Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HR-1251
V~POR-SOLID CONTACTING DEVICE
BACKGROUND OF INVENTION
This invention relates to vapor-solids contacting in a
fluidized bed, and more particularly, it relates to gas-liquid-
solids contacting in a fluldized bed in an ordered array devica
arranged to provide uniform h;ndered mixing and avoid agglomera-
tion of particulate solids in a reaction zone.
Fluidized beds are often used for contacting vapor and
particulate solid materials. Such devices have well-known
properties but the most important and significant is that the
fluid bed is normally a well-mixed bed of solid particles and
acts as a stirred tank reactor for chemical reaction purposes.
In the fluidlzed~bed cracking of heavy oils as described
in U.S. Patent No. 2,861,943 to~Finneran, there is disclosed a
multi-zone reactor having an intermediate zone for restricted
fluidiæation of a particulate carrier and stripping of adsorbed
hydrocarbons. This arrangement is illustrated in the attached
FIG. l, labelled "Current Practice" having two zones of fluidized
beds, which are each substantially isoth~rm~l but operate at
different temperatures. In this reactor, vapor passes upwardly
from zone 1 through a h;n~ered back-mixing zone comprising a
packed bed, and particulate solids pass downwardly from zone 2
through the hindered back-mixing zone into zone 1 countercurrent
to upflowing gas. This hindered, i.e., restricted zone, consists
of a bed of random packings using materials, such as Raschig
rings or spheres, supported on a grid plate having openings
smaller than the random packing material. A typical dense phase
fluidized bed exists in both zone 1 and zone 2.
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In some instances, the fluidized bed may be described as
a fast fluidized bed having high superficial gas velocity, such
as disclosed by Sc~uires in U.S. Pa~en~ 3,840,353. In this
arrangement, the general direction o~ the solids movement is
upward and solids are recirculated within the reactor to main-
tain the bed at an appropriate density. In this type bed,
there are some aspects of plug-flow behavior without any
stationary packing to provide hindered mixing of gas ancl solids.
The use of such stationary packed beds places undesirable
process restraints on those gas-solids cont~;ning processes in
which it i5 desired to provide a substantial temperature
difference across the packed bed, particularly processes for
upgrading heavy hydrocarbon feedstocks. Also, use of such
stationary packing material, for which the individual pieces
touch adjacent pieces, can cause localized agglomeration of the
particulate solids within or passing through and consequently
undesired plugging of the becl.
SUMMARY OF THE INVENTION
This invention provides a process for contacting particulate
solids with a gas within an ordered array packing zone. The pro-
cess comprises: (a) passing particulate solids through the
ordered array packing zone having multiple rows of stationary,
parallel members providing a void volume ranging from about 20
to about 80%; (b) passing a gas through the ordered array pack-
ing zone countercurrent to particuIa~e solids to fluidize the
particulate solids and to provide intimate contact between the
gas and the solids; and (c) maintaining a hindered mixing of the
solids and gas withi~ the ordered array packing zone to provide
a temperature of at least about 20F across the packing zone.
The particulate soli.ds may be passed either downward or
upward through the ordered array packing zone while the gas is
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passed countercurrent to or co-current with the flow of the
particulate solids. I'he particulate solids ha~e a diameter
of at least about 0.002 inches and the superficla]. velocity
of the gas ranges f.rom about 0.1 to ahout S.0 ft./sec. In
the process, the particulate solids pass through the ordered
array packing zone at a temperature of from about 850 to
about 1400F and the gas passes through at a temperature
ranging from about 1000 to about 1900F.
The invention also provides a reaction vessel which
includes an upper zone for containing a fluidized bed of
~articulate solids, a lower zone for containing a fluidizPd
bed of particulate solids and an intermediate packing zone
which consists of an ordered array packing zone of
stationary members separating the upper and lower zones and
providing a void volume ranging from about 20% to about 80%~
said ordered array of stationary, parallel members
comprising at least two rows of spaced, self-supporting
horiz~ntal members, the members in each row having different
horizontal spacing between the adjacent members. The members
which are stationary are fixed in horizontal rows which are
arranged at an angle of rotation between them of 0 to 90..
BRIEF DESCRIPTION OF DRAWINGS
FIG~ 1 is a schematic drawing of a prior art
configuration of a packed bed containing a fluidized bed for
gas-solids contacting;
FIG. 2 is several views illustrating typ~cal
construction features for an ordered array packing zone
according to the present invention; and
FIG. 3 is a schematic drawing illustrating a
multiple-zone reactor containing an ordered array packing
zone.
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DETAILED DESCRIPTION OF TH~ lNv4rl~lION
The vapor-solids contacting process of the present
invention is generally carried out in a reactor having two
reactor zones
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separated by an ordered array packing zone of stationary
parallel members for providing intimate vapor/solids contacting
and h1nd~red~ i.e., restricted, back-mix:Lng of the particulate
solids and gas passing through -the array. The arrangement of
the ordered array packing zone permits a temperature gradient
to be established between khe reaction zone and across the
ordered array.
In the ordered array packing zone the individual stationary
m~mh~rs are horizontally spaced apart from each other, preferably
by use of individual spacer elements. The members are usually
arranged in a plurality of horizontal rows, which can each have
variable cross-sectional shapes and spacing, the rows being
spaced vertically.
The reactor vessel in which the process is carried out,
has an upper and a lower zone which are separated by the packing
zone which consists of the ordered array of members. The solids
transfer in the reactor vessel can be upwardly from the lower
ZQne through the upper zone, or downwardly from the upper zone
through the lower zone, or there may be a net zero flux of
solids between the upper and lower zones.
