Fluid Distribution System

This invention relates to a system for distributing a fluid, such as e.g. organic solvents, water, aqueous salt solution, lyes or acids, via random or structured packing, in which the fluid trickles from the top to the bottom, preferably in countercur- rent or cocurrent flow with a gas containing e.g. SO ₃ or noxious substances, comprising at least one distribution device, from which the fluid is introduced via open- ings into a distributor channel such that below the openings a specified fluid level is obtained in the distributor channel, wherein the fluid is discharged from the distributor channel via at least one outlet slot of specified width at the lower end of the distributor channel to the packed bed by means of a guiding device.

In a known tube type irrigation system, a plurality of tubes with many bores directed upwards at an angle, through which the acid is discharged radially, extend from a main distributor tube. By means of baffle plates attached to the tubes these jets are directed downwards into the packed bed.

Such systems are used for instance for the countercurrent absorption of SO ₃ or water vapor in sulfuric acid in a packed tower. In the head of an e.g. cylindrical container, the absorber acid is uniformly distributed over the apparatus cross- section by means of an irrigation system and trickles through a packed bed from the top to the bottom. From the gas countercurrently flowing to the top, the trickling acid absorbs the SO ₃ , with the acid concentration rising correspondingly, or water, whereby the acid is diluted. In standard configurations, the absorber constitutes a packed tower constructed as counterflow apparatus, whose shell is divided into three zones: the lower part is formed by the sump with the acid outlet, the middle part for instance contains the packed bed on a support grid through which the acid, which is uniformly distributed by an irrigation system located on top of the

bed, trickles downwards. The acid inlet to the irrigation system and the gas outlet are located above the packed bed. Known issues of such systems are the reduced gas outlet area, which leads to an undesired local increase in the gas velocity and, hence promotes the entrainment of acid droplets or mists.

From US 2004/0182013 Al a distributor system is known, in which the fluid is discharged pressureless from a plurality of openings in the side wall of a distributor trough open at the top and is guided to a lower dripping edge by means of a laterally downwardly curved mesh structure, wherein the mesh structure is passed through a distributor channel forming a throttle. This device on the one hand involves the problem of the entrainment of fine acid droplets and mists, and on the other hand the individual distributor members consisting of distributor trough and mesh structure have an undesirably high space requirement, which leads to a reduction of the area available for the gas flow.

From US 5,906,773 A a liquid distributor system is known, in which the liquid is guided from a distributor trough, which in a wall includes two openings arranged one above the other at a distance and leading into a vertical guiding tube, onto an inclined baffle surface 5 on which a weir is formed which should promote the fur- ther distribution of the liquid. The liquid then flows via a vertical guiding plate 7 onto the surface of the filler packing. Apart from the space requirement of these distributor members, there is also the problem of the entrainment of liquid droplets or mists.

A similar configuration of a counterflow column is disclosed in US 6,575,437 B2, in which the liquid is passed onto the packing as a film and without pressure via a baffle plate arranged laterally with respect to a distributor trough.

In the distributor tubes known from US 5,439,620 A, the liquid emerges from open- ings in the upper surface thereof and flows via guiding surfaces provided laterally

at the distributor tubes, which have a serrated dripping edge, up to the surface of the packing. The desired uniform distribution of the liquid along the length of the distributor tubes is not positively ensured. Another issue here is the exact control of the pressure to avoid splashing of liquid from the opening.

it is the object of the present invention to achieve a rather uniform distribution of the fluid over the entire packing cross-section with little constructional effort, while minimizing the amount of fluid droplets or mist entrained with the gas flow.

In a plant as mentioned above, this objective is being achieved by the distributor element constituting a pressure conduit, from which the fluid is discharged via nozzles into a basically closed, but ventable chamber of the distributor channel formed above the fluid level, in which a pressure corresponding to the pressure existing in the container accommodating the packing can be maintained.

In this way, it is achieved that fluid droplets or mists produced when the fluid emerges from the nozzles are trapped in the substantially closed distributor channel and do not get into the gas phase. As a result, the flow velocity of the gas can be increased and the diameter of the tower hence can be reduced, which leads to a saving of costs. A nonuniform discharge of the fluid from the nozzles is compensated by the fluid level formed in the distributor channel and by the guide member adjoining thereto along the entire length of the distributor member. As a result, a uniform controlled fluid film is guided onto the packing.

In a particularly advantageous aspect of the invention it is provided that the distributor channel downwardly adjoins the distributor element and its width does not significantly exceed the diameter of the distributor element. In this way, the free area at the fluid inlet of the filler packing is maximized for the passage of the coun- tercurrently flowing gas. The specific acid inlet in proportion to the filler packing per

m ² is up to 10 times, preferably 2 to 3 times as high compared to other sprinkling systems.

Preferably, the nozzles of the distributor member downwardly open into the dis- tributor channel at an angle above the fluid level, so that the fluid jets impinge on a side wall of the distributor channel. This promotes a more uniform supply of fluid along the length of the distributor channel.

To furthermore prevent the generation of undesired fluid particles or mists, the guide member, which for instance can constitute a guide plate, extends into the filler packing, for instance down to a depth of about 100 mm.

