Multifold packing and method of forming

A packing body is formed from a sheet of foldable material by forming a first row of panels with first fold lines between adjacent panels, forming a second row of panels having a second fold line inducing a common fold line with an edge of at least one panel from the first row, the common fold line being substantially perpendicular to the first fold lines, and bending the panels in the first row along the first fold lines until the panels are positioned in a stack and bending the panels in the second row into a second stack and folding them along the common fold line above or below the first stack.

TECHNICAL FIELD 
The present invention relates to fluid contact structures for use in packed 
towers and, more particularly, this invention 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 fluids 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, partition 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. Efficiency is 
increased and processing cost is reduced. The high efficiency packing 
bodies have complex dimensional shapes, usually with numerous struts and 
projections of different 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 requires 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 volume is open space decreasing effective 
surface area. Baffle structure perpendicular to the longitudinal axis of 
the packing 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 formation. Again, 
there is substantial open area and efficiency is less than desired. 
U.S. Pat. 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 pattern 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. 
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 disclosed in copending application, Ser. No. 
08/147,806, filed Nov. 3, 1993, now U.S. Pat. No. 5,498,376, the 
disclosure of which is expressly incorporated herein by reference. The 
improved 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. However, it is difficult to automate rolling the strip into a 
spiral and latching the rolled element so that it does not unwind. Longer 
strips for large packings require a larger cavity to mold the strip. 
Packing bodies have also been produced in a simplified manner from 
elongated apertured strips as disclosed in Ser. No. 08/229,698 filed Apr. 
19, 1994, now U.S. Pat. No. 5,458,817, the disclosure of which is 
expressly incorporated herein by reference. The strips are formed into 
segments and the segments on each side of a medial segment are folded 
toward the top surface of the medial segment and segments on the other 
side are folded toward the bottom surface of the medial segment. The 
segments may be provided with single or double fold lines to facilitate 
folding the strip material without bending or stressing the strip 
material. 
Though packings made from a folded strip are easier to manufacture than the 
packings formed from a rolled strip, the packings are limited in 
complexity and size. 
STATEMENT OF THE INVENTION 
Much more complex packings are formed in accordance with the invention from 
a planar sheet of material containing a plurality of rows of perforated 
panels. The rows are connected at one end and at least two opposed panels 
in adjacent rows being separated along their common opposed edge. The 
panels can be provided with single or double fold lines to facilitate 
folding the panel into a packing. The folds need not be parallel and can 
be made in any direction. The panels can be any polygonal shape, 
preferably square or rectangular. The panels preferably contain baffle 
elements raised from the surface. 
The sheet is easily folded into a packing by folding the panels along the 
fold lines in a sequence in which adjacent top faces are folded to face 
each other followed by folding along the next fold line such that the 
bottom faces face each other. The end row is folded in the same 
alternating sequence except that the fold line will be in a direction 
normal to the direction of folding the first row. The folding of the row 
succeeding the end row will be in a direction parallel but opposite the 
direction of folding the first row. The opposed faces of the folded panels 
are preferably free of projections and/or raised baffle elements. 
A sheet of foldable material such as metal, plastic or green state ceramic 
can readily be stamped to form the panels, apertures, baffles and fold 
lines. Manufacturing is simplified and can readily be automated to form 
panels with complex shapes. 
The projections from the surface of the segments can be used 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. The projections can also be used to 
maintain separation between adjacent panels. 
The packings formed from the multifold folded strip have 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 surface 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 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 perforated 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 techniques. The packing bodies of the invention can be produced at 
much lower costs. The packing bodies of the invention are very effective 
in facilitating mass transfer while providing low pressure drop. 
These and many other features and attendant advantages of the invention 
will become apparent as the invention becomes better understood by 
reference to the following detailed description when considered in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIGS. 1 and 2, the improved multifold packing body 10 is 
formed of a sheet 12 having at least 30% open space provided by apertures 
14. The sheet 12 can have a thickness from 0.1 to 15 mm. In the case of 
metal, the thickness is usually from 0.2 to 0.4 mm. In the case of 
plastic, the thickness is usually from 0.5 to 3 mm, preferably 1 to 2 mm 
and in the case of ceramic, the strip has a thickness from 2 to 8 mm. 
The sheet 12 is divided into panels 18 by fold lines 20. The fold lines may 
be in the form of bands 23 which may optionally contain a transverse slot 
25. Score lines 27, 29 can be provided to facilitate folding along lines 
27, 29 to form the bands 23. The panels are aligned into rows. At least 2 
adjacent rows 22, 24 contain an aperture 26 along the opposed edges 28, 30 
of opposed panels 32, 34. The adjacent rows 22, 24 are joined preferably 
by an end row 36 containing at least 2 panels 38, 40 and a fold line 42 
perpendicular to the direction of folding of the rows 22, 24. A continuous 
path exists from an end wall 19 of the first panel 22 to end wall 17 of 
the last panel 24. 
Folding is continuous from a first panel 22 having a free edge 28 along the 
longitudinal axis of the row 22 across end row 36 in a direction 
transverse, preferably perpendicular to said axis, then along row 24 in a 
direction parallel to said axis. The band 44 will be adjacent band 46 from 
row 24 and will provide increased structural stability to the packing body 
10 and will aid in maintaining separation between adjacent panels. 
