EP1474223B1 - Dynamic mixer - Google Patents

Abstract

Mixer comprising a housing having filling and emptying openings, two corotating stirrers and drivers for the stirrers, one of the stirrers being arranged centrally in the housing and having at least a drive shaft and at least one transverse beam fitted to the drive shaft and at least one stirring arm fitted at their ends to the transverse beam.

Description

The invention relates to a mixer comprising at least a housing having a filling and emptying opening, two stirrers rotating in the same direction and drive means for moving the stirrer, wherein a stirrer is arranged centrally in the housing, wherein the stirrer at least one drive shaft attached thereto at least one crossbar and at least one, preferably at least two of this cross bar respectively terminally mounted Rührarmen consists.

For the mixing of liquids and solids mixers are often required to avoid deposits on walls and agitators, in which a kinematic cleaning of the surfaces is carried out by the mixing elements. Examples of such devices are twin-shaft co-rotating extruder.

FR-A-2 716 337 discloses for mixing Hefeteig a mixing device with a drive shaft, a U-shaped stirring blade and a mating blade complementary thereto.

For processes with longer residence times, a large free volume mixer is also needed. An example of an apparatus that meets this requirement is in the European patent application EP 0 917 941 A1 described.

Two levels of freedom of movement are required to clean surfaces as completely as possible. This is after the apparatus EP 0 917 941 A1 achieved by two drive shafts.

In a mixer type called a Buss co-kneader (refer to Mixing in Making and Processing Plastics, ed. Association Dt. Engineers, VDI Ges. Kunststofftechnik, Dusseldorf, 1986, p. 200 ) is superimposed on a rotational movement of an axially oscillating movement of the kneader shafts.

For high-pressure processes, devices with an eight-shaped housing (see, for example, US Pat EP 0 917 941 A1 ) not suitable.

Furthermore, apparatuses with good axial mixing are required for batch processes.

What is needed is a mixer with a cylindrical housing, which has a good in particular axial mixing in the product area and in particular is as completely self-cleaning as possible.

The invention relates to a mixer according to claim 1.

The stirring arms are extended in particular in the longitudinal direction of the agitator shaft.

Preferred is a mixer in which the stirring blades and the stirring arms are helical. This achieves good axial mixing.

In a preferred embodiment, the stirrers are rotationally symmetrical as formed below.

gehorcht,
in der n₁ die Rotationssymmetrie des zentrischen Rührers, n₂ die Rotationssymmetrie eines eingreifenden exzentrischen Rührers, ω₁ die Drehzahl der zentrischen Welle, ω₂ der Drehzahl der exzentrischen Welle bedeuten und i, j natürliche Zahlen sind.Nearly complete mutual cleaning is achieved when the symmetry of the stirrers with respect to the speed of their shafts follows the mathematical relationship (I): $$\frac{{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\omega "\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\mathrm{<figure-callout\; id="1"\; label="j\; n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">j\; </figure-callout>}}{n_{}}$$

obey,
n _{1 is} the rotational symmetry of the centric stirrer, n _{2 is} the rotational symmetry of an engaging eccentric stirrer, ω _{1 is} the rotational speed of the centric shaft, ω _{2 is} the rotational speed of the eccentric shaft, and i, j are natural numbers.

Particularly preferred is a mixer, characterized in that in formula (I) the numbers j = 1, i = 1 mean.

For i = 1, j = 1 in formula (I), ordinary internal teeth are obtained. Various other forms of gearing are also possible, e.g. an involute toothing.

Particularly preferred is also a form of the mixer in which in formula (I) the number j = 1 and i> 1 is where i is non-prime to n ₂ .

Very particular preference is given to a variant of the mixer, characterized in that in formula (I) the number j> 1, the number i> 1 where i are non-prime to n ₂ and j are non-prime to n ₁ .

For an inexpensive production, a toothing is preferred in which the stirring blades have a constant thickness over the radius. Then the stirring blades can be formed, for example, from sheet metal.