The particulate solids contained in or transferred through
the ordered array packing zone can be catalytic or non-catalytic.
Also, the members of the ordered array packing zone may contain
catalytic materials. Such catalytic materials would be selected
to provide a typical chemical reaction desired. As an example
of such a chemical reaction, a gas from the lower zone might
consist of a synthesis gas cont~1n1ng C0, H2, H20, and a catalyst
could be incorporated in or coated on the members of the packing
zone to cause the reaction equilibrium to shift towards producing
more hydrogen. Thus, the hydrogen might then be more useful in
the upper zone.
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As illustrated in FIG. 3, the entire reactor might consist
substantially of sta~ionary packing so that zone 1 and zone 2 are
reduced to near zero volume. The entire reactor would then con-
sist essentially of a fluidized bed in an ordered array in which
gradients could be obtained. Therefore, a fluid bed reactor
would be provided having a gradient through it so as to obtain,
for example, better yields of reacted products.
The present invention provides a novel reactor design con-
figuration whereby a fixed bed of packed material is used in an
ordered array configuration and vapor and solid particles are
placed in intimate contact therein. The solid par~icles as well
as being catalytic or non-catalytic, may be absorptive or non-
absorptive.
This type of reactor system using an ordered array permits
a fluid bed of solids to be used and to obtain intimate contact
between the vapor and the solid particles. At the same time, it
pennits gradients to exist within the bed which include tempera-
ture, co~centration, solids age, and the solids dimensions,
ei~her specific gravity or diametexs. Because the solids
particles are in constant random motion, they may be added to or
withdrawn from the ordered array at any point, or withdrawn from
above or below the packing zone~
According to the present invention, various characteristics
of ~he ordered array packing zone can be advantageously altered
to suit specific applications. The e characteristics include the
shape of ~he packing zone members which may be a circle, a square,
a diamond, a rectangle or a triangle, or any other suitable geo-
metric shape, the horizontal spacing between the packing members,
and the vextical spacing between the rows of the members. The
si~s of the members are additional factors of variability, as is
the angle o~ rotation between rows a further design variable. The
members may be solid, hollow, have a roughened surface or be
finned.
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Referring to FIG. 2, there are shown several construction
features for an ordered array packing zone according to the
present invention. In this fiyure, there iS illustrated two rows
of rods arranged at an angle of rotation bel:ween them of 90~
The rows of members, e.g., rods, may be arranged at an angle
of rotation between them of O to 90. Supports for the packing
zone members might be braced on shelves from the vessel wall or
can be supported directly from horizontal beams provided in the
raactor. Rows of members may be supported on saddles which
would maintain the internal dimensions of the packed array.
The appropriate choice of variables in the ordered array permits
a wide range of packing void fractions to be achieved, such as
a void volume ranging from about 5 to about 95~, and preferably
from about 20 to about 80%.
As shown in FIG. 3, the members, e.g., rods, are extended
completely across the reactor vessel, which eliminates the need
for a grid beneath the ordered array of members. Each member,
e.g., rod, being self-supporting permits a broader span to be
handled with a given material and operating temperature.
Moreover, the dimensions and spacing of the members, e.g.,
rods, should be such that the fluidized solid particles will
readily pass through them. The ordered array of members may be
arranged to gradually increase the vertical spacing between
adjacent rows of the members, e.g., rods, from the top to the
bottom, thereby assuring that any particulate solids which enter
the ordered array packing zone will pass on through.
Different sections of the ordered array might have different
purposes. As illustrated in FIG. 3, Part A, which is immediately
above the gasification or lower zone 1, could be designed to
withstand high temperatures. In this zone, a packing material
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having high mechanical strength in relation to i-ts weight would
be used. Such a section o~ specially designed material would
permit the hot gases from zone 1 to be cooled prior to entering
the ordered array packing zone. In Part B, the rods might, for
example, have a vertical spacing such that each rod is self-
supporting and no rod could sag enough to touch another.
In Part C of the ordered array, the vertical spacing
between members, e.g., rods, might be reduced to near zero. By
doing this, all of the members could act together to support the
weight of a slumped bed from zone 2.
The advantages of the invention described herein will be
further illustrated by the following example which should not be
construed as lLmiting in scope.
EXAMPLE
An ordered array according to the present-in~ention is con-
structed which consists of three rows of horizontal rods,
2.0 inches in diameter, and arranged in a staggered triangular
pitch pattern of about 2.6 inch center to center spacing. The
rods are separated by angular-shaped spacers or washers circum-
ferentially mounted on the rods to provide a void volume of about
50%. The rods are supported by structural beams attached to the
reactor inner wall, to provide an array of about 8 feet diameter
by 4 feet deep. The packed array contains a bed of inert
?articulate solids such as a clay or an alumina having a particle
~ize ,~ 0 005-0.050 inches which are fluidized by a hot reducing
-;;.s s;is~ina apwardly through the ~ed. Particulate carrier solids
-ontalning coke deposits with some hydrocarbon liquid on and
withln the particles pass downwardly through the array counter-
current to the upflowing gas. The particulate solids enter the
ordered array at the top at about 1000F and exit the ordered
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entering the array. The gas enters the ordered array at the
bo~tom at about 1800F and exits the ordered array at the top
a temperature slightly higher than the particulate solids enter-
ing the array. The pressure is about 40() psig. In the ordered
array, the particulate solids are fluidized by the upflowing
reducing gas and the hydrocarbon liquid is stripped off the
particulate solids. The particulatesolids then pass downwardly
into the lower zone for combustion and gasification of the
carbon deposits.
