Abstract:
An exchanging tower having excellent gas/liquid contact efficiency, wherein a liquid is supplied from the upper part thereof and a gas is supplied from the lower part thereof, and an exchange of heat and/or substances between the liquid and the gas is effected by contacting the gas and the liquid in the inside of the tower. A packing is placed along the longitudinal axis of the tower. The packing comprises an arrangement of a plurality of sheet-like bases (2), each of which are corrugated to form folds inclined along the longitudinal axis of the tower such that the folds cross one another, the corrugated sheet-like bases having plural continuous concave/convex channels formed on the surface thereof and extending in a lateral direction. At least a lower surface of the concave channels or an upper surface of the convex channels is in a meandering form. When the packings are placed in the tower, in each corrugated sheet-like base a wall surface (7) of a concave channel above a crest (5) of the meander of an adjacent convex channel of the sheet-like base is located on an upper side along the longitudinal axis of the tower at a position higher than a wall surface (8) of a convex channel below a trough (6) of the meander of the convex channel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a packing to be used in a substance and/or heat exchanging tower. 
     2. Prior Art 
     Conventionally, such a packing has been generally composed of sheet-like bases and used as media for the contact of a liquid and a gas to be used in a substance and/or heat exchanging tower such as a distillation tower, an absorption tower and a recovery tower. In addition, other conventional packing of this type has been composed of materials other than sheet-like bases. For example, some packings have been composed of net-like bases instead of sheet-like bases. Though a packing composed of netlike bases exhibits a good performance, the price thereof is too high for practical use. Compared with them, a packing composed of sheet-like bases is suitable for practical use due to its low price, though it exhibits a slightly inferior performance. Hence, improvement in the performance of a packing employing sheet-like bases is demanded. 
     It is known that it is necessary to heighten contact efficiency between a liquid and a gas in order to improve the performances of this type of packing. Various means have been attempted therefor. One attempt is to increase the volume of the packing per unit volume of the tower. This intends to increase a gas/liquid contact area by increasing the volume of the packing. However, there occurs one problem in this method. Namely, a larger volume of packing causes a higher pressure loss in the upward gas flow. This has a deleterious effect on the operation of a substance and heat exchanging tower. Even if the contact area is increased, improvement in contact efficiency cannot be accomplished unless sufficient diffusion of the gas and liquid is effected on the surface of the packing. 
     In the practical operation of the tower, since the viscosity and surface tension of the liquid have more influence on the operational conditions of the tower than those of the gas, it is necessary to improve the diffusion of the liquid particularly. Consequently, it has been attempted to improve the efficiency of conventional packing by improving the diffusion of liquid. 
     Japanese Patent Publication No. 15554/79 discloses a method of forming channels on the surface of a sheet-like base and thereby diffusing a liquid to the entire surface of the base. However, it is only the spread of the liquid that this method takes into consideration. 
     Further, in some conventional packings, it is intended to spread a liquid in a lateral direction by providing gatherings on the surface of a sheet-like base horizontally. 
     In the case of providing gathering or channels on a sheet-like base in order to spread a liquid in a lateral direction, it is more advantageous to effect diffusion of a liquid in a lateral direction that the depth of the fold of gathering or a channel be made larger. However, if the surface of the packing is inclined in a horizontal direction, when the packing is mounted in the tower, the liquid flows to a lower part running down the channel due to the inclination, resulting in a polarized liquid flow. In using this kind of packing, a polarized liquid flow is one of the main problems with respect to the performance of the packing. To overcome this problem, packings are provided in shallow gatherings. However, such a method still does not provide a satisfactory liquid spread. 
     In order to heighten the contact efficiency between a liquid and a gas, it is necessary not only to accomplish the diffusion of the liquid as explained above but also to improve the mutual relationship of flows of the liquid and the gas, taking the relation between the liquid and the gas into consideration. 
     One possible method for solving the above problem is to break a boundary film existing on the interface between the liquid phase and the gas phase by providing a specific shape of reliefs on the surface of the sheet-like base. Though it has been known that the breakage of a boundary film is useful for the improvement of contact efficiency, no conventional packing has been found which can accomplish both the diffusion of a liquid and the breakage of a boundary film. 
