MXPA98003228A - Packing estructur - Google Patents

Abstract

A fluid-fluid contact apparatus with a structured packing is provided which comprises a series of packing elements made of sheets of folded material in such a way that the corrugations in each sheet extend obliquely with respect to the flow direction of volume fluid through the device. Each filler element is oriented with the sheets thereof in a plane which is angularly offset with respect to the sheets of the neighboring elements. Means are provided at or near the speed of the interface between neighboring elements to reduce the pressure drop imposed on the continuous phase as it passes from one element to the next

Description

STRUCTURED PACKAGING DISCONTINUATION OF THE INVENCIC This invention relates to an apparatus for fluid-fluid contact, and in particular, for structured fillings for use in such apparatus. Typically apparatuses of the type of the invention relate to their use for operations such as distillation, absorption, purification, extraction, heat exchange, etc., in which a fluid (for example a liquid) is brought into contact with another fluid (for example a gas) with the fluids usually flowing countercurrent one in relation to the other. In the case of contact of a gas (or vapor) / liquid, the gas constitutes the continuous phase. The invention relates especially to a fluid-fluid contact apparatus in which the structured packing comprises a number of packing elements placed in succession in the direction of fluid flow through the apparatus which is usually in the form of a column or vertically placed tower. Each filler element comprises a plurality of folded sheets of material placed in a face-to-face relationship with rectilinear corrugations that extend obliquely relative to the direction of fluid flow and successive elements are placed with the sheets in an angularly offset element with respect to the fluid flow direction. to the leaves of the adjacent elements. Commercially available fill sellers of this type recommend angular displacements of 90 ° / Sulzer Brothers Limited) and 70 ° (Northon Chemical Company). In its range of packaging, one supplier (Sulzer) produces an "X" range of packaging and a "Y" range of packaging. The sheets of materials used in the two forms of packaging are considered to be identical with respect to the surface area and the surface treatment but differ in the angle of folding. In the series "Y" of packaging, the angle of folding is 45 ° with respect to the horizontal, while in the series "X", it has a folding angle at 60 ° with respect to the horizontal. The filling elements of the "Y" series have a higher efficiency but lower capacity than the filler elements of the "X" series. The efficiency of the structured filling is a property of the way in which the vapor and the liquid make contact with each other over the entire surface of the filling. The capacity of the filling is established by the capacity at the most restricted elevation. The filling elements of the "X" series impose a smaller change in the direction of fluids at the interface due to the greater angle subtended to the horizontal by the angle of folding and therefore have a greater capacity than the elements filling of the "Y" series equivalent. The pressure drop inside the filling elements of the "Y" series is greater and the use of a surface area for mass transfer is greater, therefore, the packing elements of the "Y" series have greater efficiency. Recent indications suggest that the capacity of a structured filling is governed by the behavior of the fluids at the interface between successive filling elements. For example, when a liquid-vapor contact is involved, the pressure drop in the vapor phase is greater at the interface between successive filling elements when the liquid and vapor are forced to move through a change of direction, in comparison to that which occurs in the body of each filler element and, as a result, the liquid tends to accumulate at the interface. The accumulation of liquid occurs over a larger range of operating conditions the greater the liquid face. Therefore, it is assumed that the widely recognized alteration of operation loss in structured fillings at higher pressure is due to the accumulation of liquids at the interfaces between successive filling elements that lead to poor distribution of the liquid in the next filling element in the direction of liquid flow. In accordance with an aspect of the present invention, an apparatus for fluid-fluid contact is provided in which the structured packing comprises several packing elements placed in succession in the designed direction of fluid flow, each packing element comprising a plurality of folded sheets of material placed in an expensive relationship facing the corrugations that extend obliquely in relation to the direction of fluid flow, the successive elements are placed with the leaves in an angularly offset element with respect to the sheets of the adjacent elements, characterized in that a medium is provided in or in the vicinity of the interface between successive elements to reduce the pressure drop imposed on the continuous phase at the interface. In this way, it is possible to ensure good efficiency without unduly sacrificing capacity (and vice versa) the medium can have the effect of making the pressure change rate more regular through the packaged section of the apparatus without the need to reduce the fall of total pressure through the filled section (although such a general pressure drop may occur). In particular, the means serves to reduce the rate of pressure change in the immediate vicinity of the interfaces. Such means can be implemented by configuring the corrugations