Note: Descriptions are shown in the official language in which they were submitted.
llVOQ76
HYDROCARBON-FEED DISTRIBUTOR AND METHOD
OF INJECTING HYDROCARBON FEED
SPECIFICATION
The field of art to which this invent~on pertains is hydro-
carbon processing w~th a fluidizable catalyst. More partlcularly, 1n
one embodiment the present application relates to a hydrocarbon feed
distr~butor and, in another embodiment, to a particular method of in~ec-
ting a hydrocarbon feed lnto a catalytic conversion zone, both of which
find particular util~ty in the fluidized catalytic cracking process.
The fluid catalyt~c cracking (FCC) process wherein the pre-
sent invention finds partlcular applicabtlity comprises mixing in a
r1ser reaction zone a hydrocarbon feed having a boiling range of from
about 260C. to about 649C. with a flu~d~zable catalyst and converting
therein, at conversion condit~on, the hydrocarbon feed into lighter, more
valuable, products. Typically the temperature of the hydrocarbon feed is
from about 177C. to about 371C. and the temperature of the regenerated
catalyst ~s from about 621C. to about 732C. The two are mixed together
to completely vaporize the hydrocarbon feed and to achieve a temperature within
the conversion zone of from about 468C. to about 593C. Conversion conditions
1100076
also typically include low pressures of from about atmospheric pres-
sure to about 7.8 atm. and hydrocarbon residence times of from about
O.S second to about S minutes. Catalyst is normally circulated
through the riser reaction zone at a rate of from aboutl~ to about
9.1kib~a~50f catalyst per pound of hydrocarbon feed. The catalyzed
reactions may be conducted entirely in a riser reaction zone, as in
an all-riser FCC unit, or partially in a riser reaction zone with the
~ixture of catalyst, reaction products and unconverted feed, if any,
then being discharged into a dense bed of fluidized catalyst for
further conversion of the feed or of the heavier reaction products
into lighter reaction products. The apparatus and method of this
invention find utility in either case.
A variety of techniques have heretofore been employed to
introduce a hydrocarbon feed into the riser reaction zone. U.S.
lS Patent N~. 3,152,065 for example describes a method of injecting a
hydrocarbon feedstock into a catalytic reaction zone which comprises
passing the liquid hydrocarbon as an outer stream in a generally
linear direction, imparting a centrifugal energy component to the
outer stream, passing the outer strea~ having a centrifugal component
through an annulus, and discharging the moving stream through a re-
stricted passageway in contact with an inner stream of a vaporous
material such as steam which operates to disperse the hydrocarbon
- stream into small droplets of liquid. Other vaporous or gaseous
materials such as inert gases, nitrogen, natural gas, recycle cata-
lytic cracking unit process gases, etc. can be used as the inner
stream. Also disclosed ~n that same prior art reference is a nozzle
for injecting a liquid hydrocarbon feed into contact with a catalyst
which nozzle contains components ~or imparting a centrifugal energy
component to material flowing through an outer shell o~ the noz-
zle. Both the method and the nozzle are for providing a high degree
` 110~76
.. .
of atomization of the feedstock and good contacting of the hydrocar-
bon feedstock and the catalyst. This h1gh degree of atomization ls
achieved by the use of means of imparting a centrifugal energy com-
ponent to a liquid hydrocarbon stream and by using a "vaporous mater-
ial" which operates to disperse the hydrocarbon stream into small
droplets. U.S. Patent No. 3,654,140 describes an improved catalytic
cracking process which comprises feeding a substantially liquid
hydrocarbon oil feedstock to at least one feed in~ection zone of a
fluidized catalytic cracking reaction zone, concurrently feeding
steam to said ln~ection zone in a volumetric ratio of steam to
liquid hydrocarbon ranging from about 3 to about 75, thereby impart-
ing to the resulting mixture an exit velocity relative to the fluid-
ized catalyst of at least about30.5meterSper second, whereby the oil
feedstock is essentially completely atomized forming droplets less
than about 350 microns in diameter. The process of this reference
relies on the use of steam and very high exit velocities of at least
30.5 m~sec to achieve a high degree of feedstock atomization charac-
terized by droplet sizes of less than about 350 microns in diameter.