     For instance, the packing described in Japanese Patent Publication No. 15554/79 does not include the concept of breaking a boundary film. The method according to Japanese Patent Publication No. 15554/79 is not satisfactory from the viewpoints of both the diffusion of a liquid and the breakage of a boundary film. 
     SUMMARY OF THE INVENTION 
     The present inventor has made extensive studies with a view to overcoming the defects of the prior art, and as a result, has found that much better diffusion of a liquid and a gas as well as the improvement of gas/liquid contact can be accomplished simultaneously by forming meandering concave/convex channels on the surface of a sheet-like base and corrugating said sheet-like base, and specifically define a location of portions of the concave channels and the convex channels to the longitudinal axis of the tower. 
     Referring to the accompanying FIG. 2, a first embodiment of the present invention refers to: 
     a packing to be used in a substance and/or heat exchanging tower where a liquid is supplied from the upper part thereof and a gas is supplied from the lower part thereof and an exchange of heat and/or substances between the liquid and the gas is effected by contacting the gas and the liquid in the inside of the tower, the packing being placed along the longitudinal axis of said tower, the packing comprising a laminated sheet prepared by laminating a plurality of sheet-like bases (2) which are corrugated to form folds inclined along the longitudinal axis of the tower in such a manner that the folds cross one another, said sheet-like base having plural continuous concave/convex channels formed on the surface thereof extending in a lateral direction, at least the lower surface of the concave channel or the upper surface of the convex channel being in a meandering form, characterized in that, in the state that the packings are placed in the tower, the wall surface (7) of the concave channel above the crest (5) of the meander of the adjacent convex channel of the sheet-like base is located on the upper side along the longitudinal axles of the tower, at a position higher than the wall surface (8) of the convex channel below the trough (6) of the meander of the convex channel. 
     The second embodiment of the present invention refers to: 
     a packing to be used In a substance and/or heat exchanging tower where a liguid is supplied from the upper part thereof and a gas is supplied from the lower part thereof and an exchange of heat and/or substances between the liquid and the gas is effected by contacting the gas and the liquid in the inside of the tower, the packing being placed along the longitudinal axis of said tower, the packing comprising a laminated sheet prepared by laminating a plurality of sheet-like bases (2) which are corrugated to form folds inclined along the longitudinal axis of the tower in such a manner that the folds cross one another, said sheet-like base having plural continuous meandering concave/convex channels formed on the surface thereof extending in a lateral direction, the meandering pitches between adjacent convex channels or between adjacent concave channels are shifted in relation to one another, characterized in that, in the state that the packings are placed in the tower, the wall surface (7) of the concave channel above the crest (5) of the meander of the adjacent convex channel of the sheet-like base is located on the upper side along the longitudinal axis of the tower, at a position higher than the wall surface (8) of the convex channel below the trough (6) of the meander of the convex channel. 
