Liquid dispenser with collector

Abstract

Title: Liquid distributor with collector A liquid distributor (D) for a heat and mass exchange column comprises: a peripheral ring, a series of vertical walls extending parallel to each other; leak-proof sealing means delimiting between the vertical walls alternating spaces for gas passage (G) and liquid passage (L); means allowing the upward evacuation of the gas contained in the gas passage spaces;and a perforated base arranged at the base of each liquid passage space (L) and connected with a watertight seal to each adjacent vertical wall and to the crown and a collector (B) of circular cross-section arranged with its diameter horizontally, the collector being made of perforated folded material, the folds being straight and parallel to each other and alternating folds of the collector forming a series of valleys (V) situated above the liquid passages, so that a liquid accumulating in a valley falls into the liquid passage space below. Abbreviated figure: FIG. 1;

Description

Title of the invention: Liquid dispenser with collector

[0001] The present invention relates to a liquid distributor for a heat and material exchange column, in particular a packed column. It further relates to a column equipped with such a distributor and at least one module of structured or bulk packings. It also relates to a distillation process for separating a mixture of at least two components in which the exchange of material and heat between a liquid and a gas is carried out using a distributor according to the invention or a column according to the invention.

[0002] EP0434510 describes a liquid distributor for a heat exchange column and the packing material comprising: a peripheral crown, a series of vertical walls extending parallel to each other; sealed closure means delimiting between the vertical walls alternating gas passage and liquid passage spaces; means allowing the upward evacuation of the gas contained in the gas passage spaces; and a perforated bottom arranged at the base of each liquid collection space and connected with a sealed seal to the or each adjacent vertical wall and to the crown.

[0003] The use in distillation columns of structured packings, of the crossed corrugated type, as described in document WO 89 / 10527, has significant advantages, in particular from the point of view of the pressure drop of the rising gas.

[0004] Liquid from the column is poured onto the distributor, collects in the liquid passages and passes through the perforations in the bottom. Gas rising up the column from below the distributor passes into the gas passages and is discharged upwards.

[0005] In a section packed with a gas-liquid mass transfer column, it is desirable to redistribute the liquid phase after a certain height of the exchange section. A collector and a distributor are then used. These are complex to manufacture, have a certain bulk without directly contributing to the transfer.

[0006] Two options are offered by column internal manufacturers: • use a collector which recovers the liquid while allowing the gas to pass through; it sometimes integrates the support function for the upper lined section, • use a redistributor that integrates the collection function into the distributor.

[0007] In the first case, relatively complex constructions are used, with many parts of different shapes, each being cut, folded, perforated, which are then generally assembled by welding. This complexity leads to expensive manufacturing using different machines with many manufacturing steps.

[0008] The advantage of this type of collector is that it can be easily functionalized, especially with increased re-mixing of the liquid or the addition of an inlet or outlet. On the other hand, it is generally quite bulky.

[0009] The second type of solution is a little less complex in that it generally consists of providing the gas passages of the distributor ("chimneys") with "roofs" to conduct the liquid to the distributors. These "roofs" are, however, relatively numerous.

[0010] Significantly less bulky than a separate collector, this solution leaves less flexibility for the integration of other functions, in particular re-mixing. To maintain good distribution quality, we seek to limit the horizontal liquid speeds inside the distributor chutes. The addition of new functions, even if only because of the space they require, is likely to increase horizontal speeds.

[0011] Both types of collector can act as a redistributor if their base is adapted by providing it with numerous perforations. They are then very compact but the quality of the remixing is affected.

[0012] The invention takes advantage of the effect that a wetting liquid tends under the effect of gravity to flow to the lowest point when it is in contact with a solid rather than detaching itself. This is due to the fact that the surface energy between a solid and a gas is often much higher than that between a liquid and a gas (the surface tension), in particular when the solid is a metal and the liquid is close to its boiling point (conditions found in a distillation column). This is the origin of a force which promotes the spreading of the liquid on the solid to minimize this surface energy. This force competes with the inertia of the liquid caused by the speed of the fluid and with gravity which will have all the more effect locally as the liquid accumulates.

[0013] The invention consists of arranging a collector above a conventional distributor of a column. This collector is a perforated plate, preferably metallic, which occupies almost the entire horizontal section of the column, above a liquid distributor and preferably below a section of structured or loose packings. This plate is folded (or corrugated) in a sawtooth pattern so that the low points of this plate forming valleys are located above the chutes dedicated to the liquid of the distributor.

[0014] According to one aspect of the invention, there is provided a liquid distributor for a heat and material exchange column, in particular with packing, comprising: a peripheral crown, a series of vertical walls extending parallel to each other; sealed closure means delimiting between the vertical walls alternating spaces for the passage of gas and the passage of liquid; means allowing the upward evacuation of the gas contained in the gas passage spaces; and a bottom perforated arranged at the base of each liquid collection space and connected with a watertight seal to the or each adjacent vertical wall and to the crown characterized in that it comprises a collector of circular section arranged with its diameter horizontal, the collector being made of perforated folded material, the folds being straight and parallel to each other and alternating folds of the collector forming a series of valleys located above the liquid passage spaces, so that a liquid accumulating in a valley falls into the liquid passage below.

