Note: Descriptions are shown in the official language in which they were submitted.
" 10~8~39
1 This invention relates to dumped packings and apparatus
comprising such dumped packings.
There are many areas of technology in which a li~uid
is contacted with a gas or vapour in a column packed with pack-
ing material. Examples of such processes are distillation
processes, absorption and desorption processes, gas cleaning and
scrubbing processes, liquid cooling processes, gas drying
processes and biological processes including biological or per-
colation filters. Such processes find widespread use in process
technology such as in water treatment, particularly effiuent
treatment, and in process chemistry.
In the past a wide variety of processes of this type
have been carried out using packed columns. The number and
variety of packings used to pack such columns is very wide. The
packing elements may be arranged to form a regular array inside
the column or they may be randomly distributed in the column or
distributed on some intermediate basis. Random and partially
random arrays are usually obtained by dumping a large number of
individual small packing elements into the tower.
Numerous examples of dumped packing elements are known
from the patent literature, for example those described in
German Auslegeschrift No. 1029346, United States reissue
specification 27217, German Auslegeschrift 1129931, United States
Specifications 2602651, 3484513, 3167600 and 3311356, and
British Patent Specifications 917906, 1385672 and 138673.
A number of desiderata apply to elements ~or use in
dumped packings. First of all, the gas/liquid contact
efficiency of the packing must be satisfactory for the intended
purpose and preferably it should be as efficient as possible.
One, though by no means the only, way of enhancing efficiency
7~
10"8439
1 is to ensure that the packing elements have a high surface area
per unit volume of the dumped packing. Another desideratum is
that the packing elements should flow easily to form the dumped
packing, should not tend preferentially to have any particular
adverse orientation when dumped, and in addition the individual
elements should be strong enough that the lowermost elemerts in
a bed of dumped packing elements do not collapse under the
weight of the bed above them. A further desirable quality in a
dumped packing is that the resistance to gas or vapour flow
through the packing should be relatively low.
It is an object of the present invention to provide
dumped packings having improved properties relative to previously
known packings in one or more of the foregoing respects.
According to a first feature of the present invention
there is provided a dumped packing for use in gas/liquid contact
apparatus consisting of a plurality of packing elements each
comprising a curved or polygonal base extending about an axis to
an extent of 90 to 270, each element having in section in a
radial plane including the axis the shape of a trough, the length
to depth ratio of the trough being greater than 6 and/or the
length to width ratio of the trough being greater than 3, and
the trough comprising one or more apertures.
Preferably in packings o~ this type the length of the
trough in each element, defined as the straight line distance
between the two ends of the trough (not the distance along the
actual base of the trough) is at least 6.0 times greater than
the depth of the trough. The cross section of the trough may
vary from a flat base with upstanding side walls, either extend-
ing perpendicular to the base or at an angle thereto, and being
inclined toward or away from one another to a trough of
10~8439
1 curvilinear cross section, e.g. in the form oE an arc of a
circle, a cantenary.
Preferably the base of such packing elements extends
about the axis to an extent of 170 to 190 i.e. the base of each
element is approximately in the shape of half a hollow cylinder
or frustocone or half of a polygon having at least ~ sides.
Such a polygon may be regular or irregular but preferably has 6
or more sides and is substantially regular. The ends of the
trough may be open or closed by a flange.
In another aspect, the invention provides a dumped
packing for use in gas/liquid contact apparatus consisting of a
plurality of packing elements each having a polygonal or arcuate
base and one or more oppositely directed polygonal or arcuate
sections formed on or in the base and intersecting the base at
the ends of the section at an included angle of less than 180,
preferably less than 90. Subsidiary further polygonal or
arcuate sections may be formed on or in the first arcuate
sections, these secondary polygonal or arcuate sections accord- !
ingly curving in the same sense as the base.
Packing elements for use in packings of this type
will generally extend around a notional axis at the centre of
the circle or polygon to an extent of at least 90 and they can
extend around the axis to 360 in the form of a cylinder or to
more than 360 if the packing generally has the form of a
sprial.
It is found that the provision of oppositely curved
arcuate sections or oppositely directed polygonal sections in-
creases the strength of the curved base or polygonal structure
and provides good gas/liquid contact in dumped packings.
