EP0594657B1 - Static mixer - Google Patents

Abstract

A static mixer distributes substances introduced into a flow duct as homogeneously as possible in a flow medium. The intention is to achieve complete intermixing over the shortest possible path distance. The static mixer includes a multiplicity of deflection elements which are small in relation to the diameter of the flow duct. The deflection elements are disposed in mutually parallel rows aligned transversely to the axis of symmetry of the flow duct. The deflection elements of each row are inclined equidirectionally in a direction parallel to the row and in counterdirection to the deflection elements of the respectively directly adjacent rows. The static mixer can be used for gaseous and liquid media.

Description

The invention relates to a static mixer with a plurality of deflection elements arranged in a flow channel

Static mixers are generally installed in pipelines or in other flow channels and serve to distribute substances previously introduced into the pipeline or into the flow channel as homogeneously as possible in the flow medium. For example, it can be used to mix various previously introduced gases. It can also be used to evenly distribute liquid or dusty substances in a gas stream. Static mixers can also be used in liquids.

Known static mixers consist of one or two deflection elements - mostly triangular sheets - which are anchored more or less obliquely in the flow path (see Balke Dürr, special print C56, from VGB Kraftwerkstechnik H8 / 1983, pages 676 to 678). These deflection elements generate violent eddies that downstream it leads to an intensive mixing of the gas flow and all added components, but it is a peculiarity of such static mixers that the complete mixing of the components is only achieved at a sufficiently large distance behind the static mixer or behind the deflection elements Gaseous media about 10 to 20 times the pipe cross-section, which means that there must be sufficient space behind the deflection elements before the subsequent components to which the mixture is to be fed can be connected In industrial plants, however, this space is very limited and not sufficiently available.

A static mixer has also become known in which several small deflection elements are arranged next to one another in a plane perpendicular to the axis of symmetry of the gas channel. With such static mixers, good mixing of the gases or substances previously injected into the gas stream can already be achieved at a relatively short distance from the deflection elements. However, it is a peculiarity of such static mixers with relatively small deflection elements that local concentration differences can be compensated for relatively well and also quickly. Unfortunately, large-scale differences in concentration, for example between two opposite sides of the flow channel, can only be compensated for to a very inadequate extent.

From DE-OS 2 340 483 and DE-PS 39 20 123 static mixing devices according to the preamble of claim 1 are known. They have a grid insert in the flow channel. Here, the flow channel in the area of the grille insert is divided into a plurality of subchannels, the walls of which are inclined in rows in such a way towards opposite sides with respect to the main flow direction, the flow in adjacent rows being deflected in the opposite direction. The pressure drop caused by such mixing devices in the flow channel is relatively high, however, because the flow channel must be made almost "opaque" by the mixing device for the incoming flow medium if one wants to achieve a sufficiently good mixing.

The dimensions of the deflection elements provided for this purpose, which are part of the walls of the subchannels, are at least as large as the distance between the rows, i.e. also like the cross section of the subchannel.

The invention has for its object to develop a static mixer in which the pressure drop caused is particularly low. Such a mixer with a shorter mixing distance is also able to equalize large-scale as well as local concentration differences.

This object is achieved by the features of the characterizing part of claim 1.

With such a mixer, both large-scale concentration differences and local concentration differences are equally well balanced. Large-scale concentration differences are reduced by the gas flows running along the rows and crossing the entire flow channel. Local differences in concentration on the other hand, they balance each other at the boundaries of the opposite flow directions via the edge vortices.

Overall, this means that the distance of the gas until the individual components are completely mixed in the flow direction behind the deflection elements is minimized. At the same time, such a static mixer is characterized by a particularly low flow resistance, which leads to a particularly low pressure drop in the flow channel.

In a particularly advantageous embodiment of the invention, the deflection elements can be inclined by about 10 ° to 45 ° about axes perpendicular to the direction of the rows and perpendicular to the axis of symmetry of the flow channel. This measure contributes to faster mixing.

In an expedient development of the invention, the rows can extend from one boundary wall to the opposite boundary wall of the flow channel. This promotes a large-scale concentration balance.

A particularly simple construction results from the fact that the deflection elements are fastened on a supporting grid extending transversely to the axis of symmetry of the gas channel. This construction is relatively simple, stable and space-saving to install.

A particularly intimate mixing is achieved if two in each case in a further development of the invention Adjacent rows of deflection elements are arranged in close proximity to one another in pairs. As a result, the turbulence in the region of these deflection elements is greatly intensified, which is equivalent to a further intensification of the local intimate mixing.

Further details of the invention can be found in the remaining subclaims.

