Note: Descriptions are shown in the official language in which they were submitted.
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Docket No. 479-10-005 Canada PATENT APPLICATION
Description
FOLDED PACKING
Technical Field
The present invention relates to fluid contact structures
for use in packed towers and, more particularly, this inven
tion relates to elements formed by folding strip material into
complex 3-dimensional shapes.
Background of the Invention
Packed towers are used for mass transfer operations such
as absorption, desorption, extraction, scrubbing and the like.
The type of packing is chosen for its mechanical strength,
resistance to corrosion, cost, capacity and efficiency. The
function of the packing is to facilitate mass transfer between
two fluid streams, usually moving countercurrent to each
other. Efficiency and rate of mass transfer are enhanced by
providing large surface area in the packing to facilitate
contact of the f luids and by breaking the liquid into very
fine droplets to enhance mass transfer to a gas phase.
Packing can be in the form of trays or packing bodies
that are randomly packed into a column or tower. Originally,
packing elements were ceramic or carbon rings, saddles, par
tition rings or drip point tiles. More modern packing bodies
have a uniform distribution of open cellular units and provide
higher efficiency and performance. They have very high
wettable surface area and low resistance to fluid flow. They
are effective in any orientation. The high efficiency packing
bodies can be dump loaded into a column or tower and result in
uniform distribution of the packing bodies without having
blocked regions or void regions. These packing bodies permit
streams to be processed at faster volumetric rates. Efficien-
cy is increased and processing cost is reduced. The high
efficiency packing bodies have complex dimensional shapes,
usually with numerous struts and projections of different
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sizes and disposed at different angles and positions
throughout the packing body.
However, the intricate structure of the uniform geometric
shapes required for the high efficiency packing bodies re
quires that they be formed by casting, injection molding,
stamping or extrusion, all expensive processes. Extrusion
processes are limited since they generally are used to form
shapes with axial symmetry. Also molding processes forbid the
use of shapes such as undercuts and overlapping shapes since
they cannot be released from ordinary molds. Multipart molds
are prohibitively expensive. Thus, much of the internal vol-
ume is open space decreasing effective surface area. Baffle
structure perpendicular to the longitudinal axis of the pack-
ing body is less than the optimum.
Metal packing bodies or elements are required for certain
high temperature or chemically aggressive process streams.
Most metal packing bodies are formed from metal blanks rolled
into a tubular or spherical shape . Tabs or tongues may be cut
and bent toward the interior to provide projections to
increase surface area and enhance mixing and droplet for-
mation. Again, there is substantial open area and efficiency
is less than desired.
U.S. Patent No. 4,724,593 describes an improved method
for manufacturing high performance, symmetrical, open volumed
packing bodies. The packing bodies have uniform geometrical
configurations and are formed from a wide variety of materials
into a wide variety of shapes and geometries. The process is
simple and economical. A strip of sheet material has a pat-
tern of repeating plates which are connected by intermediate
ribbons of the sheet material. The plates may be perforated
or contain projections. The plates are bent perpendicular to
the longitudinal axis of the strip. The intermediate ribbons
are then bent to bring the longitudinal axis of the bent
plates into close proximity and in substantial parallel
alignment.
CA 02157743 1999-03-22
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The high performance packing bodies have performed well
and have captured a significant share of the market. They have
been manufactured in plastic or metal materials. These
packings have low pressure drop, high mass transfer and packing
efficiency. They have a high population of drip points per
volume provided by a uniform distribution of surface elements.
An open, non-obstructive structure provides low pressure drop
while dispersing and distributing flow in both longitudinal and
lateral directions.
While the void volume of the interior structure of the
packing body is less than prior high efficiency packing bodies,
the structure normal to the longitudinal axis is still
difficult to provide and the manufacture requires several
bending and rolling operations to form the sheet material into
an element.
