Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a regular packing element
for mass transfer columns.
Regular packing elements for mass tran$fer columns
have been known, for example as described in German Patent
" Sept'~h~ ~
5. 1,253,673 issued March lg, 1974 wherein a plurality of layers
formed of corrugated, channelled, fluted, or the like plates
are placed in contact with one another and in parallel rela-
tion to the column axis. The plates define channels which are
arranged in criss-crossing patterns with the channels of ad-
10. jacent plates. These elements are useful in mass transfercolumns used for rectification, absorption, extraction and
the performance of chemical reactions, such as the separation
of isotope elemenets from a substance by a chemical exchange
reaction, e.g. the separation of deuterium from hydrogen.
15. The plates can be made, for example of metal, such
as stainless steel, or of plastics or of a self-wetting woven
or knitted fabric.
The conventional practice with the known regular
packing elements is for the plates, which are cut to size
20. from pieces of strip material, to be apertured before being
channelled or fluted or the like, so that the plain i.e.
flat, unchannelled-strips are formed with a number of rows
of spaced apart apertures. The rows are further distributed
over the strip width, the apertures in adjacent rows also being
25. disposed in aperture rows which extend perpendicularl~ to the
strip axis. The reasons for the presence of the apertures
are improved gas exchange over the cross-section of the pack-
ing element and reduction of the pressure drop along the
column axis.
30. Other kinds of aperture$ arrangements are knol~n for
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trickle packings having vertical trickle surfaces. For in-
stance, adjacent rows of apertures may be offset from one
another by half the spacing between the apertures lengthwise
of the strip. ~s will be described hereinafter, this arrange-
5. ment probably improves the spreading-out of the liquid.
When the strips are channeled or fluted or the like
at an angle, the aperture rows which were disposed perpendicu-
larly to the strip axis in the unchanneled strip become inclined
thereto. Consequently, with the channeled strip positioned
10. vertically, the apertures of any row are at a horizontal off-
set from the apertures of the adjacent row. This feature makes
this form of perforation seem very advantageous because, if
the apertures are arranged in the "plain" strip in any other
way, the apertures may finish up after ch~ling or fluting
15. or the like in rows which extend vertically of the column
axis.
Unfortunately, it has been found with the known
packing elements that the liquid phase descending the column
does not provide satisfactory distribution of the liquid over
20. the plate surfaces. When a "plain" vertical strip is devised
with rows of apertures in the known arrangement, the liauid
tends to become channeled into fall paths which extend be-
! tween the vertically superjacent apertures of the rows. This
is because the liquid descends without hindrance in such paths
~5. along the vertical fall lines and fails to spread out laterally.When the strips are formed with the inclined channeling,
i.e. when the strips are converted into the plates which will
he disposed parallel to the column axis, the aperture rows
which extend vertically in the "plain" strip are at an inclina-
30. tion to the column axis. Hence, it has previously been
1~958Z~
assumed that the liquid spread3 out laterally over the plate surface sincethe originally vertically superjacent apertures of adjacent rows are offset
from one another in the "channeled" plate. Unfortunately, and as revealed
in practice, such is not the case.
Accordingly, it is an object of the invention to assure uniform
lateral spreading out of a descending liquid in a regular packing formed
with parallel vertically disposed apertured plates.
It is another object of the invention to improve the lateral spread-
ing~out of a liquid supplied to an entry cross-section of a packing element.
It is another object of the invention to reduce channeling effects
in a regular packing element formed of corrugated plates and to enable liquid
to spread out laterally over the plate surfaces to ensure uniform wetting
thereof.
In accordance with one aspect of the invention there is provided a
regular packing element for a mass transfer column comprising a plurality of
adjacent vertically oriented corrugated plates disposed in parallel contact-
ing relation, each of said plates having a plurality of channels inclined at
an angle relative to a vertical axis and in criss-crossing relation to the
channels of one of the contacting plates, each of said plates having a
plurality of apertures therein, wherei.n with a respective plate in an initial-
ly flat uncorrugated condition said aperatures of said respective plate are
disposed in vertically adjacent horizontal aperture rows with said rows of
apertures being staggered relative to each other to define a liquid fall
path between each adjacent pair of apertures which path extends towards an
aperture immediately below said pair of apertures.
