Corrugated packing and methods of use

Disclosed is a technique for packing an exchange chamber to facilitate interaction between two fluids. Corrugated packing plates are arranged with the corrugations of next corrugated plates running in different directions. The plates feature slots breaking the ridges of the plates and having corresponding tabs projecting into the corrugation grooves. The slots may provide drip points for liquid as one fluid moving through the slots in addition to permitting flow of the second fluid through the slots. A lip at the intersection of a slot and the ridge it breaks captures liquid bridging the slot to direct such liquid to the underside of the ridge. P

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 and systems for use in exchange chambers, such 
as utilized in mass transfer or heat exchange processes, for example. 
2. Description of Prior Art 
Many commercial chemical and other processes involve mass transfer or heat 
exchange, and utilize packed columns or chambers to carry out these steps. 
Such processes can include distillation, absorption and desorption, gas 
cleaning and drying, 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 senses along a single flow axis; a 
cross-current facility features the two fluids moving along separate 
intersecting flow axes. 
The mass transfer rates and/or the reaction rates of the processes 
increases 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 one another. Packing elements are placed in the chamber to 
increase the amount of surface area available for such interfacing. One 
type of packing system that has been used includes a multi-layered 
construction of parallel, corrugated plates. 
The plates are generally made of woven sheet or solid sheet and are placed 
in contact with one another such that the corrugations, or ridges and 
grooves, are at an angle to a general flow direction while the plates 
themselves are disposed in planes parallel to such a direction. 
Consequently, the fluid flow is deflected from the general flow direction, 
and may result in non-uniform distribution of a liquid at various points 
along its general flow path. Such non-uniformity can be a severe 
disadvantage in an exchange process wherein uniform distribution is 
essential when one of the fluids is a gas. 
A further disadvantage of the corrugated-plate packing elements is due to 
the tendency of liquid to flow down the corrugations rather than evenly 
coating the plate surfaces while flowing from corrugation to corrugation. 
Such "channeling" may significantly decrease the exchange efficiency due 
to low degree of fluid mixing and reduced interfacial area. 
It is advantageous and desirable to provide a packing technique to enhance 
the opportunity for interaction between two fluids in an exchange process 
by reducing channeling effects of liquid flow, increasing the wetted 
surface area for fluid-fluid interaction, reducing the resistance to gas 
flow and generally increasing the intermixing and mutual exposure between 
two fluids in the exchange process. The present invention provides a 
technique to accomplish these ends. 
SUMMARY OF THE INVENTION 
A packing element according to the present invention for use in an exchange 
process between two fluids, comprises a corrugated plate having at least 
one slot and corresponding tab extending and partially displaced from the 
slot, permitting flow of one or both fluids through the slot. A system of 
corrugated plates may be formed whereby the plates are positioned mutually 
parallel, with the corrugations of each plate forming a non-parallel 
relationship with the corrugations of the next plate. In such a system, 
one or more of the plates may feature at least one such slot and tab 
combination. 
Each tab may extend from at least one end of the corresponding slot, where 
the tab may be attached to the plate. The slots may straddle the 
corrugation ridges, either being centered on the ridges or partially 
displaced relative thereto. The tabs then extend within the grooved sides 
of the corrugations and may serve as structural support members for the 
corrugations. 
A slot may be straight, or bent, being defined at least in part by a shaped 
edge of the plate having at least one projection extending generally into 
the slot. In the latter case, a slot projection may be positioned on the 
downside of a corrugation ridge, and serve as a drip point for liquid. 
Such a drip point may be positioned above a tab of the same corrugated 
plate, for example, so that liquid dripping from the slot projection may 
fall on the tab below. A tab may also feature a shaped edge forming at 
least one drip point for liquid falling from the tab. The projections may 
be any shape in general. Projections in the form of V points are 
illustrated herein. Where a slot intersects a ridge, the downward edge of 
the slot may feature a lip extended to capture liquid tending to bridge 
the slot so that such liquid may move on and wet the underside surface of 
the corrugation generally below the slot. One form of lip is constructed 
between two V points of a tab before the plate is corrugated. 
Next adjacent corrugated plates may cooperate to define, at least in part, 
cells in which one or more slots and tabs may be located. Such cells may 
be so defined by a ridge and the next adjacent ridge of one corrugated 
plate cooperating with a ridge and the next adjacent ridge of the next 
adjacent corrugated plate. 