     In the packing of the present invention, it is preferable that the pitch of the meandering of the convex channel and that of the adjacent convex channel (and the pitches of the adjacent concave channels) are shifted in relation to one another by a half pitch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the state that the packing of the present invention is placed along the tower axis; 
     FIG. 2 is a perspective view showing the shape of the sheet-like base according to one embodiment of the present invention; 
     FIG. 3 is a sectional view showing an embodiment out of the scope of the present invention that, in the state that the packing is mounted in the tower, the wall surface (7) of the concave channel above the crest (5) of the meander of the adjacent convex channel of the sheet-like base is located on the lower side along the longitudinal axis of the tower, at a position lower than the wall surface (8) of the convex channel below the trough (6) of the meander of the convex channel; 
     FIG. 4 is a perspective view showing the shape of the sheet-like base according to one embodiment of the present invention; 
     FIG. 5 is a perspective view showing the shape of the sheet-like base according to one embodiment of the present invention; and 
     FIG. 6 is a sectional view showing a constitution of the packing according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereunder, the effects of the present invention will be described. A packing according to the present invention has a constitution that, on the surface of a sheet-like base which is corrugated to form folds inclined to the longitudinal axis of the tower, hence the surface of the sheet-like base being inclined to the longitudinal axis of the tower, concave/convex channels extending in a lateral direction are provided, said channels have a meandering form, and a plurality of the thus constituted sheet-like bases are laminated in such a manner that the folds cross one another. As result of such a constitution in using the packing of the present invention, diffusion of a gas and a liquid can be accomplished, the flows of the liquid and the gas is made turbulent, by which breakage of a boundary film of the liquid and the gas is accelerated, and thereby gas/liquid contact efficiency is improved, and further the flow of the liquid is made smooth by defining the location of portions of the concave channels and the convex channels which are provided on the surface of the sheet-like base along the longitudinal axis of the tower and thereby preventing undesirable accumulation of the liquid. As a result, the gas/liquid contact effects are further heightened in the packing of the present invention. 
     Hereunder, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the state wherein the packing of the present invention is filled in the tower along the longitudinal axis of the tower. (1) is the longitudinal axis of the tower, (2) is a corrugated sheet-like base, (3) is a convex channel formed on the surface of the sheet-like base and (4) is a concave channel. FIG. 2 is a perspective view of the sheet-like base of the present invention. Convex channels (3) and concave channels (4) are provided alternately along the longitudinal axis of the tower. The convex channel has crests (5) formed in meander toward the upper side of the longitudinal axis of the tower and troughs (6) formed in meander toward the lower side of the longitudinal axis of the tower. In FIG. 2, (5) shows crests of the meanders of convex channels and (6) shows troughs of the meanders of convex channels. (7) shows the wall surface of the concave channel above the crest of the meander of the adjacent convex channel. (8) shows the wall surface of the convex channel below the trough of the meander of the convex channel. 
     First of all, the effect caused by the meanders of the channels will be described below. A liquid flowing downwardly from the upper side of the longitudinal axis of the tower strikes the upper surface (21) of the convex channel of a sheet-like base and is dispersed and spread on the top surface. The dispersed and spread liquid falls downwardly from the trough (6) of the meander of the convex channel. When the width of the meander of the convex channel is small and the depth of the channel is large. the spread of the liquid in a lateral direction is further continued. The liquid which has fallen downwardly further strikes the upper surface of the convex channel below it. The spread in a lateral direction and the downward flow of the liquid are repeated in the same manner. 
     In this case, if the width of the meander of the convex channel is large, the spread of the liquid in a lateral direction is disturbed and the liquid will fall downwardly from one trough without spreading, and hence it is preferable that the width of the meander between the crest (5) and the bottom (6) of the convex channel is of the order of one-fifth of the distance between the adjacent crests (5). 
     To ensure that the liquid is spread in a lateral direction on the surface of the sheet-like base, it is necessary for the surface of the sheet-like base to have a liquid-receiving angle (α) relative to the longitudinal axis of the tower (see FIG. 2). If the surface of the base does not have this angle, namely, the surface of the sheet-like base is in an almost vertical state, the liquid falls straight down and lateral spread of the liquid is not, accomplished. In practice, a preferable liquid-receiving angle (α) is of the order of 90° to 120°. 
     In the present invention, in order to provide said liquid-receiving angle, meandering concave/convex channels are provided on the surface of the sheet-like base, whereby spread of the liquid in a lateral direction is effected. The shape of the meandering channels may be of a crooked or flexed form. The sectional profile of the concave/convex channels may be in the configuration of a circle, an ellipse, a triangle, a square, a trapezoid or other polygons. 
