GB2163063A

GB2163063A - Liquid distributor for a mass transfer column

Info

Publication number: GB2163063A
Application number: GB08520391A
Authority: GB
Inventors: Eduard Blatter; Ulrich Buehlmann
Original assignee: Kuhni AG; Kuehni AG
Current assignee: Kuhni AG; Kuehni AG
Priority date: 1984-08-17
Filing date: 1985-08-14
Publication date: 1986-02-19
Also published as: GB8519419D0; GB8520391D0; FR2569129A1; CH663904A5; FR2569129B1; GB2163063B; DE3529114A1

Abstract

The liquid distributor consists of several channels (1) disposed horizontally alongside one another, to which the liquid is supplied by a pre-distributor. The outlet openings for the liquid are formed by vertical slits (11, 12). One edge of the slit lies along the plane of the side wall (2, 3), the other is formed on a part (9) separated by two vertical sections from the side wall (2, 3), and bent outwardly out of it. The slits (11, 12) are disposed in a row in the upper part of the side wall (2, 3) and somewhat wider apart one from the other than from the bottom edge (14) of the side wall (2, 3) the distance between the slits (11, 12) being more than ten times the width of the slits. The bottom edges (14) of the side walls (2, 3) protrude over the bottom of the channel (4) and are zig-zag shaped. The liquid flows out of the slits (11, 12) approximately horizontally (21, 22) along the side walls (2, 3), fans out in the longitudinal direction of the channel far above the side walls (23, 24) and drips from the serrations (19) of the bottom side wall edges (14). <IMAGE>

Description

SPECIFICATION Liquid Distributor for a Mass Transfer Column This invention relates to a liquid distributor for a mass transfer column.

Liquid distributors for mass transfer columns are used to distribute the liquid over the regular packings inserted into the column. For a complete mass transfer between the liquid and the gas phase, or for a good separation it is necessary to have the distribution of the liquid over the cross-section of the column as even as possible. This applies also where the packings themselves effect a distribution of the liquid, as otherwise their upper portion would remain substantially unused.

Known liquid distributors, of the so-called channel or box distributor type, consist of channels, rectangular in cross-section, closed at the front sides, which are disposed horizontally alongside one another. The liquid is supplied to the channels through a pre-distributor disposed transversally above them, and flows through vertical slits provided in the upper longitudinal edges of the channels.

Thus, as the liquid flows out of each slit, for an even distribution of the liquid it would be necessary to have many slits in close succession. The number of the slits, however, is restricted not only for constructional reasons but also because practice has shown, especially with the smaller liquid charges, that a large number of slits brings about partial flows which differ from each other by too much.

An object of the present invention is to provide a distributor which is simple to construct and which, with a reduced number of outlet openings distributes both large and small amounts of liquid evenly along the channel.

According to the present invention there is provided a liquid distributor for a mass transfer column comprising at least one substantially horizontal channel a side wall of which has outlet openings therein, the outlet openings being so designed and disposed relative to one another that, in use, liquid within the channel flows out approximately horizontally along the side wall and runs down in the form of layers of liquid gradually fanning out from the outlet openings along the length of the channel.

By means of the design and arrangement of the outlet openings in accordance with the invention liquid flows horizontally out of the individual outlet openings and fans out on a wide area over the side wall. In this way there is achieved an even distribution of liquid on the lower edge of the side wall, and thereby an even dripping along the entire channel. With this arrangement, to achieve even liquid distribution, only a few, simply designed, outlet openings are necessary, which permits a simple construction and inexpensive manufacture.

Preferably, the outlet openings are arranged at such a distance from one another that the fanning out areas over which the liquid spread as layers of liquid, are approximately contiguous to each other at the bottom on the side wall. It has been found that the width of the fanning out areas is almost constant for normal fluctuations of the liquid charge.

However, in order to ensure thatthe width of the fanning out areas remains almost constant even with considerably fluctuating liquid charges, the outlet openings can be so constructed that the flow resistance and/orthe outflow width along the outlet opening changes from the bottom upwardly. For example, the outlet openings may be designed as upwardly widened slits, and thus have a flow resistance decreasing from the bottom upwards and an outflow width increasing from below upwards.

