Gas-liquid contact apparatus

This vapor-liquid contact apparatus, suitable for use in fractionating tower sections, includes a plurality of grids which are arranged in a vertical stack. Each grid is formed of a plurality of parallel, horizontal elongated segments; and, the longitudinal axes of the segments are angularly turned relative to the segment axes in the grid therebeneath. Each segment has an upstanding flange which supports a downflowing film of liquid, and a trough portion for receiving liquid which has flowed from the flange. The trough portion is provided with liquid drain openings which are located to release liquid directly onto contacting upper edges of the flanges of the next lower grid. A plurality of connector portions, integral with and bent outwardly from the flange portions, are spot welded to the trough portions to interconnect these elements. The gas flows upwardly through openings which are provided between the flanges and troughs of the segments. The ascending gas strikes a blunt nose formed by the lower surface of the trough, giving the gas a slight angular velocity without a substantial pressure drop, and promoting the contact of the gas with the liquid film on the flange.

BACKGROUND OF THE INVENTION 
This invention relates to improved gas-liquid contact apparatus in which a 
fractionation tower or other vessel is provided with a packing formed of a 
vertical stack of grids. 
Packing materials are used in chemical processing apparatus to provide (a) 
a supporting surface for the downward flow of liquid and (b) openings for 
the upward flow of gases. Liquid which is introduced to the upper end of 
the packing flows downwardly as a thin film on the surfaces of the packing 
material. Gaseous vapors are injected into the lower end of the vessel and 
ascend through the openings in the packing material, moving through the 
vessel in intimate contact with the liquid film on the surface of the 
packing. Such contact between the liquid and gas can produce mass 
transfer, a chemical reaction, heat exchange and/or scrubbing of the 
gaseous stream. 
The invention described in this specification is primarily envisioned for 
use in heat exchange sections of fractionation towers, such sections 
usually being located where there is a liquid flow rate in relation to the 
gas flow rate. This occurs in pump-around sections and flash sections of 
vacuum fractionating towers where direct contact between the vapor and the 
liquid are used to remove heat from the ascending vapor. Ideally, this can 
be achieved with a minimal amount of entrainment of liquid droplets into 
the gaseous stream, a minimal pressure differential between the incoming 
gases and the outgoing gases, and a continuous downward flow of liquid 
which assures that effective heat exchange will continue throughout a wide 
range of gas flow rates. 
A variety of packings are available for the heat exchange sections of 
fractionation towers but, to the inventor's knowledge, all fall short of 
meeting the ideal characteristics listed above. Such packings may provide 
downwardly-facing surfaces which are shaped or dimensioned so as to 
provide an undue pressure drop in the gaseous stream, they may inherently 
release liquid droplets which cause splashing and promote entrainment of 
liquid in the gaseous stream, or they may have other shortcomings. The 
objectives of the present invention are to provide a superior packing 
material which deters entrainment, minimizes pressure drop and provides an 
effective contacting relationship between the gas and liquid. 
A single-layer liquid distributor for use with random packings is disclosed 
by the Moore et al U.S. Pat. No. 4,171,333. Some earlier packing materials 
are disclosed in the following U.S. Patents: 
U.S. Pat. No. 100,766, Huntington 
U.S. Pat. No. 556,811, Dold 
U.S. Pat. No. 1,118,267, Burhorn 
U.S. Pat. No. 2,591,343, Eld 
U.S. Pat. No. 2,885,195, Haselden 
U.S. Pat. No. 2,998,234, Haselden 
U.S. Pat. No. 3,533,609, Brandt et al. 
U.S. Pat. No. 3,079,134, Winn 
U.S. Pat. No. 3,343,821, Winn et al. 
A primary objective of the present invention is to provide a packing which 
is effective and results in minimal gaseous pressure drop and a minimal 
entrainment. Additionally, it is an objective to provide a packing which 
is relatively uncomplicated, easily manufactured and structurally sound. 
