Note: Descriptions are shown in the official language in which they were submitted.
Background of the Invention
The field of this invention i5 air distribution
and in particular air dis~ribution in the ca~calyst regene-
rator of a fluid catalytic cxacking unit.
U.S. Patent No. 3,433,733 discloses a method and
apparatus for fluid catalytic cracking of a hydrocarbon feed
stock in order to produce desired reaction products.
; Generally, the process consists of mixing together feed
- stock and hot catalyst in a riser/reactor prior to entry
into a tapered reactor/separator chamber. The catalyst is
removed from the reac~or/separator chamber in a spent con-
dition and is directed to a regenerator wherein the carbona-
ceous deposit on the catalyst, referred to as "coke", is
burned from the catalyst with air. The regenerated catalyst
is then re-used in the process. In U.S0 Patent NOn 3,433,733,
an air distributor is positioned in the lower portion of the
regenerator for distributing an air supply into a zone of
spent catalyst in the regeneratox. The efficiency of the
regeneration process is dependent upon a uniform distribu-
tion of air through the spent catalyst zone. It has beenfound desirable to distribute the air outwardly of the air
distributor at certain pressure differentials between air
pressure in the distributor and air pressure in the regene-
rator to cause the air to e~fectively bubble and thus distri-
bute through the zone of spent catalyst. However; it has
also been found that the velocity of the air leaving the air
ring may be so high at such desired pressure diferential
levels that the air actually causes some attrition of the
catalyst. In order to prevent this attrition, it has been
necessary to deliver the air at pressures below the higher
pressure differential levels for the most efficient distribution of the
air through the spent catalyst zone in the regenerator.
United States Patent No. 3,912,~60 discloses an air distribution
system for evenly distributing air in the spent catalyst zone of a regenera~or
in a fluid catalytic cracking process. ~ horizontal distributing ring is
positioned in the spent catalyst in the regenerator. The ring comprises
two tapered semi-circular tubes which are interconnected at their small
ends; a splitter tube joint and the two larger ends of the ~apered semi-
cylindrical tubes are connected to a pressurized air supply. Air i.s dis- .
tributed outwardly into the spent catalyst zone o the regenerator through
openings in the semi-cylindrical tubes.
Other patents of interest include United States Patent 3,~67,103
which discloses the utilization of Venturi-shaped nozzles for use in mixing
a hydrocarbon ancl acid to form an emuls:ion in a catalyt:ic conversion
apparakus. United States Patent No. 3,8~8,811 discloses a particular
structure for a nozzle which discharges a liquid such as oil iIltO a
fluidi.zed bed of particulate material such as catalyst in a fluid catalytic .cracking system. And, Uni.ted Stat~s Patent No. 3,632,304 discloses a .
heater nozzle which di.rects combustion gas into a reactor for providing
a combustion gas stream for treating catalyst. None of these patents
disclose structure which :is precisely capable of achi.eving the results
of the invention set forth herein.
Summary of the Invention
~ccording to this invention there is provided an improved air
distribution apparatus for delivering an oxygen-carrying gas such as air
at high pressure to a xone of spent catalyst in a regenerator of a fluid
catalytic cracking process with maximum desired pressure differential and
at a velocity below a level which would damage the catalyst, comprising,
(a) hollow cylindrical housing means for mounting in the regenerator, ~ :
(b) hollow header means mounted on said hollow cylindrical housin.g means, ;~
(c) a plurality of nozzle means supported by said hollow cyli:ndrical housing
means and said hollow header means for receiving the high pressure air, and
~3
(d) each of said nozzle means having a bore divergence of a hal:f angle of less
than 7 for decreasing the delivered air velocity to a spent catalyst non-
damaging velocity.