FIG 1

eine Aufsicht auf einen in einem rechteckigen Strömungskanal eingebauten statischen Mischer,

FIG 2

einen Schnitt längs der Linie II-II der Figur 1,

FIG 3

einen Schnitt längs der Linie III-III der Figur 1,

FIG 4

eine Aufsicht auf einen in einem Rohr eingebauten statischen Mischer,

FIG 5

einen Schnitt längs der Linie V-V der Figur 4,

FIG 6

einen Schnitt längs der Linie VI-VI der Figur 4,

FIG 7

eine Aufsicht auf einen in einem rechteckigen Strömungskanal eingesetzten statischen Mischer mit verstärkter lokaler Verwirbelung,

FIG 8

einen Schnitt längs der Linie VIII-VIII der Figur 7,

FIG 9

einen Schnitt längs der Linie IX-IX der Figur 7,

FIG 10

eine Aufsicht auf einen Mischer mit diagonal zum Traggitter angeordneten Reihen von Auslenkelementen und

FIG 11

einen Schnitt längs der Linie XI-XI der Figur 10.

Embodiments of the invention are explained in more detail with reference to eleven figures. Show it:

FIG. 1

a top view of a static mixer installed in a rectangular flow channel,

FIG 2

2 shows a section along the line II-II in FIG. 1,

FIG 3

2 shows a section along the line III-III of FIG. 1,

FIG 4

a top view of a static mixer installed in a pipe,

FIG 5

3 shows a section along the line VV of FIG. 4,

FIG 6

4 shows a section along the line VI-VI of FIG. 4,

FIG 7

a top view of a static mixer used in a rectangular flow channel with increased local turbulence,

FIG 8

4 shows a section along the line VIII-VIII of FIG. 7,

FIG. 9

7 shows a section along the line IX-IX of FIG. 7,

FIG 10

a plan view of a mixer with rows of deflection elements arranged diagonally to the supporting grid

FIG 11

a section along the line XI-XI of Figure 10.

1 shows a plan view of a in a rectangular flow channel, here a gas channel 1, built-in static mixer 2 according to the invention. In the illustration in FIG. 1, the viewing direction is chosen against the flow direction of the gas stream 4. These The direction of flow can be seen in the side views, that is to say FIGS. 2 and 3. In the view of FIG. 1, it can also be seen that a support grid 8 is inserted in the gas channel 1, perpendicular to its axis of symmetry 6, which consists of struts 10 which are perpendicular to one another 11, in the exemplary embodiment made of flat steel. Triangular deflection elements 12 made of sheet metal are welded on at the crossing points of the struts 10, 11 of the support grid 8. As the representations of FIGS. 2 and 3 show, these deflection elements 12 are welded onto the outflow side of the support grid 8. It can be seen from FIGS. 1 and 2 that the deflection elements 8 are inclined by approximately 30 ° with respect to the axis of symmetry 6 of the gas channel 1. 1 shows that the deflection elements 12 are arranged in rows on the support grid 8 and the deflection elements of each row 14, 15, 16, 17, 18 are inclined in the same direction in the direction of the row with respect to the main flow direction 4. The deflection elements of the respectively adjacent rows are inclined in the opposite direction, but by the same angle of inclination. It is also noticeable that the deflection elements are much smaller in their dimensions or with their edge length than the dimensions of the gas channel 1. In the exemplary embodiment, the edge lengths of the deflection elements 12 are less than one tenth of the width or length of the gas channel 1. The edge lengths can be up to a fifth of the mean transverse extent of the flow channel.

During operation of the static mixer 2, that is to say when the gas with the components to be mixed flows through the static mixer, as indicated by the arrows 4 in FIGS. 2 and 3, the deflection elements 12 of each row 14, 15, 16 induce , 17, 18 a cross flow 22 in the gas channel 1, which is a limitation the same extends to the opposite limit. The immediately adjacent rows of Deflection elements 12 produce such a transverse flow 22 from one boundary of the gas channel 1 to the opposite one, but with the opposite flow direction. As a result, a large-scale mass transfer is achieved across the entire gas channel 1 at the shortest possible distance. At the same time, the opposite directions of flow of the gas cause ring vortices 20 at their boundaries, which ensure intimate local mixing. The gas flows responsible for the large-scale mixing across the gas channel are shown in FIG. 1 with straight arrows 22, the vortices responsible for the local intimate mixing are indicated in FIG. 1 by circular arrows 20.

