EP3081285B1 - Static mixing device for flowing materials - Google Patents

Description

TECHNICAL AREA

The present invention relates to a static mixing device having a tubular, a longitudinal axis and an inner diameter having flow channel having at least one arranged in the flow channel mixing element of a length and a substantially the inner diameter of the flow channel corresponding diameter, each mixing element arranged a plurality of crosswise, with the longitudinal axis of the flow channel having an angle greater than 0 ° including webs, wherein the webs are arranged in two intersecting, a plurality of mutually parallel, separated from each other by an equal distance planes levels and in projection of the two level coulters (A, B) a projection plane lying perpendicular to the longitudinal axis (X) of the flow channel (10) has at least partially an intermediate spacing between adjacent webs.

STATE OF THE ART

Such a mixing device according to the preamble of claim 1 is known from EP 2 286 904 the applicant known, as explained below.

Static mixers are now used in all areas of chemical engineering. A characteristic feature of static mixers is that only the liquids or gases to be mixed are moved. In contrast to dynamic mixing systems, no stirring takes place, but pumps, blowers or compressors continuously convey the media to be mixed to the mixing tube, which with the Equipped mixing elements. Static mixers can be used in many applications such as mixing of pumpable liquids, dispersing and emulsifying intoluble components, mixing reactive liquids, mixing and homogenizing plastic melts, gas-liquid contacting, mixing gases, heat exchange of viscous substances and the use as residence time with narrow residence time behavior are used, to name a few key applications.

From the US Pat. No. 3,286,992 A a spiral mixer is known and has helically curved, sheet-like, alternating left- and right-handed plates or mixing elements that lined up with intersecting front edges divide the flow of substances to be mixed as they enter each element. The flow channel is the same in shape and cross section in each of the elements. The spiral mixer is used in particular for mixing in the turbulent range. In the laminar field, the spiral mixer is only partially usable because of its moderate mixing performance.

A special family of static mixers are the so-called X-mixers. These consist of intersecting webs or plates. On off AT 330 135 B Known X-mixer has in a tube at least one mixing insert in the form of a web and slots having plate pair. In each case, the webs of a plate extend through the slots of the other plate crossing therethrough. The plates are arranged inclined to one another and to the axis of the tube. The supplied stream of substances to be mixed is split by the webs as a result of the inclination of the plates in terms of time and place offset into partial streams. In this known mixer, the web approaches form strong dead zones, which can unnecessarily increase the residence time and damage critical fluids. In addition, the plates must be positioned with countless welds, which can lead to increased corrosion. The assembly of the plates is very time consuming and therefore costly. This known device is used in particular for mixing in the laminar range. In the turbulent range, it is only partially usable because of its high pressure loss.

The development of the mixer according to CH 642 564 A5 in 1979 presented an improvement in the static mixing technique for laminar flowing media dar. Since then This mixer is proven and it is used successfully in a very wide range of applications with mostly high viscosity media. He is in CH 642 564 A5 in Fig. 1 Shown as a mixer with 8 webs, also referred to as 8-bar mixer, with an L / D ratio of 1. The mixer has a very high pressure drop.

The geometry known as CSE-X mixer is in CH 693 560 A5 described. This patent shows a device for static mixing, consisting of a tubular housing with at least one mixing insert arranged therein in the form of a webs and slots having plate which is bent. Preferably, the plates have projections at the web edges and have elliptical peripheral shapes. Two curved plates, each with the webs of one plate passing through the slits of the other plate, are attached to the protrusions. The mixing inserts can be positioned one behind the other in the tubular housing, wherein the mixing inserts can touch directly or can also have spacings between the inserts. The device can mix well with this simple geometry in all flow areas. The mixing quality is determined only by the number of mixing inserts and their installation position. The mixed use was known on the market especially as 4-, 6- and 8-bar construction and also has an increasing with increasing number of webs, high pressure loss.

EP 2 286 904 B1 shows a particularly innovative mixing device with waisted mixing bars. In addition, the edge zones of the mixer are opened significantly, so that an additional reduction of the pressure loss occurs. In particular, type V has a very high mixing performance with very low pressure loss.

