U.S. patent application number 11/933173 was filed with the patent office on 2009-04-30 for stripping apparatus and process.
Invention is credited to Robert L. Mehlberg.
Application Number | 20090107884 11/933173 |
Document ID | / |
Family ID | 40581448 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107884 |
Kind Code |
A1 |
Mehlberg; Robert L. |
April 30, 2009 |
STRIPPING APPARATUS AND PROCESS
Abstract
In an FCC apparatus and process in which swirl arms are used to
discharge gas and catalyst from a riser, an anti-swirl plate is
disposed in the disengaging vessel to dampen the angular momentum
of swirling descending catalyst particles and gases.
Inventors: |
Mehlberg; Robert L.;
(Wheaton, IL) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC;PATENT SERVICES
101 COLUMBIA DRIVE, P O BOX 2245 MAIL STOP AB/2B
MORRISTOWN
NJ
07962
US
|
Family ID: |
40581448 |
Appl. No.: |
11/933173 |
Filed: |
October 31, 2007 |
Current U.S.
Class: |
208/113 ;
422/144 |
Current CPC
Class: |
C10G 11/18 20130101 |
Class at
Publication: |
208/113 ;
422/144 |
International
Class: |
C10G 11/00 20060101
C10G011/00 |
Claims
1. An apparatus for separating catalyst particles from a gaseous
product stream comprising: an elongated riser in which a
hydrocarbon feed is contacted with catalyst particles to produce a
gaseous product, said riser including a swirl outlet configured to
induce the solid catalyst particles and gaseous product stream to
swirl in an angular direction to disengage catalyst particles from
said gaseous product; a disengaging vessel in communication with
said swirl outlet of said riser, said disengaging vessel including
a lower stripper section comprising elongated strips and an outer
wall; a cyclone for further separating said catalyst particles from
said gaseous product; and a plate laterally secured to said outer
wall of said disengaging vessel to dampen the angular velocity of
said gaseous product and catalyst particles.
2. The apparatus of claim 1 further comprising a reactor vessel
containing at least a portion of said disengaging vessel; said
reactor vessel being in downstream communication with said swirl
outlet and containing said cyclone.
3. The apparatus of claim 2 wherein said reactor vessel is in
upstream communication with a plurality of passages for admitting
catalyst particles from said reactor vessel into said disengaging
vessel.
4. The apparatus of claim 3 wherein at least a portion of said
plate is disposed below said passages.
5. The apparatus of claim 1 wherein said riser extends through said
stripping section.
6. The apparatus of claim 5 wherein a second plate is secured to a
wall of said riser to dampen the angular velocity of said gaseous
product and catalyst particles.
7. The apparatus of claim 1 wherein said elongated strips in said
stripper section comprise gratings.
8. The apparatus of claim 1 wherein said elongated strips in said
stripper comprise packing.
9. An apparatus for separating catalyst particles from a gaseous
product stream comprising: an elongated riser in which a
hydrocarbon feed is contacted with catalyst particles to produce a
gaseous product, said riser including a swirl outlet configured to
induce the solid catalyst particles and gaseous fluids to swirl in
an angular direction to disengage catalyst particles from said
gaseous product; a disengaging vessel containing said swirl outlet
of said riser, said disengaging vessel including a stripper section
comprising elongated strips and an outer wall comprising plurality
of passages above said stripper section; a reactor vessel
surrounding at least a portion of said disengaging vessel, said
reactor vessel containing an outlet from said disengaging vessel
and a cyclone separator for further separating said catalyst
particles from said gaseous product; a plurality of passages to
said disengaging vessel for enabling catalyst particles from said
reactor vessel to enter said disengaging vessel through said
plurality of passages; and a plate laterally secured to said outer
wall of said disengaging vessel to dampen the angular velocity of
said gaseous product and catalyst particles.
10. The apparatus of claim 9 wherein said plate is disposed below
said passages.
