The invention will be explained in the following with reference to the drawings wherein:
FIG. 1 illustrates a part perspective view of a static mixer employing a first embodiment of a mixing element of planar layers in accordance with the invention;
FIG. 2 illustrates a part perspective view of a static mixer employing a second embodiment of a mixing element of layers with a zig-zag section in accordance with the invention;
FIG. 3 illustrates a third embodiment of a static mixer employing a mixing element of a combination of planar layers and layers with a zig-zag section;
FIG. 4
a illustrates the installation of layers with a zig-zag section in a conical mixer housing;
FIG. 4
b illustrates a section through a series of layers with a zig-zag section;
FIG. 4
c illustrates two crossing layers with a zig-zag section;
FIG. 5
a illustrates a first layer with a zig-zag section which forms a conical hollow body;
FIG. 5
b illustrates a second layer with a zig-zag section which forms a conical hollow body;
FIG. 6
a illustrates the installation of a layer with a zig-zag section into a conical mixer housing;
FIG. 6
b illustrates a marginal layer with a zig-zag section inclined relative to the main direction of flow;
FIG. 7 illustrates an arrangement of two mixing elements for a conical static mixer;
FIG. 8
a illustrates a fluid-conducting means with a square cross section;
FIG. 8
b illustrates a fluid-conducting means with a rectangular cross-section; and
FIG. 8
c illustrates two adjacent layers of a mixing element with openly crossing flow passages.
Referring to FIG. 1, the static mixer includes a fluid-conducting means or housing 1 having a conical shape with an inlet opening 9 at one end having a first cross-section which is arranged in a plane disposed substantially normal to the main direction of flow 11 in the inlet opening 9 and an outlet opening 10 at the opposite end having a second larger cross-section which is arranged in a plane disposed substantially normal to the main direction of flow 11 in the outlet opening 10.
The static mixer also includes a mixing element 12 within the housing 1. This mixing element 12 includes a number of trapezoidal installations or layers 2, each with a planar surface. However, each layer 2 may be provided with any desired surface-enlarging structures in accordance with one of the previously mentioned embodiments. In the configuration shown, a flow of a fluid mixture is guided into the region between the layers 2 from the inlet cross-section 9 to the outlet cross-section 10, with the arrow 11 indicating the main direction of flow.
The fluid mixture should in particular be understood as a gas/liquid mixture or a mixture of gases or a mixture of liquids. Each of the phases can additionally include a solid portion.
The flow is uniformly expanded and distributed by the alignment of the layers 2 matched to the shape of the fluid-conducting means 1. The number and the spacing of the layers 2 essentially depend on the mixing effect in each layer 2. This is, in turn, influenced by the flow speed and, not least, by the properties of the flowing components such as in particular their density or viscosity. Frictional effects can occur at each of the walls of the layers 2 and of the housing 51 so that the marginal flows arise which result in a lower throughput in marginal regions and wall regions because the flow close to the wall has a lower speed than the main flow due to the frictional effects.
In the example shown, the layers 2 are held together at intervals by holding devices 7, 8. In accordance with another embodiment (not shown), the layers can also be fastened to the inner wall of the actual fluid-conducting means by means of plug connections or clamp connections. The installation of layers into a conically designed fluid-conducting means can take place such that the layers are assembled with the holding devices in advance and are then inserted into the housing as a prefabricated mixing element 12. The conical shape of the housing 1 thus also effects the centering of the mixing element 12 prefabricated in this way.