Subsidiary polygonal or arcuate sections give a more open
--3--
3439
1 structure, a lower pressure drop and minimises interlocking of
the packing elements. The strength of such packing elements is
enhanced by the provision of the walls of the trough or other
appropriate flanges and according to a further feature of the
present inven~ion there is provided a dumped packing for use in
gas/liquid contact apparatus consisting of a plurality of
packing elements each having an arcuate or polygonal base extend-
ing about an axis to an extent of 90 to 270 and bearing
flanges extending in planes which intersect the base along a
curved or angled line of intersection.
The provision of such flanges, which may constitute
trough walls, or the curvature of the trough which may extend
over part or the whole of the base of any particular element, in
elements of a dumped packing acts very substantially to increase
the strength and rigidity of the individual packing elements
thus minimising the risk of packing elements at the bottom of a
dumped bed collapsing. In addition, the flanges and trough
structure aids the liquid distribution and influences the spac-
ing of the rings to give a lower pressure drop and higher
capacity.
As well as the provision of arcuate or part poly-
gonal sections as noted above, packing elements for use in dump-
ed packings according to the present invention may also bear one
or more spacing tags extending from parts thereof. This gives
the packing a more open structure with a lower pressure drop in
use. It is surprisingly found that there is little interlocking
of the packing elements when the tags from the arcuate surface
of certain types of packing elements are directed inwardly.
Tags as just noted and arcuate portions extending from
the base of packing elements may be curved in one or in two
directions.
10~8439
1 Packing elements for use in packings according to the
present invention may be made from a wide variety of appropriate
materials known for making such elements. Naturally the choice
of material will affect the possibilities of forming the element
and in the opposite sense, certain shapes of element within the
scope of the present invention will be difficult or impossible to
make in certain materials. Thus for example the elements may be
made of plastics materials e.g. by injection moulding, of
ceramic material e.g. by extrusion and forminy or by moulding,
followed by subsequent firing, or they may be made of metal e.g.
by punching, stampingand forming. The material of which the
packing elements are made should clearly be one which will with-
stand the expected conditions o~ use of the dumped packing e.g.
in terms of corrosion resistance, solubility.
The general construction of the packing elements for
use in packings according to the present invention is thus a
moulded or deformed sheet of material. The surface of the
material of the packing element may be plain or it may be
otherwise than plain for e~ample, corrugated, dimpled,
grooved. Such surface configurations may enhance the wetting
properties of the elements. The materials of which the packing
elements are made may also be solid or porous, e,g. the elements
may be made of a perforated metal gauze or they may be made of a
woven metal gauze or mesh or an analogous felted material. When
using certain materials of construction it may be desirable
further to enhance the strength of the individual packing elements
by providing bridges of material connecting one part of the pack-
ing element with another, This technique is particularly,
valuable in the production of packing elements formed of synthetic
plastics materials, e.g. by injection moulding.
In another aspect, this invention provides a packing
element for use in plurality in gas/liquid contact apparatus
8439
1 consisting of a plurality of packing elements, each element
comprising: an elongate polygonal or curved base member havin~
free ends and longitudinally extending from one free end to the
other around a first notional axis to an extent of about 90 to
about 270 to define a space which is at least partially
enclosed by said base member, said base member having one or
more apertures for gas/li~uid flow through said base member, and
at least one bridging member carried by said base member extend-
ing about a second notional axis parallel to the first notional
axis and in the opposite sense to the base member, at least
partially through said space, said bridging member and said base
member each having a base portion which is substantially flat
transversely and said base member having an L:W ratio of ~3, the
combination o~ said free ended, apertured base member and bridg-
ing member integral therewith providing an open structure to
facilitate gas/liquid flow through said element and a structure
which resists collapse o~ said element under compressive stresses
in said dumped packing.
