EP1493485A1 - Static mixer - Google Patents

Abstract

A mixing device comprises primary flow obstacles, each having geometrically modified area at surface and edge to induce local flows of a second order in the flow of a passing viscous fluid, thus the local flows of the second order are superimposed on the flows of the first order to compensate radial and axial in-homogeneities in the viscous fluid produced by the flow of the first order. A mixing device comprises primary flow obstacles (11, 11', 12) disposed to define constrictions for a flow of viscous fluid (20) and to impart a flow of a first order in the flow of viscous fluid passing through the constrictions. Each primary flow obstacle has a geometrically modified area at surface and edge to induce local flows of a second order in the flow of a passing viscous fluid, thus the local flows of the second order are superimposed on the flows of the first order to compensate radial and axial in-homogeneities in the viscous fluid produced by the flow of the first order. An independent claim is also included for a static mixer comprising a pipe defining a flow path for a low viscosity fluid; and mixing device(s) disposed within the pipe for mixing of the viscous fluid. A normal projection of the primary flow obstacles defines a cross section equal to the cross section of the pipe. The pipe is cylindrical and the primary flow obstacles form a mirror-symmetrical arrangement with a plane of symmetry in which a longitudinal axis of the pipe lies. The static mixer further comprises an infeed point in the pipe for the introduction of an additive into the pipe for mixing with a viscous flow. The viscous fluid to be mixed is transported through the static mixer in a preferred direction with a better mixing quality being achieved with respect to the preferred direction than in an opposite direction.

Description

The invention relates to a static mixer according to the preamble of Claim 1 and a method for mixing with the inventive static mixer.

The development of static mixers has become very big Manifold led by such mixing devices. To a Mischaufgabe, according to a certain mixing quality at a predetermined, maximum allowable pressure drop can be achieved, can be realize many solutions. But these solutions are different quite a lot in the design effort, the impact on the Production costs and also the cost of installing the mixer in one Plant has. Mixing devices, which said mixing task with simple installations and at the same time with a minimum number of Releasing structural elements of the fixtures are preferred. Such Mixing facilities, which are expected to become increasingly prevalent, have a short installation length (installation length = length in one) Piping, which must be provided for the internals); and they require also a short mixing distance (= distance from the dosing point of a Additivs to the point in the pipeline, where the required mixing quality is reached).

For mixing a fluid in the turbulent flow regime Solutions offered in which the pipeline contains a structure made of only a single, short mixing element, i. a minimum number of Structural elements of the internals consists (see for example US-A-5 839 828). A such solution is optimal, as far as the installation length of the structure is concerned. It But it has been shown that these known, only one mixing element Comprehensive structures can be improved because of significant deficiencies have to.

There are structures in which the short installation length with a large Pressure loss and / or associated with a long mixing distance. One Another, surprisingly found problem is the following: The Baffles of known static mixers are flow obstacles, which are from Fluid are flowed around and offset by the fluid in swirling movements becomes. Behind each obstacle, vortices with a certain frequency are released from. A similar phenomenon can occur with a cylinder in the form of the "Karman vortex street" are observed. For static mixers The vortex movements usually form a much more complicated one Process. But with the "Karman whirlwind road" is common Periodicity of the operation. The vortex bales that adhere to the obstacles Periodically peel off, are of the flow in axial, constant Carried on intervals. An additive added to the mixer is supplied by the Detaching vortex detected and carried away with these in the pipe. It arise inhomogeneities in the form of axial Concentration differences in the tube at fixed observatories as temporal fluctuations appear. This temporal phenomenon is in the Mixer described in the above-mentioned US Pat. No. 5,839,828. clearly noticeable. Also in a mixer which is known from EP-A-1 153 650 (= P.7032), corresponding inhomogeneities appear.

Usually, a mixture of a static mixer is a measure of understood homogenization, referring to the radial Concentration distribution refers: the smaller inhomogeneities of these radial Distribution, the better the mixing quality. The through the axial However, concentration gradients given inhomogeneities can same size as the inhomogeneities regarding the radial concentration distributions. This could be done with a measuring method be determined, in which the mixing quality with a high frequency (20 Measurements per second) was detected. In some applications These axial inhomogeneities or temporal variations of be of considerable importance: For example, in a fast chemical Reaction between the components to be mixed, or at a Control of the flow rate of an additive with respect to the pipe measured concentrations.