Furthermore, an inexpensive production is facilitated if the number of stirring arms is low. This is achieved for a preferred design of the type mentioned above, if in formula (I) i> 1 and j = 1.

If i is chosen to be a prime alien to n ₂ , the complete cleaning of the lateral surfaces of the eccentric smaller rotor is preserved.

The number of agitator blades is reduced for j> 1. With j being divorced from n ₁ , the cleaning of the stirring arms of the centric rotor is retained. However, the agitator shaft of the smaller rotor is no longer completely cleaned.

In a further variant of the mixer, the drive means for the eccentric stirrer on the opposite end face of the housing to the drive means of the central stirrer is arranged.

Particularly preferred is a mixer in which the stirring blades and the stirring arms mutually completely sweep each other in their caused by the drive means rotation with the exception of their end faces, as far as they are not swept by the inner wall of the housing. If it is not important to a complete self-cleaning of the mixer, but only the very short mixing time to be exploited, the geometry of the mixer can be somewhat simplified. For example, For example, concave or convex surfaces can be approximated by straight surfaces.

A stable design also has a preferred mixer, characterized in that additional stirring arms are arranged on the underside of the crossbars, and that at least one additional eccentric stirrer is arranged in the region below the transverse bars in the housing. At the same container height, the length of the stirring arms is halved.

If, during partially filled operation of the mixer, all parts in contact with the product are to be kinematically cleaned, the crossbeams of the centric stirrer should be installed in the gas space. Accordingly, a drive of the eccentric shaft is then preferably provided from below.

In first experiments with mixers of the stirrer geometry according to the invention, it was found that the mixing times of these mixers are considerably shortened compared with conventional, comparable stirrers (spiral stirrers).

The mixing action in the region of the crossbars is to be further improved and the housing wall opposite the transverse bar can be kept free of any impurities if the crossbars in a preferred embodiment of the invention have on their side facing the housing wall additional grooves or ridges which have a conveying action in the radial direction ie in the direction of the agitator shaft or away.

The same causes a corresponding helical geometry of the crossbar, which is applied in a preferred embodiment of the invention.

Preferably, a variant of the mixer, characterized in that the outer surface of the stirring arms relative to the radial to centric stirrer at an angle α of at least 10 °, preferably at least 20 °, and less than 80 °, particularly preferably at least 30 ° and less than 60 ° employed is so that it points to the inner wall of the housing.

As a result, when the stirrer is driven, a conveying direction to the outside, i. reached in the direction of the housing wall.

In a further preferred variant of the mixer heating or cooling elements may be attached to the inner wall of the housing.

Otherwise, the housing may also be provided per se with the known conventional cooling or heating means, e.g. with a through-flow of heat transfer double jacket, electric heating coils etc.

The mixer according to the invention is suitable for any mixing tasks in the chemical process technology, optionally also as a reactor for stirred reactions.

The housing does not have to be completely provided with the internals according to the invention. It can e.g. for certain processes (degassing) a gas space above the stirrer installations be kept free.

Particularly preferred is a mixer in which the stirring arms of the centric stirrer are connected to the drive shaft at each one end via transverse bars, while the respective other ends are connected to one another via a reinforcing ring.

This connection with a ring creates a rigid frame structure, so that higher viscosity products can be processed (as without reinforcing ring).

The invention will be explained in more detail by way of example with reference to the figures.

Figur 1a

die Vorderansicht eines erfindungsgemäßen Mischers; das Gehäuse 1 ist geschnitten dargestellt

Figur 1b

die Seitenansicht des Mischers aus Figur 1a, das Gehäuse ist wiederum geschnitten dargestellt

Figur 1c

eine Draufsicht des Mischers aus Figur 1a, das Gehäuse ist wiederum geschnitten dargestellt

Figur 2

die isometrische Darstellung der Rührer des Mischers aus Figur 1a

Figur 3

Schnittbilder des Mischers aus Figur 1a gemäß der Linie A-A in Figur 1a zu verschiedenen Zeitpunkten während einer halben Umdrehung des größeren Rotors

Figur 4

die isometrische Darstellung der Rotoren einer Mischervariante, ähnlich den in Figur 1a gezeigten, in dem jedoch bei dem kleineren exzentrischen Rotor nur zwei Rührblätter vorhanden sind.