In a further aspect, this invention provides a packing
element for use in plurality in gas/liquid contact apparatus
consisting of a plurality of packing elements, each element com-
prising: an elongate polygonal or curved base member having free
ends and longitudinally extending from one free end to the other
around a flrst notional axis to an extent of about 90 to about
270 to define a space which is at least partially enclosed by
said base member, said base member having one or more apertures
for gas/liquid flow through said base member; and at least one
bridging member carried by said base member extending about a
. second notio~al axis parallel to the first notional axis and in
the opposite sense to the base member, at least partially
through said space, said bridging member and said base member each
having a base portion which is substantially flat transversely
--6--
~8439
1 and said base member haylng an L:W ratio of ~3~ the co~bination
of said free ended, apertured base member and bridging member
integral therewith providing an open structure to facilitate gas/
liquid flow through said element and a structure which resists
collapse of said element under compressive stresses in said
dumped packing, and wherein:
(a) side walls are pro~ided on the long edges of the
elongate base member to form with the base member a bent trough
shape;
(b) the ratio of the length of the base member to the
depth of the trough is at least 6;
(c) each element includes further apertures wherein
from at least one edge of such an aperture there is a projecting
tag; and
(d) the strip-like bridging member is perforated by an
aperture bridged by a further bridging member~
The invention is illustrated by way of example only
with xeference to the accompanying drawinys in which;
Figures 1 to 14 sho~ in perspecti~e Yiew a number of
packing element types according to the present invention.
It will be seen that a number of packing elements
illustrated ha~e various features according to the present in-
vention. Thus the packing elements shown in ~iguxes 1 to 6, 9,
11, 12 and 14 haye an arcuate base A with one or more arcuate
sections B extending therefrom; such arcuate sections may be
made by pressing out material in the embodiments shown in Figures
1 to 6, 9, 11 and 14. In the case of Figure 12, this type must
be moulded if it is to be made in one piece~ In the case of
Figures 2, 3, 4 and 5 secondary arcuate sections C are pressed
from the primary arcuate sections, these secondary sections
curving in the same sense as the base, In the case of Figure 2,
there is a tertiary arcuate section D, Arcuate sections ~, C and
-7-
1~9l~4;19
1 D may have a rectangular cross-section or a curved oblong cross-
section.
The strength of the packing elements is enhanced in the
case of those shown in Figures 1 to 3, 5 to 9, 11 and 12 by the
flanges F on the edges of the base in each case. It is not of
course necessary to incorporate the flanges at the edges of the
base of the element, they could be incorporated e.g. at the edge
of the arcuate portion. This may be difficult to achieve in the
- case of packings formed from metal sheet by stamping and pressing
but is not of course difficult in manufacture of analogous shaped
elements by plastics injection moulding. In the case of the
elements shown in Figures 1 to 3, 5 to 9, 11 and 12 the flanges
and the base constitute a trough of length to depth ratio greater
than 6. In the case of Figure 10, the trough is of generally
U-shaped cross-section of length to width ratio greater than 3.
The elements shown in Figures 6, 7 and 8 each have
punched out tags T to give the packing a more open structure, a
lower pressure drop and higher capacity. In the case of Figure
6, the tag T also minimises interlocking of the packing elements
and ensures that they can be poured easily and quickly to form a
generally random oriented bed of packing elements in appropriate
apparatus. These tags may be curved in one or two directions,
i.e. the cross-section of a tag may be a rectangle or a cur~ed
oblong.
The packing elements illustrated in Figures 10 and 12
ha~e additional walls of material X to enhance the strength of
the elements,
In the elements shown in Figures 8 and 10, the ends of
the trough are closed by secondary flanges G. In the case of
Figure 10, the flange G has a window to prevent undesired liquids
builds up.
--8--
~oq8~9
1 Figure 13 illustrates an element on a non~arcuate base;
the base in Figure 13 is half of a regular 4-sided polygon
(square). The base M bears a first oppositely directed portion
N, which in turn bears an oppositely directed secondary portion
P. The portions N and P can be pressed out from portions ~ and
N respectively.
The elements shown in Figures 1 to 8, 11, 13 and 14
are preferably made of sheet metal by cutting and stamping.
That shown in Figure 9 is made of fired ceramic, the unfired
element being made either by moulding or by extrusion and form-
ing while the elements of Figures 10 and 12 are preferably made
of plastics by injection moulding.
The following is an example showing the improved
results achieveable with packing elements according to the
present invention.