Referring to FIG. 2, in another embodiment, a mixing element is comprised of layers with a zig-zag section (only two such layers 3, 4 are shown for reasons of clarity). The flowing mixture is guided through the layers which form V-shaped flow passages. In the case shown, the layer 3 is supported along the common edges 15 on the layer 4. One edge 15 belongs to the layer 4 and faces normally to the main direction of flow, shown by arrow 11 in the direction of the fluid-conducting means shown as an upper housing wall. One edge 15 belongs to the layer 3 and is thus in linear contact with the edge 15 of the layer 4. The sectional surfaces 13, 14 of the zig-zag section forming the respective layer run together at the edges and form a flow passage through which the components to be mixed flow. The flow passage is thus bounded by the sectional surfaces 13, 14. When the edges of adjacent layers contact one another over the total length between the inlet cross-section 9 and the outlet cross-section 10, flow passages are formed which are closed by adjacent layers and which are made up of two respective open flow passages 5, 6. A flow passage closed in this manner has a substantially diamond-shaped cross-section. For reasons of simplified installation or improved mixing of the individual part flows, it is possible to provide a spacing between the layers 3, 4—in an analogous manner as shown in FIG. 1. The edges 15 of the two adjacent layers arranged over one another then no longer contact one another so that a common edge 15 is no longer formed. An open flow passage is then formed by the sectional surfaces 13, 14.
The fastening of the layers 3, 4 as well as of further layers not shown in FIG. 2 for the forming of a mixing element can take place by means of the same fastening means as shown in FIG. 1, with the possibility also being present of provided a weld connection, in particular a spot-weld connection and/or a solder connection and/or an adhesive bond connection or the like.
Additional possibilities of the flow deflection and of the improvement of mixing result in that the passages are provided with flow-deflection means which are not shown. Perforated metal sheets, projections in the passage walls, tabs or surface-enlarged structures inserted into the flow passages and distributed in the manner of bulk material are in particular provided for this purpose. Structures of this type are used in gas/liquid absorption and as column installations, in particular Raschig rings, Berl saddles, Intalox saddles, Pall rings, Tellerette structures. Another possibility is to provide the layer itself with flow-deflecting structures, in particular with a structure which is comparable with a stretching metal, as well as with one of the structures already mentioned in the general description of the mixing element.
Referring to FIG. 3, third embodiment of a mixing element includes a combination of planar layers 2 and layers 3,4 with sectional surfaces 13, 14, in particular with a zig-zag section. The representation of further layers has been omitted for reasons of clarity. Instead of the planar layer 2, a layer with sectional surfaces can also be used which differ from sectional surfaces with a zig-zag section. Closed flow passages are formed by the layer 4 and by the two layers 2. The edge 15 of the layer 4 contacts the layer 2, but not the edge 15 of the layer 3. The flow passages thus have a substantially triangular cross-section. Analogously to the expanding cross-section of the mixing element, the cross-section of the flow passages formed by the adjacent layers 2, 3, 4 increases continuously in the main direction of flow. The advantage of a mixing element having layers forming flow passages is their low pressure loss and their contribution to the generation and/or maintenance of a homogeneous mixture with a simple constructional design. The flowing medium has to follow the course of the flow path predetermined by the fluid-conducting means; the composition of the flowing mixture therefore remains constant through the flow passage due to the continuity principle as long as no chemical reaction takes place in the static mixer. The flow is only in the fluid-conducting means for a short period since the fluid-conducting means usually only serves as a transition from a first cross-section of smaller diameter to a second cross-section of larger diameter. The path is therefore too short for real demixing effects to become noticeable along the flow passages in flowing through the fluid-conducting means. All part flows are guided together in the outlet cross-section 10, which generally coincides with an end of a flow passage.
At high flow speeds, eddies can be released in accordance with the principle of Karman's eddy path at the ends of, the flow passages lying in the plane of the outlet cross-section, whereby the mixing can be improved even more.