These prior art processes and apparatus and others have
been primarily concerned with the initial contacting of the hydro-
carbon feedstock and catalyst to achieve, at least initially, a uni-
form mixture of catalyst and hydrocarbon feed in the riser reaction
zone to avoid excessive coking of the feedstock and attendant product
loss. While the Initial fonmation of a uniform catalyst and hydro-
carbon mixture is certainly important, it is equally important that
the mixtu~e un1formity be maintained as well as possi~le across a
cross-section area of the riser reaction zone at any elevation along
the riser reaction zone. More specifically, it has been found that
in spite of the use of methods and apparatus to achieve initlal unifonm
1100~76
contacting of a hydrocarbon feed and a cracking catalyst, wide varia-
tions of catalyst density and temperature can exist across cross-
sections of typical riser reaction zones, particularly across cross-
sections at lower elevations of riser reaction zones. ~lith the use
of radiation equipmen~ and probes containing thermocouples,catalyst
densities and temperatures in riser reacticn zones at different ele-
vations have been measured and catalyst density and temperature con-
tours have been obtained. At lower-e1evation cross sections of a riser
reaction zone catalyst densities of about 961 kg/m3 have been found
near the walls while catalyst densities of less than about48 kg/m3
were found on the same cross section but near the riser centerline.
Temperature profiles have shown the same wide variation; at lower-
elevation cross sections of a riser reaction zone temperatures of
649C. and higher have been measured while temperatures near the
centerline of the riser were about 343C. Such high wall tempera-
tures cause elongation of the riser reaction zone and in many instances
exceed the design wall temperature and result in permanent deformation
of the riser reaction zone. Additionally high wall temperatures cause
overcracking of hydrocarbon feed in these regions of hi~her temperatures
and result in increased yields of dry gas (C2-). The apparatus and
method of my invention reduce these high wall temperatures and the
problems they cause. ~y apparatus and method produces temperature
profiles across a cross-section of a riser reaction zone which are
more nearly flat thus reducing overcracking and the risk of damage to
the riser reaction zone.
It is~ accordingly, an objective of the present invention to
provide an improved flu~dized catalytic cracking process which over-
comes the above noted deficiencies.
1100~
It is another objective of my invention to provide a hydro-
carbon feed distributor for use in contacting a hydrocarbon feed with
a fluidizable catalyst in a riser reaction conduit which distributor
will reduce wall temperatures in the condult thereby reducing over-
cracking and reducing yields of dry gas.
It is another objective of the present invention to provide
a method for injecting a hydrocarbon feed into contact with a fluidiz-
able catalyst in a riser reaction zone whereby the wall temperatures
in the zone can be reduced thereby reducing overcracking and reducing
yields of dry gas.
In brief summary my invention is, in one embodiment, a hydro-
carbon-feed distributor for in~ecting a hydrocarbon feed into contact
with a fluidizable catalyst under conversion conditions in a lower
end of a riser reactor conduit having a lower end, cylindrical inside
and outside walls, a center portion, a hydrocarbon-feed inlet means
entering said conduit at said lower end and a regenerated-catalyst inlet
means passing through said walls at a dlstance downstream from said
hydrocarbon-feed inlet means, said distributor comprising: a) a trun-
cated cone having a small-d1ameter end connected to said hydrocarbon-
feed inlet means and a large diameter end; b) a circular plate fitted
into said large-~iameter end, said plate having one or more first holes
and a plurality of second holes passing through said plate; and, c)
one or more first nozzles having a first inlet means fitted into said
first hole and an ou~let means positioned to dlrect hydrocarbon feed
into said center portion; and, d) a plurality of second nozzles having
second inlet means fitted into said second ho1e and having second outlet
means positioned to direct hydrocarbon feed downstream o~ said second
outlet means and impinge against said inside wall.