An improved packing body is known where the packing bodies
are also formed from a strip of material. However, the
perforated panels are not separated by ribbon connectors. A
perforated strip of material is simply rolled into a spiral or
into a concentric cylinder structure. The outer curved end of
the strip is latched to the curved surface of the preceding
revolution of the spiral. Baffle or tab elements disposed
transverse to the surface of the strip efficiently disrupt the
fluid stream. The tabs can be rod like elements raised from
the surface. The improved packing bodies have a high degree
of open space, from 30~ to 98~. Surprisingly, the rolled
packing bodies are found to provide better mass transfer and
efficiency than prior packing body structures.
Statement of the Invention
In accordance with the invention packing bodies with
complex shapes are also produced in a simplified manner from
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apertured plates.
The plates can be separate, perforated units that are
stacked in parallel relation. They are fixed in that relation
by projections from the surfaces of the plates or side members
such as bent or separate perforated side plates adhered to the
side edges of the stacked plates.
The projections from the surface of the segments can also
be used as fluid baffles to disrupt large droplets, to create
local turbulence, to increase contact between gas and liquid
and to facilitate mass transfer. The projections can be
polygonal tabs raised from the surface. The tabs can be
diamond, rectangular or circular in shape. Thin cylindrical
rod projections from the surface have been found to be very
effective in facilitating mass transfer while providing an
open volume of above 30% with very low pressure drop. The rod
projections can latch into apertures in the adjacent plate to
provide stable separation between plates.
Another method of forming efficient baffle and apertures
is to provide a pattern of slits in a strip of metal or other
expandable material. When the strip is stretched, the slits
expand and the panels of the strip of material between ad-
jacent parallel slits tilt upwardly at an angle to the sur-
face. The slit widens into an elongated aperture.
The stacked unit of plates can be formed from strips
divided into plate segments. The plate segments on each side
of a medial plate segment are folded toward the top surface of
the medial plate segment and plate segments on the other side
are folded toward the bottom surface of the medial plate seg
ment. The strip may be provided with single or double fold
lines to facilitate folding the strip material without bending
or stressing the strip material.
The folded strip has a high degree of open space provided
by perforations, at least about 30% of the strip is open
space, preferably from 50% to 98% of the strip is open space.
The baffle tabs attached to the strip provide increased sur-
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face for fluid contact. If the tabs are at an angle to the
longitudinal axis of the rolled packing body they could be in
the path of the flow liquid and will act to disrupt the liquid
into smaller droplets. The tabs can be any shape such as
5 curved, rectangular, triangular, square, etc. The tabs can be
formed by cutting a partial perimeter of the tab from the
sheet material leaving a live hinge. The live hinge is then
bent to dispose the tab away from the sheet. A strip could
also be molded with tabs raised from the surface of the strip.
The raised tabs simultaneously form apertures in the sheet.
The tabs can also act as spacers between adjacent arcuate
sections of the rolled strip. The tabs can face upwardly
and/or downwardly. The tabs can be disposed normal to the
surface of the sheet or at a lesser or greater angle, usually
from 20 degrees to 160 degrees.
The strip is formed of a material that has a flexible and
bendable first state such as metal, B-stage thermosetting
resins, thermoplastic resins or ceramic precursors such as
metal oxides dispersed in organic binder resin. The per-
forated strip can be formed by stamping, cutting and bending
operations with metal strips or certain plastic strips. Other
strips can be formed by casting, molding or extrusion of
ceramic or resin materials. After the bent strip is in its
final configuration, the bent strip can be fired to cure the
resin or convert the precursor to a final ceramic state.
The packing body of the invention can be produced from
much simpler starting materials. Even if molds are used to
form the strips, the molds are much cheaper and simpler than
molds used to form prior high performance packing bodies . The
method of the invention can be used to form packing bodies in
complex shapes that can not be practically made by other tech-
niques. The packing bodies of the invention can be produced
at much lower costs and can be made from plastic, metal or
ceramic.
