US 2630305 A
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Description (OCR text may contain errors)
March 3, 1953 R. c. SCOFIELD ET AL 2,630,305
TOWER PACKING Filed April 29, 1949 3 Sheets-Sheet l INVENTORS. 1 Z1 I fqyzzzoz'zadjcofz'eld Jsef ffr'alze :9-
March 3, 1953 R. c. SCOFIELD ETAL 2,630,305
TOWER PACKING Filed April 29, 1949 I 5 Sheets-Sheet 2 IN V EN TORS fay? azza' cofl'eld Josef fire/2e March 3, 1953 R. c. SCOFIELD ET AL 2,630,305
TOWER PACKING Filed April 29, 1949 s Sheets-Sheet 5 Patented Mar. 3, 1953 UNITED STATES PATENT OFFICE TOWER PACKING Raymond C. Scofield, La Marque, and Josef Krah, Texas City, Tex, assignors to, Pan, American Refining Corporation, Iexas City,
Tex a corporation of Delaware.
Application April 29, 1949, Serial No. 90,286
' rality of transverse cells, and more particularly I 2 perimposed foraminous packing units defining a plurality of generally symmetrical cells bounded by multi-layers of non-filming meshed structures to provide a repeatedly divided path for the liquid the invention is an improvement on that dedownwardly and laterally andatortuous but conscribed and claimed in a copending Scofield aptinuous path upwardly for the gasiform material. plication S. N. 713,333, filed November 30, 1946, The flow behavior and contact efiiciency of the which is now Patent Number 2,470,652 dated May packing of the type to Which this invention re- 17 1949 lates is, however, influenced by several character- A primary object of this invention is to proistics of the packing. Thus, the number of vide a method and means for contacting vapors foraminous sheets comprising the individual and liquids which is particularly adapted for mate, the slope of the ridges and troughs, and large diameter commercial construction and the amplitude of the undulating mats are correwherein substantially the entire cross-sectional lated to attain the optimum operation. For fracarea of the column is effective as a region for such tionation operations normally carried out at atcontacting. Another object of the invention is mospheric pressure an overall height of about to provide a prefabricated packing of simple and four inches is appropriate, the sides forming an inexpensive construction, and which is substanangle with the horizontal in the rang of from tially self-supporting for considerable heights. 40 to 50 degrees. For relatively higher liquid A further object of this invention is to provide a 20 loadings such as are encountered in elevated method and means for suppo ti g p rp pressure operation somewhat better performance undulating mats in aligned relation without 0bmay be obtained by increasing the angle with structing the flow of vapors and liquids through the'horizontal to a value in the range of from the packing. An additional object of this inven- 40 to '75 degrees. For relatively lower liquid tion is to provide positive means for maintaining loadings such as are encountered in vacuum opthe superposed undulating mats in capillary coneration the performance is improved by reductact so as to define a multiplicity of cells. ing the angle with the horizontal to a value in further object of the invention is to provide a the range of from 25 to 50 degrees. These ampliself-supporting packing which can be employed tudes and slopes change when the packing mats in the modification of existing towers. These and are deformed and if the mats are not aligned other objects of the invention will become approperly the cells may be by-passed and the flow parent to those skilled in the art as the descripof liquid may be erratic. Accordingly, the quadtion of the invention proceeds. rilateral cages are of such shape as to define the The objects of this invention are attained by cells between the adjacent undulating mats and disposing a plurality of quadrilateral skeleton maintain the walls of the cells at an angle of cages within the cells defined by the superposed between 25 and 75 degrees with the horizontal, undulating mats. These quadrilateral skeleton i. e. at these angles, with the plane of contact cages prevent the deformation of the lower mats between the adjacent mats. by the weight of the upper mats and also posi- A packing unit or mat may comprise multiple tion adjacent mats so that the troughs of the layers of self-supporting non-filming meshed upper mat are aligned with the ridges of the low structures shaped to provide inclined surfaces on er mat. To assure positive contact along the the upper and lower boundaries of the mat. ridges and troughs when the aligning quadri- More particularly, these units may comprise a lateral skeleton cages are in place, tie rods are plurality of inter-locking or integral elements provided which pass through the multiplicity of comprising filaments or strands of'metal, plastics, mats and compress the packing and force the plastic impregnated fabric mesh and the like; We mats in close engagement with each other along prefer, however, to employ sheetsof foraminous th troughs and ridges and with the quadrilateral materials such as hardware cloth, wire screening, skeleton cages therebetween. By this comb-inaexpanded metal lath and the like. The size of tion of quadrilateral skeleton cages and tie rods, the foramina is important and should be such it is possible to use mats of variable shape and to fabricate them with, greater tolerances than was possible heretofore.