In a method of the invention, two fluids may be permitted to flow through 
the corrugated plate system, with a liquid fluid passing downwardly 
through the slots, dripping off of the slot projections. If the liquid 
flow rate is sufficiently high that liquid tends to bridge the slots, the 
slot lip in each case may capture the bridging liquid and direct it to the 
underside of the respective corrugation for additional wetting. 
The liquid dripping from the slot projections and even from the tab 
projections further distributes the liquid along the corrugated plates and 
increases the exposure of the liquid to a fluid, with the second fluid 
also able to pass through the slots. The slots and tabs also enhance fluid 
turbulence, particularly in the case of a gas. 
As used herein, an exchange process includes a heat exchange, a mass 
transfer or any other chemical and/or physical process in which energy or 
mass in any form is interchanged between at least two fluids. An exchange 
chamber may be any enclosure, including a column or tower, in which the 
interacting fluids are made to flow, and wherein the packing may be 
positioned according to the present invention. A flow axis is a general 
direction along which fluid moves through such an enclosure in the absence 
of packing, for example. The insertion of packing causes the fluid to 
experience local directions from the flow axis.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A packing system according to the present invention is indicated generally 
at 10 in FIGS. 1-3, and is shown comprising a plurality (five are 
illustrated) of packing elements 12, 14, 16, 18 and 20. Each of the 
packing elements 12-20 is constructed in the same form, and oriented in 
the system 10 as indicated. For example, the foremost element 12 
illustrated in FIGS. 1 and 2, comprises a plate, or sheet, formed in 
corrugations providing, on each face of the plate, one or more ridges 12a 
alternating with one or more grooves 12b, it being understood that a ridge 
on one side of the plate is generally accompanied by a groove directly 
opposite on the other face of the plate. 
FIG. 5 shows a portion of the foremost plate 12 before the plate has been 
corrugated, and the plate is indicated as 12' in that figure. The 
locations along which ridges are to be formed on the visible side of the 
plate 12' are indicated by solid lines 12a, and the location of grooves to 
be formed on that side are indicated by broken lines 12b. As indicated, 
the shape of the unfolded plate 12' is a rhomboid, which, in elevation, 
becomes a rectangle as shown in FIG. 2 when the corrugation folds are made 
as illustrated. As shown in FIG. 2, the folding of the plate 12' results 
in corrugations, that is, ridges 12a and grooves 12b, at 45 degrees 
relative to the edges of the folded plate 12 in elevation. 
With all plates 12-20 corrugated as the foremost plate 12, the plates may 
be positioned to form the system 10 by reversing alternating plates so 
that the corrugations of one plate are oriented at an angle relative to 
the corrugations adjacent to the next plate or plates, in this case the 
angle being 90 degrees. 
Each plate 12-20 may be equipped with one or more slots 22 and 
corresponding tabs 24 as illustrated. In FIG. 5, the flat plate 12' is 
shown with an array of markings 12c at which positions the plate may be 
cut to form an array of slots and tabs when the plate is corrugated. The 
cuts may be positioned to cross the lines 12a and 12b along which 
corrugation ridges and grooves, respectively, are to be formed as 
illustrated. When the plate 12' is corrugated, the tabs 24 may be pulled 
away from the slots 22 so that the ridges are broken by open slots and the 
corresponding tab in each case extends away from the slot on the groove 
side of the plate. The tabs 24 are thus displaced, in part, from the slots 
22 at whose ends the tabs are connected to the plate 12. To provide 
sufficient material to so displace the tabs 24, and provide more gas flow 
area about the tabs, the interior angle of the fold forming a corrugation 
may be less than ninety degrees, and about sixty degrees is suggested. 
In the embodiment illustrated in FIGS. 1-5, the cuts made to form the slots 
22 and tabs 24 are angled so as to produce, for example, a V-shaped edge 
22a for each slot protruding into and defining, in part, the border of the 
opening of the slot, and a V-shaped edge 24a for each tab as illustrated. 