These and many other features and attendant advantages of
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the invention will become apparent as the invention becomes
better understood by reference to the following detailed
description when considered in conjunction with the accom-
panying drawings.
Brief Descri ption of the Drawings
Figure 1 is a top view in elevation of a first embodiment
of an apertured
strip for forming
a packing body
according to
the inventio n;
Figure 2 is a top view in elevation of a second em-
bodiment of an apertured strip for forming a folded packing
body;
Figure 3 is a top view in elevation of a further em-
bodiment of a strip for forming a folded packing body;
Figure 4 is a perspective view of a folded packing body
formed from the strip of Figure 3;
Figure 5 is a top view in elevation of another embodiment
of a strip f or forming a folded packing body;
Figure 6 is a perspective view of a packing body formed
by folding t he strip of Figure 5;
Figure 7 is a perspective view of the strip of Figure
2
folded into a packing body;
Figure 8 is a perspective view of a packing body formed
from folding the strip of Figure 1;
Figure 9 is a top view of another embodiment of a strip
containing a plurality of rod-like projections;
Figure 10 is a perspective view of a folded packing body
formed from the strip of Figure 9;
Figure 11 is a top view in elevation of yet another em-
bodiment of an apertured strip with attached plates;
Figure 12 is a perspective assembly view of the folded
strip of Figure
11 joined to
the plates;
Figure 13 is a top view in elevation of an expandable
strip with slits;
and
Figure 14 is a top view of an expanded metal strip.
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Detailed Description Of The Invention
Referring now to Figures 1 and 8, the improved packing
body 10 is formed of a strip 12 having at least 30% open space
provided by apertures 14. The strip 12 can have a thickness
from 0.1 to l5mm. In the case of metal, the thickness is
usually from 0.2 to 0.4mm. In the case of plastic, the thick-
ness is usually from 0.5 to 3mm, preferably 1 to 2mm and in
the case of ceramic, the strip has a thickness from 2 to 8mm.
The strip 12 may also include baffle elements that
project from the surface 18 of the strip 12 such as rod like
struts or polygonal elements such as rectangular baffles 16.
The strip is continuous from a first end wall 20 to a second
end wall 22. The strip is divided into segments 21 separated
by folding bands 23. The bands may contain a transverse slot
and can contain a score line, not shown, to act as a live
hinge. The medial segment 27 which is usually the middle
segment can contain a pair of side segments 29, 32. A packing
body 10 is formed by folding the front segment 31 adjacent the
20 medial segment 27 along fold band 23 at a right angle to the
longitudinal axis of the strip 12 until the top surface 33 of
the segment 31 is substantially parallel to the top surface 35
of the medial segment 27. The folding band 23 will form a
curved side edge 37 containing slot 25.
25 The next adjacent front segment 40 is then folded along
folding band 42 toward the segment 31 until the original bot-
tom surface of the segment 41 is substantially parallel to the
folded segment 31. Folded band 42 forms a second curved side
edge 44 containing a slot 25. Front segments 46, 48 and 50
are alternately folded into parallel disposition.
The rear segments 52, 54, 56, 58 and 60 are folded by
first folding segment 52 along band 62 such that the bottom
surface 64 of the segment 52 is substantially parallel to the
bottom surface of the medial segment 27. The folded band 23
forms a curved edge 62. Segments 54, 56, 58 and 60 are alter-
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nately folded along bands 23 to form a stack of segments con-
nected by curved side joints. Lower side segment 32 is folded
along slot 64 until the lower edge 66 is adjacent the end rear
segment 60. Upper side segment 29 is folded along the slot 68
until the upper edge 70 of the side segment is adjacent the
end front segment 50.
The strip has a pattern of apertures 14 formed by raised
rectangular baffle elements 16. The baffle elements in this
embodiment of a packing body are disposed parallel to the
longitudinal axis of the strip. The baffle elements are at-
tached to the surface of the strip along an edge 43 which is
joined to the strip. The baffle elements may project up-
wardly, downwardly or some may project upwardly and some may
project downwardly.
