EP1337344A1 - Solid bowl screw centrifuge comprising a distributor - Google Patents

Abstract

The invention relates to a solid bowl screw centrifuge comprising a centrifuging chamber (19) having a rotating screw (1) and a likewise rotating drum (21) surrounding the centrifuging chamber (19), in addition to a distributor (15) which is preferably embodied as a tube and is used to introduce the material to be centrifuged (S) into the centrifuging chamber (19). Said distributor is oriented in a angular manner, especially perpendicularly, in relation to the central axis (A) of the screw (1). The material to be centrifuged is guided through an axially extending inflow tube (13) into the distributor (15). At least one wall (15a) of the distributor is provided with a surface structure consisting of projections (27) in such a way that the main part of the material to be centrifuged (S) which passes through the distributor must flow around at least one of the projections (27) on the at least one wall (15a) on the radial path from the inflow tube (13) to the centrifuging chamber (19).

Description

 Solid bowl screw centrifuge with ner divider

The invention relates to a solid-bowl screw centrifuge, which has the following: a rotating drum which encloses a centrifugal space with a screw which also rotates and one which is preferably designed as a tube

Distributor for introducing centrifugal material into the centrifugal space, which is oriented at an angle, in particular perpendicular, to the central axis of the screw, the centrifugal material being guided into the distributor through an axially extending feed pipe.

In solid-bowl screw centrifuges, the centrifuged material should be accelerated to the peripheral speed of the screw at the diameter of the liquid level (surface) in the screw channel. The relative speed when entering the centrifugal chamber (liquid surface) should be as low as possible.

Accelerating to the peripheral speed of the screw at the liquid level diameter on the driver walls (of the distributor) creates a surface flow in the distributor, the speed of which increases sharply with the radius, to a value that is approximately equal to the peripheral speed of the screw at the liquid level diameter ,

It is known from US Pat. No. 5,403,486 to provide the area of the centrifugal material feed - in the broadest sense the distributor - of a solid bowl screw centrifuge with a larger number of outlet openings which are aligned at different angles to one another. However, this solution is relatively expensive and, moreover, the relative speed is not reduced.

From DE 1 293 089 it is also known to cover nozzle-like distributor openings in the centrifugal space with a baffle plate which deflects the centrifuged material in order to reduce flows. However, this measure is not sufficient for an effective reduction of turbulence.

It is therefore the object of the invention to develop the generic solid bowl screw centrifuge in such a way that the relative speed of the Spin material is reduced in a structurally simple manner when entering the liquid surface.

The invention solves this problem by the subject matter of claims 1, 2 and 20.

Advantageous refinements are specified in the subclaims.

According to a first variant, at least one wall of the distributor is provided with a surface structure made of protrusions in such a way that the major part of the centrifugal material flowing through the distributor on this at least one wall over the essentially radial and / or essentially in the direction of the centrifugal force extending from Inlet pipe in the centrifugal space must flow around at least one of the projections.

According to a further variant, at least one wall of the distributor is provided with a surface structure comprising at least two or more rows of projections which are offset radially to one another, the projections of the rows being offset axially to one another in such a way that essentially no radial free flow channels are formed on the wall are.

These variants ensure effectively, but in a simple and relatively inexpensive manner, that at least the essential part, but preferably the entire centrifugal material, can no longer flow from the inlet pipe into the centrifugal chamber in a direct radial way. “Radial” here means the direction on the distributor wall in which the centrifugal force essentially wants the centrifugal material to flow into the centrifugal force, ie the term “radial” can also include an axial movement component and / or a circumferential component , It is important that at least the essential part of the centrifuged material does not directly "in the direction of the centrifugal force" in the

Spin chamber flows. It is already known from DE PS 1 272 231 to form some grinding (crushing) bodies on the distributor wall. Between these bodies, however, there are still direct paths radially into the centrifugal space, so that the liquid essentially does not slow down but enters the centrifugal space at an unchanged high radial speed. The possibility of using projections to reduce the relative speed of the centrifuged material when entering the liquid surface in a structurally simple manner was not recognized here.

After a structurally particularly simple and yet particularly effective

As a variant, the projections are designed as circular, diamond-shaped or other n-shaped knobs in cross section.