According to one embodiment of the invent:ion an improved air dis-
tribution apparatus for delivering an oxygen-carrying gas such as air at high
pressure to a zone of spent catalyst in a regenerator of a fluid catalytic
cracking process with maximum desired pressure differential and at a velocity
below a level which would damage the catalyst, comprises, (a) a header support
assembly adapted for mounting in a regenerator of a fluid catalytic cracking
process, said header support assembly supporting a hollow header ring having
a plurality of openings therein, ~b) said header support assembly comprising
a first cylindrical housing means for supporting said hollow header ring,
~c) an air supply line attached to said header support assembly arld air supply
mcans Eor supplylng air through said.air supply line -to said llollow header
ring at a pressure which causcs a maximum effective pressure differential
between said ring and in said regenerator, (d) a plurallty of nozzles and
mount means mounting said nozzles in said openings in said header ring, each
of said nozzles having a bore therethrough which forms a nozzle inlet which
initially receives air from said header ring and a nozzle exit Eor directing
air outwardly into such spent catalyst zone, and ~e) each of sai.d nozzle bores
d:iverging .-Erom said nozzle inlet to said nozzle outlet at a hal:E angle o:E less
than 7 which decreases the velocity of said air from sai.d nozzle inlet to
said nozzle exit to a level which will not substantially damage the catalyst.
According to another embodiment of the invention an improved air
distribution apparatus for delivering an oxygen-carrying gas such as air at
high pressure to a zone of spent catalyst in a regenerator of fluid catalytic
cracking process with maximum desired pressure differential and at a velocity
below a level which would damage ~he catalyst, comprises, ~a) a header support
assembly adapted for mounting in a regenerator of a fluid catalytic cracking
process, said header support assembly supporting a hollow header ri.ng having .
a plurality of openings therein, ~b) an air supply line attachcd to said
header support assembly and air supply means :~or supplying air through
~l `,J
i2
said air supply line to said hollow header ring at a pressure which causes
a maximum effective pressure differential between saicl ring and in said
regenerator, ~c) a plurality of nozzles and mount means mounting said nozzles
in said openings in said header ring, each of said nozzles having a bore
therethrough which forms a nozzle inlet which initially receives air from
said header ring and a nozzle exit for directing air outwardly into such
spent catalyst zone, (d) each of said nozzle bores diverging from said
nozzle inlet to said nozzle outlet at a half angle of 1 which decreases the
velocity of said air from said nozzle inlet to said nozzle exit to a level
which will not substantially damage the catalyst, (e) a first cylindrical
hollow housing section having radial pipe members mounted therein and extend-
ing outwardly to support said header ring, ~f) a second cylindrical hollow
housing scction positioned on said first hous:ing secti.on, ~g) said first and
sccond housing sect:ions having openings therei.n, ~h) a plura:lity oE nozzles
mounted i.n said openings in said :Eirst and second housing sections, each
nozzle having a bore therethrough diverging from a nozzle inlet to a nozzle
exit, and ~i) mount means mounting said nozzle in said housing at the nozzle
inlets thereof.
Brief Description of the Drawings
In the accompanying drawings, which illustrate an exemplary
embodiment of the present invention:
Figure 1 is a side view in section of a regenerator of a fluid
catalytic cracking process having the air distribution system of this
invention positioned therein;
Figure 2 is a sectional vlew of the air distribution system - ~.
header ring which mounts the air distribution nozzles of the preferred
embodiment o-f this invention; and
Figure 3 is a sectional view taken along line 3--3 of Figure 2
illustrating the structural detail of the air distribution system nozzles.
Description of the Preferred Embodiment
.. . ..
Referring to the drawing, the letter R generally desig.nates a
regenerator used in a flui.d catalytic cracking process such as disclosed in
:
., ~) .
: United States Patent No. 3,433,733. The regenerator R includes a new and
improved air distri.bution apparatus, generally designated by the letter A,
adapted for mounting in the lower portion of the regenerator R. In a
fluid catalytic cracking process such as disclosecl in United States Patent
No. 3,~33,733, the lower portion 10 of the -regenelator R illustrated in
Figure 1 actually receives spent catalyst from a reactor. The spent catalyst
is in particulate form, the size of the particles being sufficiently small
that the catalyst may be fluidized in air. The air distribution system
A is designed to provide the necessary oxygen to combust with coke on the
spen~ ca~alyst to combust and burn
~ a-
the coke off the catalyst in order to rejuvenate the catalyst.