11. The apparatus of claim 9 wherein said riser extends through
said stripping section.
12. The apparatus of claim 11 wherein a second plate is secured to
a wall of said riser to dampen the angular velocity of said gaseous
product and catalyst particles.
13. The apparatus of claim 9 wherein said elongated strips in said
stripper section comprise gratings.
14. The apparatus of claim 9 wherein said elongated strips in said
stripper comprise packing.
15. A process for separating catalyst particles from a gaseous
product stream comprising: contacting a hydrocarbon feed with
catalyst particles in an elongated riser to produce a gaseous
product; inducing the catalyst particles and gaseous products to
swirl in an angular direction upon exiting said riser and entering
a disengaging vessel to disengage catalyst particles from said
gaseous product; stripping descending catalyst particles over
elongated strips in a stripping section in said disengaging
chamber; separating catalyst particles entrained with ascending
product gases from said gases; and dampening the angular velocity
of said gaseous product and catalyst particles in the disengaging
vessel by use of a laterally disposed plate.
16. The process of claim 15 further including admitting separated
catalyst particles through passages into said disengaging
vessel;
17. The process of claim 15 further including separating said
catalyst particles from ascending product gases in a reactor vessel
and admitting said separated catalyst particles into said
disengaging vessel through passages.
18. The process of claim 15 wherein said descending catalyst
particles are stripped by an ascending gas.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to processes and apparatuses for the
fluidized contacting of catalyst with hydrocarbons. More
specifically, this invention relates to processes and apparatuses
for stripping entrained or adsorbed hydrocarbons from catalyst
particles.
DESCRIPTION OF THE PRIOR ART
[0002] Fluid catalytic cracking (FCC) is a process that contacts
hydrocarbons in a reaction zone with a catalyst composed of finely
divided particulate material. The hydrocarbon feed and fluidizing
gases, such as steam, fluidize the catalyst and typically
transports it in a riser as the catalyst promotes the cracking
reaction. As the cracking reaction proceeds, substantial amounts of
hydrocarbon, called coke, are deposited on the catalyst. A high
temperature regeneration within a regeneration zone burns coke from
the catalyst by contact with an oxygen-containing stream that again
serves as a fluidization medium. Coke-containing catalyst, referred
to herein as spent catalyst, is continually removed from the
reaction zone and replaced by coke-free or reduced coke catalyst
from the regeneration zone. Fluidization of the catalyst particles
by various gaseous streams allows the transport of catalyst between
the reaction zone and regeneration zone.
[0003] In the FCC process, gaseous fluids are separated from
particulate catalyst solids as they are discharged from a reaction
conduit. The most common method of separating particulate solids
from a gas stream uses centripetal separation. Centripetal
separators are well known and operate by imparting a tangential
velocity to gases containing entrained solid particles that forces
the heavier solids particles outwardly away from the lighter gases
for upward withdrawal of gases and downward collection of
solids.
[0004] Initial quick centripetal separation may be effected by
tangentially discharging a mixture of product gases and spent
catalyst particles from a riser into a containment vessel. The
containment vessel has a relatively large diameter and generally
provides a first separation of solids from gases. In these
arrangements, the initial stage of separation is typically followed
by a second more compete separation of solids from gases in
cyclones. An example of this arrangement may be found in U.S. Pat.
No. 5,584,985. An exit from a riser conduit comprises an arcuate,
tubular swirl arm which imparts a swirling, helical motion to the
product gases and particulate catalyst as they discharge from the
riser conduit into a disengaging vessel. The swirling, helical
motion of the materials in the separation vessel effects an initial
separation of the particulate catalyst from the gases. A gas
recovery conduit communicates the disengaging vessel with cyclones
in a reactor vessel. The mixture of gases and entrained catalyst is
drawn up the gas recovery conduit and fed into cyclones to effect
further separation of the particulate catalyst from the gases. This
arrangement is known as UOP's VSS.sup.SM system.
