Note: Descriptions are shown in the official language in which they were submitted.
~ Z54~720 61936-1686
MET~IOD AND APPARATUS FOR
UNIFORMLY LOADING
PARTICULATE MATERIAL INTO
CYLINDRICAL BEDS
Fièld of the Invention
. .
The present invention relates to a method of, and
appara-tus for, uniformly loading particulate material into a
cylindrical bed or vessel. More particulary, it relates to
Catalyst Oriented Packing (COP) loading of catalytic reaction
beds by uniformly distributing catalyst particles, or the
like, over a large diameter cylindrical vessel by simultaneously
flowing catalysts into multiple concentric rings of catalyst
particles over the full circular area of the catalyst bed.
The invention is primarily directed to assuring that catalyst such
as cylindrical extrudate catalyst having a high angle of repose,
will pack uniformy in a bed with a high ratio of catalyst to
volume.
It is the particular object of the present invention
to increase the packed density of particles having a high angle
of repose, including spheroidal particles, so that the bed is
simultaneously formed by a plurality of concentric rings across
the ful] diameter of the vessel. Multiple rings of particles,
such as catalyst, are formed by uniform rotation of a single
rotary disc or rotor which divides the catalyst flow from an
overhead flow pipe into a multiplicity of radial segments, such
segment having different radii. The resulting exit velocity of
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catalyst particles from each segment or sector of the disc dis-tri-
bution surface createsa plurality of different radial throw
distances within the bed or vessel. Sin~e all segments of
the disc turn at the same speed, concentric rings of catalyst
are cast into the vessel so that they simultaneously settle into
adjacent annular rings. Such annular rings are desirably
relatively narrow in radial width, but of progressively
different radial distances from the axis of the vessel to form
a multiplicity of concentric rings to cover the catalyst bed
uniformly.
BACKGROUND OF THE INVENTION
Catalytic reactor vessels having one or more fixed
catalyst beds are now commonly filled by using a catalyst
distributor. Su~h a technique is known as Catalyst Oriented
Packing (frequently referred to as COP loading) and is
particularly useful to produce uniformity in the permeability and
overall density of the catalyst bed. In current catalytic
processing, catalyst particles are generally manufactured by
extrusion in the form of cylindrical rods of 1/16" to 1/4"
diameter. The rods are then broken into 1~4" to 1/2" lengths.
Such extrudates are typically formed of alumina, silica-alumina
or synthetic or natural zeolitic materials and are substantially
less expensive to produce than spherical catalyst. However,
such extrudate particles have a high angle of repose; the angle
at which a free standing pile of material is stable. Consequently,
they are difficult to distribute evenly over a large diameter
cylindrical vessel. Further, due to differences in size of such
\
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particles, as well as chipping and breaking during both
manufacture and loading into a process reactor, they tend
to "classify" or separate if the bed is filled by gravity alone
from a central point in the vessel.
The primary purpose of COP loading is to minimize void
spaces and consequently local "hot spots" which can occur during
exothermic reactions of hydrocarbons with the catalyst particles.
Additionally, increased packed density of the solid particulate
material, catalyst particles, improves the flow distribution
of reactants wIthin the vessel. Further, increased bed density
limits settling of the bed when the reactor is brought on stream
and subjected to hydraulic forces by fluid flow through the
reactor. In general, the amount of catalyst can be increased
several percent in an existing vessel. Conversely, several percent
less reactor volume is required for the same amount of catalyst in
a new vessel.
In general, previously known catalyst oriented loading
apparatus included a distributor disc having a uniform diameter
~nd a plurality of radial blades or fin members on top of the
rotating disc. In general the distributor is either a cone
shaped member or a flat circular plate. However, the speed of the
distributor must be varied in order to distribute catalyst across
the entire cross-sectional area of the bed, since the distance
the catalyst is thrown is proportional to the disc speed. Where
the disc is a flat plate having vanes formed thereon, a few holes
are formed in the plate so that some of the catalyst particles fall
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directly downwardly through the rotating member toward the center
of the reactor vessel.
U.S. Patent 3,804,273 Uhl is directed to apparatus
for loading a catalyst bed with a radial distributor having a
single conical surface. The only method of distributing
catalyst across the full bed diameter is to increase and decrease
the speed of the rotating disc.