Further, the cuts to form the slots 22 and tabs 24 are offset from the 
lines along which the ridges 12a and grooves 12b are to be formed in the 
plate 12'. The result, which may be appreciated by reference to FIGS. 1-3, 
is an array of slots 22 having projections in the form of V-shaped points 
22a on the downsides of their respective ridges, and tabs 24 having 
projections in the form of V-shaped points 24a on the downsides of their 
respective grooves 12b. 
When a system comprising one or more corrugated packing elements according 
to the present invention is utilized in an exchange enclosure, the 
orientation of the plate or plates may be generally parallel to the flow 
axis of one or both of the fluids involved in the exchange process, but 
with the direction along which the corrugation folds are made being 
non-parallel to the flow axis of at least one of the fluids in the case of 
each plate. For example, in FIGS. 1-4, wherein the corrugations of plates 
run generally diagonally, that is, at forty-five degree angles relative to 
the vertical, the flow axis of a liquid may be vertical, with the liquid 
moving generally downwardly, and the flow axis of a gas may be horizontal, 
parallel to the plane of the page of FIG. 2, or vertical, with gas flow in 
a general upward direction. Then, the slots 22 at the locations of the 
slot V points 22a, and the tabs 24 at the location of the tab V points 
24a, are generally L-shaped. However, the V points 22a and 24a also point 
in a general downward direction identified by the corresponding 
corrugation folds (down and to the left in FIG. 2 for plate 12). As the 
liquid moves generally downwardly through the packing system, there is a 
general drift of liquid along the corrugation direction of each packing 
plate. Consequently, the liquid may run along a plate surface and 
accumulate at the slot V points 22a and at the tab V points 24a to form 
drops in each case which then drop downwardly from the corresponding V 
points. As may be appreciated by reference to FIGS. 1 and 4, with a 
packing plate 12 oriented vertically as illustrated, a slot V point 22a is 
located generally above the tab 22 of the next adjacent groove 12b of the 
same plate. Consequently, a liquid drip from a slot V point 22a may fall 
directly down on the tab 24 below. The slot V point 22a may be bent 
outwardly to adjust its position over the tab 24 below, and to orient the 
slot V point closer to a vertical configuration to enhance its liquid 
accumulating ability to form drops. 
The breaks in the ridges 12a due to the slots 22 provide passages for 
enhanced gas flow through the packing system 10, and generally reduce the 
flow resistance of gas through the system. Additionally, the slots 24 
allow liquid to pass from one side of a plate 12 to the opposite side to 
enhance the distribution of the liquid over the plate surfaces. Thus, 
liquid flowing along the surface on one side of the plate 12 between a 
groove 12b and a ridge 12a may flow through a slot 24, forming one or more 
drops and falling downwardly toward the tab 22 below. The movement of the 
fluid from the slot V drip point 22a to the tab 24 below exposes the 
liquid generally on all sides to gas flow; likewise, liquid dripping from 
a tab V drip point 24a to the plate surface between a groove 12b and ridge 
12a below is also exposed during its fall to gas flow generally on all 
sides. The bending of a slot projection as discussed hereinbefore also 
breaks up the gas flow and may add turbulence to the gas flow. 
The behavior of liquid flow through the packing system 10 may be affected, 
to some extent, by the rate of flow of the liquid. For example, for a 
given viscosity, the flow rate of liquid along a packing element 12 may be 
sufficiently high that liquid flowing along the surface between a groove 
12b and a ridge 12a may bridge across a slot 22 rather than fall through 
from the slot V point 22a. The bridging liquid will generally continue to 
move on the top side of the plate surface between the groove 12b and the 
ridge 12a. The width of the slot 22 may be increased to provide a 
sufficiently large gap to prevent bridging where possible. 
FIGS. 11 and 12 illustrate portions of a packing element plate 30 having 
V-shaped slots 32 and corresponding V-shaped tabs 34, with slot drip 
points 32a and tab drip points 34a. Along the surface defining, in part, a 
slot 32 where the slot intersects a ridge 30a, and particularly at the 
lower edge of the slot and ridge intersection, the plate is creased into a 
lip shown generally at 36, extending into the groove side of the plate at 
that location. Each lip 36 features an upper surface 36a and a lower 
surface 36b which combine to form a scoop. The lower surface 36b is 
positioned such that liquid tending to bridge the groove 32 may, at least 
in part, be captured in the scoop by the lower surface 36b and directed 
along the underside surface of the plate 30 between the ridge 30a and the 
groove 30b on the opposite side of the plate from which the liquid 
started. More particularly, and as shown in FIG. 12, the liquid may pass 
through the slot 32 from the plate surface 30 c above the slot 32 to the 
plate surface 30d below the slot by way of being captured by the lip 
surface 36b as the liquid bridges the slot. In this way, the distribution 
of the flowing liquid over packing system surfaces is increased, thus 
increasing the interactive surfaces for the liquid and gas exchange 
process to include underside surfaces of the corrugations. 
