FR2756369A1 - Heat and/or material exchanger using rotating deflectors to mix gases - Google Patents

Abstract

Device for exchanging heat and / or material made of a stack of fixed ventilators (1A, 1B) to encourage gas mixing. Each ventilator has four deflectors (1C) whose average normals are inclined and deduced from each other by rotating about their vertical axes. The sum of the four angles of rotation is 360 deg and the ventilators are stacked in successive horizontal layers in the middle of which each deflector forms part of two adjacent ventilators turning in opposite directions and so there is sufficient space between two adjacent deflectors for the gas to flow. Process for making a device as described above in which metal or other sheets are cut and folded and / or sintered, pierced or stamped to form pleated sheets, with or without projections, with the full surfaces forming the flat, folded, curved or pierced deflectors. Installation for the separation of gas from air or hydrocarbons or carbon dioxide or isotopes in a distillation column which includes at least one device as described above.

Description

 The present invention relates to a material and heat exchange device and, in particular, to a material and heat exchange device intended to serve as a packing in distillation columns with a high number of theoretical plates, typically in the columns. distillation of air or mixtures of carbon monoxide, nitrogen, hydrogen or hydrocarbons, or in isotopic separation columns. It can also be used for isotopic distillation. Typically, it will be installed in distillation columns with a high number of theoretical plates.

 The linings ordinarily used comprise corrugated strips comprising parallel alternating corrugations each arranged in a general vertical plane and one against the other the corrugations being oblique and descending in opposite directions from one strip to the next. The perforation rate is around 10% for these so-called corrugated fillings.

 GB-A-1004046 discloses packings of the corrugated-cross type.

 CA-A-1095827 proposes an improvement of this type of filling by adding a dense perforation of small diameter to allow the liquid to pass on either side of the crossed wavy bands.

 WO-A-86/06296 and WO-A-90/10497 disclose a filling composed of horizontal and superimposed layers, each layer comprising a row of pyramids.

 In WO-A-86106296, the structure comprises pyramids with open bases, and with alternately open and closed side faces, connected by their points so as to constitute a multitude of fan blades putting the gas in rotation to intensify the contact between the gas and liquid.

A fundamental characteristic of this structure is that it can be obtained by assembling perforated and folded metal sheets. This time, the perforation is no longer only intended to optimize the circulation of the liquid but also to allow the gas to pass through the folded crossed bands, the perforation rate being of the order of 50%.

 Paradoxically, it was just at this moment of the start of a radical challenge to the lining of the cross-corrugated that it began to be used in the separation of gases from air. This relatively late use is partly explained by the high performance of cryogenic platforms compared to other platforms on the market (HETP, height equivalent to a theoretical platform, of the order of 10 cm, and low pressure drop).

 In WO-A-90/10497, the above structure is improved by making the faces of the pyramids of two successive layers coincide, which creates transverse channels with respect to the bands, and promotes transverse mixing. It clearly mentions the advantage of a double perforation: a checkerboard (therefore at 50% of perforated surface) for the gas, and a secondary perforation in the closed faces to organize the runoff of the liquid.

This latest patent gave birth to the Sulzer Optiflow product, which represents the first achievement of a new generation, giving access to significantly increased performance compared to the now conventional cross-corrugated (HETP reduced by around 25 to 30% at constant vapor flow , or congestion flow increased by around 25 to 30% at
Constant HETP).

 The fact of connecting the pyramids by the points (vertices. And corners, the points situated on the base are designated by corners) has an important drawback: due to the little material remaining at these points, the mechanical strength of the assembly requires to physically bind these points by a mechanical method of stapling, tying, welding or sewing which requires complex and expensive tools, and therefore results in a fairly high cost. We can also note that, the number of these fixings varies as the number of pyramids, that is to say as the cube of the inverse of their dimension, which limits the specific economically accessible surface of this type of lining. .

 On the other hand, the principle of checkerboard perforation leads to a fall rate of around 50%; this is particularly unfortunate when the material of the upholstery is of high cost, a fabric for example.

 It also appears that this structure is very airy and that the HETP could be further reduced if it were possible to accommodate part of the falls in the structure without degrading the turbulence of the gas or the rate of wetting of the surface.