The trade journal Pharma und Food 2/2004 describes the mikromakro® technology with static mixers. Micromacromixing is the targeted use of static mixers of various geometries and nominal diameters. Basically, first a uniform pre-distribution in the macro mixer must be achieved, then in the micro mixer the best possible fine distribution is achieved. The basics typically used are the CSE-X mixers.

If one summarizes the investigations on X-mixers of the last years, then The following possible parameters in each case vary: the L / D ratio of a mixing element, the number of web layers, the thickness of the webs, the angular position of the webs, the shape of the webs and the width of the webs.

For many years, static mixers have also been used as heat exchangers. Static mixers are equipped with a double jacket. Static mixers which are used as heat exchangers are referred to today as mixer heat exchangers. A typical design is in the DE 2'808'854 described. Further mixer heat exchangers are in the EP 2'113'732 . EP 1'067'352 . WO2008 / 141472 and DE 2'839'564, wherein the heat transfer takes place on small tubes in the mixer tube. Mixer heat exchangers are generally characterized by a high heat transfer capacity and at the same time a narrow residence time behavior. As a result, static mixer heat exchangers are increasingly used in reaction technology. The use of static mixer heat exchangers as reactors is described in detail in the Journal of Chemical Engineering Technology 2005,77. No. 6 described. Static mixers with a double jacket are preferably used as residence time reactors or as dwellers. The possible slim design of the mixer heat exchanger causes a tight retention time, which has a particularly positive effect on the product quality of the flowing product in the pipe. However, a tight design also causes shorter residence times or very long mixers. The residence time behavior in static mixers can be described by means of the Bodenstein number.

PRESENTATION OF THE INVENTION

Based on this prior art, the present invention seeks to provide a static mixing device with good mixing effect and low pressure drop, which additionally has a tighter and more defined residence time behavior as known mixer.

The mixing device should preferably be able to be used in the laminar flow region and in the transition region and a substantially complete Ensure thorough mixing. The mixing elements should be simple and inexpensive to manufacture, have a low pressure drop and mechanically stable can be assembled to mixer bars. The mixing elements should be able to be positioned as short as possible as well as long designs in the flow channel. The flow channel should be able to have a round, rectangular or square cross section.

To the inventive solution of the problem leads that different to EP 2 286 904 B1 the webs between the adjacent intersections are formed at least partially waisted and in the middle between adjacent intersections, the webs their smallest width and adjacent webs have their greatest spacing, and the inner wall of the flow channel adjacent webs between the front edge edges of the sidecut of the webs corresponding recess having the smallest width to form a largest in the middle between the front edge edges wall distance. In this case, advantageously, the measured over the diameter of the mixing element sum of the smallest width of the webs is at least 40% of the diameter of the mixing element.

In particular, the webs of the inner cross 14A, 14B have no tapered webs, so that a laminar flow profile is largely prevented. The remaining waisted webs lead to the necessary pressure loss reduction.

At the end of the webs, where an elliptical contour would form when the pipe wall touched, the webs will now only touch the pipe wall selectively, taking into account tolerances, so that the marginality is reduced to a minimum. The webs are sharpened, for example, on the tube inner wall, so that the mixer rests only at small points. A connection of the mixing elements, for example with a welded connection, must be ensured for stability reasons.

Surprisingly, it was found that the almost complete opening of the edge zone leads to no or only very little marginalities. Ultimately, the high mixing performance of the mixing element by the new design measures is not negatively influenced.

A static mixing device has a flow channel with at least one mixing element arranged in the flow channel. Each mixing element has a plurality of crosswise arranged, with the longitudinal axis of the flow channel at an angle greater than 0 ° including webs. The webs between adjacent intersections are formed waisted. The webs, which are adjacent to the inner wall of the flow channel, have, between frontal butt edges, a recess corresponding to the sidecut of the webs, forming a largest wall spacing in the middle between the end-side butt edges. In this case, the measured over the diameter of the mixing element sum of the smallest widths of the webs can be at least 40% of the diameter of the mixing element.