FIG. 4 shows a plan view of another static mixer 32 according to the invention installed in a tubular gas channel 30. Here too, the static mixer comprises a support grid 34, which is installed perpendicular to the axis of symmetry 33 of the gas channel 30, and is fastened to struts 36, 37 which are perpendicular to one another Deflection elements 38. In contrast to the exemplary embodiment in FIGS. 1 to 3, the cross struts 36 are welded here under the longitudinal struts 37 and the deflection elements 38 are not welded to the longitudinal struts 37 at the points of intersection of the struts of the supporting grid, but in between. Here too, the deflection elements 38 are arranged in rows and the deflection elements of each row are identical to one another and inclined in the opposite direction to the deflection elements of the respectively adjacent row.

When this static mixer 32 is in operation, when the deflection elements 38 are flown against by the gas stream 39, it is similar to the exemplary embodiment in FIGS 3 through each row of equally inclined deflection elements 38, a transverse flow directed across the gas channel and crossing the entire gas channel 30 is generated, which is exactly opposite to the respectively adjacent transverse flow. For this purpose, compare the straight arrows 40 in FIG. 4. Local small vortices are formed between two adjacent cross currents 40, as the circular arrows 42 show, which ensure intimate local mixing. The arrangement of the deflection elements between the crossing points of the struts 36, 37 is somewhat simpler in terms of production technology than that according to the exemplary embodiment according to FIGS. 1 to 3. With regard to the mixing function, there is no significant difference between the two variations. Both static mixers 2, 32 can also be installed in a rectangular gas channel 1 and vice versa instead of in a tubular gas channel 30.

FIG. 7 shows a top view of another static mixer 54 according to the invention installed in a rectangular gas channel 50 perpendicular to its axis of symmetry 52. Here too, the deflection elements 56, 57 are fastened to a support grid 58 made of struts 60 oriented perpendicular to one another. Here too, the deflection elements 56, 57 are arranged in rows, wherein the deflection elements of one and the same row are all inclined transversely to the gas flow 62 and the deflection elements 56, 57 of the respectively adjacent row are all inclined in the opposite direction to the gas flow.

Deviating from the exemplary embodiment according to FIGS. 1 to 6, however, the deflecting elements 56, 57 of two adjacent rows are moved close together and at the same time somewhat in the deflecting direction of the gas stream 62 shifted against each other. The inclination of two closely spaced deflection elements 56, 57 of adjacent rows are directed away from each other. The arrangement can best be seen with the aid of FIGS. 7, 8 and 9.

When this static mixer 54 is in operation, the gases to be mixed flow through the support grid 58 with the deflection elements 56, 57 in the illustration in FIG. 7 from below the plane of the drawing and this gas flow 62 in the region of the deflection elements 56, 57, i.e. in the area of the grid crossing points, on both sides of the same in the opposite direction deflected transversely to the gas flow 62. Compare the straight arrows 68. Because the deflection elements on both sides of the crossing points of the support grid 58 are inclined away from one another, part of the crossflow reaches the suction region of the respectively directly adjacent deflection element. This causes an intensive swirling between these two deflection elements, which is expressed in a spiral vortex 64 above the deflection elements. This spiral vortex can be clearly seen in FIGS. 8 and 9. For the rest, analogous to the exemplary embodiments in FIGS. 1 and 4, further rotary vortices 66 also arise between the opposite transverse flows 68 at the boundary thereof.

While there are no significant differences with respect to the large-scale mixing of the gas flow compared to the two exemplary embodiments according to FIGS. 1 and 4, there is a strong intensification in the exemplary embodiment according to FIG. 7 with regard to local mixing. This intensification of local mixing by creating many small, very intense ones Spiral vortex 64 manifests itself in a very slight increase in the flow resistance of this static mixer 54. However, here the wake-up path, behind which one can speak of complete mixing of the gas stream, has been shortened somewhat further compared to the first two exemplary embodiments.

FIG. 10 shows a top view, FIG. 11 shows a modification of the static mixer 54 of FIG. 7 in side view. Here, too, a flat support grid 70 made of struts 72 oriented perpendicular to one another is arranged in a rectangular gas channel 74 perpendicular to its axis of symmetry 76. Here, too, the same deflection elements 78, 79 as in FIG. 7 are arranged in rows and two deflection elements 78, 79 of immediately adjacent rows are pressed close together and inclined in the opposite direction to the primary gas flow 75. However, the pairs of deflection elements 78, 79 fastened along the same struts 72 are each arranged in mirror image, so that non-mirror image pairs of deflection elements can only be found in rows diagonally to the support grid 70.