Figur 5

den Schnitt gemäß Linie A-A in Fig. 1a durch einen Mischer nach Figur 4. Die relative Lage des kleineren Rotors im Verhältnis zum zentrischen Rotor wurde zu verschiedenen Zeitpunkten im Verlaufe mehrerer Umdrehungen eingezeichnet (Darstellung der Relativbewegungen)

Figur 6

die isometrische Darstellung der Rotoren eines Mischers mit Antrieb des exzentrischen Rührers von unten

Figur 7

eine Ausführung des Mischers mit zusätzlichem Versteifungsring

Figur 8

eine Ausführungsvariante des Mischers nach Figur 1a, jedoch mit einem Rührarm und einem Rührblatt

Figur 9

eine weitere Ausführung des Mischers mit zentral angeordneten Querbalken und darüber und darunter angeordneten Rührarmen

Figur 10

eine Mischervariante mit zwei exzentrischen Rührern

Figur 11

einen Radialschnitt durch einen Mischer ähnlich Fig. 4 jedoch mit blattförmigen Rührarmen, die einen rechteckigen Querschnitt haben.

Show it

FIG. 1a

the front view of a mixer according to the invention; the housing 1 is shown cut

FIG. 1b

the side view of the mixer FIG. 1a , the housing is shown in turn cut

Figure 1c

a plan view of the mixer FIG. 1a , the housing is shown in turn cut

FIG. 2

the isometric view of the stirrer of the mixer FIG. 1a

FIG. 3

Cross-sectional views of the mixer FIG. 1a according to the line AA in FIG. 1a at different times during half a revolution of the larger rotor

FIG. 4

the isometric representation of the rotors of a mixer variant, similar to those in FIG. 1a shown, in which, however, only two stirring blades are present in the smaller eccentric rotor.

FIG. 5

the section along the line AA in Fig. 1a through a mixer FIG. 4 , The relative position of the smaller rotor in relation to the centric rotor was plotted at different times in the course of several revolutions (representation of the relative movements)

FIG. 6

the isometric representation of the rotors of a mixer with drive of the eccentric stirrer from below

FIG. 7

a version of the mixer with additional stiffening ring

FIG. 8

a variant of the mixer after FIG. 1a , but with a mixing arm and a stirring blade

FIG. 9

a further embodiment of the mixer with centrally located crossbar and above and below arranged stirring arms

FIG. 10

a mixer variant with two eccentric stirrers

FIG. 11

similar to a radial section through a mixer Fig. 4 however, with leaf-shaped stirring arms having a rectangular cross-section.

Examples example 1

FIGS. 1a, b, c show a mixer according to the invention in front, side view and plan view, in each case shown in cut housing. 1

The cylindrical housing 1 is shown, the centric stirrer 2 with a shaft 6 are attached to the two crossbars 7, which carry the helical stirring arms 8, 9 and the eccentric stirrer 3 are arranged with a shaft 11 on the six helical stirring blades 12. An inlet 4 and an outlet 5 are attached to the head and bottom of the housing 1, respectively. The drive units for the stirrer 2, 3 are not shown.

The stirring blades 12 have an approximately constant over the radius thickness. (In radial section, the thickness is constant, accordingly it increases perpendicular to the plate to the rotor center.)

With n ₁ the number of stirring arms 8, 9, n ₂ the number of stirring blades 12, ω ₁ the rotational speed of the centric shaft, ω ₂ the rotational speed of the eccentric shaft and i and j natural numbers according to formula (I): $$\frac{{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\omega "\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\mathrm{<figure-callout\; id="1"\; label="j\; n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">j\; </figure-callout>}}{n_{}}$$

In this case, a stirrer geometry is selected in the present case, in which the numbers
n ₁ = 2,
n ₂ = 6,
i = 7,
j = 1 mean.