• Der Mischer weist Stege auf, die zwischen den benachbarten Kreuzungsstellen nur teilweise tailliert ausgebildet sind.
• Das innere Kreuz des Mischelementes wird nicht tailliert ausgeführt, um eine hohe radiale Mischung zu gewährleisten.
• Die Stege weisen unterschiedliche Breiten auf.
• Die Stege werden an der Rohrwand zugespitzt, so dass das Mischelement keine Totwasserzonen aufweist.
• Das Mischelement weist sechs Steglagen auf.

Preferred embodiments of the static mixing device according to the invention have one or more of the following features:

• The mixer has webs which are formed only partially waisted between the adjacent crossing points.
• The inner cross of the mixing element is not designed waisted to ensure a high radial mixture.
• The webs have different widths.
• The webs are sharpened on the pipe wall, so that the mixing element has no dead water zones.
• The mixing element has six web layers.

The mixer according to the invention has a narrower residence time spectrum compared to commercially available static mixers.

Further embodiments are given in the dependent claims.

The residence time spectrum in a static mixer is generally important. In particular, dead zones must be prevented, since the longer residence time can damage the product quality or significantly disrupt the process. On the one hand, it is known that flows with Reynolds number> 10,000 are turbulent. This applies to static mixers as well as for the empty pipe. On the other hand, flows with Reynolds numbers <20 are called laminar. In between there is a transition area.

Fig. 5 schematically shows the turbulent and laminar flow. In the laminar flow, a parabolic flow 85 is formed in the flow channel 10, which has a very poor residence time spectrum. The residence time spectrum is usually measured with a Dirac impact. The measurement and detection of a residence time spectrum is well known to those skilled in the art and will not be described in detail. It is also known that measuring a Dirac impact in the laminar flow regime is difficult because inlet and outlet perturbations can significantly affect the results. The typical measured residence-time shifts and light tailing in the curve are characteristic of a residence time distribution in a static mixer in the laminar flow regime.

und wird, um eine Lösung zu erleichtern, in dimensionsloser Form angeschrieben. Für den stationären Fall entsteht dann: $$\frac{\partial \left(\frac{c}{c_0}\right)}{\partial \left(\frac{t}{\tau }\right)}=-\frac{\partial \left(\frac{c}{c_0}\right)}{\partial \left(\frac{z}{L}\right)}+\left(\frac{D_{\mathit{ax}}}{u_z\cdot L}\right)\cdot \frac{{\partial }^2\left(\frac{c}{c_0}\right)}{\partial {\left(\frac{z}{L}\right)}^2}=0$$

Fig. 6 shows in comparison the residence time distribution of a static mixer according to the patent CH 642 564 and CH 693 560 to the 1D dispersion model. The Bodenstein number (also called Bo for short) is a dimensionless characteristic number from the reaction technique and describes the ratio of the convection current to the dispersion current. Thus, the Bodenstein number characterizes the backmixing within a system and thus allows statements about whether and how strongly volume elements or substances within the dweller mix by the prevailing currents. The Bodenstein number is usually described with the 1-d dispersion model. This model concept takes the 1-dimensional process in a flow tube (plug flow) as a starting point. In the direction z, a flow velocity u _z, which is practically constant at the respective mixers cross section A is carried out. Molecular diffusion, turbulent convection, and the parabolic velocity profile (eg laminar pipe flow) caused by edge friction (roughness) will lead to deviations from the ideal pipe flow. The size used to detect these effects is the axial dispersion coefficient D _ax , which is thus a measure of the backmixing. The equation for the 1-d dispersion model is: $$\frac{\partial c}{\partial t}=-u_z\cdot \frac{\partial c}{\partial z}+D_{\mathit{ax}}\cdot \frac{{\partial }^{2}c}{\partial {\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="imgf0003.png"\; state="\{\{state\}\}">z</figure-callout>}}^2}$$

