas distribution device of
the present invention. The F-Flute gas distributor of the present
invention would significantly decrease the maximum local velocity
below a packing or tray in a column and therefore improve the
velocity profile below the packing/tray.
[0086] The invention further provides lower temperature of the gas
flow to the packed slurry section as well as more even
distribution, these two factors result in reduction in the required
column diameter. The more even distribution of bottom gas to the
tower sections above improve the column internals efficiency for
heat and mass transfer and leads to a reduction in the overall
column height.
[0087] The novel features of the present invention have been shown
to produce this uniform distribution of gas pressure at a level
above any known prior art gas distributor. The presently claimed
F-Flute gas distributor provides a low column skin temperature by
cooling the feed gas first with the showering slurry liquid at
entry to the column inside the F-Flute gas distributor.
[0088] The claimed gas distributor reduces or eliminates "jetting"
of the superheated feed gas, whereby the superheated feed gas hits
the column wall creating dry spots and causes the column wall to
reach temperatures above the design temperature of the column
shell. In this regard, the claimed F-Flute gas distributor also
avoids column shell (i.e., wall) erosion by eliminating the jetting
effect of the superheated feed gas containing the erosive catalyst
fines that continuously and at high velocities impinge the column
wall and cause local erosion and/or thinning of the column shell in
area directly opposite to the feed nozzle. The use of the claimed
F-Flute gas distributor will remove the catalyst fines by the
showering slurry liquid inside the F-Flute gas distributor and
there will be no direct contact of the superheated feed gas with
the column shell wall.
[0089] Although the present invention has been described in
considerable detail with regard to certain versions thereof, other
versions are possible, and alterations, permutations, and
equivalents of the version shown will become apparent to those
skilled in the art upon a reading of the specification and study of
the drawings. Also, the various features of the versions herein can
be combined in various ways to provide additional versions of the
present invention. Furthermore, certain terminology has been used
for the purposes of descriptive clarity, and not to limit the
present invention. Therefore, any appended claims should not be
limited to the description of the preferred versions contained
herein and should include all such alterations, permutations, and
equivalents as fall within the true spirit and scope of the present
invention.
* * * * *