The number i is prime to n ₂ .

FIG. 2 shows stirrers 2 and 3 in an isometric projection.

FIG. 3 shows a radial section through the mixer along the line AA in FIG. 1 in 15 different snapshots of the rotation of the two waves. Indicated is the respective rotation angle of the centric stirrer 2.

Example 2

FIG. 4 shows a variant of the mixer after FIG. 1 and 2 but four of the stirring blades 12 are removed on the eccentric stirrer 3 '. It applies again: $$\frac{{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\omega "\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\mathrm{<figure-callout\; id="1"\; label="j\; n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">j\; </figure-callout>}}{n_{}}$$

It is here
n ₁ = 2,
n ₂ = 2,
i = 7,
J = 3.

The number i is prime to n ₂ ; j is prime to n ₁ .

FIG. 5 shows a radial section through a mixer FIG. 4 in superimposed snapshots. The larger stirrer 2 was held. The relative position of the smaller stirrer 3 'was drawn at different times in the course of several revolutions.

FIG. 10 gives a variation of the mixer shape FIG. 4 again, in which two eccentric stirrers 3 "and 3 '" are combined with a centric stirrer 2 in cross-section.

Example 3

FIG. 6 shows an embodiment of the mixer with three crossbars 7 and three Rührarmen 8, 9, 9 '.

For the rotors in FIG. 6 the following relationship applies: $$\frac{{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\omega "\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\mathrm{<figure-callout\; id="1"\; label="j\; n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">j\; </figure-callout>}}{n_{}}$$

It is
n ₁ = 3,
n ₂ = 2,
i = 5,
j =. 4

The number i is prime to n ₂ ; j is prime to n ₁ .

The drive of the eccentric rotor is from below.

Example 4

FIG. 7 shows the stirrer of a mixer according to the invention, in which the stirring arms of the centric stirrer are connected at one end via transverse bar 7 to the drive shaft 6, while the other ends are connected to each other via a reinforcing ring 13.

This connection with a ring 13 creates a rigid frame structure, so that with the mixer products with higher viscosity can be processed as without reinforcing ring.

The speed ratio here is 2: 5. The centric stirrer carries 3 stirring arms, the eccentric stirrer 3 'three stirring blades.

For the rotors in FIG. 7 the relationship also applies: $$\frac{{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="\omega "\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="imgf0001.png,imgf0013.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\mathrm{<figure-callout\; id="1"\; label="j\; n"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">j\; </figure-callout>}}{n_{}}$$

It is
n ₁ = 3,
n ₂ = 3,
i = 5,
j = 2.

The digit i is prime to n ₂ ; j is prime to n ₁ .

Example 5

FIG. 8 gives the stirrer combination of a mixer with only one stirring arm 8 'and a stirring blade 12' on the eccentric stirrer 3 again.

In FIG. 9 is a variant to the mixer after FIG. 6 reproduced, in which the crossbar 7 in addition to carry on its underside further stirring 18, 19, 20. In the lower part of the arrangement, a further eccentric stirrer 3 "is mounted, which engages in the stirring arms 18, 19, 20 and is driven from below.

Example 6

FIG. 11 shows a radial section through the stirrer 2, 3 a variant of the mixer according to the invention. The structure of this mixer basically corresponds to in FIG. 4 shown embodiment, however, the stirring arms 28, 29 are designed leaf-shaped and have a rectangular cross-section. The speed ratio of shafts 6 and 11 is 1: 2. The centric stirrer 2 carries two stirring arms 28, 29, which are designed in sheet form, the eccentric stirrer 3 carries two stirring blades 22. The outer surface of the stirring arms 28, 29 is in each case at an angle α = 45 ° relative to the radial employed.

This form of stirrer 2, 3 is particularly suitable for the arrangement within a container having on the inner wall heating or cooling coils 23. If the direction of rotation is set so that the centric stirrer 2 conveys to the outside, intensive flow of the heating / cooling coils 23 is achieved. This improves the heat transfer to the mix.