and is written in dimensionless form to facilitate a solution. For the stationary case arises then: $$\frac{\partial \left(\frac{\mathrm{<figure-callout\; id="0"\; label="c\; c"\; filenames="imgf0003.png"\; state="\{\{state\}\}">c\; </figure-callout>}}{c_{}}\right)}{\partial \left(\frac{t}{\tau }\right)}=-\frac{\partial \left(\frac{\mathrm{<figure-callout\; id="0"\; label="c\; c"\; filenames="imgf0003.png"\; state="\{\{state\}\}">c\; </figure-callout>}}{c_{}}\right)}{\partial \left(\frac{z}{L}\right)}+\left(\frac{D_{\mathit{ax}}}{u_z\cdot L}\right)\cdot \frac{{\partial }^2\left(\frac{\mathrm{<figure-callout\; id="0"\; label="c\; c"\; filenames="imgf0003.png"\; state="\{\{state\}\}">c\; </figure-callout>}}{c_{}}\right)}{\partial {\left(\frac{\mathrm{<figure-callout\; id="2"\; label="z\; L"\; filenames="imgf0003.png"\; state="\{\{state\}\}">z\; </figure-callout>}}{L}\right)}^2}=0$$

die mit einer "charakteristischen Länge" L des Mischer-Wärmetauscher Gehäuses definiert ist. Die exakte Lösung der stationären und dimensionslosen Gleichung lautet (nach Levenspiel und Smith): $$c_i\left\{\theta ,\mathit{Bo}\right\}=h\left(\theta \right)=\sqrt{\frac{\mathit{Bo}}{4\cdot \pi \cdot \theta }}\cdot e^{\lfloor -\frac{{\left(1-\theta \right)}^2\cdot \mathit{Bo}}{4\cdot \theta }\rfloor }$$

This contains the dimensionless parameter, namely the so-called Bodenstein number, $$\mathit{Bo}=\frac{u_z\cdot L}{D_{\mathit{ax}}}$$

which is defined by a "characteristic length" L of the mixer-heat exchanger housing. The exact solution of the stationary and dimensionless equation is (according to Levenspiel and Smith): $$c_i\left\{\theta .\mathit{Bo}\right\}=H\left(\theta \right)=\sqrt{\frac{\mathit{Bo}}{4\cdot \pi \cdot \theta }}\cdot e^{\lfloor -\frac{{\left(1-\mathrm{<figure-callout\; id="2"\; label="\theta "\; filenames="imgf0003.png"\; state="\{\{state\}\}">\theta </figure-callout>}\right)}^2\cdot \mathit{Bo}}{4\cdot \theta }\rfloor }$$

As limiting cases of the dispersion model, the displacement model without axial dispersion results for Bo = ∞ (ideal pipe flow) and the back mixing model with axial dispersion for Bo = 0 (ideal stirred tank). In the Fig. 6 correspond to the peak of an ideal flow tube 100, the other curves 109 Bo = 7, 108 Bo = 20, 107 Bo = 60, 106 Bo = 120 and 105 Bo = 400. The CFD calculation is shown with the curve 110.

• herkömmliche statische Mischer weisen auch eine Parabelströmung auf, allerdings ist diese weniger ausgeprägt als beim Leerrohr
• je kleiner der Widerstandsfaktor ist, desto ausgeprägter die Parabelströmung
• Statische Mischer weisen an den Randzonen generell schwach durchströmte Zonen auf, insbesondere dort, wo die Stege in einem Winkel zur Achse an der Rohrwand anliegen. Dies führt zu zusätzlichen längeren Verweilzeiten.

The evaluation of Fig. 6 shows surprisingly that even with a CFD calculation 110 on the one hand the shift and on the other hand the tailing is clearly visible. The curve displacement thus clearly indicates dead zones according to the theory of the real flow. These have according to Fig. 6 an estimated amount of 30%, which in turn is very unlikely. So there must be another effect causing this shift. Detailed investigations of unsteady CFD calculations surprisingly showed the following effects:

• Conventional static mixers also have a parabolic flow, but this is less pronounced than the empty tube
• the smaller the resistance factor, the more pronounced the parabolic flow
• Static mixers generally have weakly flowed through at the edge zones Zones, especially where the webs abut at an angle to the axis of the pipe wall. This leads to additional longer residence times.

