Note: Descriptions are shown in the official language in which they were submitted.
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RANDOM PACKING
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to techniques for
enhancing exchange processes between two fluids. More
particularly, the present invention relates to packing
elements for use in exchange process chambers, such as are
utilized in mass transfer or heat exchange processes, for
example.
2. Description of Prior Art
Many commercial and chemical processes involve mass
transfer (exchange) or heat exchange, and utilize packed
columns or chambers to carry out the steps. Such processes
can include distillation, absorption and desorption, gas
cleaning and drying, scrubbing and various biological
processes, such as filtrations. Two fluids, usually a gas and
a liquid, although two liquids may be utilized, are
intermingled within a chamber, typically as counter-current
flow streams wherein the two fluids move generally in opposite
senses along the same flow axis. In a co-current system, the
two fluids move generally in the same sense along a single
flow axis; a cross-current facility features the two fluids
moving along separate, intersecting flow axes.
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The mass transfer rates and/or the reaction rates of the
processes increase with increasing amounts of effective
surface area that can be wetted by liquid within the chamber
and over which the two fluids can then interface with each
other. Packing elements are placed in the chamber to increase
the amount of surface area available for such interfacing.
Packing systems are generally of two types, depending on the
packing elements and their arrangements in the transfer
chamber. Structured packing systems generally include
extended, structured packing elements that are arranged within
the chamber. Random packing systems comprise generally small,
individual packing elements which may be dumped into the
exchange chamber in a random array. Packing is generally
included in exchange process columns to enhance the
interaction between two fluids in the column, thereby
increasing the efficiency of the process. Where at least one
of the fluids is a liquid, the interaction between the fluids
may be so enhanced by providing sufficient surface area to be
wetted by the liquid, and providing drip points from which the
liquid may pass from one surface to another while being
further exposed to gas as the other liquid flowing between the
surfaces. If the surfaces provided by the packing are too
tightly-arranged, the gas may experience sufficient flow
resistance to hamper movement of the gas through the packing,
thereby diminishing the opportunity for exposure of the liquid
to the gas. Poorly designed random packing elements may
feature significant mutually-complementary structures so that
one such element may fit relatively tightly against another,
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or even extend within the lateral extent of the second
element. Such nesting of random packing elements may produce
a relatively tightly packed array of surfaces, producing
significant gas flow resistance. Further, where the liquid
flow surfaces are too tightly packed, liquid may bridge from
one surface to another without dripping. Not only does such
bridging diminish the interaction cross section with the gas,
but it may also further impede the flow of gas through the
packing.
The present invention provides random packing elements
which avoid the aforementioned disadvantages of poorly-
designed packing elements.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a
random packing element that will enhance the possibility of
interaction between two fluids in an exchange process chamber,
for example. The exchange process interaction may be so
enhanced by a packing element of the present invention
providing an arrangement of flow surfaces that are wettable by
at least one of the fluids as a liquid, for example, with the
surfaces appropriately separated to reduce flow resistance
therethrough by another fluid as a gas. It is a further
object of the present invention to provide an abundance of
drip points from the flow surfaces, with the drip points
sufficiently separated to minimize bridging of liquid from a
drip point to another flow surface. It is a still further
object of the present invention to minimize nesting of
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multiple such packing elements in a packed bed in an exchange
process chamber.