In another embodiment my invention is a method of injecting a
hydrocarbon feed into contact with a fluidizable catalyst in a catalytic
1100076
conversion 20ne having a center portion and an inside wall which com-
prises: a) passing a first portion of said feed through one or more
first nozzles having a first inlet means and a first outlet means, said
nozzle being vertically positioned in said conversion zone whereby said
first portion is directed from sald first outlet means vertically up into
said center portion; b) passing a second portion of said feed through
multiple second nozzles having second inlet means and second outlet means
and positioned in said conversion zone so that a centerline passing through
a long axis of a second nozzle is inclined toward the inside wall of said
conversion zone at an angle from a vertical centerline passing through the
center of a second inlet means whereby said second portlon exits said second
outlet means and impinges on said inside wall downstream of said second
inlet means; and, c) contacting hydrocarbon feed from said first and said
second nozzles with said catalyst at conversion conditions.
Other embodiments and objects of my invention encompass further
details such as the function and arrangement of various components of my
apparatus and operating conditions of my method all of which are herein-
after disclosed in the following discussion of each of these facets of my
invention.
Having thus described the apparatus and method of my invention
in brief terms, reference is now made to the drawings attached hereto.
While the drawings illustrate preferred embodiments of my invention it
will be understood that it is not applicant's intention to limit his in-
2~ vention to those embodiments but rather to include all alternatives,
modifications and equivalents thereof as may fairly be within the scope
and spirit of the claims appended hereto. It will also be understood
that the embodiments are only shown in such detail as is necessary for
an understand~ng of the invention and that minor items have been omitted
~o for the sake of s~mplicity.
116)QQ76
Figure 1 is a side view of a fluid catalytic cracking
apparatus in which the hydrocarbon feed distributor of my invention
is incorporated as one component of that apparatus;
Figure 2 is an enlarged side view of the lower end of the
S cracking apparatus shown in Figure 1 and in particular of the lower
end of a riser reactor conduit showing in more detail the position-
ing of the feed distributor in the riser conduit in relation to other
components of the cracking apparatus;
Figure 3 is a top view of one embodiment of a hydrocarbon
feed distributor while Figure 4 is a side sectional view of the same
distributor; and
Figure 5 is the top view of another embodiment of a hydro-
carbon feed distri~utor while Figure 6 is a side view of the same
distributor.
A particular environment wherein the present invention finds
its greatest utility is in a fluid catalytic cracking apparatus shown
in Figure 1 and comprising a riser reactor conduit 1, a feed distributor
2, a hydrocarbon inlet means 3, a regenerated-catalyst inlet means 4,
a reception vessel 6, a cyclone separation means 12, and a spent-
catalyst outlet means 16. A hydrocarbon feed, for example, a virgin
gas oil boiling within the range of from about 343C. to about 64qC. .
is introduced into the apparatus by way of hydrocarbon-feed inlet means
3. The hydrocarbon feed may be preheated by a fired heater (not shown)
or by a system of heat exchangers (not shown) before entering the unit
and it is to be understood that recycle streams may also be charged in
conjunction with the virgin feed into the unit. The hydrocarbon feed
may be in vapor phase or in liquid phase or a mixture of the two but
more typically in fluid catalytic cracking process it will be in the
--7--
11~0~6
liquid phase. Hydrocarbon feed inlet means 3 is connec~ed to hydro-
carbon feed distributor 2 through which hydrocarbon feed passes and
becomes mixed in the lower portion of conduit 1 with hot regenerated
catalyst from a regeneration zone (not shown) which enters conduit 1
through regenerated catalyst inlet means 4 which has flow regulating
means 5 located thereon to control the flow of regenerated catalyst.