One inch packing elements as shown in Figure 1 were
taken. The one inch is the distance from one end of the trough
to the other. This packing, made of 0.01" thick steel, was
dumped into a 9 inch internal diameter column and air was
passed through the column at a rate o~ 1000 or 2000 pounds per
square foot per hour. The packing density o~ the packing
elements was also noted and by way o~ comparision, equivalent
tests were carried out on 1 inch diameter metal Pall rings, 1
inch ceramic saddles and on 1 1/2 inch ceramic saddles tthough
using 12 inch internal diameter column).
The results are tabulated below:
_g_
~0C~8~39
., . .
Packing number ~P/ft ins of water
Air 1000 Air 2000
lbs/ft2hr lbs/ft2hr
_ .
1" Metal Pall Rings1330 0.17 0.72
1' Trough r~etal Packing 1670 0.13 0.48
, 1" Ceramic Saddle 1940 0.22 0.85
1 1/2" Ceramic Saddle in
l2 di~:~eer c~lumn 71~ _ 0.63
The packing was then subjected to air/water humidifi-
cation tests and it was found that the mass transfer co-
efficients for the packing according to the invention ana the
1 inch and 1 1/2 inch ceramic saddles were substantially
equivalent. Under distillation conditions, the packing of the
invention and the 1 inch Pall ring packing gave similar mass
transfer results or HETP values. The HETP value is the height
of an equivalent theoretical plate of any-particular standard
type of packing, e.g. Rashig rings.
~ It is found that for a given strength, elements used
in packings according to the present invention require less
weight of material than the prior art packing elements. This
enhances the resistance to crushing of the lowermost elements
in deep beds, and is of course, of economic advantage in that a
given bed requires ]ess raw material to make a packing to fill
it.
Although the description of this invention has been
~iven with respect to particular embodiments, it is not to be
construed in a limitin~ sense~ Many variations and modifications
will now occur to those skilled in the art~ For a definition of
the invention reference is made to the appended claims.
~10-
1~8~39
1 SUPPLE~NT~RY DISCLOSURE
According to one aspect of the present invention there
is provided a packing element for use in plurality in gas/liquid
contact apparatus consisting of a plurality of packing elements,
each element comprising: an elongate polygonal or curved base
member having free ends and longitudinally extending from one
free end to the other around a first notional axis to an extent
of about 90 to about 270 to define a space which is at least
partially enclosed by said base member, said base member having
one or more apertures for gas/liquid flow through said base
member; and at least one bridging member carried by said base
member extending about a second notional axis parallel to the
first notional axis and in the opposite sense to the base
member, at least partially through said space, said bridging
member and said base member each having a base portion which is
substantially flat transversely and said base member having an
AL:Wratioof ~3, the combination of said free ende~, apertured
base member and bridging member integral therewith providing an
open structure to facilitate gas/liquid flow through said
element and a structure which resists collapse of said element
under compressive stresses in said dumped packing.
In another aspect of the present invention there is
provided a packing element for use in plurality in gas/liquid
contact apparatus consisting of a plurality of packing elements,
each eIement comprising: an elongate polygonal or curved base
member having free ends and longitudinally extending from one
free end to the other around a first notional axis to an extent
of about 90 to about 270 to define a space which is at least
partially enclosed by said base member, said base member having
one or more apertures for gas/liquid flow through said base
1~3"8439
1 member; and at least one bridging member carried by said base
member extending about a second notional axis parallel to the
first notional axis and in the opposite sense to the base
member, at least partially through said space, said bridging
member and said base member each having a base portion which is
substantially flat transversely and said base member having an
AL:W ratio of ~3, the combination of said free ended, apertured
base member and bridging member integral therewith providing an
open structure to facilitate gas/liquid flow through said
element and a structure which resists collapse of said element
under compressive stresses in said dumped packing, wherein the
ratio of the width of the trough to the depth of the trough so
formed is greater than 6, and wherein the elongate aperture
extends along the base member to an extent of at least 65% of
the actual length of the base member.
The dimensional relationships between parts of the
elements of the invention may vary widely, but are ultimately
determinative of the characteristics of the dumped packing.
Four dimensions can be associated with most types of packing
~ elements according to the invention, Vi2. a straight-line length
of the base member l'L" defined as the straight line distance
between the two ends of the base member, an actual length o the
base member l'ALII being the length of the base member measured
along its centre, (note that since the base member is longi-
tudinally curved or polygonal, the actual length of the base
member l'ALI' is greater than the straight-line length of the base
member "Ll'), the width W of the base, and the depth ~ of the
trough formed by the presence of side walls of the base.