As disclosed in the copending application, the system broadly comprises a column including suthat liquid having a surface tension within 25-70 dynes per centimeter at working temperatures will not be supported in a continuousfirm. In general, interstices. of between 0.15 and, 0.5 inch are preferred for larg scal installations. but
other meshed structures having larger or smaller openings can be used provided that the openings are larger in size than that which will support a continuous film of the liquid.
By way of illustration, in one satisfactory method of fabrication of the packing units, a suitable foraminous or screen-like material is chosen and pressed between dies to impart a parallel series of permanent sinuous or wave-like impressions to the sheets. A number of sheets, say 3 to 12, are superimposed and then cut to shape as, for example, by means of a rotary file or high speed cut-off grinder, to form a single packing unit. The number of such units required is fixed by the height to which it is desired to fill a tower, the amplitude or perpendicular height of the waves impressed in th packing and the thickness of the individual packing units.
A particularly satisfactory material for the individual meshed structures is expanded metal sheet or lath having integral ribbon-like members and which may be fabricated from a metallic sheet by slitting a sheet of metal and operating on the slitted sheet to bend or deflect strands to produce an open diamond mesh, the bent strands extending diagonally on the sheet in opposite directions and being connected by bands extending transversely of the sheet. This structure is obtained by slitting and stretching the sheet to provide the interlocking strands.
Between about 3 and 15 layers of expanded metal lath can be arranged in mats and held together by suitable fastening devices such as bolts, wire lacing and the like. The mats may be constructed of any suitable metal including steel, nickel, copper, aluminum or other metal or alloy particularly adapted for the contemplated contacting operation. Likewise, the meshed structure can be coated or painted if desired for protection against corrosion or to alter the wetting characteristics of the individual strands.
For convenience in handling and installing packing in large diameter commercial fractionating towers, such as towers having diameters of from 3 to 8 feet, the packing unit or mat may be rolled upon itself so that it can be inserted through convenient manholes in the wall of the tower and assembled within the tower. Such rolled sections may be bound around by a removable wire, chain or the like or the edges of the mat may be spot-welded to hold the unit in the rolled shape.
An essential feature of the invention is the arrangement of the contacting mats as a series of undulating elements horizontally across the fiow area of the tower. The most convenient and preferred arrangement is that wherein the wave crests of one undulating mat is disposed immediately below the lowermost portions of the next succeeding mat. The undulating pattern of the packing mats can be conveniently obtained by corrugating, pressuring or folding the individual meshed structures to produce oppositely and alternatively pitched surfaces. The individual shaped structures can then be assembled to produce a mat of the desired thickness or capacity.
The packing units or mats are installed within the tower horizontally with the ridges of one unit parallel to and in capillary contact with the lower surface of the troughs of the unit above to create a plurality of cells. To align ridges and troughs and to prevent collapse of the cells between adjacent units, the skeleton support members or elongated cages are provided. These elongated skeleton cages do not obstruct the flow of gases and liquids through the tower but are more resistant to deformation than are the mats which form the cells. Ordinarily these cages will be quadrilateral skeletons, the sides of which form an angle of between about 25 and 75 degrees with the horizontal.
To maintain the corresponding ridges and troughs of adjacent mats and the elongated skeleton cages in close contact, tie rods are employed which traverse all the superposed mats and compress them into the desired arrangement as defined by the elongated skeleton cages. In this ccnnection, the undulating mats may be roughly formed and the skeleton cages will align the ridges and troughs in the precise size and shape desired for the intervening cells.