The length and width of the strip 12 are determined by
the nominal diameter and height desired for the packing body
10, the size of segments and the surface area. Packing bodies
generally have a diameter from 1 to 12 inches and the height
is about 1 to 10 inches. Usually the diameter to height ratio
is at least 1. A packing body will generally have a packing
factor from about 3 to 65 per foot and a surface area from
about 10 to 200 ft2/cu.ft.
The width of the strip at its widest dimension corre
sponds to the height of the packing body. Generally, the
strip will be at least 5 inches long up to 100 inches or more .
The spacing between folded segments depends on the height of
the baffle elements. Generally, the baffle elements have a
height from 1/16 to 2 . 0 inches . The packing body will have at
least 2 segments preferably from 3 to 30 segments. Random
packing bodies are generally from 1 to 5 inches in nominal
diameter, have a height from 1 to 4 inches and a baffle from
1/16 to 3/4 of an inch. The method of the invention could
also be used to produce large molecular structured packing
bodies in cubic or rectangular-shaped modules such as 1' x 1'
x 1'; 2' x 1' x 1' or 3' x 1' x 1'. The structured modules
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are placed one module at a time into the tower until the tower
is filled.
The strip can be in the form of a rectangle having paral
lel side walls as in Figures 3 and 5 or the strip can have
shaped sided walls such as convex, concave, patterned or con
verging as in Figure 2. The segments of the strip can step
down in width in discrete steps as in Figure 1. If the side
walls of the strip are parallel, the strip will fold into a
cubic or rectangular-shaped body. If the strip has tapered or
stepped side walls, it will fold into an x-shaped structure if
the smaller medial segment is disposed to the interior and
into a polygon-shaped body if the larger medial segment is
disposed to the interior of the packing body 10 as shown in
Figures 7 and 8.
The strip shown in Figures 9 and 10 has a very open
structure like a mesh or a screen. In the embodiments shown
in Figures 1-8, the strip is formed of sheet material. The
baffle elements and the apertures can be formed by stamping
and bending appropriate materials such as metal, certain plas-
tics and certain precursor ceramics or they can be formed by
molding in simple molding cavities or by casting. The aper-
tures are formed in sheet material raised from the surface
along integral connection joints to form the baffle elements.
In the case of bendable materials, the baffle element can be
cut along three sides and bent along the fourth side to form
the apertures.
In Figures 1, 3 and 5 the baffle elements are shown bent
away from the surface of the strip along a connection joint
parallel to the longitudinal axis of the strip. In Figure 2,
the baffle elements 82 are shown with cut lines 84 along 3
sides joining bend line 86 which is at a 45 degree angle to
the longitudinal axis of the strip.
The rectangular strip 90 of Figure 3 is similar to the
stepped down strip 12 of Figure 1. When the strip 90 is
folded as in Figure 1 it will form a rectangular packing body
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92 as shown in Figure 4 with the front segments 94 folded on
top of the medial segment 95 to form a top stack 96 with side
segment 98 folded upwardly. The rear segments 100 similarly
fold downwardly to form a bottom stack 102 with side segment
5 104 folded downwardly.
Figure 5 is similar to Figure 3 except that the side
segments 110, 112 are disposed on opposite sides of the end
front segment 114 and end rear segment 116. The front seg-
ments 119 are alternately folded on top of the medial segment
10 118 to form a top stack 93 and the rear segments 121 are al-
ternately folded on the bottom of the medial segment 118 to
form a bottom stack as shown in Figure 6. The side segment
110 is then folded downwardly along the side edges of the
stack and the side segment 112 is folded upwardly along the
opposite side edges of the stack to form a packing body 97.