Preferably, the ratio of AL:~ is at least 3.0, but
less than 5Ø Preferably, when side walls are present, AL:D is
-12-
1 greater than 6 and/or W:D is greater than 6. The strip-like
bridging member preferably spans at least 65% of the arcuate
extent of the base member, i.e. the distance along the base
member between the ends of the bridging member is at least 65%
of the actual length of the base member "AL`'.
It is found that the provision of walls on the sides
of the base member increases the strength of the packing element,
particularly the compressive strength across the ends of the
element, while still retaining good gas/liquid contact in
dumped packings formed of the elements. The perforation of the
base member and provision of the projecting member(s) ~both the
bridging member and any further bridging member or tags) give
a more open structure, a lower pressure drop and minimises
interlocking of the packing elements. It is important to
increase the strength and rigidity of the individual packing
elements as far as possible in order to minimise the risk of
packing elements at the bottom of a dumped bed collapsing. In
addition to the strength imparted by the side walls, the
provision of such side walls aids the liquid distribution and
influences the spacing of the elements in the dumped packing to
give a lower pressure drop and higher capacity~
Strip like projecting members on the packing element,
whether tags or bridging members, may be curved along their len- .
gth and be transversely flat, or they may be arched both longi-
tudinally and transversely.
The particular shape of the element may determine the
optimum material of construction. For example, if the base
member is substantially flat and has relatively vertical walls
at each edge, and is made of sheet metal, the wall hei~ht can-
not be very great without xisk of cracking the metal, not
10~8439
1 usually more than 1/4". No such problem arises with plasticsinjection moulding, but that technique places other constraints
on the shapes which can be made, e.g. the ability to split the
mould to remove the formed shape.
The packings according to the present invention are
distinguished from the packing elements of the prior art refer-
red to above in a number of ways. Fundamentally, the packing
elements of the present invention may be thought of as bent
strips which are bent round in substantially only one direction
but not so far round that they tend to ~orm a ring shape.
Because they are elongate and bent round only one axis they
are distinguished from various saddle-shaped type of packings.
They are also fundamentally distinguished from numerous
packings based on the idea of "s~uareness" which results in
packings having a preferential orientation when dumped, as
contrasted with the random orientation of packings according to
this invention.
In some cases, the individual packing elements of the
packings according to the in~ention are similar to portions of
known types of packing, but of course the performance of packing
elements, both mechanical and mass transfer performance, depends
on the overall element shape and not simply on constituent parts
thereof.
When a short straight line, parallel to but spaced
from an axis, is rotated about that axis, it traces out a sur-
face in space. The notional axis referred to above is the axis
which, when such a line is rotated about it, most closely
generates the shape of the elongate base of the actual element,
or (if the element has a polygonal rather than an arcuate base)
the shape of the corresponding arcuate base passing through the
"8439
1 vertices of the ~olygonal base. In many cases, packing elements
constructed in accordance with the present invention are simple
geometrical shapes and have a genuine axis of rotation. How-
ever, the base of the element need not be an arc of a circle
but may be an arc of an ellipse or other closed regular curve,
or it may even be a sprial arc. In each case the notional axis
is one which produces a "best fit". Many simple packing elements
according to the invention are symmetrical, and extend about
180 about the notional axis. In this case the notional axis is
substantially the intersection of the transverse plane of
symmetry of the element and the plane joining the two ends of
the base member.
The invention is illustrated by way of example only
with reference to the accompanying drawings in which
Figures 15 to 17 show in perspective view a number of
packing element types according to the present invention.
Figures 18 and 19 illustrate in fragmentary cross
section views of packing ele~ent material which has a surface
which is corrugated or dimpled respectively.
Figure 20 and 21 are graphs of compressive strength
for various packing elements indicated thereon,
It will be seen that all of the packing elements
illustrated on Figures 1 to 17 have an arcuate or polygonal base
member A (M in the case of Figure 13) which extends about a
notional axis~ In section in a radial plane, base member A is
substantially flat. The elements shown in Figures 1 to 3, 5 to
12 and 15 to 17 also have upstanding side walls F, the ratio of
the actual length of the base member (AL in Figure 15) to the
height of walls F (D in Figure 15) being always greater than 6.