[0005] We have found that the swirling of the mixture of gases and
entrained catalyst exiting the swirl arms of the riser continues
into the gas recovery conduit to a significant degree. The swirling
of the mixture continues into the duct that communicates the gas
recovery conduit with the cyclones. U.S. Pat. No. 6,841,133
recognized that by orienting the angular direction of the swirl
motion of the mixture leaving the swirl arms of the riser to be
counter to the angular direction of the swirl motion in the
cyclones, the mixture entering the cyclone is more likely to first
encounter the outer wall which generates the swirling motion in the
cyclone. Hence, greater separation efficiency was achieved.
[0006] A majority of the hydrocarbon vapors that contact the
catalyst in the reaction zone are separated from the solid
particles by the aforementioned centrifugal separation methods.
However, the catalyst particles employed in an FCC process have a
large surface area, which is due to a great multitude of pores
located in the particles. As a result, the catalytic materials
retain hydrocarbons within their pores, upon the external surface
of the catalyst and in the spaces between individual catalyst
particles as they enter the stripping zone. Although the quantity
of hydrocarbons retained on each individual catalyst particle is
very small, the large amount of catalyst and the high catalyst
circulation rate which is typically used in a modern FCC process
results in a significant quantity of hydrocarbons being withdrawn
from the reaction zone with the catalyst.
[0007] Therefore, it is common practice to remove, or strip,
hydrocarbons from spent catalyst prior to passing it into the
regeneration zone. The most common method of stripping the catalyst
passes a stripping gas, usually steam, through a flowing stream of
catalyst, counter-current to its direction of flow. Such steam
stripping operations, with varying degrees of efficiency, remove
the hydrocarbon vapors which are entrained with the catalyst and
adsorbed on the catalyst.
[0008] The efficiency of catalyst stripping is increased by using
vertically spaced baffles to cascade the catalyst from side to side
as it moves down a stripping apparatus and counter-currently
contacts a stripping medium. Typical stripping vessels have a
series of outer baffles in the form of frusto-conical sections that
direct the catalyst inwardly onto a series of inner baffles. The
inner baffles are centrally located conical or frusto-conical
sections that divert the catalyst outwardly onto the outer baffles.
The stripping medium enters from below the lower baffles and
continues rising upwardly from the bottom of one baffle to the
bottom of the next succeeding baffle. Examples of these stripping
devices for FCC units are shown in U.S. Pat. No. 2,440,620; U.S.
Pat. No. 2,612,438; U.S. Pat. No. 3,894,932; U.S. Pat. No.
4,414,100 and U.S. Pat. No. 4,364,905. More recent stripping
configurations have used multiple strips of metal provided in a
patterned relationship to facilitate counter-current contacting of
catalyst particles and stripping gas. Examples include gratings and
structural packing disclosed in U.S. Pat. No. 6,680,030; U.S. Pat.
No. 6,224,833 and U.S. Pat. No. 7,179,427.
[0009] Better stripping of hydrocarbons from spent catalyst brings
important economic benefits to the FCC process by reducing "delta
coke". Delta coke is the weight percent coke on spent catalyst less
the weight percent coke on regenerated catalyst. Reducing delta
coke in the FCC process permits a lowering of the regenerator
temperature. More of the resulting, relatively cooler regenerated
catalyst is required to supply the fixed heat load in the reaction
zone. Hence, the reaction zone may operate at a higher
catalyst-to-feed or catalyst-to-oil (CIO) ratio. The higher CIO
ratio increases conversion which increases the production of
valuable products. Therefore, it is desirable to decrease delta
coke by more efficient catalyst stripping.
