US2981665A - Internal structure for heat and mass exchanging columns - Google Patents

Description

April 25, 1961 HANS-JOACHIM KLoss 2,931,665

INTERNAL STRUCTURE FOR HEAT AND MASS sxcmucmc COLUMNS Filed March 18, 1958 2 Sheets-Sheet 1 q z Q9 w;

April 1961 HANS-JOACHIM KLOSS 2,981,665

INTERNAL STRUCTURE FOR HEAT AND MASS EXCHANGING COLUMNS 2 Sheets-Sheet 2 Filed March 18, 1958 INTERNAL STRUCTURE FOR HEAT AND MASS EXCHANGHQG COLUMNS Hans-Joachim Kloss, Hilden, Germany, assignor to Julius Montz K.G., Apparatebau, Hilden, Germany Filed Mar. 18, 1958, Ser. No. 722,350

Claims priority, application Germany Mar. 18, 1957 7 Claims. (Cl. 202-158) The invention relates to an internal structure for conducting a liquid trickling downwards inside a heat or mass exchanger column. The object of providingsuch internal structures is to conduct liquids which interact by heat or mass exchange in countercurrent with vapors in such manner that the transfer rate will be optimal. It is desirable that such structures should offer the minimum possible resistance to the flow of the vapors. This is a matter of especial importance in columns which operate at a fairly high vacuum, because in such circumstances even minor changes in pressure have a much greater effect on the boiling point of a liquid than in the region of normal atmospheric or higher pressures.

Whereas in columns operating at atmospheric or elevated pressures bubble caps and sieve plates are usually employed, it is preferred in vacuum columns to use internal structures consisting of irregularly heaped beds or specially shaped packing elements. The liquid is forced to trickle over these packings. They otter little resistance to the vapors which rise in countercurrent' from the bottom of the column.

It is known that optimum transfer rates are achieved if the tricklingliquid is evenly distributed over the entire cross section of the bed and if the thickness of the film is uniform over the whole surface of the packing elements and the film is steadily maintained by the trickling liquid. However, these ideal conditions cannot be created when using irregularlyheaped beds, since the liquid always flows down the steepest available gradients. In practice small localized streams will thus form and some parts of the bed will not be wetted at all.

Instead of providing irregularly packed beds recourse has already been had to the use of packing elements which consist of parallel vertical tubes of circular section in such manner that heat exchanging or mass transferring contact between the rising vapors and the liquid trickling downwardly on the inner walls of the tube will occur. However, also in such tubular structures the film of liquid will not be uniformly distributed over the entire inside surfaces of the tube. In fact, the liquid similarly tends to stream down'the tube in preferred courses. i

The invention therefore contemplates the provision of an internal structure which will conduct the liquid through the current of vapor in the form of a uniform film without offering stirfaces that will not be washed by the film.

The invention therefore proposes to provide aninternal structure consisting of narrow ribbons or Wires; arranged to occupy an overall vertical length within which they descend steadily downwards but constantly change: their though not into actual contact, that within the gap be tween the coils the liquid is held and lead by cavitation. The cross section of the ribbons or wires may be adapted to the prevailing conditions, for instance to the viscosity of the liquid. Their cross section may be round, oval, V-shaped or U-shaped. In any event the width of the ribbons or strips should be small." Generally speaking, in order of magnitude, a width of a few millimeters will be appropriate.

Preferably the helically coiled ribbons may be crossconnected by bridge members for maintaining their spacing. The ribbons or wires may also be arranged in spaced pairs, so that a considerably greater amount of liquid is held between the ribbons as on single ribbons or wires.

Instead of consisting of separate coiled ribbons the proposed structure may consist of a hollow cylindrical tube with helically slotted walls to form a plurality of parallel helical ribbons andbetween neighboring ribbons leaving bridge members. A particularly useful form of construction of such a structure is to form the hollow cylindrical tube of a helically coiled strip which is several times as wide as the ribbons formed by slotting said strip, in such manner that between neighboring convolutions a gap will remain.

Several illustrative embodiments of the invention are shown in the accompanying drawings in which:

Fig. 1 is a longitudinal section of a heat and/or mass exchanger column with internal structures contrived as proposed by the present invention;

Fig. 2 is a longitudinal section of internal structure; 1

Fig. 3 is a longitudinal section of another helically wound internal structure with two helical lines of differing diameter;

Fig. 4 is a longitudinal section of ahelically wound internal structure with three helical lines;

Fig. 5 is a hollow tube element of the internal structure;

Fig. 6 is a sheet metal ribbon for forming an element according to Fig. 5;

Fig. 7 is another hollow tube element of the internal structure with slots oblique to the middle line of the sheet metal ribbon forming the element;

Fig. 8 is the sheet metal ribbon forming the element of Fig. 7.