The present invention provides a random packing element
for use in exchange process apparatus involving at least two
fluids, with the packing element made from a generally planar
sheet of material that is separated into a plurality of strips
and projections, with the strips generally bowed to opposite
sides of the material such that the packing element has no
rotational axis of symmetry perpendicular to the original
plane of the material. The packing element may provide
attachment areas at both opposite ends of the material to
which strips and projections are attached. Attachment areas
may be provided intermediate the ends of the material, with
strips attached to such intermediate attachment areas;
projections may also be attached at such intermediate
attachment areas. The projections, or fingers, provide drip
points. Additionally, edges of the projections and/or the
strips may be serrated to provide drip points. The serrated
edges serve also to avoid nesting of multiple such packing
elements. Two strips extending between the same two
attachment areas may cooperate to form a closed loop. The
projections in particular may be of different lengths. The
strips in general may each have different shapes and/or
different positions relative to the original plane of the
sheet of material. The strips and projections, for example,
may be thus extended toward opposite sides of the material to
ensure the lack of rotational symmetry of the packing element
about an axis perpendicular to the original plane of the
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sheet. Additionally, the pattern of extensions of the strips
and, possibly the projections as well, may be such that the
lateral extent of the packing element perpendicular to the
original plane of the sheet of material may provide a net
skewed effect, or incline, so that the packing elements may
settle predominantly in inclined positions in a packed bed in
an exchange process chamber, for example. The packing element
may be made of metal or any other appropriate material, such
as plastic, which may be utilized in a particular exchange
process application, for example. A metal sheet, for example,
may be slit and then deformed from its original planar form to
bow the resulting strips and extend the resulting projections,
for example. The original slitting of the material may be
made with saw-tooth patterned cuts to provide serrated edges
along the strips and projections, for example. Alternatively,
serrations may be formed as a separate step, for example, such
as during the extending of the bows and strips.
The present invention provides a random packing element
which includes liquid flow surfaces appropriately separated to
provide minimal gas flow resistance through the random packing
element. Drip points are also provided to further enhance the
interaction possibilities between the fluids in the exchange
process application. A random packing element according to
the present invention also minimizes nesting among such
packing elements to further ensure minimal flow resistance to
gas through a bed made of packing elements according to the
present invention, and to ensure an abundance of drip points
from appropriately separated flow surfaces.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a top plan view of a planar sheet of material,
slit to define a plurality of strips and projections;
Fig. 2 is a side elevation of a random packing element
according to the present invention, formed from the slit sheet
of material of Fig. 1;
Fig. 3 is an end elevation of the packing element as
formed in Fig. 2; and
Fig. 4 is a perspective view of the packing element of
Figs. 2 and 3.
DESCRIPTION OF PREFERRED EMBODIMENTS
A generally-rectangular, planar sheet of material is
shown generally at 10 in Fig. 1; the material 10 is shown in
Figs. 2-4 formed into a random packing element according to
the present invention. The material 10 may be metal or some
other material, such as plastic. In general, the material 10
is provided with slits that define a plurality of strips and a
plurality of projections, which are shaped to deform the
planar material as illustrated in Fig. 1 into a three-
dimensionally-extending figure as illustrated in Figs. 2-4.
As may be appreciated by reference to Fig. 1, wherein the
sheet of material 10 is illustrated in its planar form, the
particular embodiment of the packing element illustrated
herein is constructed from a sheet of material whose length is
on the order of approximately two and one-half times the width
of the sheet. The slits are shown extending generally
lengthwise relative to the dimensions of the sheet 10 to form
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the strips and projections. All of the lengthwise slits
provided in the material 10 are saw-toothed to provide
serrated edges. A strip is a generally elongate portion of
the sheet of material which is attached at both ends of the
strip; a projection, or finger, is considered to be a
generally elongate portion of the sheet of the material
attached at only one end of the projection. It will be
appreciated, however, that, in any given case, the extent of
the projection away from its attached end may be greater than,
equal to or smaller than the extent of the projection measured
along the attached end of the projection. The region where
one or more strips and/or one or more projections may be
attached to the sheet of material may be referred to as an
attachment area. Consequently, a strip extends between two
attachment areas, and a projection extends from one attachment
area.
In the particular embodiment of the present invention
illustrated herein, none of the slits extends through either
end of the material 10. Consequently, a laterally-extending
end attachment area 12 is provided at one end of the material,
and a laterally-extending end attachment area 14 is provided
at the opposite end of the material. If a slit would extend
through the end of the material, then the end region of the
material would be broken into at least two attachment areas.
A single, saw-tooth slit 16 extends generally along the
center line of the material 10, from one end attachment area
12 to the other end attachment area 14. The slit 16 generally
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divides the material into two portions, as may be appreciated
particularly by reference to Figs. l, 2 and 4.