Essentially complete vaporization of the hydrocarbon feed occurs
rapidly and conversion of the feed at conversion conditions, includ-
ing the presence of regenerated catalyst, takes place as the mixture
passes upward through conduit 1 which extends vertically upward
through the bottom portion of reception vessel 6 ~nto disengaging
space 8 within reception vessel 6. Reaction products plus uncon-
verted feed, if any, pass out of conduit 1 via opening 7 located
at the upper end of conduit 1 into disengaging space 8 within re-
ception vessel 6. Some separation of hydrocarbon vapors and catalysts
occurs within disengaging space 6 because of the decrease in velocity
and the change in the direction of flow of the mixture of vapors and
catalyst. Separated spent catalyst drops down into dense bed 10 which
has an interface shown at 9. Hydrocarbon vapors and any inerts plus
any entrained catalyst in disengaging space 8 enter cyclone separation
means 12 through inlet 11 and catalyst and vapors are again separated
with separated catalyst passing downward toward dense bed 10 through
dip leg 13 and vapor passing out of cyclone separator device 12 and
out of vessel ~ through vapor conduit 17. Although Figure 1 shows
only one cyclone separation device 12, more than one such device
could of course be employed in parallel or series flow arrangements as
the volume and loading of the vapor stream and the desired degree of
separation dictate. Catalyst in dense bed 10 flows in a downward d;-
rection and passes through a lower necked-down section of vessel 6
Q76
over baffles 14 and is stripped of adsorbed and interstitial hydro-
carbons by a countercurrent stream o~ stripping medium, generally
steam, which enters the lower portion of vessel 6 through strip-
ping medium inlet means 15. Spent catalyst leaves vessel 6 through
spent-catalyst conduit 16 and passes ~o a regeneration apparatus
(not shown) wherein coke is oxidized from spent catalyst to produce
regenerated catalyst.
Hydrocarbon feed distributor 2 is shown in more detail in
Figure 2 which is an enlarged side view of a lower portion of the
apparatus of Figure 1. Riser conduit 1 has inside wall lA, outside
wall lB, center portion lC, flange lD and necked-down portion lE.
Distr~butor 2 is shown to have a cone-shaped component 2A having a
small diameter end connected to hydrocarbon-feed inlet means 3 and
having a large diameter end on which are located nozzles 2C which
have outlet means 2D. Hydrocarbon-feed inlet means 3 will typically
be joined to riser conduit 1 by flange lD. Also shown in Figure 2
is the preferred positioning of distributor 2 so that outlet means
2D of nozzles 2C are below regenerated catalyst inlet ~eans 4. It
is believed that the possibility of plugging of one of nozzles 2C
with coke, particularly at low hydrocarbon-feed velocities through
nozzles 2C as might occur on reduced throughput o~erations, will be
less when distributor 2 is thus positioned than if it were positioned
such that outlet means 2D were above regenerated-catalyst inlet means
4. Figure 2 shcws three nozzles 2D in side view; one center nozzle
and two outer nozzles. The center nozzle is positioned to direct
hydrocarbon feed exiting that nozzle vertically up into center portion
1~ of riser condui~ 1 and the outer nozzles are positioned so that
hydrocarbon feed exiting from those nozzles will i~pinge on inside
wall lA of conduit 1 downstream of outlet means 2D and preferably
g
llO~Q76
downstream of where regenerated-catalyst inlet means 4 enters con-
duit l. More preferably the hydrocarbon feed will impinge on inside
wall lA at a distance of 30.5 cm or more downstream of where
regenerated-catalyst inlet means enters conduit 1. ~ydrocarbon
feed velocity through no~zles 2C will be from about0-3to about 15.2
m/sec and more preferably from abou~-5 to about6.1 m/sec. Imping-
ing hydrocarbon feed from these outer nozzles onto inside wall lA at
these velocities breaks up the wall effect and reduces the wall tem-
peratures so that temperatures at any point on a horizontal cross-
sectional plane through conduit l become more nearly the same. The
beneficial consequences of reduced wall temperatures are reduced over-
cracking of the hydrocarbon feedstock and reduced yields of dry gas.
