EP2782679A1

EP2782679A1 - Discontinuous centrifuge comprising a rotatable centrifuge drum that has a jacket, and method for the production of said jacket

Info

Publication number: EP2782679A1
Application number: EP12788582.0A
Authority: EP
Inventors: Hans-Heinrich Westendarp; Dirk SPANGENBERG
Original assignee: BMA Braunschweigische Maschinenbauanstalt AG
Current assignee: BMA Braunschweigische Maschinenbauanstalt AG
Priority date: 2011-11-24
Filing date: 2012-11-23
Publication date: 2014-10-01
Anticipated expiration: 2032-11-23
Also published as: US20140256529A1; MX2014006058A; CN103648654A; MX345190B; RU2014118498A; DE102012002351A1; CN103648654B; US9463475B2; RU2587087C2; WO2013076243A1; BR112014001481B1; EP2782679B1; BR112014001481A2

Abstract

A discontinuous centrifuge comprises a rotatable centrifuge drum (10) that has a jacket (13). The cylindrical centrifuge jacket (13) has holes (50) for discharging the liquid separated during the centrifuging process. The cross-section of the holes (50) has an elliptical shape and widens from the inside to the outside, while the wall of the holes is continuous. In the direction running parallel to the drum axis, the diameter of the cross-sections of the holes on the inside of the jacket (13) is the same as the diameter of the cross-sections of the holes (50) on the outside of the holes (50). In the circumferential direction, however, the diameter of the cross-sections of the holes (50) on the inside of the jacket (13) is smaller than the diameter of the cross-sections of the holes (50) on the outside of the jacket (13). The surface area of the elliptical holes can be additionally subdivided by webs.

Description

Discontinuous centrifuge with a rotatable centrifuge drum with a jacket and method of manufacturing the jacket

The invention relates to a discontinuous centrifuge with a rotatable about a drum axis centrifuge drum with a jacket in which the cylindrical centrifuge shell is provided with holes for the passage of a liquid formed during centrifugation, which holes have a cross-section with an elliptical shape, the invention relates to addition a method of making a jacket for such a batch centrifuge. Furthermore, the invention relates to a method for operating such a discontinuous centrifuge.

A centrifugal separator with radial openings is known from EP 0 804 291 B1 corresponding to DE 696 09 594 T2. The rotor of the centrifugal separator is constructed with passages in the form of the radial openings so that in the radial passages the risk of blockages or wear is reduced and that by a special design of the cross section of the passages a reduction of the generated noise level and an influence on the Frequencies of the sound generated in the passages occurs. For this to be the case, the passage is formed so that its radially inner cross-section to the outside is initially constant or increases slowly and then jumps discontinuously in the middle of the passage outward Shen. For this purpose, either an initially approximately constant and then funnel-shaped widening shape or a transition from a constant to a spherical cap or in a similar form is provided. This conception may be useful for certain applications, but so far has not turned out to be usable in the sugar industry, for example. Discontinuous centrifuges are also used in particular for the separation of sugar crystals from sugar crystal suspensions.

From above, a feedstock is supplied, for example, a magma with enriched crystal suspensions, and then treated in the centrifuge drum so as to be deposited on the inner surface of a jacket of the centrifuge drum a product, for example, here a crystals, settles. The syrup exits through a working sieve, which lies on the mantle.

This crystals or these crystal layers must then be cleared from the centrifuge drum, so that it is ready for the next use or the next batch.

Such a design, also known as a periodic centrifuge for centrifuging filling compounds, is already known from DE 1 916 280 B. Holes are provided in the centrifuge jacket, through which the liquid separated from the sugar crystals during centrifuging is discharged to the outside and leaves the centrifuge drum.

For the cross-sectional shape of these holes, DE 1 916 280 B proposes an elliptical shape for mechanical reasons, since this is advantageous for stability. These considerations have been confirmed. The stresses in the centrifuge shell in the region of the openings are thus reduced, thereby improving the durability and stability of the entire centrifuge drum. In another form of sugar centrifuges, namely in continuous centrifuges, elliptical holes, ie holes with an elliptical cross section, are known from EP 1 693 1 12 B1.

In view of the large number of discontinuous centrifuges used, especially in the sugar industry, there is considerable interest in further improving the centrifuge shells as well.

The object of the invention is therefore to propose a discontinuous centrifuge which has a further optimization of the centrifuge shell.

Another object of the invention is to provide a method for producing such a centrifuge.

The first object is achieved in a generic discontinuous centrifuge by means of the invention in that the cross section of the holes is continuous from the inside out that the diameter (a ₂ ) of the cross sections of the holes parallel to the drum axis on the inside of the shell is equal to or nearly equal to the diameter (ai) of the cross sections of the holes parallel to the drum axis on the Au ßenseite the holes and in that the diameter (l ₂ ) of the cross sections of the circumferential holes on the inside of the shell is smaller than the diameter (12) of the cross sections of the circumferential holes on the outside of the shell, so that the cross sections of the holes expand outwardly. In a generic method, the object is achieved by means of the invention in that the jacket is provided before or after the rounding of the jacket plate by means of water jet cutting with openings in elliptical shape.

Surprisingly, a considerable improvement in the behavior is made possible by this formation of the holes in the centrifuges, which initially appears slightly changed at first sight.

The reason for this is as follows: The centrifugal force causes the liquid in the drum, the centrifugal acceleration a _z . However, since the liquid is retained by the wall, the liquid has a velocity close to zero in the direction perpendicular to the drum wall. If a liquid particle enters the opening, it loses contact with the rotating reference system and thus the centrifugal acceleration also becomes zero. Since the particle is not further accelerated, so it takes a relatively long time to leave through the opening of the drum. It is very likely that it will be overtaken by the elliptical wall opening by the rotation of the drum and thus get back in contact with the rotating reference system. Here it is forced to the rear opening in the direction of rotation. There again the centrifugal acceleration acts and the particle is accelerated radially.