The invention claimed in this application is an improvement to the packing 
disclosed in U.S. patent application Ser. No. 267,494 filed May 27, 1981. 
However, in addition to the attributes of the previously disclosed 
packing, the present invention provides a packing which requires less 
material for manufacture. 
SUMMARY OF THE INVENTION 
In one respect, the present invention involves a gas-liquid contact 
apparatus in which each grid in a vertical stack has a plurality of 
parallel elongated upstanding flanges, a plurality of trough portions 
which lie between the flanges and extend parallel thereto and a plurality 
of gas openings which are located between the trough portions and the 
flanges to permit an ascending stream of gas to flow over and in contact 
with a film of liquid which is disposed on the flanges. The trough 
portions each lie in contact with the upper edges of the flanges on the 
next lower grid, and liquid drain openings are provided in the troughs 
where they contact the flanges of the next lower grid so that liquid in 
the troughs will drain gravitationally onto the flanges of the next lower 
grid. To conserve material during fabrication, the flanges are connected 
to the trough portions by a plurality of connector portions which are 
integral with and bent outwardly in opposite directions from their 
respective flanges. 
In another respect, the invention involves a grid formed of a group of 
segments which each have a bottom wall and at least one upstanding flange. 
The bottom wall is formed of a trough portion and a plurality of spaced 
apart connector portions which collectively provide an upward 
liquid-supporting surface which is sloped downwardly to a lowermost 
liquid-releasing distribution point on the flange. To conserve material 
during fabrication, the flanges are connected to the trough portions by a 
plurality of connector portions which are integral with and bent outwardly 
in opposite directions from their respective flanges. The distribution 
point is in contact with an upper edge of an upstanding flange of a grid 
therebelow so that liquid from the distribution point will flow onto the 
upstanding flange therebelow. The bottom wall has gas openings which lie 
between the flange, connector portions and trough portion. The connector 
portions are located where they will be struck by liquid which may fall 
through the openings of the grids thereabove and, due to the sloping of 
these connector portions downwardly to the trough portions, they carry to 
the distribution points both the liquid which flows onto the connector 
portions from the upstanding flange and the liquid which strikes the 
connector portions. 
From another perspective, the invention relates to gas-liquid contact 
apparatus in which each grid in a vertical stack of grids is formed of a 
plurality of segments which have longitudinal axes which are parallel to 
each other and are angularly tuned relative to the segments in the grid 
therebeneath. Each segment has a trough portion, a flange portion and 
connector portions. The trough portions extend longitudinally of the 
segments and they are provided with a first set of spaced apart openings 
which are drain openings for the gravitational drainage of liquid 
therefrom. The flange portions have upstanding orientations and they 
extend longitudinally of their respective segments. The flange portions 
are spaced from the trough portions, and they have surfaces for supporting 
thereon a downwardly-flowing film of liquid. The connector portions are 
integral with the flanges, and they are bent outwardly from their 
respective flanges in opposite directions. The connector portions are 
longitudinally spaced apart on their respective segments and they are 
connected to the trough portions. The connector portions slope downwardly 
from the flange portions to the trough portions and they have surfaces for 
carrying liquid from the flange portions to the trough portions. 
Between the spaced apart connector portions, there is a set of gas openings 
which permit a stream of gas to pass upwardly through the segments in 
contact with the liquid on the wall portions. The drain openings in each 
grid have edges which lie in contact with the flange portions of the grid 
therebeneath so that liquid will flow from the troughs of one grid on to 
the upstanding flanges of the grid therebeneath. 
There are also a number of preferred features according to the invention. 
For example, to minimize pressure drop and to enhance the effectiveness of 
the gas-liquid contact, each of trough portions has a lower surface which 
is rounded to provide a blunt nose for diverting the ascending gas toward 
the gas openings. In its preferred form, the gas openings in each grid 
have an area which a vertical projection is at least 60% of the total area 
of the grid in vertical projection. The drain openings are preferably 
spaced apart a distance which is equal to the spacing between the upper 
edges of the upstanding flanges of the given segment. Each trough is 
located midway between two of the flanges. To promote the distribution of 
liquid across the surface of the flanges, it is desirable to provide the 
flanges with holes which lie directly below the drain openings of the grid 
thereabove. These holes are operable to divert the film of liquid across 
the surface of the flange.