U.S. Patent 3,972,686 Johnson et al, discloses a flat
disc having vanes and a plurality of slots or holes through
which some of the catalyst may fall near the center of the bed;
the remainder of the catalyst is thrown toward the vessel side.
This system also requires variation in the speed of the rotating
disc to load catalyst so that it covers the entire level of a
catalyst reactor bed.
A particular disadvantage of such prior arrangements
lies in the fact that at one speed the catalyst is thrown into
a circular or annular mound which tends to classify catalyst
particles falling on it. The larger particles roll to the botton
and outside of the mound while the smaller particles stop on the
mound itself. While to a certain extent, these difficulties are
alleviated by varying the speed of the rotating disc, slo~/ing disc
speed significantly increases the loading time for the reactor bed,
because loading rate is proportional to such speed. On the other
hand, excessive speed of the disc results in catalyst flying
of the disc without sufficient residence time thereon to control
the radial throw distance. Further, it is difficult to control
disc speed to achieve a desired radial throw distance because
1~5~2V 61936-1686
the interior of such a bed is usually too full of dust to permit the
operator to actually see the catalyst bed from the loader. Accord-
ingly, lt is necessary to determine the probable level of distri-
bution by the number of drums of catalyst that have been loaded at a
given bed level. Such a procedure is time consuming and not
necessarily accurate enough to permit level filling of the bed. In
fact, it is general practice to fill the bed at the outer edge
higher than necessary say 6 to 12 inches and then alternately
increase the height of the center level above that at the outer edge
by a similar amount, and 50 forth, up the reactor as the depth of
the bed or beds is increased throughout the reactor. The problem is
further aggravated where the vessel contains several separate beds,
each supported by a separate support "screen" and the lower beds
must be filled through accessways in the center of the overlying
bed support. Visual inspection is thus made more difficult.
U.S. Patent ~,306,829 Loutaty et al disclose a distribu-
tor for catalyst particles in a reactor or grain storage in a silo.
The distributor includes flexible straps pivotally supported by
hooks along the length of a drive shaft. The straps may be formed
of reinforced rubber and are either of equal length or progressively
longer away from the feed hopper discharge. The examples indicate
t.he system to be satisfactory for filling a model of reactor vessel
60 cm (about 2 feet) in diameter. It appears that the active
lengths of the rotating straps vary in diameter with the speed of
the drive shaft and their interaction with falling catalyst
particles. Efficient loading of vessels with each of
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the above noted arragements has been limited to relatively
small diameter xeactors, for reasons noted above.
U.S. Patent ~1433~707 - Farnham, assigned to the
assignee of the present invention, discloses a method and
apparatus for uniformly filling a reactor vessel at each level
with an even distribution of catalyst particles from the center
of the vessel to its outex wall by using a plurality of discs
of differing diameters rotated at the same speed by a single
drive shaft. Desirably, three conical discs are used with the
largest diameter nearest the supply hopper feed tube. The upper
discs include a central openings to permit catalyst to be fed to
each of the lower discs. Because the discs are of different
~iameters each spreads catalyst to a different area around the
vessel with the drive shaft rotating at constant speed. Such a
system is quite satisfactory for delivery of catalyst to vessels
Of smaller diameter and deep beds,where adequate "head" room is
available at the top of the vessel or above each of several beds.
However, the method is also limited to laying down only a few
annular rings simultaneoulsy, without changing rotor speed.
Federal Republic of Germany patent 2,703,329 issued
March 1978 discloses another particle loading system using a~ially
spaced multiple discs rotated by a common drive shaft. The mode of
operation is similar to the above-noted Farnham pa-tent.
SU~ARY OF THE INVENTION
In carrying out the method of the present invention,
a single catalyst distributor is positioned at a suitable level
above a bed to be filled. Catalyst is then supplied to the
l~S~
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distributor from a hopper having a feed tube positioned so that
a substantially cylindrical column of catalyst falls on the
sinyle rotor or disc member.
Catalyst particles are then distributed by the single
disc across the full diameter of the bed with substantially
uniformly high density by forming a multiplicity of annular rings
of catalyst concentric with the center of the vessel or bed.