The object of the invention is to provide a static mixer, the at Use of a single mixing element or a minimum number of Structural elements of the internals the disadvantages in terms of axial Inhomogeneities does not have and so - despite low installation costs - a ensures high quality of the mixture. This task is done by the im Claim 1 defined static mixer solved.

The static mixer for a low-viscosity fluid contains mixed effective Built-in in a pipe or a fluid conducting container are arranged. The geometry of the internals is largely that of one Basic structure. The internals comprise structural elements in the form of flat, folded or curved sheet-like flow obstacles as well as intermediate bottlenecks. By internals in the form of The basic structure is a flow of the first order achievable, which in downstream mixing areas the pipe contents globally mixing flow is. Leave the structural elements of the basic structure describe themselves as segments, webs, plates and / or wings. The Structural elements - hereinafter referred to as "primary flow obstacles" - are geometrically modified on surfaces and / or on edges. By these modifications are inducible to local second order currents, the overlap the flow of first order and so the mixing quality improve. Namely, there are radial and axial inhomogeneities in the fluid better than balanced by the flow of first order. secondary Flow obstacles form the modifications through which the turbulence is locally intensified and / or reverse currents are induced.

The dependent claims 2 to 8 relate to advantageous embodiments of the mixer according to the invention. Method for mixing with a Static mixers according to the invention are the subject of claims 9 and 10.

Fig. 1

einen ringförmigen Teil eines erfindungsgemässen Mischers mit Einbauten, deren Strukturelemente lamellenförmige sekundäre Strömungshindernisse aufweisen,

Fig. 2

eine Kreuzkanalstruktur mit zwei weiteren Beispielen von sekundären Strömungshindernissen,

Fig. 3

Einbauten eines erfindungsgemässen Mischers mit zwei segmentartigen Strukturelementen,

Fig. 4

ein Detail zur Struktur der Fig. 3,

Fig. 5

eine Einbaute mit zwei Leitschaufeln als Strukturelementen,

Fig. 6

sekundäre Strömungshindernisse (vier Teilbilder), die rippenförmig sind und auf einer überströmten Oberfläche eines primären Strömungshindernisses angeordnet sind,

Fig. 7, 8

sekundäre Strömungshindernisse in Form von linearen Elementen, die gezahnte Kanten bilden bzw. aus separaten Zähnen zusammen gesetzt sind,

Fig. 9

diverse Zahnformen (drei Teilbilder),

Fig. 10

gefräste sekundäre Strömungshindernisse (drei Teilbilder), die in Form von linearen Elementen an einem Rand des primären Strömungshindernisses angeordnet sind, und

Fig. 11

sekundäre Strömungshindernisse (drei Teilbilder), die jeweils am primären Strömungshindernis durch Biegen der Ränder hergestellt sind.

The invention will be explained with reference to the drawings. Show it:

Fig. 1

an annular part of a mixer according to the invention with internals whose structural elements have lamellar secondary flow obstacles,

Fig. 2

a cross-channel structure with two other examples of secondary flow obstacles,

Fig. 3

Internals of a mixer according to the invention with two segment-like structural elements,

Fig. 4

a detail of the structure of Fig. 3,

Fig. 5

a built-in with two vanes as structural elements,

Fig. 6

secondary flow obstacles (four partial images), which are rib-shaped and arranged on an overflow surface of a primary flow obstacle,

Fig. 7, 8

secondary flow obstructions in the form of linear elements forming serrated edges or composed of separate teeth,

Fig. 9

various tooth forms (three partial images),

Fig. 10

Milled secondary flow obstacles (three partial images), which are arranged in the form of linear elements on one edge of the primary flow obstruction, and

Fig. 11

Secondary flow obstacles (three partial images), which are each made on the primary flow obstacle by bending the edges.

A mixer 1 according to the invention, which has a special configuration, is partially shown in FIG. 1. This static mixer 1, with a low viscosity fluid 20 is homogenizable, consists of a section a pipe 3 and mixing internals 10, which are arranged in the tube 3 are. Only one annular part 30 of the tube 3 is shown. This part 30 is mounted on a flange transition of the pipe 3, not shown. The Mixable internals 10 of this embodiment can also in a pipe 3 may be arranged at a location that does not serve as a flange transition is trained.