The rejuvenated catalyst is then re~used in the fluid cata-
lytic cracking process. The spent catalyst is collected in
a zone or bed 11 in the lower por~ion 10 of the regenerator
R. The purpose of the air distribution system A is to
distribute bubbled air through the spent catalyst zone or bed
11 so that the coke covering the spent catalyst is combusted
with the air and burned off the catalyst.
In the preferred embodiment of this invention, the
air distribution syste~ A includes a blower 12 which provides
air under pressure to regenerator opening 14 through air
supply line 15. A central housing 16 is mounted over the
openiny 14 in the regenerator R.
The housing 16 includes a first housing section
16a and a second housing section 16b. The housing section
16a is basically a hollow, cylindrical structure which is
mounted over the regenerator opening 14 by any suitable
means such as welding. The housing section 15a includes a
dome-shaped top section 17 having opening 17a therein.
The second housing section 16b is welded or other-
wise mounted over the first housing section opening 17a.
The second housing section 16b is also a hollow and generally
cylindrical section. The housing section 16b is enclosed at
the top thereof.
The hollow housing se~tions 16a and 16b cooperate
to form a plen~n ch~nber 18 which receives air through the
air supply line 15. The first housing section 16a has a
circumferential row of openings 19 positioned in substan-
tially horizontal alig~nent. Each of the openinys 19 has
mounted therein a nozzle N o~ the preferred embodiment of
_5_
this invention as illustrated in detail in Fig~ 3. The
second housing section 16b also has a row of circumferentially
spaced openings 20 therein which receive nozzles N of this
invention.
Three radial support arms 21, 22 and 23 are
welded in three openings 24 in the first ho~sing section
16a. Each of the radial support arms 21-23 are hollow pipe
memkers having an approximate L-shape as viewed in Fig. 1.
The three radial supports arms 21-23 cooperate
with the first and second housing sections 16a and 16b to
provide a header support assembly for supporting a hollow,
header ring 25.
The header ring 25 includes three openings 26
which aliyn with and receive the radial support arms 21-23,
which are attached to the header ring Z5 by welding or other
suitable means. The header ring 25 further includes two
rows 30 and 31 of nozzles N which are mounted in -two rows of
header ring openings 30a and 31a, respe~tively. In addition,
several drain nozzles D, which are of the same configuration
as the nozzles N to be described herein, are positioned in
header ring openings 33 which are located at the very bottom
of the header ring 25 and are circumferentially spaced about
the ring. The number of drain nozzles D is sub6tantially
fewer than -the number of nozzles N in rows 30 and 31 in the
header ring 25.
Complete distribution of air through the air dis-
tribution system A into the spent catalyst zone 11 in re-
generator R is critical to eficient rejuvenation of the
catalyst. The nozzles N of the preferred embodiment of this
invention are designed to deliver air to the spent: catalyst
6~
J~
zone 11 in the regenerator R at a safe velocity level in
order ~o proviae for maximum dispersion of the air through
the spent catalyst zone 11.
It has been found desirabl~ to have a sufficiently
high pressure differential between the pressure of the air
in the header ring 25 and the pressure of air ~xiting the
nozzles N (which is the same as air pressure in the be~ 11)
to cause the air to uniformly disperse for high area contact
with the spent catalyst particles. However, it has been
found that ai.r in prior art systems such as disclosed in
U.S. Patent No. 3,912,460 which exits a header ring at such
sufficiently high pressure dif~erential levels has a velocity
that is so high that it may actually cause some attrition o
the catalyst. The nozzles N of the preferred embodiment of
this invention are designed to deliver air to the spent
catalyst zone 11 at a velocity below a potentially damaging
level.