The strip 120 shown in Figure 2 is tapered in both direc-
tions. It has a medial segment 122 and adjacent front and
rear segments 124, 126 with bending bands 128 separating the
segments. The baffle elements 82 are rectangular with the
sides rotated 45 degrees with respect to the longitudinal axis
of the strip 120.
When the top segments 124 are folded and stacked on top
of the medial segment 122 and the bottom segments are folded
and stacked along the bottom of the medial segment 122. A
packing body 140 having hexagon cross-section as shown in
Figure 7 is formed. The side segment 123 is folded upwardly
and the other side segment 125 is folded downwardly.
If the strip is formed of resilient material, the shape
of the packing body can be stabilized by providing latches
between apertures in adjacent segments by securing the side
edges of the segments to each other or to the medial segment
or by securing the side edges of the segments to the side
segments by mechanical latches, adhesives or thermal bonding
in the case of thermoplastic resins or metals.
A further embodiment of a packing body is shown in
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Figures 9 and 10. A strip 200 has a very open structure
provided by apertures 202. A pattern of rod-like baffle
elements 204 are raised from the surface 206 of the strip 200.
Some of the elements 207 are longer and are adapted to enter
an aperture 205 in an opposed segment and latch the segments
together.
Each segment is separated from the adjacent segment by a
band 208 containing a set of parallel score lines 210, 212.
The band may also contain an elongated aperture 214. As shown
in Figure 10 as the first front segment 216 is folded, the
band 208 will fold along the live hinge 220 formed at score
line 210 and the band 208 will be disposed at a right angle to
the medial segment 218. The vertical band 208 will then fold
along score line 212 at a right angle to the next front seg-
ment 222 to form a second live hinge 224. The front segment
222 is bent to be disposed parallel to the medial segment 218.
Some of the longer baffle elements 207 projecting from
the surface of the medial segment 218 are snapped into the
opposed apertures 205 in the folded segment 216. The rear
segments 230 and 240 are then alternately folded to form the
packing body 250 shown in Figure 10.
Another method of assembling a packing body is shown in
Figures 11 and 12. A strip 400 has three segments 402, 404,
406 containing apertures 408 and baffles 410 and a series of
panels 401, 403 connected by tabs 405 between projections 407.
The panels 401, 403 also contain apertures 408 and baffles
410. The end segments 402, 406 are bent upwardly along scored
fold lines 418, 412 to form a u-shaped shell 409. The panels
401 and 403 are separated by breaking the tabs 405. The in-
dividual panels 401, 403 having the same length and width as
the medial segment 404 are placed within the shell 409 in a
position parallel to the medial segment 404. The side projec-
tions 407 are inserted into the apertures 408 in the segments
402, 406 to lock the structure together into a packing body
430. The individual segments could be adhered together with
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a set of side strips or individual side plates or segments.
Another way to form an apertured, baffled strip in a
single operation is shown in Figures 13 and 14. A strip 300
of expandable material such as metal contains a pattern of
slits 302. The slits 302 are preferably disposed transverse
to the longitudinal axis of the strip 300. The slits 303 in
a first row 304 overlap the ends 306 of two slits 308 in an
adjacent row 310. As the strip 300 is expanded the panels 312
between slits such as 303 and 306 in adjacent rows will tilt
upwardly to form baffle elements 314 and apertures 316. The
strip 300 can be rolled to form a cylindrical packing body or
folded along fold lines 320, 322 to form a rectangular folded
packing body, not shown.
The invention provides high performance packing bodies in
complex shapes by simple, low cost fabrication techniques.
The intricate shapes are defined in planer materials readily
formed by casting, molding, stamping or extrusion. The manu
facture is completed by a simple folding step. By use of
strips having different widths, lengths or thicknesses, pack
ing bodies having complex shapes can be produced. Packing
bodies of different sizes can be filled into a tower.
It is to be realized that only preferred embodiments of
the invention have been described and that numerous substitu-
tions, modifications and alterations are permissible without
departing from the spirit and scope of the invention as de-
fined in the following claims.