In the case of further variants, on the other hand, the projections have a meander shape. In this case, as well as in other versions, it is advantageous if the projections are designed as sheets.

According to a further variant, which is also to be considered independently, at least one wall of the distributor is provided with a step-like surface structure which extends in the circumferential direction and which also brakes, among other things. by

Turbulence.

Exemplary embodiments are described in more detail below with reference to the drawing. It shows:

Figure 1 is a sectional view of a solid bowl screw centrifuge.

Fig. 2 shows the inlet area of a distributor in a centrifugal space

Solid bowl Schneckenzentrifiige;

Fig. 3 is a schematic representation of a section through the drum of Fig. 1;

4a-e different cylindrical knob arrangements;

Fig. 5-11 different structures of projections on walls of distributors; Fig. 12 is a diagram illustrating the speeds of the

Centrifuged.

1 shows a solid-bowl screw centrifuge with a screw 1, which has a screw body 3 and, in this case, a spiral surrounding the screw body 3

Has screw blade 5. A screw channel 7 for conveying / transporting a centrifugal material to be processed is formed between the screw flights x, x + 1, ...

The screw body 3 has a cylindrical section 9 in its rear area in FIG. 1 and a section 11 which tapers in steps (alternatively: conically) in its front area adjoining this in FIG. 1.

Centrifuged material S is fed through the centrally arranged inlet pipe 13 into a distributor 15 and from there through radial openings 17 in the distributor 15 into the centrifugal space

19 with the screw 1 and the drum 21 surrounding the screw 1.

When the distributor 15 passes through and when it enters the centrifugal chamber 19, the centrifuged material S is accelerated. The action of the centrifugal force causes the solid particles to settle on the drum wall in a very short time.

The screw 1 rotates at a slightly lower or greater speed than the drum 21 and conveys the ejected solid F to the tapered section 11 from the drum 21 to the solids discharge 23.

In contrast, the liquid L flows to the larger drum diameter at the rear end of the drum 21 and is drained there (overflow 25).

The structural design of the centrifugal material feed from the inlet pipe 13 into the centrifugal chamber 19 - that is to say in particular the construction of the distributor - is intended below

15 - be considered in more detail.

For this purpose, reference is first made to FIG. 2. FIG. 2 again shows the inlet pipe 13, which projects into the distributor 15, which here has an essentially rectangular cross section (perpendicular to the image plane of FIG. 2) or is essentially designed as a rectangular pipe. Alternative off

5 educations are of course conceivable, so an education of the distributor as

Pipe construction from two intersecting rectangular tubes or as tubes, which are not aligned perpendicular to the drum axis but arbitrarily arbitrarily to it. Cross-sectional geometries deviating from a rectangular cross-section can also be realized.

[0

The centrifugal material S entering the distributor 15 moves at the moment of exit from the inlet pipe 13 with the axial flow velocity in the inlet pipe 13. When it enters the distributor 15, it is then carried along by the distributor 15. The centrifuged material S thus rotates with the distributor 15 and

L5 moves essentially radially outward as a result of the centrifugal force in the distributor 15.

In the area of the openings 17 on the outer radial edge of the distributor 15, the centrifuged material has the absolute speed x (see FIG. 3) with which it is the distributor 15

10 leaves (see also Fig. 3). The speed vector x has both

Component u in the circumferential direction of the drum 21 and also called a component v - relative speed. The relative speed v can contain a component in the radial direction as well as other components in other directions (e.g. axial).

25

In the case of many products to be spun, the relative speed component v should be as small as possible when the material to be centrifuged enters the centrifugal space 19, for example in the case of products which are relatively prone to foam formation or have sensitive structures which are not as in the state of the art

30 Technology may be destroyed or damaged (e.g. flocculants that should not be destroyed). The centrifuged material S should ideally only enter the centrifugal chamber at the circumferential rotational speed of the screw body 3 and without a relative speed v (see also FIG. 12). In order to reduce the relative speed v or, in particular, to prevent excessive acceleration in the radial direction, at least the walls 15a, d of the distributor, which are in the opposite ones, are provided

5 ends of the distributor 15, the centrifugal material essentially when the

Take distributor 15 with them - or in addition to provide the side walls 15b (or alternatively all walls) of the distributor which are perpendicular thereto, with a surface structure which consists, in particular, of walls formed directly on wall 15a, d or of at least one separate one that can be attached to the wall

[0 sheet 29 can be formed projections 27. A multilayer arrangement comprising a plurality of sheets 29 lying one above the other with projections 27 can also be realized (FIG. 3).