Ore preferred embodiment of feed distributor 2 is shown in
more detail in Figures 3 and 4. Figure 4 shows truncated cone 2A hav-
ing a small-diameter end and a large-diameter end which is fitted with
plate 2B. The diameter of the small-diameter end will be about the
same as that of the hydrocarbon-feed inlet means to which the small-
diameter end attaches and the diameter of the large-diameter end will
be such ~hat it will pass through the flange connecting the riser con-
duit and the hydrocarbon-feed inlet means and also pass through the
necked-down portion of the riser conduit. Plate 2B has a first circu-
lar hole passing through the center of the plate and has second circu-
lar holes passing through the plate and equally spaced around a circle
deseribed by a radius from the center of plate 2B. Cylindrical nozzles
2C have inlet means 2F which are inserted into the first and second
holes and have outlet means 2D through which hydrocar~on feed leaves
nozzles 2C and distributor 2. A first nozzle 2C is loca~ed in the cen-
ter of the plate and is positioned at a right angle with respect to
plate 2B, that is, a vertical centerline will pass through the centers
10~
l~OQ~6
of inlet means 2E and outlet means 2D of that center nozzle. Hydro-
carbon feed is thus directed un through this center nozzle up into
the center portion of the riser conduit. As illustrated in Figure
4, second nozzles 2C are arranged in the circle around the center
nozzle and are positioned such that a centerline passing through the
long axis of a second nozzle is inclined away from the center nozzle
at an angle "a" from a vertical centerline passing through the center
of an inlet means 2E of a second nozzle so that hydrocarbon feed pass-
ing through these nozzles will impinge on the inside wall of the riser
conduit downstream from nozzle outlet means 2D and more preferably 12
inches or more downstream of where regenerated catalyst inlet means
enters the riser conduit. Preferably angle "a" will be from about 10
to about 30. Although seven second nozzles are shown, there may be
from 3 to about 30 second nozzles so positioned on plate 2B. The
nozzles will be sized in both total number and inside diameter to ~ass
hydrocarbon feed at velocities of from about to about / and
1 .~
more preferably from about to about 6.1 m/sec,
Another preferred embodiment of feed distributor 2 is shown in
more detail in Figures 5 ~nd 6. Like Figure 4, Figure 6 shows truncated
cone 2A having a small-diameter end and a large-diameter end which is
fitted with plate 2B. In this embodiment however plate 2B has first
circular holes passing through plate 2B and equally spaced around a first
circle described by a first radius from the center of plate 2B and has
second circular holes passing through plate 2B and equally spaced around
a second circle, lar~er than the first circle, described by a second
radius from the center of plate 2B. Cylindrical nozzles 2C haYe inlet
means 2E which are inserted into the first and second holes and have
outlet means 2D through which hydrocarbon feed leaves nozzles 2C and
distributcr 2. First nozzles 2C are located on the first circle on the
1 1
76
p1ate and are positioned at right angles with respect to plate 2B,
that is, a common vertical centerline will pass through the centers
of inlet means 2E and outlet means 2D of each first nozzle 2C.
Hydrocarbon feed is thus directed through these first nozzles up
into the center portion of the riser conduit. Second nozzles 2C
are arranged around the second circle and are positioned such that
a centerline passing through the long axis of a second nozzle is in-
clined away from the first nozzles at an angle "a" from a vertical
centerline passing through the center of an inlet means 2E of a
second nozzle so that hydrocarbon feed passing through these nozzles
will impinge on the inside wall of the riser conduit downstream from
nozzle outlet means 2D and more preferably 12 inches or more down-
stream of where the regenerated catalyst inlet means enters the riser
conduit. Preferably angle "a" will be from about 10~ to about 30.