The geometry of the internals 10 is largely that of a basic structure, the Structural elements 11, 11 'and 12 in the form of segment or wing-like Has flow obstacles. Through between the structural elements lying bottlenecks flows the fluid 20, the flow through arrows 21st is indicated. The structural elements of the basic structure, posing as Segments, webs, plates and / or wings can be described hereinafter referred to as "primary flow obstacles". This primary Flow obstacles 11, 11 'and 12 are geometric at the edges modified, namely by secondary flow obstacles 11a, 11a 'and 12a, which are lamellar in the embodiment of FIG.

a) Durch die Modifikation wird der Turbulenzgrad der Strömung erhöht. Wie bereits bei bekannten Mischern beobachtet worden ist, verbessert sich die Mischgüte, wenn die Strömung auf der Eintrittssseite eine hohe Turbulenz aufweist. Eine solche erhöhte Turbulenz kann beispielsweise die Folge eines stromaufwärts angeordneten Krümmers mit Leitblechen sein. Ein ähnlicher oder noch stärkerer positiver Effekt kann erzielt werden, wenn im Mischer selber durch sekundäre Strömungshindernisse der Turbulenzgrad lokal gezielt erhöht wird. Besonders wirkungsvoll sind die Hindernisse, wenn sie in der Nähe der Stelle angeordnet sind, wo das Additiv zugegeben wird. Dort sind die Konzentrationsgradienten noch vergleichsweise stark ausgeprägt, und eine Verbesserung der Mischungwirkung in diesen Bereichen wirkt sich besonders positiv auf die Effektivität des Mischers aus.

b) Mit Hilfe der sekundären Strömungshindernisse 11a, 11'a und 12a können gezielt Rückströmungen erzeugt werden, in denen ein Additiv verdünnt wird, bevor es ausgewaschen und in den sich ablösenden Wirbeln fortgetragen wird. Dadurch werden die zeitlichen Konzentrationsschwankungen reduziert. Generell können durch Rückströmungen axiale Unterschiede ausgeglichen werden, auch solche, die durch eine nicht zeitkonstante Zugabe der zu mischenden Komponenten bedingt sind.

c) Die sekundären Strömungshindernisse 12a bewirken eine Kanalisierung der Strömung. Dadurch wird der Quertransport hinter dem zentralen Flügel 12 verbessert, wodurch die radialen Konzentrationsgradienten im Nachlauf der Einbauten 10 reduziert werden.

d) Durch die verstärkte Turbulenz und dadurch bedingte erhöhte turbulente Viskosität wird ausserdem die Strömung stabilisiert, d.h. Fluktuationen werden unterdrückt. Die sekundären Strömungshindernisse 11 a, 11 a' und 12a sind auch mit Vorteil so angeordnet und ausgeführt, dass der Strömungsabriss klar lokalisiert wird und somit nicht von der Reynoldszahl abhängt. Die Ausprägung der Strömung ist somit nicht von der Durchflussmenge abhängig und besser kontrollierbar.

By means of internals 10, which are formed in the shape of the basic structure, there results a first-order flow, which is a flow that globally mixes the pipe contents in the downstream mixing areas. There is a mixing in these areas over the entire pipe cross section through large-scale movements, in particular by periodically peeling and propagating vortex movements. Due to the modifications of the basic structure by means of the secondary flow obstacles, second-order local flows are induced which positively influence the effectiveness of the mixing process by the following effects:

a) The modification increases the degree of turbulence of the flow. As has already been observed in known mixers, the mixing quality improves when the flow on the inlet side has a high turbulence. Such increased turbulence may, for example, be the result of an upstream manifold with baffles. A similar or even stronger positive effect can be achieved if the degree of turbulence in the mixer itself is selectively increased locally by means of secondary flow obstacles. The obstacles are particularly effective when placed near the point where the additive is added. There, the concentration gradients are still relatively pronounced, and an improvement in the mixing effect in these areas has a particularly positive effect on the effectiveness of the mixer.

b) With the help of the secondary flow obstructions 11a, 11'a and 12a, backflows can be selectively generated in which an additive is diluted before it is washed out and carried away in the detaching vortices. This reduces the temporal concentration fluctuations. In general, axial differences can be compensated by backflow, even those caused by a non-time-constant addition of the components to be mixed.

c) The secondary flow obstacles 12a cause a channeling of the flow. As a result, the transverse transport is improved behind the central wing 12, whereby the radial concentration gradients in the wake of the fixtures 10 are reduced.

d) Due to the increased turbulence and consequent increased turbulent viscosity, the flow is also stabilized, ie fluctuations are suppressed. The secondary flow obstacles 11 a, 11 a 'and 12 a are also advantageously arranged and designed so that the stall is clearly localized and thus does not depend on the Reynolds number. The expression of the flow is thus not dependent on the flow rate and better controllable.