FIGS. 13 and 14 illustrate portions of another packing element plate 40 
having W-shaped slots 42 and corresponding W-shaped tabs 44, with slot 
drip projections in the form of V points 42a and tab drip projections in 
the form of V points 44a and 44b, respectively. Before the plate 40 is 
corrugated, it is broken by W-shaped cuts to define the slot and tab edges 
such that the slot and tab points 42b and 44b, respectively, lie along the 
intended ridge lines. When the plate 40 is corrugated, the slot V point 
42a may provide a drip point located generally downward from the ridge 
line similar to the slot V point 22a in the case of the V-shaped slots of 
plate 12 in FIGS. 1-3. Similarly, the tab V point 44b may be positioned on 
an L to serve as a drip point generally downward from the corresponding 
groove line similar to the tab V points 24a of the plate 12 in FIGS. 1-3. 
Additionally, each W-shaped tab 44 of plate 40 features a second V point 
44b generally higher than the drip point 44a, but which may also serve as 
a drip point. 
The recess in the cut forming the tab V points 44a and 44b provides an 
upwardly-extending, V-shaped lip 46 which protrudes generally into the 
slot 42 when the plate 40 is corrugated. The lip 46 may be angled 
generally upwardly from the plane of the corrugation surface, as shown in 
FIGS. 13 and 14. Then, liquid moving generally downwardly along the upper 
plate surface 40c encountering the slot 42 and tending to bridge the slot 
may be captured, at least in part, by the upwardly-extending lip 46 and 
directed to the underside plate surface 40d. Thus, the distribution of the 
flowing liquid over the packing system surfaces is increased to include 
underside surfaces of the corrugations to increase the interactive 
surfaces for the liquid and the gas exchange process. It will be 
appreciated that the cut in the plate 40 to form the upper portion of each 
slot, establishing the slot points 42a and 42b, may be V-shaped rather 
than W-shaped, eliminating the ridge point 42b while retaining the drip 
point 42a. 
In general the packing element plates may be made from any material 
sufficiently rigid to be corrugated and retain its shape when positioned 
within an exchange enclosure, for example. Sheet metal that is continuous 
other than for the breaks provided by the slots and tabs may be employed 
as illustrated in FIGS. 1-5, 11 and 12. However, other types of materials 
may also be utilized. For example, FIGS. 8-10 illustrate portions of a 
packing element sheet 50 that is in the form of a mesh, with corrugation 
ridges 50a and grooves 50b. The mesh plate 50 is cut to form slots 52 and 
corresponding tabs 54 across the ridge lines 50a in much the same manner 
as the continuous sheet plate 12 is provided with slots 22 and tabs 24. 
However, the slots 52 and tabs 54 of the mesh plate 50 are not structured 
to provide the V-shaped drip points, and are bisected by the ridge lines 
50a, that is, the slots and tabs are generally centered on the corrugation 
ridges. 
The mesh quality of the plate 50 allows the passage of low viscosity liquid 
through the plate for liquid flow on virtually all plate surfaces without 
the need for a lip such as shown at 36 in FIGS. 11 and 12 or such as the 
lip 46 in FIGS. 13 and 14. Further, low viscosity liquid able to pass 
through the mesh to wet both sides of the plate 50 will tend to bridge the 
gaps in the ridge lines provided by the slots 52 only at high flow rates, 
for sufficiently wide slots. Otherwise, liquid encountering a slot 52 will 
tend to pass through the slot and drip downwardly onto the plate surface 
below. 
The slots and tabs of a packing element according to the present invention 
may be formed by stamping the plate of which the element is constructed. 