As shown in Fig: 1 the column comprises a bottom chamber 12, a central, chamber 2 and an upper chamber 3. i

The lower chamber 12 is separated from the central chamber 2 in the column by a dividing floor e. The

a helically wound I upper chamber 3 issimilarly separated from the central direction in such manner thatthe length of each *indichamber 2 by adividing floor 5. Fixed to floor 5 is a majornumber ofvertical tubes 6 which project through floor 4 into the lower, chamber 12, of the column. The lower chamber 12 of the column has an inlet opening. 7 for the admission of the vapor which is to interact by heat or mass exchange withthe liquid, Moreovencha'mber 2 is provided with an inlet 10 and an outlet 9 for a coolant. A branch S Imay be connected with amenhaustingor vacuum system and may possibly be used for the withdrawal of vapor. The lower extremity off each tube 6 carries a stirrup 11 for attachment thereto offan internal structure or helical. spring 1' of which. the bottom end is retained" by' a. transverse" wire 13 secured to the wall of chambert 12 insthe columni [So-that: the invention-1 may begthe;niorereadilyunden' stood thestructures thare shownwin Fig. 1 as being to arrange them as closely as possible: togfihen. Without 2,981,665 Patented Apr. 25,1961

liquid trickling down the inside walls of the tubes 6, over the stirrup member 11, and on to the helical springs 1. Whilst travelling down this lengthy path the liquid comes intointimate contact with the vapors which enter through inlet opening 7, for interaction therewith by heat or mass exchange. o v V The helical convolutions of the structures 1 offer very little resistance to the rising vapors. On theother hand, they conduct the liquid steadily downwards in a uniform film along a path which is substantially longer than the axial length of the structures. Should the film loading of the helical structures 1 become excessively high, droplets of liquid will jump from one structure 1 to the next, thus causing an exchange of liquid between the individual structures 1 with the effect of equalizing the concentration over the entire column cross section.

Although it may as a rule be preferred to give the ribbons or wires a helical configuration, the invention is by no means confined to this form of construction. The important feature of the invention is that the ribbons or wires shall descend but constantly change their direction in such manner that each ribbon or wire will conduct the liquid through the vapor along a path which is several times as long as that traversed by the vapor which may flow longitudinally or transversely into relation thereto.

Fig. 2 shows two circular wires 1a, 1b wound to two coaxial and parallel helical lines with a coil distance w and with a coil diameter a. In axial direction the helical lines have a constant distance a within which the liquid is lead by cavitation as indicated at 14.

Fig. 3 shows two circular wires 10, 1d with differing diameters d d and with a coil distance W. The horizontal distance a between the wires 1c,'1d is such that the liquid is lead between these wires at 15 by cavitation.

.Fig. 4 shows a similar arrangement with three helically wound wires 12, 1 1g.

The element illustrated in Figs. 5 and 6 consists of two similar helically coiled sheet metal strips which are provided with longitudinal slots 16, 16', 16" which divide the strip into four narrow ribbons 17, 18, 19 and 20. At intervals, equal, for instance to the length of the periphery of the completed structure, the slots are interrupted by transverse bridge members connecting neighboring ribbons together. For example the'ribbons 17 and 18 are cross-connected by bridge members 21 and the ribbons 18 and 19 by bridge members 22. The bridge members 21 and 22 are no wider than necessary to hold the neighboring ribbons together and they are therefore approximately as wide as the ribbons 17, 18, 19, 20 themselves. If possible they maybe even narrower. The bridge members 21 and 22 are staggered in such a way that a droplet of liquid trickling from one ribbon 17 acrossa bridge member 21 to the neighboring ribbon 18 cannot cross overthe bridge member 22 which connects this ribbon 18 with the next following ribbon 19 until Figs. 7 and 8 show an hollow tube element formed by an helically wound strip 25. The slots 23, 24 formed on the strip 25 run oblique to the middle line of the strip 25 and are staggered such way that the liquid trickles along the slot 23 .or 24 and, after leaving one 7 of the slots, 23 or 24, along the next slot 23 or 24 following in the direction of the strip 25.' In this way no liquid can collect in the lower part of the strip by traversing the bridge members of the slots, but the liquid trickles down uniformly.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a heat and mass exchanger column, in combination, an elongated hollow substantially vertical en closure having a vapor inlet and a vapor outlet located at a higher elevation than said inlet so that vapor entering said enclosure through said inlet moves upwardly along the interior of said enclosure to said outlet; condensing means located in said enclosure at an elevation higher than said inlet and lower than said outlet for condensing at least some of the vapor moving upwardly along the interior of said enclosure toward said outlet; and a plurality of elongated liquid film supporting elements arranged substantially vertically in said enclosure at an elevation higher than said inlet and beneath said condensing means communicating with the latter to re ceive the condensed liquid therefrom and to guide the liquid in the form of film along said film supporting elements downwardly in said enclosure in countercurrent to the upwardly moving vapor, said plurality of film supporting elements each having a length several times greater than the distance between its ends and said film supporting elements being located close to but out of contact with each other and out of contact with said enclosure so that the condensed liquid received by each supporting element is forced to flow along the whole length of the respective element and so that the film on each supporting element can be enveloped in the vapor.