When this static mixer 80 is in operation, the gases to be mixed flow through the support grid 70 with the pairs of deflection elements 78, 79 in the illustration in FIG. 10 from below the plane of the drawing upwards. The opposite deflection of the gas flow 75 at the deflection elements 78, 79 of each pair creates a spiral vortex 82 above these pairs. These spiral vortexes are indicated in FIG. 10 by the circular arrows 84. Because these spiral vortices have a mirror-inverted sense of rotation at adjacent supporting grid positions, they induce cross currents 86 which run diagonally to the supporting grid and are indicated by straight arrows 88 are indicated. In comparison to the other three exemplary embodiments, the intensity of the local mixing has been further increased in this static mixer 80 at the expense of the large-scale mixing. This static mixer 80 is therefore particularly suitable for intensive mixing of substances which are already mixed to a certain extent evenly in the inflowing gas stream.

These static mixers shown here can also be used in liquid media. In this case, however, the inclination of the deflection elements with respect to the basic flow will be somewhat reduced. In the case of both liquid and gaseous media, it is advantageous to gradually increase the inclination of the deflection elements from their base surface on which they are attached to the supporting frame to their head ends, that is to say to curve the deflection elements within themselves. This allows the cross currents to be strengthened.

The static mixers disclosed can be used not only in process engineering for uniform mixing of different material flows, that is to say gases, liquids and / or solids transported therein. With such static mixers, even more uniform mixing of different reactants can be carried out in the chemical industry over relatively short distances. For example, the denitrification of flue gases in power plants and in waste incineration can be favorably influenced by mixing the reducing agent - mostly NH ₃ - with the flue gas very evenly.

Claims (11)

1. Static mixer (2, 32, 54, 80) having a multiplicity of deflection elements (12, 38, 56, 57, 78, 79) which are disposed in a flow duct (1, 30, 50, 74), are small in relation to the transverse extent of the flow duct (1, 30, 50, 74) and are disposed in mutually parallel rows aligned transversely to the axis of symmetry (6, 33, 52, 76) of the flow duct (1, 30, 50, 74), the deflection elements (12, 38, 56, 57, 78, 79) in each row being inclined equidirectionally in a direction parallel to the row and in counterdirection to the deflection elements (12, 38, 56, 57, 78, 79) of the respectively directly adjacent rows, the deflection elements (12, 38, 56, 57, 78, 79) being fastened on a supporting grid (8, 34, 58, 70) extending transversely to the axis of symmetry (6, 33, 52, 76) and only one deflection element (12, 38, 56, 57, 78, 79) being present in each case in the flow direction (4, 39, 62, 75) of a flow medium passing through the flow duct (1, 30, 50, 74), characterized in that the deflection elements (12, 38, 56, 57, 78, 79) protrude freely into the flow duct (1, 30, 50, 74).
2. Static mixer according to Claim 1, characterized in that the deflection elements (12, 38, 56, 57, 78, 79) are inclined by about 10° to 45° in relation to axes perpendicular to the direction of the rows and perpendicular to the axis of symmetry (6, 33, 52, 76) of the flow duct (1, 30, 50, 76).
3. Static mixer according to Claim 1 or 2, characterized in that the rows reach from the one limit wall to the opposite limit wall of the flow duct (1, 30, 50, 74).
4. Static mixer according to one of Claims 1 to 3, characterized in that respectively two directly adjacent rows of deflection elements (56, 57, 78, 79) are disposed in pairs tightly next to each other.
5. Static mixer according to one of Claims 1 to 4, characterized in that the deflection elements (56, 57, 78, 79) of respectively two adjacent rows are disposed in pairs pushed tightly against each other.
6. Static mixer according to one of Claims 1 to 5, characterized in that the deflection elements are bent one-dimensionally in upon themselves.
7. Static mixer according to one of Claims 1 to 6, characterized in that the deflection elements (12) are fastened on the junction points of the supporting grid (8).
8. Static mixer according to one of Claims 1 to 6, characterized in that the deflection elements (38, 56, 57, 78, 79) are fastened on the struts (37) between the junction points of the supporting grid (34, 58, 70).
9. Static mixer according to one of Claims 1 to 8, characterized in that the edge lengths of the deflection elements (12, 38, 56, 57, 78, 79) are less than one-fifth of the mean diameter of the flow duct (1, 30, 50, 74).
10. Static mixer according to one of Claims 1 to 8, characterized in that the edge lengths of the deflection elements (12, 38, 56, 57, 78, 79) are less than one-tenth of the mean diameter of the flow duct (1, 30, 50).
11. Static mixer according to one of Claims 1 to 10, characterized in that the rows of equidirectionally inclined deflection elements (78, 79) are aligned diagonally to the supporting grid.

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