BRIEF SUMMARY OF THE INVENTION
[0010] We have discovered that catalyst discharged from a swirl
exit of a riser to separate the spent catalyst from product gases
may continue to swirl and fall along the outside wall of a
disengaging vessel. The catalyst descending along the outside wall
can bypass much of the stripping internals that comprise elongated
strips of metal of structural packing or gratings in the lower
disengaging vessel. This phenomenon can particularly affect spent
catalyst entering the disengaging vessel though passages from a
vessel such as a reactor vessel. The entering catalyst can be
picked up in the vortex and also be induced to tend toward the
outside of the stripping internals. We have invented a process and
apparatus for dampening the angular momentum of the swirling gases
and catalyst particles by installing one or more lateral plates
below the swirl exit of the riser. By dampening the tendency to
swirl, the descending catalyst particles are urged toward the
center of the stripping section to ensure that the exposure of
catalyst to the stripping internals is maximized and bypassing is
avoided.
[0011] Additional details and embodiments of the invention will
become apparent from the following detailed description of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic cross-sectional view of an FCC
unit.
[0013] FIG. 2 is an enlarged partial view of an anti-swirl plate of
the present invention.
DESCRIPTION OF THE INVENTION
[0014] The present invention is most appropriately used in any
apparatus or process for conducting FCC in which catalytic
particles and gases must be separated. The typical feed to an FCC
unit is a gas oil such as a light or vacuum gas oil. Other
petroleum-derived feed streams to an FCC unit may comprise a diesel
boiling range mixture of hydrocarbons or heavier hydrocarbons such
as reduced crude oils. In an embodiment, the feed stream may
consist of a mixture of hydrocarbons having initial boiling points,
as determined by the appropriate ASTM test method, above about
230.degree. C. (446.degree. F.), often above about 290.degree. C.
(554.degree. F.) and typically above about 315.degree. C.
(600.degree. F.) and end points no more than about 566.degree. C.
(1050.degree. F.). The reaction zone of an FCC process is
maintained at high temperature conditions which may generally
include a temperature above about 425.degree. C. (797.degree. F.).
In an embodiment, the reaction zone is maintained at cracking
conditions which include a temperature of from about 480.degree. to
about 590.degree. C. (896.degree. to 1094.degree. F.) and a
pressure of from about 69 to about 517 kPa (ga) (10 to 75 psig) but
typically less than about 275 kPa (ga) (40 psig). The
catalyst-to-oil ratio, based on the weight of catalyst and feed
hydrocarbons entering the bottom of the riser, may range up to 20:1
but is typically between about 4:1 and about 10:1. Hydrogen is not
normally added to the riser generating an absence of substantial
added hydrogen in the reactor, although hydrogen addition is known
in the art. On occasion, steam may be passed into the riser to
effect catalyst fluidization and feed dispersion. The average
residence time of catalyst in the riser may be less than about 5
seconds. The type of catalyst employed in the process may be chosen
from a variety of commercially available catalysts. A catalyst
comprising a zeolite base material is preferred, but the older
style amorphous catalyst may be used if desired.
[0015] The catalyst regeneration zone is preferably operated at a
pressure of from about 69 to about 552 kPa (ga) (10 to 80 psig).
The spent catalyst being charged to the regeneration zone may
contain from about 0.2 to about 15 wt-% coke. This coke is
predominantly comprised of carbon and can contain from about 3 to
about 12 wt-% hydrogen, as well as sulfur and other elements. The
oxidation of coke will produce the common combustion products:
water, carbon oxides, sulfur oxides and nitrous oxides. As known to
those skilled in the art, the regeneration zone may take several
configurations, with regeneration being performed in one or more
stages.
[0016] FIG. 1 is the schematic illustration of an FCC unit
embodying the present invention. The FCC unit includes an elongated
riser or reactor conduit 10. Hot catalyst is delivered to a lower
section of the riser 10 from a conduit 54 at which a fluidizing gas
from a distributor 8 pneumatically conveys the catalyst particles
upwardly through the riser 10. As the mixture of catalyst and
conveying gas continues up the riser 10, a nozzle 40 injects
hydrocarbonaceous feed and perhaps steam into the catalyst. The
contact with hot catalyst vaporizes the hydrocarbons and further
conveys the mixture of gas and catalyst through the riser 10 while
cracking the hydrocarbons to desirable lower boiling products.