Such action is achieved without varying the disc speed by
deflecting the cylindrical column of catalyst into a plurality
of arcuate sectors or portions of different radial lengths on
the single rotating disc. Preferablyr each arcuate portion has
a volume proportional to one of the annular areas of the bed
within the cross~sectional area of the vessel. The desired
volume is formed by both the radial length of the arcuate
sector and its included angle on the disc. In a preferred form
of the disc, each adjacent arcuate sector or portion desirably
has a different volume to form such annular rings of catalyst
in the bed with substantially equal widths.
Dependin-g upon the overall cross-sectional area of the
vessel, the cylindrical volume of catalyst flowing from the feed
tube may be divided into an outer annular column and an inner
cylindrical column. In a preferred embodiment this may be done by
a frusto-conical member extending upwardly and inwardly into the
feed tube from the r.lain di~tribution surface of the disc. The
major base of the conical member and the main disc form an
auxiliary hopper or storage volume which supplies catalyst to
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another plurality of separate arcuate flow paths of different
radial lengths at substantially right angles to -the column.
Each of such other plurality of flow paths is also rotated by
the single rotor or disc. Desirably, each of these flow paths
is shorter than the radius of any of the arcuate portions
formed by the disc above.
By uniformly rotating the disc each of the plurality of
arcuate flow paths lays down a concentric annular ring of
different diameter. These rings substantially cover the
surface area of the catalyst bed support in the vessel with
catalyst. Because each ring is formed simultaneously, at all
levels, the depth of catalyst is uniform across the full vessel or
bed diameter and the resulting catalyst bed has a higher
average density for the same vessel or bed volume.
Furhter objects and advantages of the present invention
will become apparent to those skilled in the art in light of the
following detailed description of the preferred embodiments of
the invention taken in conjunction with the drawings which form
an integral part of this specification.
BRIEF DESCRIPTION OF THE DRAWINGS
-
In the drawings:
Fig. 1 is an elevation view partially in cross-section
through a large diameter hydrocarbon reactor and illustrates the
method of the present invention using a single rotor distributor
to lay down a plurality of concentric rings of catalyst to form one
l~S4~;20
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of several beds within the vessel;
Fig. 2 is a cr`oss-seetional plan view, taken
in the direction of arrows 2-2 in Fig. 1, illustrating
the concentric rings of catalyst particles being east by the single
rotor distributor of the present invention;
Fig. 3 is a p]an view of the primary eatalyst
distributor rotor shown in Fig. 1, partieularly illustrating
a preferred arrangement of radial lengths and areuate spans
required for laying down a plurality of eoneentrie circles of
catalyst particles of similar depth, as shown in Fig. 2;
Fig. 4. is an elecation cross-sectional view
through the rotor of Fig. 3 taken in the direction of
arrows 4-4 and also illustrates the eooperation of the
conical portion of the rotor to divide flow from the
hopper feed tube to the upper distributor plate and the
lower distributing ehannels earried by the rotor;
Fig. 5 is a plan view taken in the direction
of arrows 5-5 in Fig. 4, partially in eross-section,
through the lowe portion of the rotor assembly whieh
illustrates the distribution of eatalyst to the multiple
tubes and distribution holes, partieularly useful in
filling the inner annular rings of a large diameter
vessel;
iZ$4'~20
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Fig~ 6 is a plan view, taken in the direction of
arrows 6-6 in Fig. ~ of the lower distribution assembly and
particularly illustrates further distribution by the lower
plate for simultaneously filling the innermost portions of a
catalyst bed; and
Fig. 7 is an exploded view of the rotor assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
OF T~IE INVENTION
Fig. 1 illustratesapplication of the method of
the present invention to oriented catalyst loading in a large
diameter catalytic reactor vessel 10 using a preferred form of
catalyst loading apparatus 12 to lay down concentric rings of
catalyst particles. As indicated in Fig. 2, such a plurality of
concentric rings 14 or similar annular width, or average radial
length, simultaneously cover the full diameter or vessel 10 to
fill bed 16 with catalyst to equal depths and density across
the full diameter. Such method is particularly directed to
loading catalyst having a high angle of repose, such ascylindrical
extrudate particles of catalyst which are relatively immobile
after deposition.