Several calculations have been made to compare the residence time spectrum of the mixers, with no run-in and run-out disturbances. For comparison of the residence time spectra, preferably the residence time cumulative curve can be used. Fig. 7 shows a comparison of different mixing elements. The curve 200 shows the ideal behavior; no proportions of the fluids flowing through the mixing element have a residence time t for the mean residence time τ (Tau) of less than 1. With a ratio q greater than 1, this is 100%, which is given as H (q) = 1. The mixer according to CH 693 560 has a relationship with the dashed curve 202, the mixer according to EP 2 286 904 B1 a ratio according to curve 201. The solid curve 203 finally shows the residence time behavior for a mixer according to an embodiment according to the invention. It is noticeable that in this mixer, on the one hand, the curve intersects the value H (q) = 0.5 at q = 1; 50% of the fluid components have an above-average residence time (q <= 1) and 50% have a below-average residence time (q> = 1). Thus, there is a compensation of faster by slower proportions in a symmetrical manner, while in the prior art, some rapidly passing through the mixer fluid components face a larger proportion of slower fluid fractions. The speed spread is much lower in the invention. This is associated with the second difference, which is that the slower fluid portions, indicated by the reference numeral 210, have less residence time than the cut; there are almost no fractions with a q <0.75 and essentially the fluid fractions are with a q> 0.85.

The features according to the invention make it possible with such a mixer to achieve a significantly improved residence time behavior. The comparison is based on identical flow conditions, the same diameter and the same mixer lengths. Thus, the resistance factor can be used as a power comparison. The resistance factor of the mixer 1 is standardized at 100%. As expected, the mixer decreases EP 2 286 904 B1 with 38% the worse residence time behavior than the mixer after the CH 693 560 on. It is therefore all the more surprising that the mixer according to the invention with 60% compared to the mixer after CH 693 560 a considerable one has better residence time behavior.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

eine Seitenansicht eines Teils eines Strömungskanals mit zwei aneinander grenzenden Mischelementen mit sechs Stegen gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 2

die Sicht auf ein Mischelement im Strömungskanal von Fig. 1 in Blickrichtung der Längsachse des Strömungskanals;

Fig. 3

die Draufsicht auf Stegplatten vor dem Schweissen zu einem Mischelement mit zu verbindenden Stegen;

Fig. 4

die Draufsicht auf eine Stegplatte eines Mischelementes mit sechs Stegteilen vor dem Schweissen zu einem Mischelement;

Fig. 5

eine schematische Darstellung von turbulenter und laminarer Strömung in einem Lehrrohr, in einer Prinzipdarstellung und an Mischern gemäss dem Stand der Technik und gemäss der Erfindung;

Fig. 6

die Verweilzeitverteilung von statischen Mischern gemäss CH 642 564 und CH 693 560 im Vergleich zu verschiedenen Bodenstein-Zahlen nach dem 1D Dispersionsmodell;

Fig. 7

Verweilzeitsummenkurven von verschiedenen Mischern des Standes der Technik und gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 8

eine perspektivische Darstellung eines statischen Mischers gemäss Fig. 1;

Fig. 9

die Draufsicht auf eine Stegplatte eines Mischelementes mit vier Stegteilen vor dem Schweissen zu einem Element nach Fig, 10;

Fig. 10

die Draufsicht auf die Stegplatten von Fig. 9 vor dem Biegen zu einem Mischelement mit zu verbindenden Stegen und

Fig. 11

eine perspektivische Darstellung eines statischen Mischer gemäss Fig. 1 mit zusätzlichen Rohr oder Profilelement zur Verstärkung resp. zum

verbesserten Wärmeübergang.Further explanations, advantages, features and details of the invention will become apparent from the following description of preferred embodiments and with reference to the drawings, which are merely illustrative and not restrictive interpreted. The drawings show schematically in FIG

Fig. 1

a side view of a portion of a flow channel with two adjacent mixing elements with six webs according to an embodiment of the invention;

Fig. 2

the view of a mixing element in the flow channel of Fig. 1 in the direction of the longitudinal axis of the flow channel;

Fig. 3

the plan view of web plates before welding to a mixing element with webs to be joined;

Fig. 4

the top view of a web plate of a mixing element with six web parts before welding to a mixing element;

Fig. 5

a schematic representation of turbulent and laminar flow in a teaching tube, in a schematic diagram and on mixers according to the prior art and according to the invention;

Fig. 6

the residence time distribution of static mixers according CH 642 564 and CH 693 560 compared to different Bodenstein numbers according to the 1D dispersion model;

Fig. 7

Residence time cumulative curves of various mixers of the prior art and according to an embodiment of the invention;