In accordance with a further advantageous embodiment in accordance with FIG. 4a, provision can be made for the better mixing that no linear contact of two adjacent edges 15 occurs in accordance with FIG. 2 or of one each of the edges 15 with the layer 2 arranged therebetween in accordance with FIG. 3, but that two crossing adjacent layers 3, 4 with a zig-zag section are provided as are shown by way of example in FIG. 4c in which the edges 15 only contact one another at one point. This point-like contact takes place at the contact point 17 for the edges 15 and it is thereby achieved that two adjacent layers 3, 4 are arranged at an angle to one another. It is thereby effected that the edge 15, which belongs to a first layer 3, only has one contact point 17 with the edge 15 of the layer 4. The angle alpha between two edges 15 of adjacent layers lies between 0° and 120°, in particular between 60° and 90°. In a particularly advantageous embodiment, one edge 15 of the layer 3 is inclined by alpha/2 with respect to one side; one edge of the adjacent layer 4 is inclined by alpha/2 with respect to the other side in relation to the main direction of flow. This arrangement produces the “cross-passage structure” mentioned later as is described in CH 547 120. The edges of the layer 3 in the embodiment of FIG. 4a, 4b or 4c form a plane which is called the interface 16 of the layer (see FIG. 4b). The interface 16 contains all the contact points of adjacent layers when adjacent layers are arranged such that they form a common interface. The substantial advantage of this arrangement, also known as a cross-passage structure, in accordance with this embodiment is found in the fact that the flowing mixture does not always flow in the same flow passage as in the previously shown variants, but is located in another flow passage at every time that is continuously changes the flow passage. In this case, the flowing mixture is deflected substantially more pronouncedly than in the preceding embodiments, which results in an additional improvement in the mixing.
The fitting of layers 3, 4 with a zig-zag section and planar interfaces is shown in FIG. 4a, with only every second layer 3 being shown, whereas the adjacent layers 4 have been omitted to increase the clarity of the representation. The layers have been made such that the shortest possible spacing of two adjacent edges, measured in a cross-section normal to the main direction of flow, increases continuously from the inlet cross-section 9 to the outlet cross-section 10. It is equally possible for the normal spacing between two adjacent interfaces 16, measured in a cross-section normal to the main direction of flow, to increase continuously from the inlet cross-section 9 to the outlet cross-section 10, or also to be kept constant, whereby the interfaces of the layers come to lie parallel to one another.
In accordance with the embodiment shown in FIG. 4a, adjacent interfaces are expanded in the manner of a diffuser from the inlet cross-section 9 to the outlet cross-section 10.
At least some of these contact points 17 can be made as weld spots to join adjacent layers 3, 4 together to form a mixing element.
In accordance with a further variant, the interfaces 16 of adjacent edges 3, 4 do not coincide, but rather have a small spacing from one another so that adjacent layers do not contact one another. Some of the flowing mixture is not completely deflected by this measure so that the flow is slowed down less. The effects on the mixing are dependent on the components to be mixed, the proportions of the different phases and on the tendency to demixing. The pressure loss of the static mixer is also influenced by the change in the spacing of the layers.
Where possible, the layers should directly adjoin the inner wall of the fluid-conducting means, as is indicated in FIG. 4a, so that at most a small spacing remains between the layer 3 and the inner wall.
With a linear contact of the layer 3, conical sections, that is, depending on the inclination of the layer to the inner wall, elliptical, parabolic or hyperbolic boundary lines, result as sectional curves of a layer which is planar or folded in any desired manner and is made up of planar segments and has a conical inner wall, which is shown in FIG. 5a and FIG. 5b. Each of the layers described above, of which one is shown in FIG. 5a, can be developed in one plane; a development can therefore be generated by means of drawing programs from the desired position of the layer in the mixer. These developments also include the bending lines in addition to the boundary lines so that an economical manufacture of the layers is also possible in cases in which each angle is different and very complex bending procedures are therefore necessary.
In FIG. 5a, a cross-section through such a cross-passage structure is shown, with only every second layer 3 being shown, as in FIG. 4a. If the design of the layers corresponding to the cross-passage structure is used, it is possible that dead spaces arise because the layer at the inlet cross-section 10 flow paths are blocked by the angular alignment of the part of the layer which is adjacent to the inner wall. For this reason, the passages on the housing side, that is on the inner wall, are checked and opened as required after the assembly of the layers to form a mixing element. The wall gap between the mixing elements and the inner wall of the fluid-conducting means 1 is smaller than the normal spacing of two adjacent interfaces 16, in particular smaller than the height of a flow passage 5, 6 of a surface-enlarging structure, in particular of the zig-zag section shown, so that a so-called “channelling effect” demonstrably does not occur.