 The object of the present invention is to create a device for exchanging heat and material with simplified manufacture compared to those of the prior art and therefore making it possible to produce practically very fine linings, therefore with an even smaller HETP.

 According to an object of the invention, there is provided a material and heat exchange device constituted by superposition of layers included between two horizontal planes, each layer comprising deflectors.

 These deflectors have an elongated shape, substantially symmetrical with respect to their longitudinal axis, like tree leaves, they are not necessarily strictly planar. they are inclined relative to the horizontal so that their longitudinal axis is a line of greatest slope.

 To describe their arrangement in a horizontal layer, they are provided with two immaterial vertical axes A and B passing near their outline approximately halfway between the upper and lower ends: a row is generated step by step from a deflector initial by alternating rotations of angle a around the axis A and of angle -a around the axis B.

Each rotation generates a new deflector and a new axis. The rows are then deducted from each other step by step by alternating rotations of 1800 around vertical axes A 'and B' neighboring axes A and B respectively, see Figures 1, Ibis, 1ter. We thus obtain, around each axis
A 'or B' a set of four deflectors which are oriented like the blades of a fan. It goes without saying that, the deflectors being substantially symmetrical, any of them can be subjected to symmetry about the vertical plane passing through its longitudinal axis without altering the structure. In the same way, the same structure can be made up of four families of deflectors of neighboring shapes, positions and orientations, not rigorously deduced from each other by the rotations defined above.

 The structure thus described makes it possible to create the vortex flow of the gas which improves the exchange with the liquid film trickling over the deflectors and the gas. It has the advantage of giving great freedom of design to define the shape and the links of the deflectors. This freedom should be used to better perform the other functions of the product and reduce its cost.

It can be noted that the open pyramid structure of the above patents is a very special case of the general structure which has just been described when the following conditions are simultaneously fulfilled:
1. The deflectors are diamonds
2. The value of the angle a is 90 "
3. The axes of rotation pass strictly through the ends of the small diagonals of these diamonds
4. The upper vertices of the diamonds of a layer coincide with the lower vertices of the immediately upper layer.

 According to another object of the invention, there is provided a material and heat exchange device comprising folded and / or curved and / or twisted strips arranged in a general vertical plane and against each other in which a first strip engages with a second adjacent strip by engagement of a projection of the first sheet which engages in a hollow in the second sheet.

 According to another object of the invention there is provided a material and heat exchange device consisting of sheets comprising support points connecting successive deflectors of the same sheet. These points can define facets which are substantially vertical and parallel to the general direction of the leaves. A simple way to make them is to delimit them by two cuts and two parallel folds. These pairs of folds being oblique and descending in opposite directions from one sheet to the next. These two folds can also be separated by one or more other folds. However, these two folds can be replaced by bending, the facet then takes a cylindrical shape tangent to the two deflectors while retaining good bearing properties.

 According to another object of the invention, there is provided a method of manufacturing a material and heat exchange device in which metal sheets are cut and folded and / or bent and / or twisted to form sheets with flat, curved or wavy support zones.

 There is also provided a method for separating gas from air, or hydrocarbons, or carbon monoxide or isotopes in a distillation column comprising at least one device according to one of claims 1 to 36.

Other aspects of the invention are now described, with reference to the following drawings, including:
FIG. 1 and 1A show schematic side and top views of the deflectors of a device according to the invention,
- Figure 1B shows the position of the axes A, B of a first row (Ao, A1, ... Ai, Bo, B1, ... Bi) and of a second row (Ao, A1, .. Ai , Bo, B1, .. Bi) deduced from the first row,
FIG. 2 shows a first arrangement of deflectors promoting the flow of a liquid,
FIG. 3 shows a second arrangement of the deflectors promoting the flow of a liquid,
FIG. 4 shows the ideal shape of a deflector,
FIG. 5 shows a folded strip with a pair of fold lines, before (5A) and after (5B) fold,
FIGS. 6 and 7 show unfolded strips which can be folded, bent or twisted and then assembled to form a device according to the invention,
FIG. 6A shows a strip of FIG. 6 folded,
- Figure 8 shows a connection between four deflectors of the structure
FIG. 9 shows a section of folded strip,
The documents cited above are silent on the circulation of the liquid.