of the sheets so as to ensure a reduced pressure drop. In one embodiment, instead of using rectilinear corrugations, at least part (preferably most, if not all) of the sheets of each filling element have at least part (preferably most if not all) of corrugations whose oblique angle varies between opposite sides of the packing element so that the obliquity angle is greater in the vicinity of at least one (preferably both) of the faces compared to the larger angle of obliquity within the body of the element of packaging. By "obliquity angle" at a particular point along the length of a corrugation, we mean an angle between the corrugation axis at that point and a plane containing the point and parallel to opposite faces. Therefore, in a typical implementation of this embodiment, each sheet of filler element can be provided with corrugations which impart a change in the direction of flow as the fluids flow through the body of the filler element from one face to the face opposite, the corrugations have portion or terminal portions (depending on whether the particular corrugation extends to one or both opposite sides) which intersect the faces at an angle of up to 90 °, while the intermediate portions of each corrugation over at least part of the length thereof extend at somewhat lesser angle, for example, typically less than 60 °. The obliquity angle of each corrugation preferably changes progressively in the longitudinal direction although the possibility that the change is of a discontinuous nature is not excluded. By imparting a variable obliquity angle to the sheets of the filler elements, the mass transfer within the core of each filler element can be maximized and the use of a greater obliquity angle in the vicinity of the filler element prevents a change end in the directions as the fluid passes from one filling element to the next. In another embodiment of the invention, the medium in the vicinity of the interface between successive elements to reduce the pressure drop at the interface can be implemented by producing at least part (preferably most, if not all) of the corrugations. in at least part (preferably most, if not all) of the sheets of each filler element having a reduced cross section in the vicinity of at least one (preferably both) of the faces of the filler element thereby reducing the surface area and pressure drop in such position. The localized reduction in the cross-sectional area of the corrugations can be carried out by a reduction in depth. The reduction in depth is preferably progressive as the corrugations approach the end faces of the filler elements. If desired, such localized reduction in the cross-sectional area of the corrugations may be combined with variation in the obliquity angle as described above or the reduction may be used with corrugations which are otherwise of conventional configuration. The reduction in the cross-sectional or depth area may take place progressively or may be to such an extent that the corrugations end up short of the appropriate edges of the sheets, ie, so that the marginal edges of the sheets are flat ( not corrugated). Because a reduction in depth will result in sheets that are out of contact with each other, if desired, necessary means can be provided to support the sheets in separate relation to each other and / or increase the stiffness of the structure in the regions in the that the depth of the corrugations is reduced. Such means may comprise spacer elements extending between adjacent sheets or the sheets may be provided with formations along these edges which limit the interfaces between adjacent filler elements, formations which may be designed to cooperate (eg interdigitate) at the interface to maintain sheet separation and / or improve rigidity. In still another embodiment of the invention, the medium in the vicinity of the interface between successive elements to reduce the pressure drop at the interface can be implemented by providing a fluid flow control means between successive packing elements so that the The localized flow direction of fluid leaving a packing element becomes more compatible with the next packing element so that the pressure drop is reduced. In this case, the successive filling elements are separated from each other in the direction of volume flow of fluid through the apparatus and the fluid flow control means is located in the separation. Such control means may comprise an open structure having a series of walls which extend between the successive filling elements and which may, for example, be generally parallel to each other and / or may be placed in two sets with an assembly of walls intercepting the other. Thus, for example, the control means may comprise an open grid structure having cells through which the fluid exiting a filler element passes before entering the next filler element, the cells having axes which are substantially parallel to the flow direction of fluid volume through the apparatus or at least with a closer parallelism to the volume flow compared to the corrugations. Alternatively, the control means may comprise an arrangement of objects with regular or irregular shapes, such as Raschig and / or Pall rings, preferably oriented in the main part of their surface areas extending predominantly in the direction of the flow direction of volume so that the fluid passing from one filling element to the next has a flow direction which is predominantly parallel with the volume flow direction. In a further embodiment of the invention, the medium in the vicinity of the interface between successive elements to reduce the pressure quality at the interface can be implemented by providing a separation between successive filling elements.