DESCRIPTION OF THE INVENTION 
FIGS. 1 and 2 show a vapor liquid contact apparatus in which three 
generally horizontal grids 2 are arranged in a vertical stack. Each grid 
has a plurality of longitudinally extending parallel upstanding flanges 4 
which are preferably vertical and provide the primary surfaces for 
supporting the liquid during its contact with the ascending gas stream. 
Beween each pair of flanges 4, there are longitudinally extending bottom 
walls 6 which slope downwardly in a shallow V-shape at an inclination 
angle which preferably is no greater that about 30.degree.. The upper 
surfaces of the bottom walls 6 are utilized to support downflowing liquid, 
preventing the introduction of the liquid into the gaseous stream and 
directing the liquid to a distribution point where it will be able to flow 
directly onto the flanges of the next lower grid 2. 
More specifically, as shown in FIGS. 2 and 4, the bottom wall has a 
plurality of longitudinally spaced sloped connector portions 8 and 
longitudinally extending parallel trough portions 10 which preferably lie 
midway between the flanges 4. Each of the trough portions 10 is provided 
with a plurality of liquid drain openings 12, the edges of which lie in 
contact with the upstanding flange portions 4 of the next lower grid. This 
provides a number of distribution points 14 where liquid flows from the 
troughs 10 of one grid directly onto the upstanding flanges 4 of the grid 
therebeneath. 
As shown in FIG. 2, the gas openings 16 are relatively large. They are 
located in the bottom walls 6 and they are bounded by the connector 
portions 8, the troughs 10 and the upstanding flanges 4. The precise 
configuration of these openings 6 is not considered critical, and it is 
believed that the apparatus will work equally well if not better if each 
of the illustrated generally rectangular openings were replaced by a set 
of four spaced apart circular openings. 
The lower surface of the trough has a blunt nose for diverting the gas 
toward the openings 16, imparting to it a slight rotational motion which 
enhances its contact with the liquid on flange 4. Preferably, this nose is 
somewhat rounded, having a radius of about 0.625 inch. 
Although each complete grid may be of a unitary nature, it is preferred 
that it be formed of a set of interconnected discrete members. The 
structure of one such member for the grids of FIGS. 1, 2 and 5 is best 
seen in FIGS. 3 and 4 wherein FIG. 3 shows a blank 18 used for forming the 
member and FIG. 4 shows an upper grid which utilizes such a member when 
bent to its final configuration. In this drawing, it will be seen that the 
member has one complete flange 4 and one partial flange 20. On the partial 
flange 20, there is a set of spaced apart dimples 22. At a corresponding 
spacing, the complete flange 4 is provided with outstruck tabs 24. As 
shown in FIG. 5, the tabs 24 provide the flange 4 with two parallel 
surfaces 26 and 28 which lie in spaced parallel planes and are capable of 
receiving therebetween the partial flange 20. When the pieces are properly 
fitted together, the edge portion of the partial flange 20 has one surface 
bearing against the outer surface 26 of flange 4 and its other surface 
bearing against the inside surface 28 of the tab. The resilience of the 
tab 24 holds the dimple 22 in the recess formerly occupied by the tab, 
thereby preventing inadvertent separation of the members. 
In order to promote the distribution of liquid horizontally across the full 
extent of the upstanding flanges, it is desirable to provide the 
upstanding flanges with holes 30, best seen in FIG. 4, which are located 
directly below the drain openings 12 of the next higher grid. The liquid, 
when arriving at the holes 30, will be diverted laterally so that a larger 
surface area of the vertical flange will be wetted. 