The invention will now be described by way of example with reference to the accompanying ~ > drawings, in which: Figure 1 is a perspective view of a portion of a channel of a liquid distributor for a mass transfer column; Figure 2 is a section along line Il-Il in Figure 1, on an enlarged scale; Figure 3 is a section along line Ill-Ill in Figure 1, on an enlarged scale; Figure 4 is a section corresponding to Figure 3 through an alternative of the outlet openings; Figure 5 is a section through a portion of channel of a first alternative of the liquid distributor; Figure 6 is a perspective view of a portion of channel of a second alternative of the liquid distributor; Figure 7 is a section along line VIl-VIl in Figure 6;; Figure 8 is a section through the side wall of a channel of a third alternative of the liquid distributor; and Figure 9 is a side view of a portion of a channel of a fourth alternative of the liquid distributor.

In all the embodiments represented in the drawings the liquid distributor consists of several horizontal channels disposed in parallel side by side. The channels are open on top and closed at the sides, and a pre-distributor of usual type extends transversally above the channels through which liquid is supplied to the channels. The predistributor and the channels are disposed, in the manner usual for open channel or box distributors, in the head of a mass transfer column (not shown on the drawing).

The channel portion 1, rectangular in cross-section, shown in Figure 1, is made of sheet metal and has two vertical side walls 2, 3 as well as a horizontal bottom 4. The side walls 2, 3 have a number of rectangular holes 6 formed in their upper portion and disposed at equal intervals along the length of the channel. The holes are shielded by covers 9 spaced away from them and joined integrally with the side walls by means of straps 7, 8 (Figure 3). (On manufacture, the covers 9 may be formed and press-formed from the side wall 2, 3 by means of an appropriate punch). Because the covers 9 are spaced away from the holes 6, vertical outlet slits 11, 12 are formed between the longitudinal edges of the covers 9 and holes 6 for the liquid.The slits 11, 12 or the two longitudinal sides of each slits preferably lie on a plane perpendicular to the side wall 2, 3 and the covers 9 extend parallel with the plane of the side wall. The width b (inside width) of the slits 11, 12 is very narrow and is less than one fifth of the slit length I.

The bottom edges 14 of the side walls 2 and 3 are of zig-zag construction and protrude downwardly from the bottom 4forming a dripping rim. The zig-zag design, in this arrangement is selected such that the vertical centre lines 16, 17 between adjacent outflow slits 11, 12 each extend through the apex 18 of the cut-out between-two adjacent downwardly protruding teeth 19.

In the drawing a liquid charge is shown in which the liquid level 20 reaches a medium height of holes 6. The liquid flowing out of a hole 6 divides into two separate streams of liquid coming out of the two outlet openings 11 and 12, the direction of flow of these streams, indicated bythe arrows 21,22 being approximately horizontal and parallel with the side wall 2,3 as a consequence of the covering 9. The distance between adjacent covers 9 and respective outflow slits 11, 12 is slightly greater than the distance of the outlet slits from the bottom edge 14 of the side walls 2,3 and is more than ten times the slits width b.As a result of this separation between the outflow slits, the streams of liquid issuing horizontally have a substantially unobstructed path such that the liquid flows in the form of liquid layers 23,24fanning out gradually in the longitudinal direction of the channel on the side wall 2,3 downwardly as shown in Figure 1. With the given distance of the outflow slits it has been found that the areas of widening 23, 24 over which the streams of liquid coming out of the outflow slits 11, 12 fan out are approximately contiguous to one another at the edge 14, so that the liquid is evenly distributed along the channel over the entire edge 14. The liquid then flows or drips from the teeth 19~as shown by the arrows 26~downwards onto the uppermost packing of the column.

It has been found that the chosen zig-zag path of the dripping edge ensures a dripping or running of the liquid evenly distributed overtheteeth 19,the arrangement ofthe cuts 18 in the centre lines 16,17 ensuring uniform distribution also under the covers 9 and at the centre 17 between the covers 9.

As will be seen on the drawing, the outlet slits 11, 12 are disposed in the upper portion of the side wall 2 or 3 and are positioned in a row extending in the longitudinal direction of the channel, and they form the only outset openings of the channel. In particular, the channel has no outlet openings below this row, so that no turbulence can be caused by more liquid flowing out into the liquid layers 23,24.