In this embodiment, the filler elements can be supported in a separate relationship with a gap therebetween sufficient to ensure a significant reduction of the pressure drop imposed on the continuous phase as they pass from one filler element to the next. Preferably, the spacing, ie, the perpendicular distance between planes containing the ends of successive filler elements at each interface, is at least 2 cm, more usually at least 4 cm. When the filler elements are separated from each other in this manner, without any interposed structure such as a support grid between them, it may be desirable to control the descending liquid phase so as to promote efficient transfer from a filler element to the next element. of filling below or that may otherwise be present in the tendency for the liquid phase to run along the sheet edges at the interface with the possibility of maldistribution. For example, the edges of the sheets on the lower faces of the filling elements can be contoured to promote the collection of liquid at well-defined sites so that the liquid phase then drips from these sites into the lower packing element. Thus, for example, the leaf edges on the lower faces can have a zigzag configuration so that the liquid phase is collected, and drips from the vertices. It will be appreciated that the zigzag configuration will be such that a large number of drip sites are distributed substantially uniformly across the interface. The sheet manufacturing materials can be selected from those commonly used in structured fillings, for example materials similar to thin sheets (metal or other material), gauze materials, etc. The sheets can be perforated to allow fluid to pass from one side of the sheet to the other as fluids flow through the fill. The surface of the sheet material may be regular or may be textured by an appropriate technique to improve wetting, liquid distribution and intermixing properties, for example. The profile of the corrugations in the cross section can take various forms commonly used in structured fillings, for example, semicircular V-shaped, etc. Likewise, the dimensions of the corrugations can generally be the same as those used in commercially available structured fillings such as those sold by Sulzer and Northon Chemical Company. Corrugations do not necessarily need to be continuous through the fill element. For example, as used in a commercially available structured backfill, the corrugations may be interrupted within the body of the backfill element, for example, so that a first series of corrugations extends away through the element and a second series of corrugations then it happens to the first series and extends through the rest of the element, the peaks and valleys of the first series are laterally deviated in relation to those of the second series and the openings are formed in the leaves at the junctions between the two series , so that in this way the fluids can pass from one side of the sheet to the other. According to the present invention, the image transfer to the interfaces can be reduced at the interfaces between filler elements. Accordingly, the depth dimension (considered in the direction of volume flow through the apparatus) of a packing element according to the invention can be optimized with respect to the efficiency that can differ (and typically is greater than) that that of a conventional structured element that has the same efficiency. The invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of a packed column; Figure 2 is a fragmentary view of a packaged element schematically showing the configuration of the corrugations in adjacent sheets; Figure 3 is a fragmentary view showing (a) the corrugation profile in an inwardly moved position from the interface between adjacent packing elements, and (b) the corrugation profile in a position immediately adjacent to the interface; Figure 4 is a fragmentary view showing an alternative embodiment; Figure 5 is a fragmentary view showing a modality corresponding to the embodiment of Figure 3; and Figure 6 is a fragmentary view showing a modality corresponding to the embodiment of Figure 4. With reference to Figure 1, the invention will be described with reference to a packed column or tower 10 for use, for example, in transfer of mass or heat exchange between a liquid descending phase and a rising vapor phase. At its upper end, the column 10 is provided with a liquid distributor 12 and a vapor outlet 14. At its lower end, the column is provided with a steam inlet 16 and a liquid outlet 18. Various structured filling elements 20, stacked vertically above a support 22. Each filling element comprises a series of parallel sheets or lamellae placed in planes extending substantially vertical with the sheets of each filling element placed at an angle with respect to to those of the adjacent filler elements. This angle can be 90 ° for example, but other angles are possible. The filler elements are manufactured so that they extend across the entire length of the column and are of a convenient depth for installation.