Referring in particular to Figs. 2 and 3, each of
the nozzles N is formed of a frustro-conical, cylindrical
section 40 having a bore 41 therethrough. Each nozzle N
diverges or flares in the bore 41 from nozzle inlet or
entrance 42 to nozzle exit 43. Each nozzle N is an inteyral
unit ~ormed of cast Stelli-te or other suitable material.
Mount means yen~rally designated by the number 44
iæ provided for mounting each of the nozzles N in opening~
such as 30a in the header ring 25. The mount means 44
includes a mounting ring 46. When cast Stellite is utilized,
the frustro-conical sec~ion 40 is formed by casting. However,
cast ~tellite is no~ capable of direct attachment to the
header ring 25 throuyh welding. In order to render the
7~
:
. , -.................. . ' ~ ' ' '.'. '~, ' ' ~
.
frusto-conical section 40 attachable to -the header ring 25
by welding, the mounting ring 46 is attached to the frusto-
conical section 40 during casting. The mounting ring 46 may
then be welded to the header ring 25. If another suitable
nozzle material is utilized which can be welded to the
header ring 25, it is contemplated to form the mounting ring
as an inteyral portion with the frusto-conical section for
direct welding connection to the header ring 25. Nozzle
entrance 42 is formed by an inside nozzle rim 47 which is
posi~ioned flush with interior wall 25a of the header ring
25.
The nozzl~ N may be defined as having a cross-
sectional interior, ci.rcular area Ai at nozzle entrance 42
and a cross-sectional interior, circular area Ae a-t nozzle
exit 43. The cross-sectional area Ai, and thus the interior
diameter at -the nozzle entrance 42, is less than the cross-
sectional area Ae, and thus the interior diameter at the
nozzle e~it 43, such that the bore 41 tapers outwardly or
diverges from the nozzle entrance 42 toward the nozzle exit
43. The half angle of such taper may be def.ined at 48 as
being up to 15, but preferably 7~. The length 1 of the nozzle,
as well as the angle 48 of taper, will vary accoxding to
application .
The air distribution system A provides air to the
header ring 25 in a pressure range to provide a sufficiently
high pressure differential between the pressure in ring 25
~which is approximately the same at entrance pressure Pi) -:
and the pressure in bed 11 (which is the same at nozzle exit
pressure Pe) to provide for maximum uniform distribu~ion of : -
air into bed 11. At such pressure levels, the tape:red
interior bore 41 of the nozzle section 40 acts to reduce the
entrance velocity Vi of air to a lesser exit velocity Ve
which will not cause signiflcant damage to the catalyst.
Thus utilizing the nozzles N of this invention, the air
distribution system A can deliver air to the spent catalyst
zone 11 at maximum pressure differential levels to cause
maximum uniform dispersion of the air into the spent catalyst
zone 11 but at a s~fe, reduced velocity level which will not
cause substantial attrition of the spent catalyst.
EXAMPLE
In a fluid catalytic cracking unit such as described
in U.S. Patent No. 3,433,733, the nozzle N of thls invention
has a length 1' exterior to the header 25 of three inches.
The area Ai at the nozzle entrance 42 is defined by a diameter
of 1.55 inches (3.875 cm.) and the area Ae at the exit is
defined by a diameter o 1.65 inches (4.19 cm.). The air
pressure in the ring 25 is at 40.0 psi (2.80 kg./sq. cm.)
and the pressure drop from the ring 25 to the bed 11 is 1.5
(105.95 gr./sq. cm.) to 2.5 psi (175.76 gr./sq. cm.). The
divergence of the bore 41 causes a reduction in velocity
from an entrance velocity Vi f 219 feet per second (66.75
m./sec.) to safe exlt velocity Ve f 175 feet per second
(53.34 m./sec.),
The foregoing disclosure and description of the
invention are illustrative and explanatory thereof, and
various changes in the size, shape and materials as well as
in the details of the illustrated construction may be made
without departing from the spirit of the invention.