 Each deflector of the present invention is supplied with the liquid of one or two deflectors of the layer immediately above (Figure 2).

This then flows to one or two deflectors in the next lower layer. These transfers can be ensured by runoff along a physical link of any shape in a downward slope between two successive deflectors, but they can also include a path in free fall. In both cases, it is not necessary for a lower end of a deflector to coincide strictly with an upper end of a deflector fed by it. Again there is great design freedom to assemble the deflectors.

 FIG. 2 shows two deflectors 1A, 1B of an upper layer which pour liquid on the deflector 1C of a lower layer. The physical link 2A connects the lower end of the deflector to the upper end of the deflector 1C. On the other hand, the liquid coming from the deflector 1B flows on the extension 2B and falls in free fall on the upper surface of the deflector iC. The deflector 1C is therefore supplied by two deflectors of the layer immediately above. However, all the liquid from the faces falls on the upper face of the deflector 1C, it is therefore useful to provide one or more secondary perforations in the deflector 1C in order to return liquid to the lower face of 1C.

 In FIG. 3, the deflector 1L of an upper layer pours liquid on the deflectors 1M, 1N of an adjacent layer. The deflector 1L has several collection points, each of which supplies a deflector. In this way, the deflector 1N is connected to the deflector 1L by a physical link 35A constituted by an extension of the collection point and the deflector 1M is supplied with drops of liquid falling in free fall from point 35A of the deflector IL.

 It is of course necessary that the maximum surface area of the deflectors is wet. This remark is enough to outline the best shape to give to the deflectors.

 The upper part must be pointed so as to follow the spreading of the liquid from its supply point. On the other hand, once this spreading has been obtained, the deflector can keep its maximum width over a certain distance. Collecting is easier and can be done on edges of slight slope with a slightly sloping contour. This leads to the bulging shape illustrated in FIG. 4.

 Thus the liquid flows from a supply point 30 to a substantially triangular spreading zone 31. From there it passes to a uniform flow area 32 before being concentrated at the bottom of the deflector on one or more collection points 34, 34A by the collection edges 33. It will be noted that this shape corresponds to a sheet shape with a pointed end 30, a central zone of substantially constant width 32 and an abrupt end 34.

 The effectiveness of a packing depends very much on its ability to ensure transverse mixing of the fluids. It is desirable to ensure the passage of the liquid in directions transverse to the overall circulation of the gas. We can collect the liquid falling from a deflector at two different points and send these two liquids to two different deflectors, therefore in different directions (Figure 4). In this way the liquid can meet different gas threads and this will help to compensate for the inevitable local defects of the distillation.

 For cost reasons, these deflectors must be able to be made from sheet material. Unfortunately, the perforation-folding and / or perforation-bending technique used until now to manufacture structured packings does not allow a richness of forms to be obtained which meets the needs of the architecture described above.

 However, there is a method which makes it possible to obtain very rich shapes from a flat product: cutting and folding. It is enough to be convinced to look at certain embossed books or certain cardboard packaging. Folding is well known for making polyhedra. To our knowledge, this process has never been used to manufacture structured packings. Although very rich in possibilities, this process can be particularly economical since the successive cutting and folding operations can be integrated in the same press tool.

 In the following figures, the folds or twisted lines are represented by short dotted lines, the cutouts by solid lines.

 FIG. 5A shows on an example how the cutting-folding makes it possible to achieve the connection and the cohesion between two rectangles 30, 31 in contact by the media on two sides and deduced from each other by rotation around an axis vertical and slightly intersecting, The angle of rotation here is 900. The short diagonal BD of the parallelogram ABCD is the trace of this facet on the median horizontal plane. We see that the development of the intersection of the strip folded with this plane is a broken line (shown in long dashes), it follows that the deflectors are slightly inclined in the sheet before folding. This inclination is all the greater when the ABCD facets are large relative to the deflectors.

 The folds AD and BC are of the valley type, that is to say that the strip on each side of the fold approaches when folding and the corners X, Y protrude when the strip is folded.

 So that the part made up of the two rectangles and their facet of connections can fit into the part obtained by rotation of 1800 around the line IJ, it suffices to choose the angles of the cuts with the folds, BAD and BCD. The ABCD facet then constitutes a support face. The IBJD diamond delimits the contact area of the two parts. The assembly thus obtained constitutes a set of four rectangular deflectors capable of rotating a fluid circulating in the direction of the straight line AC.