Typically 30 cm deep. Each filler element in the embodiment of Figure 1 is located in an abutting relationship with its neighbors, with the interfaces 21 between them. With reference to Figure 2, each sheet or lamellas 24 is formed with a series of corrugations 26 with peaks or ridges 28 extending generally obliquely between the upper and lower faces of the respective filling element and adjacent sheets which are oriented with the corrugations of the same that intercept in a transversal way. The adjacent leaves make contact with each other at the points of intersection between the peaks of a leaf and those of the neighboring leaves. In contrast to commercially available structured fillings, the corrugations are not rectilinear along the entire length - instead, each corrugation 26 has a terminal portion or portions 30, 32 (depending on whether it extends just one or both of the upper faces). and bottom of the filling element) placed at an angle different from the intermediate portion of the corrugation. As shown, the corrugations 26 change direction progressively between the upper and lower faces of the filling elements so that the terminal portions 30, 32 have axes which are substantially perpendicular to those faces while the intermediate portions are inclined with respect to to the vertical. In Figure 2, the solid lines show the peaks 28 of the corrugations on the face of the sheet presented to the observer while the discontinuous lines 28 'show the peaks of the corrugations on the corresponding face of the sheet immediately behind, with one being observed. Although in Figure 2 the terminal portions 30, 32 of the corrugations intersect the upper and lower faces substantially perpendicularly, it will be understood that the advantages of the invention can still be ensured even if the angle of intersection is less than 90 °. With reference to figure 3, in this embodiment the corrugations can be oriented generally as shown in figure 2 or they can be made of rectilinear configuration used in commercially available structured fillings such as the filling elements of the "X" or "series" And "manufactured and sold by Sulzer Brothers Limited. A reduced or increased pressure drop is ensured in this case by reducing the depth of the corrugations in the vicinity of the interfaces 21 of the filling elements (see Figure 1). Therefore, the profile shown in (a) in Figure 3 represents the form of corrugation in inward positions removed from the interfaces 21 of the packing element while the profile shown in (b) represents a form of corrugation of reduced depth in or immediately adjacent to the interfaces 21. It will be understood that the reduction in depth will mean that the adjacent sheets will no longer have peak-to-peak contact with others in these regions. If necessary, spacers or the like (not shown) can be provided to maintain uniform spacing between the sheets and / or improved stiffness of the structure when there is no peak-to-peak contact. In the embodiment of Figure 1, the structured packing elements 20 are stacked vertically in a face-to-face stop relationship. However, as indicated in Figure 4, the packing elements 20 (which may comprise the commercially available elements such as those previously described) are placed in a vertically spaced relationship to reduce the pressure drop between successive packing elements, fluid control means 40 are located between the successive filling elements in order to make the flow of fluids of a filling element more compatible with the orientation of the next filling element. The fluid control means may, as shown, be in the form of an open grid structure with grid cells having walls whose surfaces are in planes extending substantially vertical so that the liquid and vapor exit. of a filler element at an angle imposed by the obliquely extending corrugations is considered to pass through the grid structure before entering the next filler element. In this way, the flow exit angle is modified so that it is substantially vertical before the liquid and vapor enter the corrugations oriented differently from the next fill element. Although not shown in this way, the corrugations in the filling elements and the grids can be positioned in such a way that the cells in the grids effectively form continuations of the corrugations and serve to regularly divert the flow of the continuous phase from an element. fill to a flow direction corresponding to the orientation of the corrugations in the next fill element. Although the invention is described with reference to vapor-liquid contact, we do not exclude the possibility of other forms of fluid-fluid contact, particularly the liquid-liquid contact in which a liquid, usually the less dense liquid, forms the continuous phase. Corresponding to Fig. 3, Fig. 5 shows an embodiment with rectilinear configurations 26 and terminal portions 32 adjacent to the interface 21 with a shape of reduced depth configuration. The depth of the corrugations 26 is a, the reduced depth at the interface 21 is b. At any height of the end portions 32, the total length of the folded sheet (i.e., the non-folded length of any horizontal intersection line) is equal to the corresponding length of the corrugations 26. Corresponding to Figure 4, the Figure 6 shows an embodiment of the fluid control means 40 located between successive filling elements 20 in the form of a grid. The squared cells form a continuation of the corrugations. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (14)