By way of example, a suitably dimensioned apparatus according to the 
invention may have a transverse distance of 2.25 inches between the 
upstanding flanges 4 and a corresponding 2.25 inch longitudinal distance 
between the drain openings 12 in the trough 10. These drain openings 12 
have a width of 0.25 inch and a length of 0.5 inch. They are elongated to 
assure that they will contact the upper edge of the flange 4 of the next 
lower unit when there is some misalignment or when there are generous 
fabrication tolerances. The holes 30 in the vertical flanges 4 may have a 
diameter of about 0.5 inch. The overall height of each segment is about 
2.25 inches, and the height of the flange portion thereof is about 1.625 
inch. With these dimensions, the apparatus has approximately 40 to 50 
distribution points per square meter. 
A preferred embodiment of the present invention, shown in FIGS. 6 and 7, 
has essentially the same proportions, orientation and operating 
characteristics as the apparatus of FIGS. 1-5, but it is superior in the 
respect that it requires less material. In this version which is the 
subject of the present invention, the upstanding flanges 104 and connector 
portions 108 are integral with each other and are formed from a flat blank 
such as the one shown in FIG. 6. Prior to the final assembly of a grid, 
the connector portions 108 are bent outwardly and downwardly from their 
respective flanges 104. This disposition is shown in FIG. 7, where it will 
also be noted that the connector portions in each pair extend in opposite 
directions from their respective flange 104. 
Separately formed trough members 110 lie midway between and parallel to the 
flanges 104. These trough members are spot welded to the outer ends of the 
connector portions 108, and they are provided with liquid drain openings 
112 which release liquid onto the vertical flanges 104 of the next lower 
grid. The troughs 110 contact the flanges 104 at a number of distribution 
points 114 where liquid flows directly from an upper trough to the 
upstanding flanges of a lower grid. 
The outward bending of connector portions 108 provides the flanges 104 with 
openings 130. These openings 130 are located directly below the drain 
openings 112 of the next higher grid, and they promote the longitudinal 
distribution of liquid along the flanges. 
As in the embodiment of FIGS. 1-5, the structure of FIGS. 6 and 7 provides 
a large open area for the ascending gas, and the troughs 110 have blunt 
noses which give the gas a slight rotational movement and divert it toward 
the openings formed between the elements 104, 108 and 110. 
Persons familiar with chemical processing apparatus will recognize that the 
apparatus will normally be installed in a fractionating tower, with the 
ends of the grids being trimmed to fit closely against the interior wall 
of the vessel. To prevent liquid or vapor bypass, it may be necessary to 
provide a mechanical sealing means around the circumference of each grid. 
A thin annular split ring of sheet metal having a width of one or two 
inches may be used between each grid to close off gaps between the vessel 
wall and the end of the grid segments. 
Within the fractionating tower, means are provided for distributing liquid 
onto the upper end of the packing. A spray nozzle distributor may be used, 
but it is preferred to use a set of perforated pans or apertured tubes 
with openings which release streams of liquid onto the grids. Below the 
grid system, there is provided a means for introducing the gas and a means 
for withdrawing the liquid. A gas outlet is provided in the vessel at some 
point above the packing. 
Another potential location for this novel packing material would be in 
connection with random packings such as pall rings, saddles and the like. 
Two or more stacked grids may be placed directly upon a random packed bed 
to provide a precisely spaced set of contact points where liquid is 
distributed into the random packings. 
In larger diameter towers, each grid may be formed by a set of panels which 
have, for example, nine parallel upstanding flanges 4 or 104. The 
outermost flanges of adjacent panels will be face-to-face against each 
other. In the FIG. 7 embodiment, the two outermost flanges 104 of each 
panel will have its connectors 108 bent only inwardly toward the center of 
the panel. The lower edges of these outermost flanges will lie in a plane 
which includes the lower surfaces of the troughs 110 of the panel. In this 
respect, the outermost flanges have their lower edges located somewhat 
lower than the lower edges of the other flanges 104 of the panel. When 
such a panel is placed in a tower, the troughs and the lower edges of the 
two outer panels will be supported by the underlying grid and/or internal 
supports which are installed in the tower.