 FIG. 5B represents an assembly of this type in another particular case where the parallelogram ABCD is a diamond and where the two diamonds have been brought into contact over their entire surface, therefore by deducing the second part from the first by rotation around the diagonal AC, although the rectangles of the first part are not strictly deduced from each other by rotations of axis parallel to AC. The assembly nevertheless constitutes a sort of fan with four blades. This illustrates that the object geometry of the present invention does not require a very rigorous implementation.

 We will see another example with the gargoyle in Figure 7.

All these examples show that the main function of the cutouts of a cutting-folding is not to remove material but to separate the edges of the facets to allow them to unfold in space.

 For all the following figures, the parts designated P are full and the parts designated V are empty.

 FIG. 6 shows the flattening of an exemplary embodiment in which the shape of the deflector sketched in FIG. 4 has been used as well as the support facets illustrated in FIG. 5A for horizontally connecting the deflectors.

 The principle proposed here consists simply in connecting the deflectors by vertical bearing faces, having the general direction of the sheets, and of the sockets, so that it suffices to compress the sheets to ensure the cohesion of the stack.

We find the facets ABCD (left) and A'B'C'D '(right) horizontally linking the deflector ABCGHIC'D'A'EF to its neighbors. Points A ', C,
G, I of the deflector ABGHIC'D'A'EF protrude into the space of the adjacent vertical sheets when the strip is folded along the dotted lines AB and CD.

 FIG. 6A gives the appearance of the strip after folding. It will be noted that the vertical link W ′ with the immediately upper deflector of the same sheet is not folded or curved but twisted, which is easier to produce and does not harm either the assembly or the operation.

 The folds AB, CD are parallel; during folding, the adjacent solid surfaces P approach each other. After folding, the diamonds are alternately the highest and lowest parts of the structure.

The strip comprises approximately 30% of void in the form of a polygonal cut, two of the edges of which are defined by the line between H and
In FIG. 7, the liquid flowing at the bottom of the deflector has been divided into two equal parts. The right half simply drips towards the immediately lower deflector of the same sheet. The other, the one on the left, is collected by the point next to this link. When folding, this point protrudes above the top of a deflector of the adjacent sheet on which it drops its liquid like a gargoyle. Each deflector therefore receives its liquid from the two deflectors situated above it, in the same sheet or in the adjacent sheet.

 Figure 8 shows the structural node connecting the lower and upper ends of four adjacent deflectors and the circulation of the liquid there. A secondary perforation is useful for returning part of the liquid to the underside of the lower deflectors.

 We find the pairs of folds W of Figure 7 of two strips juxtaposed.

 The device of the present invention can be assembled by fitting the adjacent sheets, the assembly of the assembly being obtained by simple compression of the sheets stacked on each other.

 In Figure 9, there is a sectional view of a sheet 11 according to the prior art, the sheet being folded to form accordion folds.

 FIGS. 9b, 9c and 9d illustrate sheets according to the invention in which a bearing face is planar and delimited by two folds (fig. 9b) or is curved (fig. 9c) or uses more than two folds ( fig. 9d).

 In these three cases, the slits cut at the ends of the segments 13 allow the edges of the adjacent facets to protrude.

 In FIG. 9a, the metal sheets are deformed to form curved surfaces between the folds of a pair 13.

 The sheets can even be wavy.

 Figure 9b shows the case where the facet inside a pair of folds is flat.

 The examples show the case where the surface between pairs of folds is flat.

Claims (33)