The projections 27 are distributed on the at least one wall 15a of the distributor 15 such that at least the major part of the centrifugal material S entering the distributor 15 flows around at least one, but preferably several, of the projections 27 on the radial path outwards got to.

The at least one wall 15a is also preferably essentially of the same type with the projections to ensure a sufficient “braking effect”

27 provide that there are essentially no radial (or perpendicular to the outside) free flow paths 33 for the centrifuged material.

The projections 27 are preferably distributed over an area of 30 to 70% of the at least one wall 25 15a of the distributor 15.

The projections 27 are preferably also formed at least in the radially outer region of the distributor wall 15a, d. This has the following advantage.

50 Since the centrifugal force is proportional to the square of the angular velocity and proportional to the radius r (F _z = mω ² r), it is immediately clear that the acceleration of the centrifugal material is greater in the outer radial area of the distributor 15 than in the inner area, so that in the outer radial area of the divider 15a, the braking effect of the projections 27 counteracts this acceleration particularly advantageously. For this reason, the projections 27 are preferably also formed up to the outer radial edge of the distributor 15 or up to the discharge opening 17 on the wall 15a of the distributor 27. The radially inner part of the distributor (for example the inner 30 or 50% of the wall surface of the wall 15a), on the other hand, can be designed to be smooth, ie without protrusion, without the "braking effect" being significantly reduced.

Since the centrifugal acceleration also increases with increasing radius, a variant of the invention has also proven to be particularly advantageous in which at least one or more wall (s) 15a, d of the distributor or the plate 29 with the projections 27 placed on the wall 15a extends radially beyond the edge of the opening 17 into the centrifugal chamber.

2, the projections 27 are designed as cylindrical knobs 27a, b - preferably of different diameters - which are fastened in bores 31 of the wall 15a, e.g. are welded.

Alternative geometries are conceivable, such as triangular cross-sections, rectangular cross-sections, rhombuses, etc.

The projections 27 can also widen or taper away from the wall 15a. Spherical shapes are also conceivable.

The extension of the projections 27 perpendicular to the distributor wall 15a is selected such that in the preferred application (for example fruit juice extraction etc.) and with the maximum throughput of centrifuged material, the projections 27 are at least as high as the liquid level on the wall 15a. The projections are preferably approximately twice as high as the average liquid level. The projections can alternatively also be designed as rods which pass through the distributor 15 from the wall 15a to the opposite wall 15d.

The knobs 27 can also be formed as stampings or in another way can be formed directly in one piece with the wall 15a, d or the sheet 29. This one-piece formation can also be carried out in the casting process or by milling out the knob structure from a correspondingly thick wall panel. ^'

L0

According to FIG. 2, an inner radial region of the wall 15a is designed without protrusions or nubs. This inner radial region is adjoined by a central radial region with four rows of knobs 27a aligned parallel to the drum axis A, each of which has a first diameter a. On the middle one

15 area, an outer area is closed with three rows of knobs

27b, which have a smaller diameter b in comparison to the diameter a and are also closer to one another, so that the flow channels 33b running between the knobs 27b and oriented obliquely to the drum axis A are narrower than the flows remaining between the wider knobs 27a.

20 channels 33 a.

The knobs 27a, b are each arranged in rows which are aligned parallel to the drum axis A. The rows are axially offset from one another by half the distance between two adjacent knobs 27a, b in such a way that the centrifuged material S is prevented from flowing directly in the radial direction. The axial distance d between the knobs 27a, b is somewhat larger than the diameter of the knobs 27a, b. The distance between the centers of the knobs in the radial direction corresponds approximately to their diameter a, b.