According to another aspect of the invention there is provided a
regular packing element for a mass transfer column comprising a plurality of
vertically oriented corrugated plates disposed in parallel contacting re-
: lation, each of said plates having a plurality of channels inclined at an
angle relative to a vertical axis and in criss-crossing relation to the
channels o one of the adjacent contacting plate, each of said plates having
a plurality of apertures therein, wherein with a respective plate i.n an
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initially flat uncorrugated condition, said apertures of said respective
plate are arranged in several horizontal rows with each said horizontal row
being horizontally offset from the horizontal row immediately thereabove,
and each pair of adjacent apertures in a horizontal row defining a liquid
fall path therebetween which extends toward an aperture in a horizontal row
immediately therebelow whereby said latter aperture deflects a descending
liquid laterally.
Briefly, the invention is based on the knowledge that the circum-
stances involved in the formation of free fall paths causing unwanted chan-
neling of the liquid remain the same even after the plates have been formedwith their inclined channeling. The fall lines which extend vertically in
the "plain" strip follow the direction of the channel flank planes in the
channeled plates. Consequently, the inclination of the fall line in pro-
jection of a plane parallel to the plate is the same as that of the vertical
rows of apertures in the "plain" i.e. flat uncorrugated strip. The flow
relationships of the liquid are therefore the same in both cases.
Thus, the invention provides a regular packing element comprising
a plurality of vertically oriented
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corrugated plates disposed in contacting relation with each
plate having a plurality of channels inclined at an angle
relative to a vertical axis and in criss-crossing relation to
the channels of a contacting plate. The plates are each aper-
5. tured with the apertures in each plate disposed in verticallyadjacent rows when the plate is in a flat uncorrugated con-
dition. For practical reasons, it is impossible to have uni-
form distribution of the liquid over the top edge of all the
plates right from the beginning. Also, it must always be borne
10. in mind that random disturbances may cause the liquid to re-
combine and form relatively large rivulets or streams or the
like. Therefore, the rows of apertures are staggered rela-
tive to each other to define a liquid fall path between each
adjacent pair of apertures which path extends towards an aper-
15. ture immediately below the pair of apertures.
The liquid must not flood over the apertures, andso aperture diameters of the order of magnitude of from approxi-
mately 2 to 6 millimeters (mm) have proved satisfactory.
Advantageously, the vertically adjacent rows of
20. apertures are offset from one another by an interval or spac-
ing greater than the diameter of a single aperture. Very ad-
vantageously, the vertically adjacent aperture rows are off-
set from one another by half the spacing between two adjacent
apertures.
25. Because of the manner in which the apertures ~re
arranged in accordance with the invention in the "plain"
strip,,apertures of rows disposed below the rows above are
always present in the fall paths. Consequent~y, there is a
lateral deflection of the liquid at the edges of the apertures
30. concerned even on a "plain" vertical strip. ~s previously
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explained, these flo~ circumstances remain the same even after
a strip has been formed with inclined channeling or fluting or
the llke. That is, a satisfactory uniform lateral spreading-
out of the liquid over the surfaces of the plates forming a
regular packing element is provided.
The effect according to the invention does not as-
sume that all the apertures are of the same diameter or that
the vertical interval (i.e. horizontal spacing) between verti-
cally adjacent aperture rows is everywhere the same.
As experiments have shown, it is advantageous for
the total perforate area of a plate to be of the order of from
5 to 20% of the imperforate plate area to provide an adequately
; large wetted surface on which effective mass transfer depends.
To make very sure that there is no possible risk of
the liquid being channeled along the channels troughs as a
result of possible capillary action in the troughs, the holes
must be statistically evenly distributed over the whole surface.
This is achieved by having the spacings between the apertures
of the aperture rows which extend transversely of the column
2a axis not be in a simple relationship to the pitch of the chan-
neling. That is, the quotient of the between aperture spacing
to the pitch is not to be 1, 2, 3 and so on, for it then becomes
:~ certain that a number of the apertures which are disposed in a
statistical distribution over the plate surface are always near
the channel troughs. In addition one has to ensure that the
holes are not preferentially aligned in directions nearly parallel
to the angle of the crimping. ~or example, the angular inclina-
tion of an inclined ~ow of apertures must always have an angle to
the direction of the crimping. Otherwise, if one hole lies in
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a trough all the holes in the direction will also lie in the
trough and vice versa.