2. In a heat and mass exchanger column as claimed in claim 1, in which said condensing means comprises a plurality of condensing elements, equal to said plurality of liquid film supporting elements, said liquid film supporting elements respectively communicating with said condensing elements.

3. In a heat and mass exchanger column as claimed in claim 2, the upper end of each of said liquid film supporting elements being secured to said associated condensing elements, and means attached to said enclosure for holding the lower ends of said plurality of liquid film supporting elements in place. 7

4. In a heat and mass-exchanger column as claimed in claim 1, said individual liquid film supporting elements being spaced closely but without mutual contact for the formation of individual uniform films with exchange of droplets from one of said liquid film supporting elements to an adjacent one.

5. In a heat and mass exchanger column as claimed in claim 1, each of said individual film supporting elements being shaped as a small-pitch spiral having spaced turns and a narrow slowly descending channel extending substantially the length of said spiral, the axial length of said spiral exceeding several times its width.

6. In a heat and mass exchanger column as claimed in claim 5, each of said spirals comprising two coaxial equal-pitch, equal-diameter helices, the pitch of said helices exceeding their axial spacing to form a narrow slowly descending channel therebetween.

7. In a heat and mass exchanger column, as claimed in claim 5, each of said spirals comprising two coaxial equal-pitch different diameter helices, the turns of said helices being aligned in horizontal planes'to form a narrow slowly descending channel therebetween.

References Cited in the file of this patent Germany May 5, 1923

Claims (1)

1. IN A HEAT AND MASS EXCHANGER COLUMN, IN COMBINATION, AN ELONGATED HOLLOW SUBSTANTIALLY VERTICAL ENCLOSURE HAVING A VAPOR INLET AND A VAPOR OUTLET LOCATED AT A HIGHER ELEVATION THAN SAID INLET SO THAT VAPOR ENTERING SAID ENCLOSURE THROUGH SAID INLET MOVES UPWARDLY ALONG THE INTERIOR OF SAID ENCLOSURE TO SAID OUTLET, CONDENSING MEANS LOCATED IN SAID ENCLOSURE AT AN ELEVATION HIGHER THAN SAID INLET AND LOWER THAN SAID OUTLET FOR CONDENSING AT LEAST SOME OF THE VAPOR MOVING UPWARDLY ALONG THE INTERIOR OF SAID ENCLOSURE TOWARD SAID OUTLET, AND A PLURALITY OF ELONGATED LIQUID FILM SUPPORTING ELEMENTS ARRANGED SUBSTANTIALLY VERTICALLY IN SAID ENCLOSUR AT AN ELEVATION HIGHER THAN SAID INLET AND BENEATH SAID CONDENSING MEANS COMMUNICATING WITH THE LATTER TO RECEIVE THE CONDENSED LIQUID THEREFROM AND TO GUIDE THE LIQUID IN THE FORM OF FILM ALONG SAID FILM SUPPORTING ELEMENTS DOWNWARDLY IN SAID ENCLOSURE IN COUNTERCURRENT TO THE UPWARDLY MOVING VAPOR, SAID PLURALITY OF FILM SUPPORTING ELEMENTS EACH HAVING A LENGTH SEVERAL TIMES

Images