The sheet 12 also includes baffle elements 16 that project from the top 
and/or bottom surfaces of the sheet 12 such as rod like struts or 
polygonal elements such as rectangular baffles 16. The sheet 12 has a 
pattern of apertures 14 which can be formed by raised baffle elements 16 
bent up or down from the sheet along live hinge 15. The baffle elements in 
this embodiment of a packing body are disposed parallel to the 
longitudinal axis of the strip. The baffle elements are attached to the 
surface of the sheet along an edge 15 which is joined to the sheet. The 
baffle elements may project upwardly, downwardly or some may project 
upwardly and some may project downwardly. 
The length and width of the sheet 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 
ft.sup.2 /cu.ft. 
The width of the strip at its widest dimension corresponds 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 panels 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 
panels preferably from 3 to 30 panels. 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, modular, structured packing bodies in 
cubic or rectangular-shaped modules such as 1'.times.1'.times.1'; 
2'.times.1'.times.1' or 3'.times.1'.times.1'. The structured modules are 
placed one module at a time into the tower until the tower is filled. 
The sheet may contain a wide aperture between outside rows sufficient to 
accommodate at least one interior row of panels. Referring now to FIGS. 3 
and 4, this embodiment of a packing 50 utilizes a sheet 48 which contains 
parallel rows 52, 54, 56 of panels 18 separated by apertures 58, 60, 61 
and connected by an end row 62 containing 3 panels. The number of panels 
in the end row equals the number of parallel rows. Folding starts by 
folding the top surface 66 of panel 64 in the intermediate row 54 onto the 
top surface 68 of adjacent panel 70 to form a band 72. The sheet 48 is 
then folded under panel 74 alternately folding along rows 56 across row 62 
and down row 52 until the end and ninth panel 78 has been folded to form 
the packing 80 shown in FIG. 4. 
The folding path in the first two illustrated embodiments follows a spiral 
path. The folding path in the sheet 82 shown in FIGS. 5 and 6 follows a 
sinusoidal path. The sheet 82 has three rows 84, 86, 88. The intermediate 
row 86 is separated from the end rows 84, 88 by an upper cut line 90 and a 
lower cut line 92, respectively. The folding path proceeds by folding top 
panel 94 onto adjacent panel 96 then folding the first two folded panels 
onto the bottom surface of the adjacent panel 98 in row 86 and 
consecutively folding panels 100, 102, 104 to form the packing body 106 
shown in FIG. 6. 
In FIGS. 7 and 8, the end rows 108, 110 are separated by 2 intermediate 
rows 112, 114. The side rows 108, 110 are joined by an end row 116 
containing 4 panels 18. The sheet 113 contains a continuous slot 118 
running between rows 108 and 112 across the bottom of the intermediate 
panels in end row 116, down between panels 120, 122 between rows 110 and 
114 on and across the bottom of panel 130. Folding proceeds from top panel 
124 alternating as described up row 108, across end row 116, down side row 
110, across bottom panels 126, 128, up row 112 and ending with end panel 
130 to form the packing 132 illustrated in FIG. 8. 
FIGS. 9-12 illustrate forming packings from a sheet 150 (150') containing 
rectangular panels 152 (152'). The sheet 150 can be stamped from 
continuous material or screen or expanded metal material 150' as shown in 
FIGS. 11-12. The sheet 150 (150') contains 2 side rows 154 (154'), 156 
(156') joined by an end row 158 (158'). The separation bands 160 (160') 
between the panels 162 (162') and 164 (164') in the side rows 154 (154'), 
156 (156') are not as wide as the separation band 166 (166') between the 
end panels 168 (168'), 170 (170') present in the end row 158 (158'). Each 
aperture 192 (192') is cut to form two baffles 194 (194') and 196 (196') 
which are on opposed sides of the aperture 192 (192'). 
Folding proceeds by folding top panel 162 (162') onto end panel 168 (168') 
to form the separation band 160 (160') and then transversely onto the 
second end panel 170 (170') to form the narrower separation band 166 
(166') and finally onto end panel 164 (164') to form the packing 190 shown 
in FIGS. 10 and 12. 
The sheet shown in FIGS. 11 and 12 has a very open structure like a mesh or 
a screen. In the embodiments shown in FIGS. 1-10, 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 plastics 
and certain precursor ceramics or they can be formed by molding in simple 
molding cavities or by casting. The apertures 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. 
The baffle elements can be bent away from the surface of the strip along a 
connection joint parallel to the longitudinal axis of the strip or the 
baffle elements can be cut along 3 sides joining a bend line which is at a 
45 degree angle to the longitudinal axis of the strip. 
The invention provides high performance packing bodies in complex shapes by 
simple, low cost fabrication techniques. The intricate shapes are defined 
in planar materials readily formed by casting, molding, stamping or 
extrusion. The manufacture is completed by a simple folding step. 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 substitutions, modifications and 
alterations are permissible without departing from the spirit and scope of 
the invention as defined in the following claims.