These and other objects and advantages of the inven-
tion will become more apparent from the follo~ing detailed de-
scription and appended claims taken in conjunction with the
.
accompanying drawings in which:
Fig. la illustrates a diagrammatic form of part of
a conventionally perforated strip;
Fig. lb illustrates a diagrammatic form of the strip
1~ of Fig. la after channeling;
Fig. lc illustrates a view taken on line Ic-Ic of
Fig. lb ~Fig. lc);
Fig. 2 illustrates a diagrammatic view of a flat or
"plain" apertured plate according to the invention;
Fig. 2b illustrates a diagrammatic view of the plate
, o~ Fig. 2a in corrugated form according to the invention;
Fig. 2c illustrates a view taken on line IIc-IIc of
Pig. 2b;
Pig. 3 illustrates a perspective view showing the
2n discrete plates of a packing element according to the invention;
and
Fig. 4 shows part of a mass transfer column compris-
ing three regular packing elements according to the invention.
- Referring to Fig. la, the portion shown of a con-
ventionally perforated strip 1 is formed with vertically asso-
ciated rows of apertures 2. If the strip be regarded as a
vertically upright unchanneled or "plain" plate, the aper-
ture of adjacent rows are in a vertical alignment, the aper-
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tures of the horizontal rows being disposed at equidistant
intervals a. As shown, fall paths s arise between the aper-
tures in the route of fall lines f and a liquid can descend
in the paths s unhindered and without spreading out laterally.
5. Thus, the zones between vertically adjacent apertures remain
at least substantially unwetted.
Fig. lb shows a portion 1' of a plate formed from
the "plain" strip 1 shown in Fig. la, the plate having
channelings 3 which are at an inclination to the vertical
10. and which have a pitch w (Fig. lc). As can be gathered from
~ig. lb, the flow conditions of the channeled plate 1' remain
the same as for the "plain" strip 1, i.e. although the fall
lines f' of Fig. lb are at an angle to the vertical, the fall
lines are still routed over the same apertures while the fall
15. paths s' arise between the apertures.
Referring to Fig. 2a, in accordance with the inven-
tion, a "plain" i.e. flat uncorrugated plate 4 is provided
with apertures disposed in vertical rows and horizontal rows
with each horizontal row being horizontally offset from the
20. horizontal row immediately above. Each pair of adjacent
apertures 5 in a horizontal row defines a fall path which ex-
tends toward an aperture in a horizontal row immediately ~elow
whereby the lower aperture deflects a descending iiquid later-
ally.
25. Referring to Fig. 2a the use of a plate 4 which has
been perforated in accordance with the invention obviates the
channeling of the liquid which occurs in the strip of Fig. lb
since the fall paths disposed between any two apertures 5 of
any upper row has an aperture of a lower row in the way. The
flowing liquid thus undergoes lateral deflection at the aper-
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ture edges, as indicated by arrows, and spreads out over the imperforate
surface of the plate 4
Since the flow conditions remain the same after the plate has been
formed with inclined channeling, the surface of the channeled plate 4' is
wetted completely In the embodiment shown (cf. Figure 2b) the channelings
have the same inclination and pitch as the channelings 3 of Figures lb and lc.
As shown in Figure 2a, the apertures 5 are arranged so that the resulting
inclined rows of apertures form along a line 7' which always forms an angle
to the direction of crimping 6'.
Figure 3 shows a regular packing element 7 embodied from plates 4'
devised as shown in Figures 2b and 2c; the plates 4' are shown in the sequence
in which they will subsequently be placed one upon another and combined to
form a packing element 7 and then introduced into the mass transfer section
of a cylindrical column. The drawings make clear the fact that the various
plates differ in size, plate size so increasing from the two outsides towards
the center that the plates when brought together form a cylindrical member.
Figure 4 shows a portion 8 of the mass transfer part of a column
in which there are three elements 7, each at a 90 offset from one another.
The plates can be made, e.g. of metal plate.
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