The invention will be more readily understood from the following description and the accompanying drawings which illustrate preferred embodiments thereof and wherein:
Figure 1 is an elevation, partly in section, showing a column with a plurality of packing units with skeleton cages in the cells;
Figure 2 is a top plan view showing details of the apparatus assembly;
Figure 3 is a bottom plan view of the apparatus shown in Figure 1;
Figure 4 is a view in perspective showing the details of one form of the spacer element;
Figure 5 shows another form of elongated skeleton cage which is fabricated from a foraminous sheet;
Figure 6 illustrates the details of construction of the cartridge hold-down assembly;
Figure '7 illustrates one method of rolling the individual mats for introduction through a manhole;
Figure 8 is a view in perspective showing a method of installing cartridges of packing;
Figure 9 illustrates a ring seal used with cartridges of packing;
Figure 10 is an elevation in section showing a method for the support and seal of packing cartridges;
Figure 11 is an elevation in section showing a method for installing packing in small towers.
Each foraminous sheet is roughly shaped to the undulating pattern having oppositely and alternately pitched surfaces and a plurality of the roughly shaped sheets of foraminous material is nested and formed into a single unit or mat Ill by compression, for example under a dropforge hammer. The unit is then cut to the desired size and shape to fit the tower. In order to minimize short circuiting of the units I0, a packing may be employed between the unit and the tower wall. Adjacent the tower shell, a packing comprising asbestos fiber, glass rope, or the like, and a cylindrical screen or expanded metal sheet can be provided to retain the packing.
In the installation of packing within a tower, or in prefabricating a cartridge of acking the method of assembling the packing is essentially the same. The mats ID are superposed with the ridges I3 of one and the valleys M of the other being aligned to provide the cells I5 of substantially quadrilateral cross-section. Within the cells 15 is placed an elongated skeleton cage l6 and various embodiments of this cage are illustrated in the drawings. These cages define a generally quadrilateral skeleton and support the superposed mats while permitting the ridges l3 and the valleys H to remain in contact.
. "is Thus, the cases is align the adjacent mats. l and prevent distortion or collapse of the cartridge due to its elongated shape and substantial resistance to deformation by the weight of the superposed mats or by the pressure applied by the tiebol't assembly. I The skeleton. cages may comprise: a rigid wire framework as shown Figure 4'. In this embodiment, the end frame members are in the form of open quadrilateral loops I1 and Ila which correspond to the cross-sectional shape and size of the cells l5 between adjacent "superposed mats 1'0; The loops l1 and Ila are rigidly spaced from each other by communicating elements [8 and l8a, thereby producing the rigid skeleton which is adapted to retain. the cells in their original configuration without obstructing the flow of gases or va ors through the packing unit.
In addition to the preferred embodiment of'the elongated skeleton cage shown in Figure 4, it is contemplated that skeleton cages I6 may be fabricated from folded sheets of heavy f'orami- .nous material capable of resisting deformation.
In this embodiment, the ides l9 and Na contact the upper wall of the cell l5 and sides 20 and 20a of the cage shown in igure 5 contact the lower wall or fioorof the cell l5. Thus, the four sides of the folded cage shown in Figure 5 positively and firmly contact the upper and lower walls of the cell l5. Accordingly, the cage being constructed of heavy foraminous or expanded metal sheet successfully resists deformation of the cell while 'aligning the ridges and valleys.
Still another embodiment of the skeleton cageis may comprise quadrilateral segments of toraminous material. such as heavy expanded metal sheet, shaped similar to the cross-section of cells l5. These rigid segments are jointed by tie mem ers to form an elongated skeleton cage.
The folded quadrilateral cages of expanded metal sheets, such as shown in Figure 5, possess the additional feature of preventing relative movement of the su erposed mats laterally and tend to anchor the adjacent mats. Furthermore, the continuous sheet in bridging the point of capillarv contact between adjacent mats provides an auxiliary path for the flow of the liquid.