[0015] According to other optional features: • each valley lies along its entire length above a single liquid passage space. • alternating folds of the collector form ridges located above the gas passage spaces. • each ridge lies along its entire length above a single gas passage space. • no valley in the series is located above a gas passage space. • no peak in the series is located above a liquid passage space. • the collector is perforated such that the opening rate is greater than 80%. • valleys and ridges are formed between two flat surfaces at an angle oblique to each other. • the collector consists only of flat surfaces arranged at an acute angle to the horizontal. • the folds forming the valleys are themselves oriented downwards to make the liquid flow towards the crown. • the folds forming the valleys are themselves oriented downwards to make the liquid flow towards the inside of the collector. • the collector is made of metal, possibly expanded metal or mesh. • each valley has the same length as the liquid passage space above above which it is located • each ridge has the same length as the gas passage space above which it is located

[0016] According to another object of the invention, there is provided a column comprising at least one module of corrugated-crossed or loose structured packings and above this module a distributor as described above.

[0017] The column may comprise at least one module of corrugated-cross or loose structured packings and below this module a distributor as described above, the collector serving as a support for the packing module above the distributor.

[0018] According to another object of the invention, there is provided a distillation process for separating a mixture of at least two components in which the exchange of matter and of heat between a liquid and a gas is carried out using a distributor as described above or a column as described above.

[0019] It is naturally necessary to cut the plate constituting the collector to the dimensions of the column section.

[0020] The perforation rate and the size of the perforations are adjusted so that the liquid does not detach before reaching a low point. To achieve this, slopes that give excessively high speeds in stall zones are also limited.

[0021] Thanks to folding, the total surface area of ​​the perforations can approach or even exceed the cross-sectional area of ​​the column. An opening rate greater than 80%, or even 100%, for the folded material of the collector, makes it possible to minimize pressure losses for the gas.

[0022] The high points forming the ridges of the folded collector plate serve as support for the structured or loose packings above the collector. A perforated plate can easily be sized to support significant loads as evidenced by its widespread use in the building and public works sector.

[0023] An advantage of the collector is that only a single perforated metal plate is used, folded and cut around the edge. This very simple construction limits manufacturing time and requires few machines.

[0024] The invention will be described in more detail with reference to the figures in which

[0025] [Fig-1] illustrates a partial cross-section in elevation of the distributor.

[0026] [Fig.2] is a top view of the dispenser.

[0027] [Fig.3] is a top view of the dispenser.

[0028] The part of the distributor shown in [Fig. 1] comprises a distributor D consisting of a peripheral crown R, a series of liquid accumulation passage spaces L separated by the passage spaces which are the gas flow passages G. These spaces are formed by a series of vertical walls extending parallel to each other. Sealing means close the gas passage spaces G on the side delimiting between the vertical walls the alternating gas passage spaces G and liquid passage spaces L. Means allowing the upward evacuation of the gas contained in the gas passage spaces G, these means being able to consist of a chimney, an opening in the upper part of the profiles or an opening at the top of the gas passage space G. The passage spaces of G can be open upwards as in the figure or surmounted by half-roofs.

[0029] The liquid flows from top to bottom and exits the liquid passage spaces L through perforations in the circular bottom of the distributor. The gas rising in the column passes into the gas spaces and exits through openings at the top of the gas spaces. Here only three liquid passage spaces L and two gas passage spaces G are illustrated to explain the principle of the invention.

[0030] The distributor and manifold are typically made of stainless steel or aluminum.

[0031] Above the distributor is a collector B which receives liquid from a point at the very top of the column or from a module of structured or bulk packings which carry out an exchange of mass and heat between the gas and the liquid.

[0032] A regular mesh of perforations is observed over the entire surface of collector B.

[0033] The collector B being made of perforated folded material, the folds C, V being straight and parallel to each other. Alternating folds V of the collector form a series of valleys located above the liquid passages L, so that liquid accumulating in one valley falls into the liquid passage L below.

[0034] The collector perforation rate has a value equal to a percentage between 30 and 60%, to be multiplied by between 1.4 (^2 for 45°) to 2 (for 60°) with the inclination angle (x 1 / cos(0)).

[0035] The hydraulic diameter of the perforations is between 1 and 5 mm.

[0036] The gas rising from the gas spaces passes through the collector through its perforations.

[0037] Alternating folds C, constituting the rest of the folds of the collector, form ridges where the liquid does not accumulate, these ridges being preferably arranged above the gas spaces G.

[0038] The valleys V and the ridges C are each formed between two flat surfaces at an oblique angle to each other.

[0039] Preferably, the collector B consists solely of flat surfaces arranged at an acute angle with the horizontal, for example between 45° and 60°. Thus, the fold angle is between 60° and 90°.