As particularly shown in Fig 1, vessel 10 may include
a plurality of beds 16, each formed on a catalyst support
structure or screen 18. As indicated, a plurality of support
structures 18 may be provided so that each of the several
serially interconnected flow beds 16 is located one above the
other. To assure that each of beds 16 is filled with uniform
i;~S~7Z~
10 - 61936-1686
density throughout its height or depth it is also important
that the axial length of the catalyst distribution apparatus
be rela~iuely short so th~t the top of the bed, beneath upper
support structure 18, or the top of vessel 10, may be ~illed as
full as possible, with little or no headroom above catalyst
bed 16. For this reason, the catalyst distribution rotor
member 20, constructed in accordance with the present invention,
includes a primary distribution surface formed by plate 22 that
is divided into a plurality of arcuate sectors or segments 24
having a common vertex at the rotational axis 30 of disc member 22.
~ut as shown, for dynamic rotor stability each segment or sector
has a different radius than either of its adjacent sectors. As
indicated desirably two equal area segments are located diametric-
ally opposite to each other to balance the rotor dynamically.
In the particular embodiment shown in Figs. ~ and 4,
radial rib members 26 form sectors 24 and have different radial
lengths as indicated. Rib members 26 extend axially away from
and generally perpendicular to the distributing surface of plate
22. It is also to be particularly noted that individual sectors
or segments 24 have different included angles and that such angles
together with the depth of ribs 26 determine the total volume of
catalyst that may be thrown to each ring on the surface of bed 16.
It will, of course, be understood that the total volume of each
individual sector or segment is proportional to the area of the
corresponding catalyst ring 14 to be cast on top o~ bed 16~ In
general such volumes of the sectors 24 will be proportional to the
:~2~4'72V
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circumferential areas of the rings and the width of each ring
relative to adjacent rings formed by other sectors or segments 24.
As particularly shown in Fig. 4, catalyst is supplied
to the distribution surface formed by plate 22 and individual
segments 24 by a feed tube 28 having an axis 30 which is
substantially coaxial with the drive shaft 32 to which the
distributor plate 22 is attached as by hub 34 and key or drive pin
36.
As illustrated in Fig. 1, the distribution system of
the present invention may be used with conventional catalyst
oriented packing apparatus. As there seen, hopper 38 is loaded
with catalyst and by gravity feeds catalyst through supply tube 40
to lower feed hopper 42. Hopper 42 maintains a constant head
cf catalyst above distribution disc 20 and preferably is
supported~ as by pivoted arms 49, over manway 44 formed in upper
grid 18, or on upper flange 46 of vessel lO. Rotary disc 20 may
then be driven by a local air, or electric, motor 48 mounted on
lower hopper 42 to drive shaft 32 and rotor 20 at the desired
speed. Drive motor 48 may be through an air hose, or electric
cable, 50. Alternatively, shaft 32 may be rotated by extending
drive shaft 32 above flange 46 to an external motor (not shown).
A particular problem in the distribution of catalyst
in large diameter vessels is to get even catalyst distribution
near the center of the vessel. To lay catalyst evenly across the
full diameter of a vessel of, say of 8-15 feet, including the
center portion, is quite critical. Merely dumping catalyst
- 12 - 1 ~ S 47 2 0 61936-1686
through the center of the distributor plate and allowing it
to spill outwardlv from a center heap is quite unsatisfactory.
In accordance with the preferred embodiment of the present
invention this problem is solved by -the use of a plurality of
rectangular tubes or channels 52, 54, 56 and 58, each of different
radial lengths. As best seen in Fig. 5, these channels, together
with plate 60 supported on lower collar 62, provide additional
annular catalyst distribution rings. Plate 60 is supported below
collar 62 by a plurality of threaded studs 64 and nuts 66 which
permits plate 60 to be properly spaced relative to ~lange 68 of
collar 62. Plate 60 itself serves as a further distributor of
catalyst through the action of radial bar 70 carried on its top
surface. A suitable port 72 radially spaced from the axis
of rotation of plate 60 controls the amount of catalyst permitted
to flow to the innermost ring.