For the uniform distribution of fluid by avoiding an undesired transfer of acid particles to the gas flow it is advantageous when the fluid level in the distributor chan- nel is maintained between about 10 and 100 mm, preferably between about 15 and 80 mm, above the outlet slot.

The width of the outlet slot of the distributor channel for instance lies between about 3 and 20 mm, preferably between about 5 and 15 mm.

The distributor element used, a plurality of which can be arranged at a distance from each other above the filler packing, preferably have a diameter between about 30 and 300 mm, more preferably between about 50 and 250 mm.

In practice, the operating conditions preferably are chosen such that an excess pressure between about 0.2 and 6 bar, preferably between about 0.5 and 1 bar exists in the distributor element.

In accordance with the invention, a venting device can be provided in the chamber of the distributor channel, in order to avoid an undesired increase in pressure and splashing of fluid out of the outlet slot.

It is also advantageous when the distributor channel is downwardly tapered.

The system of the invention can for instance be used in a reactor, in which fluid trickles over a packing.

Further objectives, features, advantages and possible applications of the invention can be taken from the following description of an embodiment and the drawing. All features described and/or illustrated form the subject-matter of the invention per se or in any combination, also independent of their inclusion in individual claims or their back-reference.

Fig. 1 schematically shows by way of example a vertical section of a fluid distributor arranged above a filler packing, which consists of a distributor member, distributor channel and guide member, a plurality of which can be arranged at a distance from and parallel to each other for forming an entire sprinkling system in accordance with the invention.

Fig. 2 schematically shows a top view of a packed tower with the fluid distributor in accordance with the invention.

The fluid distributor shown in the drawing includes a distributor member 1 constituting a tubular pressure conduit, which preferably is arranged parallel to the surface of a packing PA. The distributor member 1 must be supplied with the fluid to be distributed over the packing PA such that an excess pressure of between about 0.2 and 6 bar, preferably between about 0.4 and 4 bar exists in the same.

Without an increase in cross-section, a distributor channel 2 adjoins the distributor member 1 in downward direction. At its lower, tapered end 4, the distributor channel 2 has an outlet gap 3 substantially extending along its entire length for the fluid accumulating in the distributor channel 2 up to a level FP, which by means of nozzles 6 distributed aiong the iength of the distributor member 1 is sprayed into a closed chamber 7 formed above the fluid level FP and defined by the same and by the walls of the distributor channel and of the distributor member. The system is operated such that the fluid level FP is maintained between a maximum value FP _ma χ (e.g. about 100 mm) and a minimum value FP _mi n (e.g. about 20 mm).

The nozzles 6 are disposed at an angle, so that the jet of fluid first impinges on a side wall of the distributor channel 2. Fluid droplets or mists formed cannot be transferred to the counterflow gas, but are trapped at the fluid level and hence in- side the chamber 7. In the Figure, one direction of the nozzles is shown by way of example; the nozzles can of course also be directed to the other side wall. An alternating nozzle position or dual nozzles in different directions are also possible. Likewise, the nozzles need not be arranged radially, but can be arranged tangen- tially or point in other directions.

In the chamber 7, a pressure is maintained which approximately corresponds to the pressure in the packed tower. By means of the constructive configuration and the pressure conditions it can be ensured that a uniform fluid film emerges from the outlet gap 3 and an undesired flooding of the filler packing PA is avoided. With its lower end, the plate-shaped guide member 5 adjoining below the outlet gap 3 reaches into the filler packing PA down to about 100 mm, for instance, so that an undesired formation of fluid droplets or mists likewise is avoided at this point. In practical operation, the fluid level FP can for instance lie between about 10 and 100 mm, preferably between about 20 and 70 mm, the width of the outlet gap 3 can lie between about 3 and 20 mm, preferably between about 8 and 10 mm, and

the diameter of the distributor member 1 can lie between about 30 and 300 mm, preferably between about 50 and 250 mm.

To maintain the desired pressure in the chamber 7, the same can be equipped with a venting device and particularly preferably with an overflow conduit, so that no pressure can buiid up when too much fluid is supplied.

The chamber or its side walls can be configured different from Figure 1 , without leaving the actual idea of the invention, namely discharge of a rather undisturbed fluid flow from the chamber and passing the rather compact fluid flow onto the fillers.

In particular, the walls can have a symmetrical, tapered, straight or special shape. Likewise, the guide member 5 need not protrude vertically into the packing plane, but can also be angled. Furthermore, it is possible to use not one, but a plurality of outlet gaps and in particular also a plurality of guide members, which point in different directions.

The outlet gap likewise need not be inclined, but can in particular be open directly downwards or laterally.

As shown in Fig. 2 by way of example, a plurality of, here four, distributor members 1 are provided one beside the other above the packing PA, in order to uniformly distribute the fluid over the entire tower cross-section. The distributor mem- bers 1 are supplied with sulfuric acid via a common supply conduit 8.

In a particular aspect of the invention, the nozzles 6 can have no uniform diameter or shape, but different diameters in dependence on the distance from the supply conduit.

List of Reference Numerals

1 distributor member

2 distributor channel

3 outlet gap

4 tapered end

5 guide member

6 nozzles

7 chamber

8 supply conduit

FP fluid level PA packing