At the midpoint of the top half of the sheet of material
as viewed in Fig. 1, a laterally-extending, intermediate
attachment area shown generally at 18 is unbroken by any
slits. Similarly, a laterally-extending, intermediate
attachment area shown generally at 20 is provided about the
midpoint of the bottom half of the sheet of material 10 as
illustrated in Fig. 1.
In the upper half of the material as viewed in Fig. 1,
two parallel saw-tooth slits 22 and 24 extend from the end
attachment area 12 to the intermediate attachment area 18, and
two parallel saw-tooth slits 26 and 28 extend between the
intermediate attachment area 18 and the end attachment area
14. A laterally-extending slit 30 extends between the two
slits 22 and 24, and a laterally-extending slit 32 extends
between the two slits 26 and 28.
The slit 22 cooperates with the outer edge of the sheet
of material 10 to define, in part, a strip 34 which extends
between the end attachment area 12 and the intermediate
attachment area 18. The slit 24 cooperates with a portion of
the slit 16 to define, in part, a strip 36 extending between
the attachment areas 12 and 18 as well. The two slits 22 and
24 provide a projection 38, which ends at the slit 30 and is
attached, between the strips 34 and 36, at the end attachment
area 12. Similarly, a projection 40 is formed to extend from
the intermediate attachment area 18 to the slit 30, bounded
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also by the slits 22 and 24. The strips 34 and 36 are
mutually parallel in the configuration of Fig. 1.
The slit 26 cooperates with the outer edge of the sheet
of material 10 to define, in part, a strip 42 which is
generally aligned with the strip 34 in Fig. 1. The slit 28
cooperates with a portion of the slit 16 to define, in part, a
strip 44 which is mutually parallel with the strip 42 and
generally aligned with the strip 36 in Fig. 1. Both of the
strips 42 and 44 extend between the attachment areas 14 and
18. The slits 26 and 28, as well as the slit 32, cooperate to
form a projection 46 extending from the end attachment area
14. The slits 26 and 28, as well as the slit 32 also
cooperate to form a projection 48 extending from the
intermediate attachment area 18. The projections 38, 40, 46
and 48 are generally aligned in Fig. 1.
A similar construction of strips and projections is
provided in the lower half of the sheet of material 10 as
viewed in Fig. 1, again provided by an array of slits, most of
which are illustrated as saw-tooth in profile. Slits 50 and
52 are generally mutually parallel, and aligned generally with
slits 54 and 56, respectively. Laterally-extending straight
slits 60 and 62 help define projections. Thus, the slit 50
cooperates with the outer edge of the sheet of material 10 to
define, in part, a strip 64 extending between the attachment
areas 12 and 20. Slit 52 cooperates with a portion of the
slit 16 to define a strip 68, also extending between
attachment areas 12 and 20 and being mutually parallel with
the strip 64. Between the strips 64 and 68 are projections 70
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and 72, defined, in part, by the slits 52, 50 and 60. The
projection 70 extends from the end attachment area 12 while
the projection 72 extends from the intermediate attachment
area 20.
The slit 54 cooperates with the outer edge of the sheet
of material 10 to define, in part, a strip 74, while the slit
56 cooperates with a portion of the slit 16 to define a strip
76. The strips 74 and 76 are mutually parallel in
Fig. 1, and extend between the attachment areas 14 and 20,
with the strip 74 generally aligned with the strip 64 and the
strip 76 generally aligned with the strip 68. The slits 54,
56 and 62 also define, in part, projections 78 and 80
positioned between the strips 74 and 76 and extending from the
attachment areas 14 and 20, respectively. In Fig. 1, the
projections 70, 72, 78 and 80 are generally mutually aligned.