Although 5 first nozzles and 10 second nozzles are shown, there may
be from 2 to about 10 first nozzles and from 3 to about 20 second
nozzles. The nozzles will be sized in both total number and inside
diameter to pass hydrocarbon feed at velocities of from abouP-3to
about 15.2 m/sec.and more preferably from about to about6.1 m/sec.
Features common to my distributor in any of its embodiments
are that there be one or more first nozzles at ri~ht angles to plate
2B; that there be second nozzles positioned in plate 2~ such th~t
they are inclined away from a first nozzle and toward the inside wall
of the riser conduiti and, that the second nozzles ~e equally spaced
around a circle on plate 2B. First nozzles are positioned at right
angles to plate 2B to avoid dead space or regions of slow flow in the
center o~ the conduit. As previously explained, second nozzles are
inclined toward the inside wall of the riser conduit so that hydrocar-
bon feed exiting the second nozzles will impinge upon the inside wall
11~00~6
thus breaking up the stagnant boundary layers of hot catalyst near
the inside wall of the conduit and reducing the wall temperature of
the conduit. Second nozzles are equally spaced on a circle on plate
2B so that hydrocarbon feed from the second nozzles impinges evenly
around the inside wall of the riser conduit thus avoiding localized
high wall temperatures.
Materials of construction for building my distributor
shall be materials which are able to withstand the sustained
abrasive, high-temperature conditions found in the lower section
of a riser conduit. Specifically, metals such as carbon steel or
stainless steel are contemplated. Typically nozzles 2C will be
made out of schedule 80 to schedule 160 pipe and plate 2B and
truncated cone 2A will be made of 1.3 ~m steel plate. The top
surface of plate 2B will preferably be covered with 1.3 to 2.5 ~m
l~ of refractory concrete to provide additional abrasion resistance.
The present invention also contemplates a method of in-
jecting a hydrocarbon feed into contact with a fluidizable catalyst
in a catalytic conversion zone having a center portion and an inside
wall which comorises: passing a first portion of the hydrocarbon
feed through one or more first nozzles having a first inlet means
and a first outlet means, the nozzle being vertically positioned in
said conversion zone whereby the first portion is directed from the
first outlet means vertically up lnto the center portion; passing
a second portion of the hydrocarbon feed through multiple second
nozzles having second inlet means and second outlet means and posi-
tioned in the catalytic conversion zone so that a centerline passing
throu~h a long axis of a second nozzle is inclined toward the inside
wall of the conversisn zone at an angle from a vertical centerline
passing through the center of a second inlet means whereby the second
llOG076
portion exits the second outlet means and impinges on the inside wall
downstream of the second inlet means; and, contacting hydrocarbon feed
from the first and second nozzles with catalyst at conversion condi-
tions. In one embodiment the first portion of hydrocarbon feed will
be passed through a single first nozzle~ in another embodiment it will
be passed through multiple first nozzles. The first and second portions
of hydrocarbon feed will be passed through the first and second nozzles
at velocities of from- to about1s 2 m/sec and more preferably at velo-
cities from aboutl 5to about 6.1 m/sec. Preferably the second portion
of the hydrocarbon feed will exit the second outlet means and tmpinge
on the inside wall of the conversion zone at a distance of 30.5 cm
or more downstream of the second inlet means. The hydrocarbon feed
can be in liquid or vapor phase or in both liquid and vapor phase but
preferably it will be in liquid phase at a temperature of from about
177C. to about 371C. Hydrocarbon feed will contact hot catalyst
entering the conversion zone at a temperature of from about 621C. to
about 732C. Other conversion conditions within the conversion zone
will include a total pressure of from about atmospheric pressure to
about 7.8 atm. and a hydrocarbon residence ~ime of from about C.5 seconds
to 5 minutes and more preferably from about 0.5 seconds to about 2 minutes.
Conversion conditions may also include the presence of steam or other
vaporous material to aid in fluidizing the catalyst and to reduce the
hydrocarbon partial pressure whtch aids in the cracking reaction.
-14-