While not shown in detail, it will be understood that
feed tube 40 is adjustably positioned relative to the conical
surface of frus-to-conical disc 86 so as to proportion the amount
of catalyst that flows annularly to multiple sectors 24, as
compared to the amount of catalyst that flows cylindrically over
the upper and inner edge 87 of disc 86. Chamber 88 formed by
frusto-conical section 86 and plate 22 then serves to distribute
catalyst to tubes 52, 54, 56 and 58 and plate 60. Similarly, the
opening between 60 ard collar 68, as noted above, controls the
total catalyst flow fromthe edge of plate 60, with the aid of
bar 70, and through orifice 76.
il~S~72~
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As best seen in ~i~g. 5, the supply of catalyst
:Elowing in the internal cylindrical portion from feed tube
40 flows to the four rectangular tubes 52, 54, and 58 through
square openings 84 in plate 22 while catalyst passing to
distributor plate 60 passes through four circular openings 90 also
formed in plate 22.
By forming tubes 52, 54, and 56, and 58 with different
radial lengths, each shorter than any of the radial paths
of the sectors 24, the inner diameter rings or annular portions
of the catalyst bed are filled simultaneously as catalyst is being
thrown by sectors 24 to the outer portions of the bed or vessel.
Also, at the same time catalyst passing through openings 90 is
selectively laid down at the innermost part of the bed by
control of the spacing oE plate 60 from collar 68 and the radial
placement of bar 70 and the~ size of orifice 76. In the present
embodiment it will accordingly be seen that a single rotor makes
possible distribution of catalyst to a multiplicity of bands
which in the present embodiment form sixteen separate rings
comprising then laid down by arcuate segments 24, four laid
down by tubes 52, 54, 56 and 58 and two by plate 60.
In the present arrangement collar 62 and plate 60 are
disconnectably connected to distribution plate 22 by screws 80.
Tubes 52, 54, 56, and 58 are formed as a permanent part of plate
22. Alternatively, the entire rotor assembly may be made
as one piece, or other portions permanently connected or
disconnectably connected to distributor plate 22. It will also
~zs~zv
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be apparent to those skilled in the art that plate 22 may be
conical rather than flat, if desired.
Because the single catalyst distribution disc or
rotor includes a multiplicity of flow paths, each arranged to
lay down concentric annular rings of limited, but approximately
e~ual radial width, across the entire circumferential area, of
vessel 10, the rotor is preferably turned at a constant speed.
The speed is re~ulated to such a constant value, determined by the
bed diameter, so that the rotor will cast catalyst over the
entire cross-sectional area of the vessel. Once adjusted, that
speed is maintained substantially constant for complete filling
of each bed from support 18 to the top of the bed 16. Such
uniform laying of the bed throughout its dep-th results in
increased density of the total catalyst volume that can be loaded
into an individual bed or throughout the vessel. In actual
practice, an increase in density of about 106 has been found, as
determined by the total weight of catalyst that can be loaded into
a known volume of the vessel, as compared to prior methods of
COP loading, using varying speeds of a rotatable disc. Since the
conversio.n rate of hydrocarbon feed passing through the vessel
is dependent upon such total volume of catalyst, the present
invention makes possible either a higher rate of hydrocarbon
feed through the reactor for yield of the same products or an
increased hydrocarbon conversion at a constant feed rate in the
same volume of vessel. Both of these conditions are greatly
- 15 - ~ ~ ~ 4 ~ ~70 61936-1686
desirable in processing hydrocarbon feeds for catalytic
conversion and represent significant cost savings in such
processing.
The above described embodiments of the inventi.on are
particularly directed to loading extrudate catalyst particles
across the full cross-sectional area of a large diameter reactor
vessel. However, the method and apparatus are also applicable to
load other particulate material, such as spherical or pellet
catalyst or grain, as in a silo. Other contacting materials in
particle form, such as sulfur sorbers, and ion exchange materials
are also frequently loaded in large diameter vessels. The present
invention is particularly useful for such service to insure high
density throughout a bed of solid particles in a large diameter
vessel.
From the foregoing description, various modifications
and changes in the apparatus and in the method of operating such
apparatus will occur to those skilled in the art, all such
modifications or changes coming within the scope of the appended
claims are intended to be included therein.
` ~'J