With the various slits provided in the sheet of material
as illustrated in Fig. 1, the resulting strips and
projections may be bent or otherwise deformed to provide the
packing element as illustrated in Figs. 2-4. For example, if
the positions of the end attachment areas 12 and 14 are taken
to define the original plane of the sheet of material 10 as
viewed in Fig. 1, then the intermediate attachment area 18 is
positioned to one side of that plane while the other
intermediate attachment area 20 is positioned to the opposite
side of that plane. Then, as viewed in Figs. 2 and 4, the two
strips 64 and 74 are bowed upwardly while the two strips 68
and 76 are bowed downwardly. It will be appreciated that
strips 64 and 68 both extend between the same two attachment
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- areas 12 and 20, and, as mutually separated in the plane of
the paper as illustrated in Fig. 2, form an extended but
closed loop. Similarly, a closed but extended loop is formed
by separating the strips 74 and 76, which extend between the
same two attachment areas 14 and 20.
The two strips 34 and 42 are bowed downwardly, (Figs. 2
and 4) while the two strips 36 and 44 are bowed upwardly.
Thus, an extended but closed loop is provided by the two
strips 34 and 36 which extend between the same two attachment
areas 12 and 18. Also, an extended but closed loop is
provided by the two strips 42 and 44 which extend between the
same two attachment areas 14 and 18.
The four closed loops thus formed by the pairs of strips
extending between corresponding attachment areas are mutually
displaced in the plane of the paper in Fig. 2 as well as
laterally displaced as viewed in Figs. 3 and 4.
As viewed in Figs. 2 and 4, the projections 40 and 48 are
positioned to extend upwardly from the intermediate attachment
area 18, while the projections 38 and 46 are positioned to
extend downwardly from their respective end attachment areas
12 and 14. Also, projections 72 and 80 are made to extend
downwardly from the intermediate attachment area 20 while
projections 70 and 78 are positioned to extend upwardly from
their respective end attachment areas 12 and 14. It will be
appreciated that the angles at which the projections are
positioned in Figs. 2 and 4 may be varied. It will also be
noted that the lengths of the projections may vary, and are
shown as being different in the drawings. Further, it will be
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appreciated that the free ends of the projections may be
serrated by providing the slits 30, 32, 60 and 62 as saw-
toothed; for example.
The size of the packing element may be adjusted according
to the application, as may therefore be the dimensions of the
projections and strips, for example. It will be appreciated,
however, that regardless of the overall dimensions of the
packing element according to the present invention, the
element provides extensive flow surfaces combined with
sufficient openings between the flow surfaces to minimize gas
flow resistance through the packing element. The ends of, the
projections provide drip points, as do the serrations along
the edges of the projections and strips. The attachment areas
provide additional flow paths, joining adjacent strips and
projections, for example. Additionally, the attachment areas
add to the structural rigidity of the finished packing
element. Generally, each strip may have a different shape
and/or different horizontal position, as particularly
illustrated in Fig. 2. Further, with the intermediate
attachment areas 18 and 20 positioned to opposite sides of the
plane defined by the end attachment areas 12 and 14, for
example, the end-view profile of the packing element is
generally inclined at an angel A as shown in Fig. 3.
Consequently, as a packing element is dropped into a process
chamber, for example, there is a considerable probability that
the packing element will fall to reside in an inclined
position, with all of the strip and projection surfaces
inclined, relative to the horizontal, for example. Additional
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packing elements dumped on the first packing element, for
example, will take random orientations. However, the serrated
edges particularly of the strips will prevent strip-nesting,
that is, nesting of adjacent packing elements with strips from
two packing elements generally closing off flow paths through
the packing elements.
It will be appreciated that the shape of the packing
element as illustrated is such that there is no axis of
rotational symmetry passing through the original plane of the
packing element material 10, defined by the positions of the
end attachment areas 12 and 14, for example. The present
invention provides a packing element which, used in a packing
bed of like packing elements in an exchange process chamber,
for example, provides an abundant supply of liquid flow
surfaces, drip points and flow-through passages for gas to
enhance the interfacing of two fluids in the exchange process
apparatus.
The foregoing disclosure and description of the invention
is 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 within the scope of
the appended claims without departing from the spirit of the
invention.