Figures 1, 2, and 3 show an assembled packing cartridge. In this cartridge, tie bolts 2! are provided extending between the bottom packing support grid 22 and the topmost mat in the cartridge. The supporting grid 22 comprises a parallel series of bars or tubes 23 which are transverse to the ridges l3 and the valleys M of the mats ID. The lower ends of the tie bolts 2! are fixed to the sup orting grid 22 so that a force applied by tie bolts 21 tends to move the packing toward the grid 22. The upper ends of the tie bolts 2! are threaded to engage the nut 24 and sleeve 25 which coacts with the grid22 to urge the adjacent mats into positive contact. This resilient contact can be made more positive, if necessary, by drawing down on the sleeves 25 after the assembled cartridge is in place. A lat-'- eral tie member 26 extends between the outer tie bolts 2| and central tie bolt 23 as shown in Figures 1 and 2 of the drawings. This member 26 is illustrated as comprising a wire loop which is shortened by twisting.
In addition to pre-fabricating the cartridge outside of the tower, the invention contemplates the fabrication of the packing assembly within the shell or tower. Thus, the individual packing unit or mat may be rolled on itself about an axis substantially parallel to the ridges and vanleys and bound by a removable wire, cord or strap 2'! as shown in Figure 7 These bound rolls are then passed through a manhole and unroll'ed within the tower. The individual mats are then threaded over the tie bolts 2| after placing the desired number of skeleton cages it within the valleys of the exposed mat. In connection with this mode of assembly, the skeleton cages l6 perform the added function of. supporting the workmens weight. In those instances where there is no justificationfor installing packing to the full diameter of a given tower, the packing cartridge may be built up within the tower in the manner illustrated in Figure 8. Sheet metalmay be employed to build up the walls of the cartridge, restrained by rings 29 or circular bands. Normally, the pressure drop across lap joints 28 is so small that the amount of leakage encountered does not justify welding for urposes of seal at the lap joints; Figure 9 illustrates a manner of'e'fifecting a seal between the cartridge and tower wall by inserting an annular ring 30 and employing circumferential welds for purposes of seal. Bolted gasket seals may be used in place of welds.
In small diameter towers the cartridge form of installation shown in Figure 10 may be employed. The packing is first installed and supported in a cartridge shell and this in turn is supported and sealed within the tower by a ring 31 inserted between flanges 32 and 32a.
Another means of utilizing packing in small towers is shown in Figure 11. This method utilizes short enough tower sections for convenience in installing packing and then assembling these sections after the packing has been installed. Each section has its own sup orting grid 33 and is joined to the next section by a circumferential weld 34.
The packing illustrated in the drawings is in the form of a modified sine curve. but other shapes are contem lated. Mats having simple -shaped valleys and ridges may be used and by means of the skeleton cage supports a proper alignment and contact between the ridges and trou hs of adjacent mats can be obtained.
Although we have described our invention with particular reference to certain embodiments thereof, this'is for the purpose of illustration only and the invention is not limited thereto. Accordingly, it is contemplated that modifications coming within the scope of our invention can be made by those skilled in the art without departing from the spirit thereof.
What we claim is:
1 A contacting apparatus comprising a shell and a pro-fabricated cartridge including a bottom support grid, a plurality of superimposed mats constructed of a plurality of layers of wire fabric in capillary contact and having alternate ridges and valleys on their plane surfaces; the ridges of one mat coinciding with and contacting the Valleys of th'e mat next above to provide a plurality of cells of generally quadrangular cross section disposed transverse to the vertical axis of the cartridge, elongated quadrangular skeleton cages in at least some of said cells adapted to maintain the adjacent mats in aligned relation while permitting capillary contact of the meeting ridges and valleys, tie rods extending longitudinally through the cartridge upwardly from said support grid and terminating above the topmost mat in said cartridge, and means for drawing coacting ridges and valleys of said mats into capillary contact between said topmost mat and said grid support means.
2. In an apparatus for contacting wherein a plurality of superimposed porous mats consisting of nested contiguous foraminous sheets with alternately and oppositely pitched plane surfaces defining a plurality of parallel quadrilateral elongated cells, the improvement which comprises longitudinally adjustable tie rods extending through said mats and adapted to maintain adjacent mats in capillary contact, said mats tending to spread in a direction transverse to said cells when placed under compression by said tie rods, and a plurality of elongated quadrilateral skeleton cages removably disposed within said cells between adjacent mats to maintain the mats in the desired spaced relation and to cooperate with other skeleton cages in adjacent cells to maintain the mats in non-spreading alignment.