1. An apparatus for fluid-fluid contact, characterized in that the structured packing comprises various filling elements arranged in succession in the designed direction of fluid flow, each filling element comprising a plurality of folded sheets of material placed in a face-to-face relationship with the corrugations extending obliquely in relation to the direction of fluid flow, successive elements are placed with the leaves on an element angularly offset with respect to the sheets of adjacent elements, the apparatus is characterized in that means are provided in the vicinity of the interphase between successive elements to reduce the pressure drop imposed on the continuous phase at the interface.

2. The apparatus according to claim 1, characterized in that the means is constituted by a localized change in the configuration of the corrugations immediately adjacent to the interfaces.

3. The apparatus according to claim 2, characterized in that at least part of the sheets of each filling element has at least some corrugations whose obliquity angle varies between opposite sides of the filling element so that the angle of obliquity is greater in the vicinity of at least one of the faces that the largest angle of obliquity within the body of the filling element.

4. The apparatus according to claim 3, characterized in that the corrugations have a terminal portion or portions which interconnect the faces at an angle of up to 90 ° while the intermediate portions of each corrugation over at least part of the length thereof. they extend at a somewhat smaller angle.

5. The apparatus according to claim 3 or 4, characterized in that the obliquity angle of each corrugation changes progressively in the longitudinal direction.

6. The apparatus according to any of claims 1 to 5, characterized in that at least part of the corrugations in at least some of the sheets of each filling element are formed with a reduced cross section in the vicinity of at least one of the faces of the filling element, whereby the surface area and the pressure drop in that position are reduced.

7. The apparatus according to claim 6, characterized in that at least part of the corrugations have a localized reduction in depth, in the vicinity of at least one of the faces of each filling element.

8. The apparatus according to any of claims 1 to 7, characterized in that the means in the vicinity of the interface between successive elements to reduce the pressure drop at the interface comprises a fluid flow control means.

9. The apparatus according to claim 8, characterized in that the successive packing elements are separated from each other in the direction of volume flow of fluid through the apparatus in the fluid flow control means which is located in the separation.

10. The apparatus according to claim 1, characterized in that the medium in the vicinity of the interface between successive elements to reduce the pressure drop at the interface comprises an effective separation to produce a significant reduction in the pressure drop imposed in the continuous phase in the interface.

11. The apparatus according to claim 10, characterized in that the separation is at least 2 cm.

12. A structured packing element comprising a plurality of folded sheets of material placed in face-to-face relationship with the corrugations extending obliquely relative to the direction of fluid flow, the successive elements are positioned with the leaves on an angularly displaced element with respect to the sheets of the adjacent elements, the corrugations have a localized change in the configuration of the corrugations immediately adjacent to at least one face of the element so that, when two such elements are located face to face, the localized change in configuration it is effective to reduce the pressure drop imposed in the continuous phase in the interface.

13. The element according to claim 10, characterized in that the localized change in configuration comprises a change in the obliquity angle in the vicinity of at least one of the faces of the element so that the angle of obliquity is greater in such position in comparison with the inward compositions removed from a face.

14. The element according to claim 10, characterized in that the localized change in the configuration comprises a reduction in the depth of the corrugations in the vicinity of at least one of the faces of the element.