Claims (16)

1. Mixer at least comprising housing (1) with a filling (4) and emptying opening (5), two corotating stirrers (2) and (3) and drive means for moving the stirrers (2) and (3), one stirrer (2) being arranged centrally in the housing (1), the stirrer (2) comprising at least one drive shaft (6), at least one, preferably at least two, transverse beams (7) fitted on the latter and at least in each case one stirring arm (8, 9) fitted on this transverse beam (7), in each case at the ends, the other stirrer (3) comprising at least one drive shaft (11) and one or more stirring blades (12) and being arranged eccentrically in the housing (1), characterized in that, in the course of the rotation of the stirrers (2) and (3) brought about by the drive means, the stirring blades (12) and the stirring arms (8, 9) brush over one another with the exception of their end faces, unless they are brushed over by the inside wall of the housing (1).
2. Mixer according to Claim 1, characterized in that the stirring blades (12) and the stirring arms (8, 9) are formed in a helical manner.
3. Mixer according to Claim 2, characterized in that the helixing of the stirring blades (12) and stirring arms (8, 9) is either both right-handed or both left-handed.
4. Mixer according to one of Claims 1 to 3, characterized in that the symmetry of the stirrers (2) and (3) with respect to the rotational speed of their shafts (6) and (11) obeys the following mathematical relationship (I): $$\frac{{\omega }_1}{{\omega }_2}=\frac{n_{2}j}{n_{1}i}$$

   

   
   in which n₁ denotes the rotational symmetry of the central stirrer (2), n₂ denotes the rotational symmetry of an engaging eccentric stirrer (3), ω₁ denotes the rotational speed of the central shaft (8), ω₂ denotes the rotational speed of the eccentric shaft (9) and i, j are natural numbers.
5. Mixer according to Claim 4, characterized in that the numbers mean j = 1, i = 1.
6. Mixer according to Claim 4, characterized in that the number j is = 1 and i is > 1, with i being prime to n₂.
7. Mixer according to Claim 4, characterized in that the number j is > 1, the number i is > 1 with i being prime to n₂ and j being prime to n₁.
8. Mixer according to one of Claims 1 to 7, characterized in that the stirring blades (12) have a constant thickness over their radius.
9. Mixer according to one of Claims 1 to 8, characterized in that the drive means for the eccentric stirrer (3) is arranged on the opposite side of the housing (1) from the drive means of the central stirrer (2).
10. Mixer according to one of Claims 1 to 9, characterized in that the stirring blades (12) and the stirring arms (8, 9) brush completely over one another with the exception of their end faces, unless they are brushed over by the inside wall of the housing (1).
11. Mixer according to one of Claims 1 to 10, characterized in that the stirring arms (8, 9) of the central stirrer (2) are connected to one another at their ends via a reinforcing ring (13).
12. Mixer according to one of Claims 1 to 11, characterized in that additional stirring arms (8', 9') are arranged on the underside of the transverse beams (7), and in that at least one additional eccentric stirrer (3') is arranged in the housing (1) in the region beneath the transverse beams (7).
13. Mixer according to one of Claims 1 to 12, characterized in that the transverse beams (7) have a spiral geometry, which brings about a radial conveyance during the rotation of the stirrers (2, 3).
14. Mixer according to one of Claims 1 to 11, characterized in that grooves or ridges, which bring about a radial conveyance during the rotation of the stirrers (2, 3), are provided on the side of the transverse beams (7) facing the inside wall of the housing.
15. Mixer according to one of Claims 1 to 14, characterized in that the outer surface of the stirring arms (8, 9) is set with respect to the radial to the central stirrer (2) at an angle α of at least 10°, preferably at least 20°, and less than 80°, particularly preferably at least 30° and less than 60°.
16. Mixer according to one of Claims 1 to 15, characterized in that heating or cooling elements (23) are provided on the inside wall of the housing (1).

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