Fig. 8

a perspective view of a static mixer according to Fig. 1 ;

Fig. 9

the top view of a web plate of a mixing element with four web parts before welding to an element Fig. 10 ;

Fig. 10

the top view of the web plates of Fig. 9 before bending to a mixing element with webs to be joined and

Fig. 11

a perspective view of a static mixer according to Fig. 1 with additional tube or profile element for reinforcement resp. to the

improved heat transfer.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows a side view of a portion of a flow channel 10 with two adjoining mixing elements 12 with six webs according to an embodiment of the invention. The following description is also based on the Fig. 2 with a view of the mixing element 12 of Fig. 1 in the flow channel 10 in the direction of the longitudinal axis of the flow channel 10; on the Fig. 3 with a plan view of web plates before welding to a mixing element 12 with webs to be joined, on the Fig. 4 with a plan view of a web plate of a mixing element 12 with six web parts before welding to a mixing element, on the Fig. 9 with a view of a web plate of a mixing element with four web parts before welding to a mixing element and finally to the Fig. 10 with a plan view of the web plates of Fig. 9 before bending to a mixing element with webs to be joined. The Fig. 8 Finally, a perspective view of a mixer follows Fig. 1 ,

An in Fig. 1 shown, tubular flow channel 10 having a longitudinal axis x and an inner diameter D has two adjoining, a length L having identical mixing elements 12 with a substantially the inner diameter D of the flow channel 10 corresponding Umhüllungsdurchmesser. The two mixing elements 12 are arranged with respect to the longitudinal axis x of the flow channel 10 at an angle of 90 ° to each other rotated. The mixing element 12 consists of a plurality of intersecting webs 14A, 14B. The webs 14A, 14B are arranged in mutually parallel planes separated from each other by an equal distance and forming two intersecting planes A, B. The two level shares A, B close with the longitudinal axis x of the flow channel an angle α of 45 ° and with each other an angle of 90 °. The mixing element 12 shown by way of example in the drawing has six web layers, each with two webs 14A, 14B which intersect alternately, and thus corresponds to a 6-web mixer. A common other number of bars is four or eight.

From the in Fig. 2 shown projection on a perpendicular to the longitudinal axis x of the flow channel 10 lying projection plane can be seen that the webs 14A, 14B are formed symmetrically waisted between intersections 16 and all have in the middle between adjacent intersections 16 the same smallest width b which is 50% of the width b 'at the intersections 16. All the webs 14A, 14B are waisted in the same way and have the same dimensions. In the present case, the greatest intermediate distance a of adjacent webs 14A, 14B corresponds to the location of the smallest web width b.

All webs 14A, 14B extend within the mixing element 12 via their respective maximum length which is limited by the end faces of the mixing element 12 and by the inner wall of the flow channel 10, the contour of the webs 14A, 14B close to the wall being the circular cross-section of the wall Flow channel 10 is only partially adapted so that in the near-wall webs 14A, 14B - as in the other webs - only front end portions 22 adjoin the inner wall of the flow channel 10 with little play. The adjoining the inner wall of the flow channel 10 webs 14A, 14B are provided on the directed against the inner wall side with a recess 24 which extends between the end-side end portions or butt edges 22 with the inner wall of the flow channel 10 and corresponding to the waist of the webs largest Wall distance c have, which in the present case is 50% of the greatest distance between a adjacent bars 14A, 14B.

Like from the Figs. 3 and 4 or Figs. 9 and 10 Recognizable, the webs 14A, 14B at each intended intersection point 16 a notch 18 or the notch depth of the notch 18 corresponding, a projection 20 generating cutback on.

The assembly of the mixing element 12 is carried out in a simple manner of two in Fig. 10 shown web plates 26 with four arranged alternately, the four in Fig. 9 shown webs 14A, 14B corresponding half webs 14A ', 14B' and the four in Fig. 9 illustrated webs 14A, 14B. Here, two web plates 26 are bent around an axis by an angle of 90 ° and in the in Fig. 1 shown connected by ends 28 of the two middle web halves 14A ', 14B' by welding together. In the Fig. 9 shown four webs 14A, 14B are placed over the notches 18 and projections 20 at the intersections 16 on the curved and welded together web plates 24 and partially welded at the intersections 16.