     By constituting the channels as mentioned above, the liquid can fall from the troughs (6) of the convex channels even if the channels are deepened. Further, the surface area of the packing can be increased by deepening the channels. Therefore, the spread of the liquid in the lateral direction, the prevention of a polarized flow and the increase of a contact area can be accomplished simultaneously. This has never been accomplished by a conventional packing. In addition, the flow of the liquid becomes turbulent as a result of providing the channels in a meandering form, and hence gas/liquid contact effects can be improved. Here, as a further effective method can be mentioned the following method. This is to shift the pitches of the meander between adjacent two convex channels and those between adjacent concave channels (see FIG. 4). In this way, liquid falling from the trough (6) of the convex channel strikes the crest (5) of the convex channel located below it and is dispersed and spread in the lateral direction, and further flows down and strikes the crest of the convex channel one after another; thus dispersion and spread of the liquid can be repeated. 
     With respect to a gas, when a gas rises upwardly from the lower part of the tower, it is dispersed by means of the crest portions of the meander of the convex channel facing the lower side of the longitudinal axis of the tower. The flow of the gas can be made turbulent thereby, and the turbulent flow of the gas enhances the gas/liquid contact efficiency of the packing. When the pitches of the meanders of the channels are shifted in relation to one another in the manner described above, more excellent dispersion and diffusion of the gas can be accomplished and gas/liquid contact efficiency can also be improved, as in case of a liquid. 
     The form of the crests of the meander of the channels may be sharp or rounded. 
     As described above, more excellent diffusion of a gas and a liquid can be accomplished by allowing channels to meander, and at the same time, boundary films of the liquid and the gas can be broken by providing turbulent flows thereof. 
     The above is an explanation regarding the effects resulting from meandering of the channels; next, means of preventing a liquid from accumulating will be described. 
     In a packing of this kind, performance is determined by how much contact between a gas and a liquid is effected within a unit volume. In order to accomplish a better performance, it is necessary to provide a larger gas/liquid contact area per unit volume. When an exchanging tower is operated by using a packing having a large gas/liquid contact area, the liquid falls down while being held on the surface of the packing in a larger amount compared with the case of operating using a packing with a small gas/liquid contact area. An important point with respect to the operation of a tower is that all of the liquid maintained on the surface of the packing falls down when the operation is stopped. This is effected because liquid which remains and accumulates on the packing after the operation has been stopped is considered to prevent proper contact with the gas. Since the amount of a gas/liquid contact area is directly proportional to the amount of an accumulating liquid in general, when a gas/liquid contact area is increased in order to raise gas/liquid contact efficiency, the amount of the liquid accumulating on the packing generally increases. Consequently, improvement in efficiency of the packing cannot be effectively accomplished. 
     The present invention prevents the unnecessary accumulation of a liquid, by paying attention to this point. 
     In the packing of the present invention, the sheet-like base has been corrugated to form folds inclined along the longitudinal axis of the tower, and hence their surfaces face in two directions. One surface faces the upper side of the longitudinal axis of the tower and the other surface faces the lower side of the longitudinal axis of the tower. Comparing these two surfaces, the surface of the sheet-like base facing the upper side of the tower plays the more important role regarding the spread and accumulation of the liquid. Accordingly, the following description is provided concerning the surface facing to the upper side of the longitudinal axis of the tower of the sheet-like base. 
     Regarding the shape of channels of the sheet-like base, in a packing such as that according to the present invention, the channels are generally formed by subjecting a sheet-like base to an embossing process, and hence the upper surface (21) of the convex channel which forms a liquid-receiving angle (α), has an angle of aperture (β) of more than 90° to the basic surface of the sheet-like base (see FIG. 2). Here, if the sheet-like base with a channel having a liquid-receiving angle (β) of more than 90° formed thereupon is used in the tower in such a state as to stand vertically without being corrugated, the liquid falls down along the surface of the sheet-like base and strikes the upper surface (21) of the convex channel. The liquid spreads over the upper surface (21) in a lateral direction, and then falls down from the trough portion of the meandering (6) of the convex channel. Accordingly, in such a case, even if the liquid-receiving angle (β) of the channel is 90° or the depth of the channel is large, the liquid can fall down from the trough portion (6) of the convex channel by way of the meander of the channel. 