 1. A material and heat exchange device constituted by the superposition of layers included between two horizontal planes, each layer comprising deflectors (1) having an elongated shape, substantially symmetrical with respect to their longitudinal axis.  2. Device according to claim 1 wherein the deflectors are inclined relative to the horizontal so that their longitudinal axis of symmetry is a line of greatest slope.  3. Device according to claim 1 or 2 in which a row of deflectors is generated step by step from an initial deflector by alternating rotations of an angle a around a first axis A and an angle -a around, a second axis B where the axes A and B are immaterial vertical axes intersecting a deflector approximately halfway between the upper and lower ends thereof.  4. Device according to claim 3 in which the rows of deflectors of a layer are deduced from each other step by step by successive rotations of 1800 around axes A 'and B' neighboring axes A and B respectively.  5. Device according to one of the preceding claims wherein  i) the deflectors are not diamond-shaped or  ii) The angle a is not equal to 90 "or  iii) the axes of rotation do not pass through the ends of the small diagonals of the diamond-shaped deflectors, or  iv) the upper vertices of the diamonds of a layer do not coincide with the lower vertices of the diamonds of the next higher layer.  6. Device according to one of the preceding claims comprising sheets (11), cut, perforated, folded, curved or twisted, the solid surface of the sheets constituting the deflectors (1).  7. Device according to claim 6 wherein the holes represent at most 45% of the surface of the sheet (11) before folding.  8. Device according to claim 6 or 7 wherein the sheets are cut to form protrusions (15) after folding.  9. Device according to claim 8 wherein the deflectors (1) of a sheet (11) penetrate into the adjacent vertical sheet.  10. Device according to one of the preceding claims wherein each deflector (1) comprises at least one distributor point (34) and preferably at least two distributor points (34A) for supplying the immediately lower layer with liquid.  11. Device according to one of the preceding claims in which the deflectors (1) are perforated with or without symmetry of the deflector with respect to the vertical plane passing through its longitudinal axis or in which the deflectors of a layer belong to four distinct families, of which the shapes and positions are close to those obtained by the above rotations.  12. Device according to claim 6 wherein the sheets (11) are arranged in a generally vertical plane against each other, the planes defined by consecutive coplanar deflectors being oblique and descending in opposite directions from one strip to the next. .  13. Device according to claim 12 wherein the sheets (11) comprise bearing faces.  14. Device according to claim 13 wherein the support facets are parallel to the plane of the sheet and delimited by parallel folds  15. Device according to claim 13 in which there is a third fold between the folds 13 of a pair of folds delimiting a support facet.  16. Device according to claim 13 wherein the support facets are cylinder portions.  17. Device according to claim 11, wherein the means for connecting the sheets (11) comprise protrusions (15) which fit into notches or slots in the adjacent sheet.  18. Material and heat exchange device comprising cut and folded sheets (11) and / or curved and / or twisted arranged in a general vertical plane and one against the other.  19. Device according to claim 18, in which a first sheet engages with an adjacent second sheet by engagement of a projection (15) of the first sheet which engages with a hollow in the second sheet and vice versa or in which the deflectors of a layer belong to four distinct families whose shapes and positions are close to those obtained by the above rotations.  20. Device according to claim 19, in which the sheets (11) are arranged in a general vertical plane against each other, the planes defined by consecutive coplanar deflectors being oblique and descending in opposite directions from one sheet to the next. .  21. Device according to claim 18 wherein the sheets (11) comprise bearing faces connecting successive deflectors of the same sheet.  22. Device according to claim 18 wherein the support facets are parallel to the plane of the sheet and delimited by parallel folds.  23. Device according to claim 18 in which there is a third fold between the folds 13 of a pair of folds delimiting a support facet.  24. Device according to claim 18 wherein the support facets are cylinder portions.  25. Device according to one of claims 18 to 22 wherein holes, having dimensions of the same order of magnitude as the space between the pairs of folds, extend in the space between two pairs of folds.  26. Device according to one of claims 18 to 23 in which holes extend in the space between two plies of a pair.  27. Device according to one of claims 18 to 26 in which the sheets fit together.  28. Device according to one of the preceding claims wherein the sheets are secured by squeezing and / or interlocking.  29. Method for manufacturing a material and heat exchange device in which metal sheets are cut and folded and / or bent or twisted to form accordion sheets comprising flat, folded, curved or twisted facets.  30. The method of claim 29 wherein less than 45% of the metal sheets is removed by cutting.  31. Process for separating gas from air, or hydrocarbons, or carbon monoxide or isotopes in a distillation column comprising at least one device according to one of claims 1 to 28.  32. Installation for separating gas from air or hydrocarbons or carbon monoxide or isotopes comprising a distillation column containing at least one device according to one of claims 1 to 28.  33. Metal strip cut and folded and / or bent and / or twisted intended to be assembled with other identical strips in order to create a device according to one of claims 1 to 28.