A layer 3 in the marginal region of the mixing element is shown in FIG. 5b. The layer 3 has sectional curves 18 which are adjacent to the inner wall of the fluid-conducting means. If the sectional surfaces (13, 14) of the layers were directly adjacent to the inner wall, no flow would take place through flow passage 5. These sectional surfaces are therefore arranged at least partly at a spacing from the inner wall or are opened for the flow after the assembly of the mixing element.
In accordance with a further embodiment in accordance with FIG. 6a and FIG. 6b, each layer forms a hollow body 19 having surface-enlarging structures. The surface-enlarging structure of the hollow body 19, in particular the ribs, jags or waves, are inclined at an angle of 0° to 180° relative to the main direction of flow. A plurality of hollow bodies of this type can be made such that they can be plugged into one another. In the present case, the hollow body 19 can be completely integrated into the hollow body 20 in that hollow body 19 is plugged into hollow body 20. In the embodiment shown, the hollow bodies 19, 20 have a zig-zag section. The outwardly directed and also the inwardly directed edges each form an interface which is conical. If hollow body 19 has an excess dimension relative to hollow body 20, which only means that the inner interface of hollow body 20 comes to lie within the outer interface of hollow body 19, the two hollow bodies 19, 20 are canted on installation such that it is possible to completely dispense with an additional fixing of the hollow bodies, such as by weld spots or fastening devices, in the event of forces through the flowing medium onto the hollow body in the installed state of the mixing element. The clamping forces provide sufficient security against a positional change of the layers in operation. If it is possible from the aspect of the place of installation, a mixing element of this type, which has a substantially vertically arranged main axis of flow, can be installed such that the mixture flows through the static mixer from bottom to top. If there is a risk that the layers can become displaced with respect to one another or even carried along through the outlet cross-section by the flow, because they are made of a light material such as a light metal or plastic, a retaining device can optionally be provided in the region of the outlet cross-section 10.
FIG. 7 shows two mixing elements 12 for a conical static mixer which are arranged directly adjacent to one another. These mixing elements are made up of layers 3 which in particular have the zig-zag section in accordance with one of the preceding embodiments, with adjacent layers being inclined with respect to one another by an angle other than 0°. Each mixing element 12 has high stability, because the layers support one another and are supported against the inner wall of the fluid-conducting means. The main direction of flow is shown by the arrow 11.
In accordance with a further variant, not shown, the two mixing elements 12 can also be arranged at a spacing from one another.
In FIG. 8a, a fluid-conducting means having a square cross-section is shown. The cross-sectional surface increases continuously from the inlet cross-section 9 to the outlet cross-section 10. In this process, each side length of the square increases continuously.
In FIG. 8b, a fluid-conducting means having a rectangular cross-section is shown. The cross-sectional surface increases continuously from the inlet cross-section 9 to the outlet cross-section 10. In this process, only every second side length of the rectangular cross-section increases continuously; in FIG. 8b this is the side length 21. In FIG. 8b, the interfaces 16 of the layers of the mixing element are indicated.
FIG. 8
c shows the arrangement of two adjacent layers 3, 4 with a zig-zag section for one of the embodiments shown in FIG. 8a or FIG. 8b. Further layers are only indicated by their interfaces 16 so as not to make FIG. 8c too complex to view. In this variant, no special machining steps are required for the execution of the marginal layers adjacent to the inner wall of the fluid-conducting means 1 so that the manufacturing effort for a mixing element having a fluid-conducting means 1 with sectionally planar jacket surfaces is lower.
Reference is made to the possibilities for zig-zag sections shown under FIGS. 4a to 4c, which should in turn be exemplary for all other embodiments of the layers mentioned in the text, with respect to the possibilities of the expansion of the passages of the individual layers from the inlet cross-section to the outlet cross-section 10.
The invention provides a static mixer that can be used for various purposes and in various industries. For example, the static mixer may be arranged in the inlet region of a heat exchanger, or used for natural gas processing and/or for emission denitrification, or for the carrying out of catalytic and/or biogenic reactions.
Patent Application
20070263486