According to FIG. 2, the knobs 27 have a diameter that gradually decreases radially outwards. The flow channels 33 are also smaller or narrower. This design causes an increasing braking of the centrifugal material radially from the inside out, that is, it acts on the increasing Acceleration due to the increasing centrifugal force. The distance to be covered for the centrifuged material S becomes longer by the knobs 27a, b.

4 to 10 show further variants of knob structures.

4a, the rows of knobs 27a are each offset from one another by the diameter of the knobs, the distance between the center points or central axes of the cylindrical knobs 27a in each row corresponding to the diameter d of the knobs 27a.

The axial misalignment of the rows of knobs relative to one another is reduced from FIGS. 4a to 4d. In a direction oblique to the drum axis A there are obliquely outwardly narrowing throughflow channels 33. These can also be avoided entirely if the diameter of the knobs 27a, b as in FIG. 2 or the offset of the rows of knobs varies from row to row or is further reduced (see Fig. 4e). A wide variety of flow characteristics can be achieved through a suitable design of the rows of knobs.

It is conceivable to produce the knobs using pot cutters. A wide variety of materials such as steel, cast iron or even plastics are conceivable for the knobs. Plastic has the advantage that the knobs are slightly flexible or movable, which can increase the braking effect.

4e shows a variant in which the knobs of a row are so closely spaced from one another that when the rows of knobs are axially offset by half the distance between two adjacent knobs, no linear flow channels 33 extending perpendicular to the central axis A of the centrifuge remain.

5, the Norsprünge are diamond-shaped. The connecting lines of the tips of the diamonds 227 are perpendicular and parallel to the central axis A of the

Centrifuge. The tips of the diamonds 227 also point towards each other in the various rows of diamonds, with flow channels 33 between the diamonds 227 in oblique remain in a straight or inclined direction to the central axis. The flow channels 33 or diamonds 227 can be produced, for example, by a milling process.

6a shows a variant of the invention, in which at least two rows of sheet metal strips 127 are attached to the wall 15a of the distributor instead of rows of knobs.

These sheet metal strips 127 are each oriented at an angle to the central axis A of the centrifuge and are so close to one another in mutually opposite rows of angular displacement that in turn there are no flow channels in the radial direction on the

Distribution wall remain but a strong deflection and braking takes place. The angle here is approximately 30 °. The smaller the angle to the central axis, the higher the speed must be so that no deposits form on the metal strip. The angle could also decrease towards the outside, possibly up to the value 0.

The sheet metal strips 127 could also not be perpendicular to the screw body, but could be of any angle (see FIG. 6b) and / or L-shaped or U-shaped or T-shaped and / or arranged (see FIGS. 6c and 6d by way of example). In places with high speed the angle to the central axis should be larger than at

Set at a lower speed.

A variant is shown in FIG. 7. A first very flat plate 127 leads to strong braking in a labyrinth arrangement 128 made of further, bent plates 127, which is designed such that again no radial flow is possible.

8, the projections have a kind of meander shape. The zigzag-like meanders 327 intermesh in such a way that again no flow channels remain radially outward in the distributor 15.

9 to 11, a type of step-like surface structure (step construction 427) has been implemented in the distributor 15 or on the walls 15a of the distributor shaft. Both in Fig. 9 and in Fig. 10, the liquid flow must "Steps" flow in the circumferential direction. The effect is again optimal if the step construction extends into the liquid level.

According to FIG. 9, the step contour is made from several sheets 428, alternatively 5 the contour can also be formed from a workpiece (e.g. milled).

The sheets 428 have an angled cross-section, i.e. they each consist of a section 428a which runs essentially parallel to the distributor wall and a section 428b which is angled in relation thereto and which here has an example of an inclination of [0 approx. 30 ° to the vertical on the distributor wall.

The section 428a of the first plate 428, which runs essentially parallel to the distributor wall, is placed directly on the distributor wall. The sections of the following sheets 428 running parallel to the distributor wall 428a are respectively L5 attached to the rear sides of the angled sections 428b of the preceding sheets, so that a kind of swirl space is created between the successive sheets 428.

This arrangement has the following advantages.