FIGS. 6 and 7 show a combination of a stamp 60 and a die 62 shaped to form 
slots and tabs in a packing element plate according to the present 
invention. A plate 70' that has not yet been corrugated is placed in 
position across the top surface of the die 62. The stamp 60 is moved 
sharply downwardly into the interior shape 62a of the die to cut a slot 72 
and form a tab 74 with the material removed to form the slot, as indicated 
by the arrow A, which also indicates the subsequent removal of the stamp 
60 from the die interior. The plate 70 may then be lifted from the die 62, 
withdrawing the tab 74 from the interior 62a of the die. 
To facilitate removal of the tab 74 from the die interior 62a, and to give 
a strengthening bevel to at least a portion of the tab 74, the stamp 60 
features downward interior curvature along each cutting edge 60a. The die 
62 features generally complimentarily shaped receiving trenches 62b. 
Consequently, when the stamp 60 extends the tab 74 to the bottom of the 
die interior 62a, the tab material is molded to form a 
downwardly-extending curved edge 74a, as illustrated in FIG. 7. 
Thereafter, as the plate 70 is lifted from the die 62, the downward 
curvature of the tab edges 74a facilitates removal of the tab 74 from the 
die interior 62a without bending or distortion of the tab due to dragging 
of the tab along the interior walls of the die. 
Providing at least portions of tab edges beveled, as illustrated in FIG. 7, 
strengthens the tabs. Further, since the tabs extend across grooves of the 
plates, the tabs act as support struts between corrugation surfaces to 
further strengthen the packing plate to retain its corrugated 
configuration. Generally, the tabs may be further shaped as desired, to 
insure placement under a slot V drip point to receive liquid dripping 
therefrom, for example. Such additional bending and shaping may be 
appreciated by reference to the tabs 24 illustrated in FIG. 4, wherein the 
tabs are so bent to insure placement under corresponding slot V drip 
points. 
In addition to enhancing the mingling of two fluids passing through the 
packing system, the slots and tabs of such a system provide additional 
avenues for flow through by the two liquids, and break up the flow of each 
liquid. For example, the dripping of the liquids through the slots onto 
the tabs, and from the tabs onto lower surfaces, provide liquid movement 
which would not ordinarily be present. The slots not only provide an 
avenue for passage of gas through the plates, but may add to the 
turbulance of the gas flow. 
It will be appreciated by reference to FIGS. 1-5 that adjacent packing 
plates define an area, or cell, by cooperation between a pair of mutually 
adjacent corrugation ridges on one plate and a pair of mutually adjacent 
corrugation ridges on the next plate where the two pairs of ridges face 
each other. The slots and tabs of the plates may be so positioned that a 
selected number of slots and tabs of one such plate is positioned within 
such a cell. 
While slots and tabs with single drip points and tabs with double drip 
points are shown and described herein, it will be appreciated that slots 
and tabs having any number of projections, or drip points, may be 
utilized. Further, the slot and tab drip projections may be rounded, 
pointed, or any appropriate shape to permit liquid dripping therefrom. 
It will be appreciated that a single packing element such as 12 may provide 
the packing system for an exchange process. Further, the actual periphery 
of the packing elements may vary from that illustrated herein to a 
particular shape accommodating the specific exchange enclosure in which 
the system is to be utilized, for example. The flow axes for the fluids 
involved may be at different angles rather than the vertical and/or 
horizontal discussed hereinbefore in relation to FIGS. 1-3, but it is 
preferred that corrugations not be parallel to a flow axis for either 
fluid. While the packing system 10 as illustrated in FIGS. 1 and 3 has 
corrugated packing elements directly mutually adjacent, the packing plates 
may be spaced apart and even interspersed with other packing devices or 
sheets (not shown). Further, the array of slots and tabs on a given sheet 
may be varied in a regular patent other than that illustrated herein, or 
in an irregular pattern. The number of slots and tabs, and their density 
on a packing element, may be varied, and a packing element may comprise 
just one such slot and tab combination. Finally, not all corrugated 
elements need be provided with slots and tabs in a given packing system. 
The foregoing disclosure and description of the invention is illustrative 
and explanatory thereof, and various changes in the method steps as well 
as in the details of the illustrated apparatus may be made within the 
scope of the appended claims without departing from the spirit of the 
invention.