     However, in the packing according to the present invention, the sheet-like base is corrugated to form folds inclined along the longitudinal axis of the tower, and a phenomenon different from the above-mentioned flow of the liquid occurs, which gives rise to the accumulation of liquid. With respect to the sheet surface facing the upper side of the longitudinal axis of the tower, even if, for example, an angle of aperture (β) is 90° relative to the basic surface of the sheet-like base, a liquid-receiving angle (α) in this part becomes less than 90° when the packing is mounted in the tower, since the basic surface itself of the sheet-like base is inclined along the longitudinal axis of the tower. The larger the inclination of the basic surface of the sheet-like base becomes, the smaller is the liquid-receiving angle (α) of this part, and when the depth of channels is large and/or when the width of the meandering of the channels is small, the liquid tends to be held in the concave channels. Consequently, though the liquid flows smoothly when the sheet-like base stands vertically without being inclined along the longitudinal axis of the tower, the exact flow of the liquid on the packing of the present invention is disturbed by the Inclination of the sheet-like base, which is inconvenient. 
     In the present invention, the following constitution was adopted in order to overcome this problem. That is, the packing of the present invention is characterized in that, in the state that the packing is mounted in the tower, the wall surface (7) of the concave channel above the crest (5) of the meander of the adjacent convex channel of the sheet-like base is located on the upper side along the longitudinal axis of the tower at a position higher than the wall surface (8) of the convex channel below the trough (6) of the meander of the convex channel. Namely, as shown in FIG. 3, when the inclination of the basic surface of the sheet-like base to the longitudinal axis of the tower (1) is large and the depth of channels is deep, such a case may occur as the wall surface (7) of the concave channel above the crest (5) of the meander of the adjacent convex channel of the sheet-like base is located on the lower side along the longitudinal axis of the tower at a position higher than the wall surface (8) of the convex channel below the trough of the meander of the convex channel. Line 20 in FIG. 3 shows the horizontal line. In such a relationship, liquid accumulates in the concave channels. Accordingly, the relationship of the location of channels is defined as described above in the present invention. 
     By thus defining the relationship of the location of the channels, it becomes possible to accomplish a smooth downward flow of the liquid and retainment of the liquid in an amount needed for gas/liquid contact by adjusting a liquid-receiving angle, even in the case that the inclination of the basic surface of the sheet-like base along the longitudinal axis of the tower is large or the depth of channels provided on the surface of the sheet-like base is large. 
     As described above, the present invention has accomplished a large improvement in the gas/liquid contact efficiency by allowing channels to meander and thereby reduce the accumulation of liquid in the channels caused by the inclination of the basic surface of the sheet-like base along the longitudinal axis of the tower. 
     Hereunder, other various embodiments of the present invention will be described. 
     FIG. 4 is a perspective view of the sheet-like base according to the present invention, showing an embodiment in which pitches of the meanders between adjacent channels are shifted. In FIG. 4, meandering pitches between the adjacent convex channels are shifted by half a pitch, but this is not an indispensable requirement of the present invention. Besides, as shown in FIG. 5, pores (9) with any size may be provided at any position along the sheet-like base. 
     As shown in FIG. 6, one or a plurality of sheet-like bases, net-like sheets or expanded metal sheets or a combination thereof (10) without being corrugated may be held between the corrugated sheet-like base (2). 
     Moreover, the corrugated sheet-like base may be formed by laminating a plurality of sheet-like bases together. 
     Further, the concave/convex channels of the sheet-like base may be formed by laminating one sheet-like base upon another sheet-like base. 
     The packing according to the present invention may be made of a metal, plastic, glass or ceramic. 
     As described above, the packing of the present invention is characterized in that, in the state that the packing is mounted in the tower, the wall surface (7) of the concave channel above the crest (5) of the meander of the adjacent convex channel of the sheet-like base is located on the upper side along the longitudinal axis of the tower, at a position higher than the wall surface (8) of the convex channel below the trough (6) of the meander of the convex channel. However, it will be apparent to those skilled in the art that it is sufficient for the above relationship to be established on the surface of the sheet-like base facing to the upper side of the tower.