20

If the liquid jet strikes from one step or a plate 428 to the next step or the next plate 428, it is directed (in FIG. 9 to the left and right) in the direction of flow and counter to this in different directions and swirled, which in turn has a braking effect causes.

25

Since the plates 428 are offset from one another, the liquid jet moves somewhat counter to the direction of rotation (to the right in FIGS. 9 and 10, arrow P3) along the dashed line.

30 When it strikes, the liquid is divided in the direction of rotation and counter to the direction of rotation (arrows Pl, P2). This division and the swirling of the jet ensure a particularly advantageous braking effect. The braking effect is composed here, as it were, of the effect of the oblique sections of the metal sheets 428 and the shadow effect of the intermingling (arrow P2).

Fig. 10 differs from Fig. 9 not only in that the step construction 427 was realized in one piece from a cast or milled part, but in that the step construction is designed in such a way that the section 429a of the steps 429, which runs essentially parallel to the distributor wall, is in each case joins the ends of the angled portions 429b of the previous stage so that there is no swirl space between the successive stages.

An alternative to FIGS. 9 and 10 is shown in FIG. 11. In this FIG. A type of “waterfall brake inflow is realized. Here too, a type of step contour 427 is realized, but here the individual steps 430 are again formed by rows of projections 431 running essentially parallel to the drum axis, or rows of grooves 432 are milled into a plate. The rows of grooves 432 in turn have an angled cross-section, ie they each consist of a section 432a which runs essentially parallel to the distributor wall and an angled section 432b which, for example, has an inclination of approximately 30 ° to the vertical on the distributor wall. The sections 432a of the rows of grooves which are essentially parallel to the distributor wall are essentially flush with one another, ie they lie in one plane, which makes the manufacture cheaper compared to the variant in FIG. 10 (less waste during milling or less casting material required). It is advantageous in the example shown here that the oblique section 432b has an angle of approximately 30 ° to the vertical on the distributor wall and that the liquid jet also strikes the next step at an angle of, for example, 30 °. LIST OF REFERENCE NUMBERS

Snail 1

Snail body 3

Snail blade 5

Worm channel 7 cylindrical section 9 fertilizing section 11

Inlet pipe 13

Distributor 15

Walls 15a-d

Discharge openings 17

Spin chamber 19

Drum 21

Solids discharge 23

Overflow 25

Projections 27

Knobs 27a, b

Sheet 29

Holes 31

_0 flow channels 33

Sheet metal strip 127

Maze arrangement 128

Lozenges 227

Meander 327

.5 step construction 427

Sheets 428

Sections 428a, b

Levels 429

Levels 430

50 projections 431

Groove rows 432

Sections 432a, b

Drum axis A

55 Centrifugal material S

Diameter: knobs a, b,

Distance: nubs axial d

Worm threads x, x + l,.