[0017] The riser 10 extends upwardly into a reactor vessel 12 as in
a typical FCC arrangement. The riser 10 preferably has a vertical
orientation within the reactor vessel 12 and may extend upwardly
through a bottom of the reactor vessel 12. The reactor vessel 12
includes a disengaging vessel 16 defined by an outer wall 24. The
outer wall 24 of the disengaging vessel 16 has sections, some of
which may be cylindrical. The riser 10 terminates in the
disengaging vessel 16 at exits defined by the end of swirl arms 14.
Each of the swirl arms 14 may be a curved tube that has an axis of
curvature that may be parallel to the riser 10. Each swirl arm 14
has one end communicatively connected to the riser 10 and another
open end comprising a discharge opening 22. The disengaging vessel
16 is in downstream communication with the discharge opening 22, so
swirl arm 14 discharges a mixture of gaseous fluids comprising
cracked products and solid catalyst particles through the discharge
opening 22 into the disengaging vessel 16. Tangential discharge of
gases and catalyst from the discharge opening 22 produces a
swirling helical motion in an angular direction about the
cylindrical interior of the disengaging vessel 16. Centripetal
acceleration associated with the helical motion forces the heavier
catalyst particles to the outer portions of the disengaging vessel
16 to effect disengagement of the catalyst particles from the
gaseous product. Catalyst particles from the discharge openings 22
collect in the bottom of the disengaging vessel 16 to form a dense
catalyst bed 38. The gases, having a lower density than the solid
catalyst particles, more easily change direction and begin an
upward spiral. The disengaging vessel 16 includes a gas recovery
conduit 18 with an inlet 20 through which the spiraling gases
ultimately travel. The gases that enter the gas recovery conduit 18
through the inlet 20 will usually contain a light loading of
catalyst particles. The inlet 20 recovers gases from the discharge
openings 22 as well as stripping gases from a stripping section 28
which may be located in the disengaging vessel 16 as is hereinafter
described. The loading of catalyst particles in the gases entering
the gas recovery conduit 18 are usually less than 16 kg/m3 (1
lb/ft3) and typically less than 3 kg/m3 (0.2 lb/ft3). The gas
recovery conduit 18 of the disengaging vessel 16 includes an exit
or outlet 26 contiguous with an inlet or entrance 30 to one or more
cyclones 32 in the reactor vessel 12 that effect a further removal
of catalyst particulate material from the gases exiting the gas
recovery conduit 18 of the disengaging vessel 16. The reactor
vessel surrounds and contains at least a portion of the disengaging
chamber and is in downstream communication with the discharge
openings 22 of the swirl arms 14. The disengaging vessel 16, the
gas recovery conduit 18 thereof and the cyclones 32 may be directly
connected, meaning that they are in fluid communication with each
other and sealed against substantial leakage. Hence, substantially
all of the gases and solids exiting the disengaging vessel 16
through gas recovery conduit 18 may enter the cyclones 32. It is
envisioned that the reactor vessel 12 could be dispensed with, in
which case one or more external cyclones 32 would be in downstream
communication with said swirl outlet 22.
[0018] The cyclones 32 create a swirl motion therein to establish a
vortex that further separates solids from gases. A product gas
stream, relatively free of catalyst particles, exits the cyclones
32 through vapor outlet pipes 50 into a fluid-sealed plenum chamber
56. The product stream then exits the reactor vessel 12 through an
outlet 25. Each cyclone 32 may include an upper cylindrical barrel
section 31 contiguous with the entrance 30. The barrel section 31
may be connected by a first frustoconical section 33 to a hopper
section 35. The hopper section 35 may be contiguous with a second
frustoconical section 37 which may be contiguous with a dipleg 34.