All embodiments have in common that the areas of the ends 28, which lie in known mixers in the context of the game on the inner wall of the flow tube, are cut out. The cutouts can, as in Fig. 4 to recognize straight cuts 122 at the ends which leave a small end portion which further adjoins the flow tube. The cutout 122 at the longest land portion is steeper than the cutout 122 at a shorter land.

In the Figs. 9 and 10 the cutouts 122 can be seen with respect to the usual non-cutout end regions 22, the latter being shown in dashed lines. These lines 22 correspond to the inner diameter of the flow tube. In this case, some cutouts 122 are concave, others have a polygonal course, for example, two sections meeting at a concave point. In this case, the end region 28 may have an edge region adjoining the tube, have only one point or, as at the web 14A 'in FIG Fig. 10 bottom right, be cut from both sides, so that even the top of the convex here polygon no longer touches the wall of the flow tube.

Fig. 5 schematically shows the turbulent and laminar flow. In the laminar flow, a parabolic flow 85 is formed in the flow channel 10, which has a very poor residence time spectrum. In other words, there are very slow fluid fractions 86 at the tube edges, while there are fast fluid fractions 87 in the middle. For a turbulent flow, a distribution results according to curve 82, while with a mixer according to the invention a distribution according to curve 81 can be achieved, in which both the edge flow and the center flow have comparable speeds.

The Fig. 6 shows the residence time distribution of static mixers according to CH 642 564 and CH 693 560 compared to different Bodenstein numbers according to the 1D dispersion model and the Fig. 7 shows dwell sum curves of various Mixers of the prior art and a mixer according to an embodiment of the invention. It is shown that the opening of the edge regions by recesses between the inner tube edge 22 and the web end by cutting 122 of the edge-side end regions accelerates the volume flow in the edge regions by a Mass that a high homogeneous velocity distribution as the flow 81 after Fig. 5 results. In the plan view along the longitudinal axis x, the mixing elements continue to be substantially full-surface, in particular on the main axis along the intersection 16, so that a good mixing takes place. In addition to the wall clearance c produced in the width direction of the webs by the recesses 24, an additional lateral wall clearance is created, which is defined by the angle of the straight cuts, the depth of the concave round recesses or the depth of the polygons with a point. Advantageously, the alternating concerns of edge regions 22 and the removed portions 122, so that there is a mixing in the edge regions.

In FIG. 11 another embodiment is shown. In a mixer according to FIG. 1 an additional elongated, rod-shaped profile element 30 is arranged, which extends parallel to the longitudinal direction of the mixer and passes through it. Preferably, exactly one profile element 30 is present. However, the mixer can also be penetrated by several such profile elements.

The at least one profile element 30 is slidably held in the mixer or firmly connected to the mixer. It is preferably made of metal. The at least profile element 30 is hollow or solid, depending on the embodiment. completed formed. It preferably has a round cross-section. If it is hollow, in particular designed as a tube, it may be empty. Preferably, however, at least one temperature sensor is arranged in the tube. Alternatively or additionally, the tube may include a heat transfer medium, for example a thermal oil or water.

The profile element serves as a mechanical reinforcement of the mixer and / or improve the heat transfer. LIST OF REFERENCE NUMBERS 10 flow channel 201 Residence sum curve of EP 2 286 904 12 mixing element 14A ( ') web 202 Residence sum curve of CH 693 560 14B ( ') web 16 intersection 203 Residence cumulative curve in a mixer according to the invention 18 notch 20 head Start 22 end-side end regions 210 slower fluid fractions 24 recess 30 profile element 26 web plate a largest distance between the bars 28 The End 81 turbulent flow b smallest width of the webs 82 turbulent flow b ' largest width at a crossing point of the bridges 85 parabolic flow 86 slow edge flow c largest wall distance of the webs 87 fast central flow 100 ideal residence time FROM Plane sets of the respective webs 14A and 14B 105 Residence time at Bo = 400 106 Residence time at Bo = 120 X Longitudinal axis of the flow channel 107 Residence time at Bo = 60 108 Residence time at Bo = 20 D Inner diameter of the flow channel 109 Residence time at Bo = 7 110 CFD calculated residence time L Length of the mixing element 122 cut off end-side end portions 200 ideal residence time cumulative curve