The combination of these effects a) to d) gives an improved radial and axial homogenization.

Although the secondary flow obstacles 11 a, 11 a 'and 12 a increase the Pressure loss. The pressure loss increase is smaller, however, than if instead additional primary flow obstacles according to the obstacles 11, 11 'and 12 - ie additional mixing elements - would be used. Such would be necessary if the secondary flow obstacles 11 a, 11 a ' and 12a would be waived. Thus, the secondary obstacles are too regarding the use of energy. The primary Flow obstacles 11, 11 ', 12 are therefore on surfaces and / or on Rims through the secondary flow obstacles 11 a, 11 a and 12 a geometrically modified so that by these modifications local Second order flows are inducible, which are the first flow Overlay order and thus improve the quality of mixing. The mixing quality improves in that radial and axial inhomogeneities in the fluid better than being balanced by the flow of first order, without that at the same time an increase of the pressure drop by more than 100% results.

The secondary flow obstacles 11 a, 11 a and 12 a are on Edge portions of the primary flow obstacles 11, 11 'and 12 are arranged. They thus form modifications of the primary flow obstacles 11, 11 ' as well as 12 and locally intensify the turbulence and / or induce Backflows of the fluid 20, whereby the mixing is improved.

Advantageously, the secondary flow obstacles 11a, 11'a and 12a lamellar or rib-shaped and transverse to the local flow direction the flow of first order at or on the primary Flow obstacles arranged.

Through the pipe 3 is a main flow direction perpendicular to Tube cross section defined. The pipe cross section is through a Normal projection of the primary flow obstacles 11, 11 'and 12 in Main flow direction largely completely covered. As a result of the Requirement that the mixing internals a minimum number of structural elements, the pipe cross section is through the Normal projections of the individual flow obstacles 11, 11 'and 12 not covered several times; or the projection is only marginal Overlap zones on.

In the embodiment of Fig. 1, the tube 3 is cylindrical and the Primary flow obstacles 11, 11 'and 12 form one mirror - symmetric arrangement, with a symmetry plane in which the Pipe axis is. The pair 11, 11 'of segmental, largely in one common structure elements form a bottleneck, within the wing or web-shaped structural element 12, the plane of the two other structural elements 11, 11 'is arranged crossing.

In the illustrated in Fig. 2 insert 10, the basic structure is a Cross-channel structure, in which a plurality of zigzag folded Sheets 13, 14 (and dash-dotted line indicated plates 13 ', 14') the form primary flow obstacles. Ribs 13a and / or wire-like Elevations 13b are on the metal surfaces of the cross channel structure arranged. Of these secondary flow obstacles 13a, 13b only one example shown. The ribs 13a are advantageous sharp-edged and serve as demolition edges on the overflowed Fold edges.

Fig. 3 shows internals 10 of an inventive mixer 1 with two segmental structural elements 15. The secondary flow obstacles 15a of the structural elements 15 are lamellar. The inside of the tube 3 is indicated by the dotted lines 31. A cross section through the Structural elements 15 is shown in FIG. 4. The arrows 21 indicate that How back flows form behind the structural elements 15.

Fig. 5 shows a built-in with two vanes 15 as structural elements. at one of the vanes 15 are secondary flow obstacles 15a shown.

In Fig. 6 are secondary flow obstacles 16a in four fields shown in the first as a perspective view and in the other Partial images only as cross-sectional profiles. These obstacles 16a are ribbed and on an overflowed surface of a primary Flow obstruction 16 is arranged.

FIGS. 7 and 8 show secondary flow obstacles 17a and 18a, respectively; the linear elements form: one with toothed edge and one with separate teeth 19. Examples of other forms of the teeth 19 are in three Sub-images of Fig. 9 shown. The linear element 17a may instead of a toothed edge also have a wavy edge. Such geometric modification at the edge of the primary flow obstacle gives an extension of the edge, which advantageously a reinforced Training turbulence entails.

FIG. 10 shows milled secondary flow obstacles (three partial images) which are shown in FIG Form of linear elements on one edge of the primary Flow obstruction are arranged.

Fig. 11 shows secondary flow obstacles, each at the primary Flow obstacle produced by forming its edges: slightly bent (first part), strongly bent (second part) and bent twice (third partial image), as indicated by arrows. Similar forms of flow obstacles may also be due Welding of metal strips to the primary flow obstacles will be realized.