Centrifuged material S 0 solid F

Liquid L

Radius r

Inclination angle α, αl

Arrows P1 - P3

Claims

claims 1. VoUmantel-screw centrifuge, which has the following: - a rotating drum (21) which encloses a centrifugal chamber (19) with a rotating screw (1), a distributor (15), preferably designed as a tube, for introducing centrifugal material (p ) in the centrifugal chamber (19), which is angled, in particular perpendicular, to the central axis (A) of the screw (1), - the centrifuged material through an axially extending feed pipe (13) is passed into the distributor (15), characterized in that at least one wall (15a) of the distributor is provided with a surface structure made of projections (27) in such a way that the major part of the centrifugal material (S) flowing through the distributor on it At least one wall (15a) must flow around at least one of the projections (27) on the essentially radial and / or substantially in the direction of the centrifugal force from the inlet pipe (13) into the centrifugal chamber (19). 2. VoUmantel-screw centrifuge, in particular according to claim 1, characterized in that the at least one wall (15a) of the distributor is provided with at least two or more radially offset rows of the projections (27), the projections (27) of the rows such are axially offset from one another so that essentially no radial and or essentially flow channels extending in the direction of the centrifugal force are formed on the wall (15a). 3. VoUmantel-screw centrifuge according to claim 1 or 2, characterized in that the projections are formed as circular in cross-section, diamond-shaped or other n-shaped knobs (27). 4. VoUmantel-screw centrifuge according to claim 1 or 2, characterized in that the projections (227) have a meander shape. 5. VoUmantel screw centrifuge according to claim 1 or 2, characterized in that the projections (127) are designed as sheet metal strips and / or are produced by welding, milling or the like. 6. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the sheet metal strips (127) are each angled - preferably 30 ° - to the central axis A of the centrifuge and are lined up so closely together, especially in mutually angular rows that no flow channels in radial direction remain on the distributor wall. 7. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the angle (α) preferably between the sheet metal strips (127) and the central axis A with increasing radius of the Remove the distributor (15) or with increasing distance from the drum axis. 8. VoUmantel screw centrifuge according to one of the preceding claims, characterized in that the sheet metal strip (127) is a labyrinth Train the centrifugal chamber. 9. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the knobs (27) from the wall of the distributor (15) from tapering or widening or circular or spherical or constant in diameter have a contour. 10. VoUmantel screw centrifuge according to one of the preceding claims, characterized in that the knobs (27) are integrally formed with the wall (15 a) or the sheet (29). 11. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the knobs (27) are welded into bores in the plate (29) or the wall (15a). 12. Solid bowl screw centrifuge according to one of the preceding claims, characterized in that the knobs (27) have such a height substantially perpendicular to the wall (15a) that the liquid level on the wall (15a) at maximum throughput of centrifuged material (S) is lower than the height of the knobs. 13. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the diameter and / or the distance of the knobs (27) decreases radially outwards. 14. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the diameter and / or the distance of the knobs (27) is constant radially outwards. 15. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the wall provided with the projections (15 a) or the plate (29) on the wall together with the projections extend over the peripheral wall of the screw body into the centrifugal chamber (19). 16. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the projections (27) are formed at least in the outer radial region of the distributor (15). 17. VoUmantel screw centrifuge according to one of the preceding claims, characterized in that the surface structure with the projections (27) covers at least 40% of the area of the wall (15a). 18. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that in the distributor (15) on the at least one wall (15a) several superimposed layers of sheets provided with the projections are arranged so that the distributor through- 5 flowing centrifugal material flow is divided into several parts. 19. VoUmantel screw centrifuge according to one of the preceding claims, characterized in that the projections (27) and / or the sheet metal, cast or plastic receiving the projections or _. Rubber loading 0 stand. 20. VoUmantel screw centrifuge, which has the following: a rotating drum (21) which encloses a centrifugal chamber (19) with a screw (1) which also rotates, 15 - a distributor (15), preferably in the form of a tube, for introducing centrifugal material (S) into the centrifugal chamber (19), which is oriented at an angle, in particular perpendicular, to the central axis (A) of the screw (1), the centrifugal material being itself axially extending feed pipe (13) is passed to the distributor (15), characterized in that .0 - at least one wall (15a) of the distributor is provided with a step-like surface structure - step construction (427) - which extends in the circumferential direction. 21. VoUmantel-screw centrifuge according to one of the preceding claims, .5 characterized in that the step construction (427) from several in Sheets (428) lying on / against one another in the circumferential direction. 22. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the step construction (427) consists of a one-piece metal or plastic body. 23. VoUmantel screw centrifuge according to one of the preceding claims, characterized in that the plates (428) have an angular cross-section and each consist of a section (428a) running essentially parallel to the distributor wall and a section (428b) angled thereto. 24. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the substantially parallel to the distributor wall section (428a) of the first plate (428) is placed directly on the distributor wall and that the sections parallel to the distributor wall (428a) following sheets (428) are each attached to the rear of the angled sections (428b) of the previous sheets, so that a swirl space is created between the successive sheets (428). 25. VoUmantel screw centrifuge according to one of the preceding claims, characterized in that the step construction is designed such that the section running essentially parallel to the distributor wall (429a) each step (429) each at the end of the angled section (429b) of the previous stage. 26. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the individual stages (430) are formed by rows of grooves (432) running essentially parallel to the drum axis, which preferably have an angular cross-section. 27. VoUmantel-screw centrifuge according to one of the preceding claims, characterized in that the sections (432a) of the rows of grooves (432) which run essentially parallel to the distributor wall lie essentially in one plane.