Catalyst solids recovered by the cyclones 32 exit the bottom of the
cyclone through diplegs 34. The diplegs 34 may comprise conduits
that may have one or more sections. Other cyclone configurations
will be suitable. The diplegs 34 extend downwardly in the reactor
vessel and may terminate at a flapper valve which prevents gas from
entering the dipleg 34 but allows catalyst particles to exit into
dense bed 37 at a bottom of the reactor vessel 12 surrounding the
disengaging vessel 16.
[0019] Catalyst particles in the reactor vessel 12 are admitted by
passages 36 into the disengaging vessel 16. The passages 36 may
comprise windows between the reactor vessel 12 and the disengaging
vessel 16 to allow catalyst to flow from the dense bed 37 into the
dense bed 38 or a port or opening through which diplegs 34 or other
conduit may transfer catalyst particles from cyclones 32 in the
reactor vessel 12 into the disengaging vessel 16. The reactor
vessel 12 and/or the cyclones therein are in upstream communication
with the passages 36. Catalyst particles in the dense catalyst bed
38 enter the stripping section 28 located in the disengaging vessel
16. Catalyst particles pass downwardly through and/or over a
plurality of elongated metal strips 44 arranged together in a three
dimensional array in the stripping section 28. The strips may have
straight portions set at angles to other strips or other portions
of the same strip which may be straight. Layers or arrays of strips
may be stacked in the stripping section. The metal strips 44 may
define a structural packing or may define gratings with or without
downcomers. Examples of suitable structural packing may be found in
US 2005/0205467 and suitable gratings may be found in U.S. Pat. No.
6,680,030 for use in stripping vessels. A stripping fluid,
typically steam, enters a lower portion of the stripping section 28
through at least one distributor 46. Counter-current contact of the
catalyst with the stripping fluid over the metal strips 44
displaces product gases adsorbed on the catalyst as it continues
downwardly through the stripping section 28. Stripped catalyst from
the stripping section 28 may pass through a conduit 48 to a
catalyst regenerator 52. In the regenerator, coke deposits are
combusted from the surface of the catalyst by contact with an
oxygen-containing gas at high temperature. Following regeneration,
regenerated catalyst particles are delivered back to the bottom of
the riser 10 through the conduit 54. Flue gas exits the regenerator
52 through nozzle 56.
[0020] We have found that the swirling motion induced by the
product gases and catalyst particles issuing from the swirl arms 14
of the riser 10 may continue as the catalyst descends in the
disengaging vessel. Catalyst particles due to swirling or other
reasons tend to descend along the sides of the disengaging vessel.
Consequently, the catalyst can descend in the stripping section
down along the outer wall 24 of the disengaging vessel 16 a
substantial depth before elongated metal strips in the stripping
section 28 distribute the catalyst particles to the center of the
stripping section. As a result the full effect of the stripping
section is not realized for a substantial portion of the stripping
section 28 during which avoiding intimate contact with the
ascending stripping gas. The swirling and/or descending catalyst
also tends to catch the catalyst particles passing through the
passages 36 from the dense bed 37 in the reactor vessel 12 into the
dense bed 38 in the disengaging vessel and push it toward the outer
wall 24 as well, causing the same deficiency. This biasing of
catalyst to the outer wall 24 also compounds deficiencies by
biasing stripping gas inwardly, further avoiding intimate
contacting of stripping gas with catalyst particles. Biasing
catalyst also can further concentrate catalyst particles to erode
equipment in the stripping section 28.
[0021] The present invention is further illustrated with reference
to FIG. 2 which is an enlarged partial version of a top of the
disengaging vessel 16 of FIG. 1. An outer baffle 60 is disposed in
the disengaging vessel to direct descending catalyst particles away
from the outer wall 24 of the disengaging vessel 16. The
disengaging vessel is preferably a cylindrical vessel, so a
plurality of the passages 36 may be circumferentially spaced around
the wall of the disengaging vessel 16. The outer baffle 60 is
disposed below the swirl outlet 22, preferably above the stripping
section 28 and preferably may be disposed under each passage 36.