In the embodiment of Figures 1 to 3 the width of the outflow slits 11, 12 is constant over their entire length (Figure 3). With this arrangement, within usual working ranges i.e. with not very large deviations in the liquid charge, there is achieved a substantially even distribution of liquid. Where there are large deviations i.e., very small to very large liquid charges, the outflow slits are preferably arranged in such a manner thatthe flow resistance and/or the outflow width changes along the slit. For this purpose, and in the simplest case, there may be provided a slit width which increases constantly from the bottom of the slit upwardly, i.e. the covering 9 may be bent further outwardly at the top than at the bottom as shown in Figure 4. Thereby, the flow resistance decreases in the upward direction and the flow width increases in the upward direction.In this way the width of the fanning out areas 23, 24 always remains the same even when there are large variations in the amount of the liquid charge. The central width of the outflow slit shown in Figure 4 is substantially the same width as the outflow slits 11, 12 and the distance between adjacent covers is similarly calculated as at least ten times greater than the central slit width.

In orderto avoid the loss of pressure caused through the channels at high gas charges, the channel represented in Figure 5 has an inclined bottom 27. In this arrangement only the wider side wall 28 is provided with outlet openings 29 and with a zig-zag shaped edge 49 protruding over the bottom 27. The narrower side wall 30 is joined flush with the upper side edge of the inclined bottom 27.

It is also possible to form at least the lower part of the or each channel side wall provided without outlet openings so that it is arched or sloping. In this case, (which is not shown in the drawings) the channel side walls, each provided with outlet openings extend together into a common suitable notched dripper edge. The outlet openings formed by slits are present in the upper, preferably vertically, extending part of the two side walls.

The channel portion shown in Figures 6 and 7, which illustrates an alternative liquid distributor, differs from the channel portion represented in Figures 1 to 3 by the different configuration of the outlet openings and the absence of the zig-zag edge.

The side walls 32,33 of the channel portion 31 have notches spaced along the length of the channel and extending vertically from the upper edge downwards. The two parts of the sidewall adjoining a notch are denoted in the drawing by 34, 35. The one part of side wall 34 is bent outwards from the plane of the side wall so that its longitudinal edge 36 (Figure 7) is spaced outwardly of the longitudinal edge 37 of the other part of side wall 35, and the surface 38 of the part of side wall 34 adjoining the longitudinal side 36 extends parallel with the plane of the side wall. The outflow slits defined by the longitudinal edges 36, 37 are referenced 39.The distance between adjacent outflow slits 39, out of which the liquid streams in the same direction-as shown by the arrows 4#is somewhat greater than the distance of the slit ends from the bottom edge 43 of the side wall 32 or 33 constituting a dripping edge, and is more than five times the width of the slit.

The liquid flows according to the arrows 40 approximately horizontally along the sidewall 32, is distributed over it in the longitudinal direction of the channel and drips-as indicated by the dashed arrow 41~down from the dripping edge 43 formed between the side wall 32 and the bottom of the channel 42. Even dripping along the edge 43c is effected only when the edge is directed exactly horizontally and has no uneveness otherwise drips form at the points of uneveness which may be positioned irregularly. In order to ensure dripping at evenly distributed places the side walls 32,33, in a similar manner to the side walls 2,3 may be provided with a serrated edge.

If the side walls of the section of channel are of adequate thickness the outlet openings, as Figure 8 shows, may also be formed by means of inclined slits 45 which extend at an angle through the side walls, and which may be disposed in a similar manner to the slits 39. A precondition for the liquid to flow out approximately horizontally along the side walls is, in this connection, that the angle at which the slits 45 extend with respect to the plane of the side wall, should be small and preferably not greater than 45% Instead of being vertical the slits 11, 12,39 and 45 may also be slanted. Figure 9 shows such a slanting arrangement of the slits.

Here, the coverings 50, corresponding to the coverings 9, taper downwardly so that the slits 51, 52 converge downwards, and the bottom slit end 53, with respect to the outflow direction 54, is staggered back with respect to the upper slit end 55. The bottom part of covering 50 which merges into the side wall 2 and by means of which the two bottom ends 53 of the slits 51,52 are separated, should be dimensioned to be sufficiently wide so that the horizontal outflow speed at the bottom slit ends 53 may be ensured.