In each case, set on the base member A is an arcuate or part
~098439
1 polygonal bridging section B (N in the case of Figure 13)
spanning an aperture in the base member A. Such arcuate sections
may be made by pressing out material in the embodiments shown
in Figures 1 to 6, 9, 11 and 13 to 17. In the case of Figures
10 and 12, these types must be moulded if they are to be made
in one piece due to the presence of the additional walls of
material X. In the case of Figures 2 to 5 and 13 secondary
arcuate or part polygonal bridging members C (P in the case of
Figure 13) are pressed from the primary bridging member B, these
secondary sections being in the same sense as the base member.
In the case of Figure 2, there is a tertiary arcuate section D.
Sections B 7 C and D may have a rectangular cross-section as
shown or if desired may be curved transversely as well as
longitudinally, i.e. so that they have a curved oblong cross-
section. These secondary arcuate sections minimise interlocking
of the elements when they are dumped to form a packing, and
give a more effective use of the surface area of the packing
element by reducing the pressure drop (and as a consequence
improving the capacity) and improving the mass transfer per-
formance.
The elements shown in Figures 6 to 8, 16 and 17 each
have punched out tags T to give the packing a more open struc~
ture, a lower pressure drop and higher capacity. In the case oE
Figure 6, the tag T also minimises interlocking of the packing
elements and ensures that they can be poured easily and quickly
to form a generally random oriented bed of packing elements in
appropriate apparatus. These tags T may be straight as shown
in Figures 6 to 8 and 16, curved in one direction as shown in
Figure 17 or curved in two directions, i.e. longitudinally and
transversely.
-16-
1098439
1 In the element shown in Figure 16, the ends of the
trough formed by base A and walls F are closed by flanges G.
Any of the elements of Figures 1 to 12 and 14 to 17
may be modified by having a non-arcuate base member, e.g. a
base member made of 3, 4 or 5 flat sections forming half of a
regular 6, 8 or 10-sided polygon respectively. The elements
shown in Figures 15 to 17 are preferably made of sheet metal by
cutting and stamping. All of the packing elements shown in
Figures 1 to 17 are designed to fall and settle relatively
randomly when they are dumped, e.g. into a suitable treatment
tower or column. Put another way, the elements illustrated have
no marked tendency to align themselves in the dumped bed, which
is characteristic of many types of elements.
It is found that for a given strength, elements used
in packings according to the present invention require less
weight of material than the prior art packing elements. This
enhances the resistance to crushing of the lowermost elements in
deep beds, and is of course, o economic advantage in that a
given bed requires less raw material to make a packing to fill
it. This resistance to crushing arises in particular from the
provision of side walls F, and Figures 20 and 21 illustrate
this.
In each case, a set of comparable pac]cing elements
were made by cutting and stamping sheet metal blanks. The
different elements are shown in side view in the box on the
graph, and the dimensions are also given in the box in mm.
Packings Nos. 4 and 10 on Figures 20 and 21 respectively are of
the configuration shown in Figure 1, Packing No. 7 on Figure 20
and No. 11 on Figure 21 are of the configuration shown in
Figure 5.
:.
~0~3439
1 In order to test the strength of the packing element
it was placed with its two ends between two pressure plates and
an attempt made to push the two ends together. The graphs show
the load in kg applied across the ends of the base member
against the deflection measured in mm, i.e. the reduction in the
straight line distance between the two ends of the packing
element.
Figure 20 shows clearly how the packing elements with
a flat base member with walls at its edge (Nos. 3, 4, 6 and 7)
were much more resistant to bending than those where the base
member had no walls. Figure 21 which shows curves for four
other members shows that the stiffness and strength increase as
the trough formed by the side walls becomes deeper (compare
packing No. 9 with packing No. 8). Aperturing the base member
with curved bridges across the aperture increases the strength
further and (though this is not evident from Figures 20 and 21)
greatly enhances the mass transfer efficiency of the packing.
Although the description of this invention has been
given with respect to particular embodiments, it is not to be
construed in a limiting sense. Many variations and modifactions
will now occur to those skilled in the art. For a definition of
the invention reference is made to the appended claims.
-18-