3. The apparatus of claim 2 including at least two tie rods in alignment along a diameter transverse to the ridges and valleys of the mats, and a lateral tie means extending between the upper ends of said tie rods above said mats whereby groups of such mats and skeleton cages can be drawn laterally between the tie rods.
4. A contacting apparatus comprising a shell and a prefabricated cartridge including a bottom support grid, a plurality of superimposed mats constructed of a plurality of layers of foraminous sheets in capillary contact with each other and having alternately and oppositely pitched plane surfaces producing a series of parallel ridges and valleys, each said mat having compliance about the axis of said ridges and. valleys, the ridges of a lower mat coinciding with and contacting the valleys of the mat next above to provide a plurality of cells of generally quadrangular cross section disposed transversely to the vertical axis of the cartridge, elongated quadrangular cages in at least'some of said cells, said cages having open ends and four walls of foraminous sheet material, the walls of said cages being adapted to contact corresponding oppositely and alternately pitched surfaces of adjacent mats to maintain the adjacent mats in aligned relation for capillary cont-act of the coacting ridges and valleys, tie rods extending longitudinally through the cartridge upwardly from said bottom support grid and terminating in the topmost mat in said cartridge, and means carried by said tie rods above said ridges for compressing said mats toward said bottom support grid and into contact with said cages.
5. The contacting apparatus of claim 4 which includes a temporary lateral draw means extending between the ends of at least two tie rods for temporarily reducing the dimension of the cartridge transverse of the valleys and ridges whereby the cartridge can be lowered into a chamber and a tight wall fit obtained by releasing the temporary draw means and permitting the cartridge to expand laterally in place.
6. A packing for a vapor and liquid contacting apparatus adapted to be arranged within a vertical cylindrical shell comprising in combination a multiplicity of prefabricated mats composed of a plurality of foraminous sheets and having alternately and oppositely pitched plane surfaces which produce a parallel series of alternate ridges and valleys, a first mat across the entire flow area of the shell, a plurality of elongated quadrangular open-ended cages within each of the valleys of the first mat, a second mat over the first mat, arranged with the ridges of the lower first mat parallel to the valleys of the upper second mat and in capillary contact over said cages, and additional alternate groups of cages and of superposed mats above said first and second mats to provide the packing of the desired depth.
'7. An apparatus adapted to be installed as a prefabricated contacting unit within a cylindrical chamber comprising in combination a base grid, a series of superposed mats on said grid and having alternately and oppositely pitched plane surfaces, the superposed mats producing a series of parallel cells deformable only in a direction transverse to the axis of the parallel cells, a plurality of such superposed mats threaded over at least two tie rods arranged along a diameter of said chamber transverse to the axis of said cells, a plurality of quadrangular skeleton cages removably disposed within said cells, means for temporarily drawing the upper ends of said tie rods toward one another so as to deform said cells and progressively reduce the diameter of the series of superposed mats, and means carried by said tie rods for applying compression to said cartridge by drawing down on said superposed mats whereby said cartridge unit is maintained in wall-sealing contact with the wall of said chamber.
8. The apparatus of claim 2 wherein said cages comprise a folded foraminous sheet.
9. The apparatus of claim 2 wherein said cages comprise open quadrilateral loops rigidly spaced from each other by rod-like elements.
10. The apparatus of claim 6 wherein the packing is encased by metal walls separable from the cylindrical shell.
11. The apparatus of claim 6 wherein each of said cages comprises folded foraminous sheet.
12. The apparatus of claim 6 wherein each of said cages comprises a pair of spaced open quadrilateral loops held in a rigid array by rodlike elements.
RAYMOND C. SCOFIELD. J OSEE KRAHE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,436,483 Cox Nov. 21, 1922 1,749,256 Sontag Mar. 4, 1930 2,047,444 Stedman July 14, 1936 2,332,110 Podbielniak Oct. 19, 1943 2,336,060 Bragg Dec. 7, 1943 2,470,652 Scofield May 17, 1949