The liquid distributor may also be a closed channel or tube distributor with channels or tubes rectangular in cross-section, and be connected, for example, in the manner of a grid or grating. The channels or tubes may, in this arrangement, be constructed correspondingly to portion 2 or 31 and be closed at the top by means of a covering. The liquid, in this case, may be kept in the distributor under pressure, e.g. in a supply container under the hydrostatic pressure of the liquid column. Thereby, the horizontal outflow speed of the liquid from the outlet slits 11, 12,39 and thus also the width of areas 23,24 are increased, so that the outflow slits are to be disposed at still greater intervals than with the open distributors according to Figures 1 and 6, and still fewer outlet slits are necessary.

Claims

1.A liquid distributor for a mass transfer column comprising at least one substantially horizontal channel a side wall of which has outlet openings formed therein; the outlet openings being so designed and disposed relative to one anotherthat, in use, liquid within the channel flows out approximately horizontally along the side wall and runs down in the form of layers of liquid gradually fanning out from the outlet openings along the length of the channel.

2. A liquid distributor according to claim 1 wherein the outlet openings are separated from one another by a distance such that the areas of the side over which the liquid streams fan out in use do not overlap or overlap one another only slightly at the bottom on the side wall and preferably approximately adjoin one another.

3. A liquid distributor according to claim 1 or 2 wherein the outlet openings are formed by slits, one longitudinal edge of which lies along the plane of the side wall, and the other longitudinal edge of which lies at a distance outside the plane of the side wall.

4. A liquid distributor according to claim 3 wherein the other longitudinal edge is formed on a part connected at the bottom and preferably also at the top integrally or closely with the side wall.

5. A liquid distributor according to claim 3 or 4, wherein the two longitudinal edges lie on a plane approximately perpendicular to the side wall or overlap one another.

6. A liquid distributor according to any one of claims 3 to 5 wherein the slit length (I) is a multiple of the slit widths (b), preferably at least five times.

7. A liquid distributor according to one of claims 1 to 6 wherein the outlet openings are so designed that their flow resistance and/or their outflow width alters from below upwards to achieve a width of the fanning out areas which remains almost constant even when the liquid charges vary considerably.

8. A liquid distributor according to one of claims 1 to 7 wherein the outlet openings are formed of slits which are inclined in the longitudinal direction of the channel so that the bottom slit end is staggered back, in terms of direction of outflow, with respect to the upper slit end.

9. A liquid distributor according to one of claims 1 to 8 wherein the distance between adjacent outlet openings out of which liquid streams flow, either directed one towards the other or pointing in the same direction, is a multiple of the width (b) of the outlet openings, preferably, in the case of streams of liquid directed one towards the other, is at least ten times as great, and in the case of streams pointing in the same direction, at least five times as great.

10. A liquid distributor according to one of claims 1 to 9 wherein the distance between those adjacent outlet openings out of which liquid streams flow, directed one towards the other or pointing in the same direction, lies in the same order of magnitude as the distance of these outlet openings from the bottom edge of the side wall.

11. A liquid distributor according to one of claims 1 to 10 wherein the side wall provided with outlet openings protrudes downwardly beyond the bottom of the channel, their bottom edges having serrations or, preferably, being constructed of zigzag shaped.

12. A liquid distributor according to one of claims 1 to 11 wherein the outlet openings are provided only on one side wall of each chennel, and the channel bottom extends from this one side wall at an inclined angle or in arched fashion upwardly to the correspondingly more narrowly dimensioned other side wall.

13. A liquid distributor according to one of claims 1 to 12 wherein the outlet openings in the upper portion of the side wall are disposed in a row extending along the channel, and wherein that part of the sidewall situated below the row is closed so that liquid, which could otherwise cause turbulence, cannot flow into the fanning out areas.

14. A liquid distributor for a mass transfer column comprising an elongate channel having outlet openings formed in a side wall thereof, the openings being configured so that the flow direction for liquid is longitudinally of the channel whereby, in use, liquid escaping from the outlet openings fans out along the side wall of the channel.

15. A liquid distributor substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

16. A liquid distributor according to one of claims 1 to 10 and 13, characterised in that at least the lower part of each channel side wall provided with outer openings is arched or sloping and the side walls extend together into a dripper edge common to both side-walls.