Claims (16)

1. A static mixing device having a tubular flow channel (10) with a longitudinal axis and an inner diameter with at least one mixing element (12) arranged in the flow channel (10) and which mixing element (12) having a predetermined length and an inner diameter substantially corresponding to the diameter (D) of the flow channel (10), wherein each mixing element (12) has a plurality of crosswise arranged webs (14A, 14B) which enclose an angle greater than 0° with the longitudinal axis (x) of the flow channel (10), wherein the webs (14A, 14B) are arranged in two families of planes (A, B) which intersect one the other and each comprising a plurality of planes being parallel one to the other and being separated by an equal distance from each other and wherein, when the two families of planes (A, B) are projected on a projection plane being perpendicular to the longitudinal axis (x) of the flow channel (10), adjacent webs (14A, 14B) at least partially have an intermediate distance, and wherein the web ends abut only selectively at the tubular wall, so that nevertheless the attachment of the mixing elements to a mixer rod is ensured, wherein at least one each of the webs (14A, 14B) is formed waisted between adjacent intersection points (16) and wherein, in the middle between adjacent intersection points (16), the webs (14A, 14B) have their smallest width (b) and adjacent webs (14A, 14B) have their greatest spacing (a), characterized in that the edge regions of the webs (14A, 14B) being adjacent to the inner wall of the flow channel (10) have a recess (122) relative to the inner wall of the flow channel (10).
2. The mixing device according to claim 1, wherein the recess (122) of the edge regions adjacent to the inner wall of the flow channel (10) has a recess of the smallest width (b) corresponding to the amount of waist of the webs (14A, 14B) to form a largest wall distance (c) in the center between the end-face butt edges (22).
3. The mixing device according to claim 2, wherein the measured sum of the smallest widths (b) of the webs (14A, 14B) over the diameter of the mixing element (12) is at least 40% of the diameter of the mixing element (12).
4. The mixing device according to any one of claims 1 to 3, wherein adjacent to the recess edges are butt edges (22) of the webs (14A, 14B), which adjoin the inner wall of the flow channel (10).
5. The mixing device according to any one of the preceding claims, wherein the recesses are straight cuts or concave recesses (122) of the butt edges of the webs (14A, 14B).
6. The mixing device according to any one of the preceding claims, wherein the webs (14A, 14B) are tapered on the inner wall of the flow channel (10), so that the mixing element (12) has no dead water zones, in particular that the webs (14A, 14B) do not touch the inner wall of the flow channel (10).
7. The mixing device according to any one of the preceding claims, wherein the inner cross of the mixing element (12) is made non-waisted.
8. The mixing device according to any one of the preceding claims, wherein the webs (14A, 14B) have different widths, and / or wherein all the webs (14A, 14B) have the same smallest width (b).
9. The mixing device according to any one of the preceding claims, wherein all webs (14A, 14B) form an angle (α) of 45 ° with the longitudinal axis (x) of the flow channel (10).
10. The mixing device according to any one of the preceding claims, wherein the mixing element (12) has four, six or eight web layers.
11. The mixing device according to any one of the preceding claims, wherein all adjacent webs (14A, 14B) have the same largest intermediate distance (a).
12. The mixing device according to any one of the preceding claims, wherein the smallest width (b) of the webs (14A, 14B) is 50% of their width (b') at the intersections (16) of the webs (14A, 14B).
13. The mixing device according to any one of the preceding claims, wherein the smallest width (b) of the webs (14A, 14B) is equal to the largest intermediate distance (a) of adjacent webs (14A, 14B).
14. The mixing device according to any one of the preceding claims, wherein the largest wall distance (c) is 50% of the smallest width (b) of the webs (14A, 14B) and is 50% of the largest intermediate distance (a) between adjacent webs (14A, 14B).
15. The mixing device according to any one of the preceding claims, wherein at least one elongate profile element is present, which passes through the mixer.
16. Use of a static mixing device according to any one of the preceding claims for mixing media, wherein at least one of which is a laminar flowing medium, in particular a polymer melt or another highly viscous fluid.

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