The embodiment of FIG. 1 contains a feed point in the pipe section 30 100 for additives. The feed 100 opens with advantage in a zone of Mixed areas, in which the influence of the flow through the geometric modifications is particularly strong. It can Also, a plurality of feed 100 may be provided. Is more advantageous but a single feed 100, so with respect to the fixtures 10th can be optimally arranged. Experience has shown that one Multiple Feed Points 100 for a single additive with problems is connected, which are omitted at a single feed 100.

The mixer 1 according to the invention is used to carry out a Used mixing method in which the fluid to be mixed 50 in a Preferred direction is transported by the mixer 1. Regarding this Preferred direction is a better mixing quality than in the reverse Achieved direction.

As already mentioned, the mixing quality improves when the Flow on the inlet side is turbulent. It can therefore also for the inventive mixing method be advantageous if the fluid 20, before it is passed into the mixing internals 10, in one hydrodynamic state is brought in which it is turbulent Having flow components or increased turbulence.

Claims (10)

Static mixer (1) for a low-viscosity fluid (20), with mixing internals (10), which are arranged in a tube (3) or a fluid-conducting container and whose geometry is largely that of a basic structure, which internals structural elements (11, 11 ', 12) in the form of flat, folded or curved sheet-like flow obstacles and intervening bottlenecks, wherein by internals in the form of the basic structure a flow of first order is achievable, which in the downstream mixing areas is a pipe contents globally intermixing flow, and the Structure elements of the basic structure can be described as segments, webs, plates and / or wings,
characterized in that the structural elements - hereinafter referred to as "primary flow obstacles" (11, 11 ', 12) - are geometrically modified on surfaces and / or edges, so that local currents of second order are inducible by these modifications, the flow of the first Superimpose order and thus improve the quality of mixing, namely such that radial and axial inhomogeneities in the fluid are better balanced than by the first-order flow. Static mixer according to claim 1, characterized in that secondary flow obstacles (11a, 11a ', 12a) form the modifications by which the turbulence is intensified locally and / or reverse flows are induced, the secondary obstacles advantageously at peripheral parts of the primary Flow obstacles (11, 11 ', 12) are arranged. Static mixer according to claim 2, characterized in that the secondary flow obstacles (11a, 11a ', 12a) are lamellar or rib-shaped and transverse to the local flow direction of the first-order flow at or on the primary flow obstacles (11, 11', 12) are arranged. Static mixer according to one of claims 1 to 3, characterized in that through the pipe (3) has a main flow direction is defined perpendicular to the pipe cross section, that the pipe cross-section by a normal projection of the primary flow obstacles in the main flow direction largely completely (11, 11 ', 12) covered is and that the tube cross-section is not covered by the normal projections of the individual flow obstacles more than once or has only marginal overlap zones. Static mixer according to one of claims 1 to 4, characterized in that the following applies at least approximately that the tube (3) is cylindrical and the primary flow obstacles (11, 11 ', 12) form a mirror-symmetrical arrangement, with a plane of symmetry in which the tube axis is, and that a pair of segmental, in-plane structural elements (11, 11 ') form a bottleneck within which in particular a wing or web-shaped structural element (12) crossing the plane of the two other structural elements is arranged. Static mixer according to one of claims 1 to 5, characterized in that the basic structure is a cross-channel structure in which a plurality of zigzag-folded sheets (13, 14) form the primary flow obstacles, and that ribs (13a) and / or wire-like elevations ( 13b) are arranged on the sheet metal surfaces of the cross-channel structure, wherein the ribs are advantageously sharp-edged and serve as trailing edges on overflowed fold edges. Static mixer according to claim 1 or 2, characterized in that the geometrical modifications result in an extension of the edges on the primary flow obstructions (11, 11 ', 12), for example by secondary flow obstacles having a wave-shaped or serrated edge or the secondary flow obstacles (17a) have a wavy or serrated edge and are arranged on an overflow surface of a primary flow obstruction (17). Static mixer according to one of claims 1 to 6, characterized in that the tube contains a feed point (100) for additives and that the feed point opens into a zone of the mixing regions, in which the influence of the flow through the geometric modifications is particularly strong. A method of mixing with a static mixer (1) according to any one of claims 1 to 8, characterized in that the fluid to be mixed (20) is transported in a preferred direction through the mixer, with respect to this preferred direction a better mixing quality than in the reverse direction is achieved. A method according to claim 9, characterized in that the fluid (20), before it is passed into the mixing internals (10), is brought into a hydrodynamic state in which it has turbulent flow components or an increased turbulence.

Images