Preferably, the outer baffle 60 may be a single annular baffle that
encircles the disengaging vessel 16 disposed under each of the
plurality of passages 36. Preferably, the outer baffle 60 is
suitably secured to the outer wall 24. The outer baffle 60 may be
disposed at an angle with respect to the vertical outer wall 24 of
preferably 20 to 60 degrees with 45 degrees being suitable. The
outer baffle 60 should have a horizontal projection of about
one-third of the open dimension R of the stripping section 44. In a
stripping section 44 in which the riser 10 extends through the
stripping section 44 of the disengaging vessel 16 to form an
annular stripping section 44, the open dimension R is the radial
distance between a point on the inner surface of the outer wall 24
and the closest point on an outer surface of an outer wall 62 of
the riser 10. An inner baffle 64 may also be provided to direct
descending catalyst away from the outer wall 62 of the riser 10.
The outer baffle 60 and the inner baffle 64 may be disposed at the
same height in the disengaging vessel 16. The inner baffle 64 may
be disposed at an angle with respect to the vertical outer wall 62
of preferably 20 to 60 degrees with 45 degrees being suitable. The
inner baffle 64 may also have a horizontal projection that is
one-third of the open dimension R, such that together outer baffle
60 and inner baffle 64 direct catalyst to the middle annular
one-third of the stripping section 44. Other depths of projection
of outer baffle 60 and inner baffle 64 may be suitable.
[0022] Baffles 60 and 64 are shown with perforations 66 therein to
fluidize a top surface of the baffles. The perforations may also be
equipped with tubes to define jets (not shown) about the
perforations. Baffles 60 and 64 may also be equipped with skirts 68
to increase the pressure head below the baffles. Baffles 60 and 64
are also preferably submerged in the dense catalyst bed 38 and are
preferably lined with refractory to avoid excessive erosion by
gusting catalyst particles.
[0023] Baffles 60 and 64 direct descending, swirling catalyst from
discharge opening 22 of swirl arms 14 toward the center of the
stripping section 28. Consequently, catalyst particles begin their
descent through the elongated metal strips 44 of the stripping
section at the center. This assures that the catalyst particles
contact the full range of elongated strips 44 which fosters
intimate mixing with ascending stripping gas. It is believed that
this apparatus and process will improve stripping efficiency of
stripping vessels that use elongated strips for stripping
internals.
[0024] FIG. 2 illustrates anti-swirl plates 70 disposed in the
disengaging vessel 16 below the discharge openings 22 to dampen the
angular motion of swirling catalyst particles and gases. One or
more anti-swirl plates 70 can be laterally disposed and preferably
radially disposed in the disengaging vessel so as to provide a
broad face opposed to the angular momentum of swirling catalyst
particles and gases. At least a portion of each anti-swirl plate 70
may be disposed above, partially above, even with, partially below
or preferably below the passages 36 to prevent entering catalyst
from being picked up in the swirling motion of descending catalyst
particles and gases. The anti-swirl plates 70 may be secured to the
outer wall 24 such as by welding. The anti-swirl plates are
preferably secured to the respective outer baffle 60 which is
secured to the outer wall 24 both such as by welding. The
anti-swirl plates 70 are preferably on a top surface of the outer
baffle 60, in which case each plate 70 may be inclined at the same
angle as the baffle 60. The anti-swirl plates 70 are preferably
submerged in the dense catalyst bed 38 and are preferably lined
with refractory to mitigate erosion. If a plurality of passages 36
are disposed in the outer wall 24, one anti-swirl plate may be
disposed adjacent and preferably subjacent to each passage 36 to
prevent catalyst particles admitted through the passage 36 to be
swept into the swirling, descending gas. One or more anti-swirl
plates 70 may also be secured to the inner baffle 64 with or
without the same positioning as an anti-swirl plate 70 on the outer
baffle 60.
* * * * *