[0040] Above the collector is a module of structured packings composed of a stack of corrugated-crossed or loose lamellae, in a known manner. The collector can serve as a support for this module, the collector itself being fixed to the wall of the cylindrical column which contains it or being attached to the distributor which is fixed to the column.

[0041] The column, the collector C and the distributor D are all of circular section, the collector and the distributor each having a diameter substantially equal to the internal diameter of the column.

[0042] [Fig.2] shows a distributor D with 10 gas spaces G and liquid passage spaces L between each pair of gas passage spaces G. Here we see the circular shape of the plate forming the collector B and the crown R forming the circular edge of the distributor D.

[0043] This solution is also very compact and integrates the function of supporting the fillings. By adjusting the position of the low points, additional functions can also be integrated, in particular re-mixing.

[0044] In this example, the perforated plate B is folded at 90°, alternately in one direction and the other, over its entire width and thus extends over the entire section of the column above the distributor. The low points are located at the level of the lower folds V where the liquid falling from the packing will accumulate and detach. They are positioned above the chutes or liquid passage spaces L of the distributor. If the liquid flow rates require it, jet breakers can be added under the low points. Here the low points are all at the same height above the bottom of the distributor.

[0045] The position of the low points can be optimized to minimize interference with gas inlets or to improve remixing. For example, a plate with folds can be formed alternating the position of the low points on one side or the other of the column. Thus, the liquid collected at one location in the column is conducted to another. This can be better controlled by adjusting the position of ramps or pre-distribution tanks.

[0046] With certain types of packing, the composition of the liquid is somewhat heterogeneous over the section of the packing module, due to an imperfect redistribution of the liquid descending along the pack and "edge effects". If this heterogeneity risks having consequences at a given level of the column, the variant shown in [Fig. 3] can be used. [Fig. 3] illustrates an embodiment where the perforated plate is folded in a manner similar to the embodiment shown in [Fig. 2]. This time the lower folds V are oriented downwards, the orientation changing direction, from one liquid passage space to another. Thus we see that the ends of the valleys V of two adjacent liquid passage spaces are not at the same height. The valley V descends towards the bottom from left to right while the adjacent valley V descends towards the bottom from right to left.Thus the liquid flows towards one side of the crown R of a valley V and on the other side of the crown of the adjacent valley V. This allows the liquid to be better distributed and eliminates a concentration or variation in flow rate on one side of the column. A peripheral crown P in the distributor D acts as a pre-distribution ramp to promote re-mixing between the different chutes. It returns the liquid flowing along the wall to the center.

[0047] If expanded metal is used as perforated plates, costs can be further reduced. This is because it is a relatively cheap manufacturing method with a very wide sizing range.

[0048] Alternatively, sheets of welded mesh or wire mesh may also be used, which are considered to be perforated plates in this context.

Claims

Claims

1. Liquid distributor (D) for a heat and material exchange column, in particular with packing comprising: a peripheral crown (R), a series of vertical walls extending parallel to each other; sealed closure means delimiting between the vertical walls alternating gas passage spaces (G) and liquid passage spaces (L); means allowing the gas contained in the gas passage spaces to be evacuated upwards;and a perforated bottom disposed at the base of each liquid passage space (L) and connected with a watertight seal to the or each adjacent vertical wall and to the crown, characterized in that it comprises a collector (B) of circular section disposed with its diameter horizontal, the collector being made of perforated folded material, the folds being straight and parallel to each other and alternating folds of the collector forming a series of valleys (V) located above the liquid passage spaces, so that a liquid accumulating in a valley falls into the liquid passage space below.;

2. A dispenser according to claim 1 wherein alternating folds of the collector (B) form ridges (C) located above the gas passage spaces (G).

3. A dispenser according to claim 1 wherein no valley in the series is located above a gas passage space (G).

4. Dispenser according to one of the preceding claims in which the collector (B) is perforated such that the opening rate is greater than 80%.

5. A dispenser according to any preceding claim wherein the valleys (V) and ridges (C) are formed between two flat surfaces at an oblique angle to each other.

6. Distributor according to one of the preceding claims in which the collector (B) consists solely of flat surfaces arranged at an acute angle with the horizontal.

7. Dispenser according to one of the preceding claims in which the folds forming the valleys are themselves oriented downwards to cause the liquid to flow towards the crown (R).

8. Distributor according to one of the preceding claims in which the collector (B) is made of metal, possibly expanded metal or mesh.

9. Heat and material exchange column comprising at least one module (G) of corrugated-cross or loose structured packings and above this module a distributor (D) according to one of claims 1 to Q.

10. O. Column according to claim 9 comprising at least one module (G) of corrugated-cross or loose structured packings and below this module a distributor (D) according to one of claims 1 to 8, the collector (B) serving as a support for the packing module above the distributor.

11. Distillation process for separating a mixture of at least two components in which the exchange of matter and heat between a liquid and a gas is carried out using a distributor (D) according to one of claims 1 to 8 or a column according to one of claims 9 or 10.

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