Therefore, to assist in the above-described effects, the opening area should become larger toward the outside. At the same time, a larger area is advantageous against which the liquid can "lean". The introduction of such outward Shen extended elliptical holes is initially quite complex. It should be noted that the extension of the elliptical holes to the outside should not be done in every direction to the same extent. As is clear from the above considerations on the motion of the sugar particles or particles, it is mainly about perforated walls, which should behave differently in different directions. It turns out, in fact, that the cross-sections of the holes in a dimension parallel to the axis of the drum should not rise from the inside to the outside or at least not increase significantly. In this direction, parallel to the drum axis, there is no movement or only slight evasive movements of the particles in the centrifuge drum, and an enlargement or narrowing of the hole in this dimension is therefore not meaningful and, as has been found, not at all desirable.

Assuming that the diameter of the cross sections of the holes parallel to the drum axis on the inside of the shell should be equal to the diameter of the cross sections of the holes parallel to the drum axis on the outside of the holes, it is understood that these two diameters are less than 5% should differ from each other. A slight deviation, in particular a slight extension of the cross section to the outside Shen also in this dimension is still tolerable, although it should be as low as possible.

Instead, the expansion of the cross-sections from the inside to the outside is by one dimension in the circumferential direction of the centrifuge drum, ie at the same time in the direction of movement of a rotating drum.

The wall of the hole should therefore be designed differently in the different areas of the hole wall.

This is possible by a particularly careful processing of the jacket plate of the centrifuge drums with different methods. However, it is particularly preferred if the holes are introduced by means of a water jet cut before the rounding of the sheet to form the cylindrical centrifuge shell as openings in a cladding sheet.

It has been found that with a particularly skillful manufacture of the centrifuge coats such as described above differently outwardly extended design of the elliptical holes can be done very reliable, precise and at the same time cost.

This is particularly beneficial when the ellipses are placed in a still flat sheet, and this sheet is then rounded to form the cylinder of the drum. If the ellipse is introduced almost vertically into the sheet, it will get a slightly conical shape in only one dimension when rounding. Exactly this effect is advantageous because it accelerates the discharge of the liquid. The effect can be increased by the fact that the opening is already introduced in a manner "conical" in the flat sheet metal in this respect.Already small angles in the range of 0.1 ° to 10 °, preferably from 0.2 to 3 °, to achieve great effects.

Advantageous here is the introduction of the openings by means of abrasive water jet cutting, since here the inclination of the cut surface can be easily adjusted to the sheet surface and at the same time can be ensured that no skewing takes place in the second, perpendicular thereto dimension.

In order to reinforce the Austrageffekt by larger areas, in an embodiment, an ellipse with running parallel to the drum axis web in the middle can be realized, which divides the ellipse into two halves symmetrical to each other. This has the advantage that with the web additional surface is created, which additionally accelerates the liquid and therefore the liquid leaves the drum faster. Preferably, the web surface is also slightly sloping outward in the direction of rotation here. Even embodiments with ellipses with more than one bar have advantages, but increase the production cost, so that no more than 5 bars are technically useful.

The inventive design of the centrifuge shell can still use another effect. The cross-sectional shape of the holes in the form of an ellipse favors a centering opening surface, which then fewer holes are required in total. Namely, the ellipse has a multiple of area compared to a hole having a circular cross section at the same dimension in the axis-parallel direction. For a smaller number of holes, fewer separate manufacturing steps are needed. Accordingly, for the forwarding and further processing of the fluids passing through the elliptical holes, fewer positions are to be taken into account at which the fluids exit on the outside of the centrifuge drum.

Further preferred embodiments are given in the dependent claims or explained in more detail in the description of the figures.

In the following an embodiment of the invention will be explained in more detail with reference to the drawing. Show it:

Figure 1 is a schematic sectional view of a discontinuous

Centrifuge in an embodiment of the invention, with a

Cut vertically through the centrifuge parallel to the axis of a centrifuge drum;

Figure 2 is a section through the discontinuous centrifuge of Figure 1 taken perpendicular to the axis of the centrifuge drum; a jacket plate for producing a centrifuge casing according to the invention; a first example of a formation of a hole in a centrifuge shell according to the invention; a second embodiment of a formation of a hole in a centrifuge shell according to the invention; a third embodiment of a formation of a hole in a centrifuge shell according to the invention; and a plan view of an embodiment similar to Figure 4 showing a three-dimensional effect.

The centrifuge drum 10 has a drive spindle 1 1, which also forms the vertically arranged axis of the centrifuge drum 10 and the rotary drive for the. In the schematic view in FIG entire centrifuge drum 10 provides. In the figure 1, the drive spindle 1 1 is indicated only schematically. The direction of rotation 12 is additionally marked by an arrow. The centrifuge drum 10 also has a jacket 13, which is rotated by the rotary drive 1 1 in a rotary motion. The jacket 13 is substantially cylindrical and covered on its inner wall by a not-shown working screen.

In the centrifuge drum 10, a magma is given that in particular sugar crystals still has with their mother syrup. This magma is thrown off the high speed driven centrifuge drum 10, wherein the sugar crystals do not penetrate the working screen, while the syrup exits through the working screen and exit from holes (50) not shown in this figure in the jacket 13 to the outside.

After further work steps, for example a washing of the crystals deposited in this way with a pure liquid, the sugar crystals remain on the inside of the jacket 13 in the form of a crystallizate 14 and form a kind of sugar layer there.

Down the centrifuge drum 10 is closed by a bottom 15. The bottom 15 is arranged substantially perpendicular to the axis of the centrifuge drum 10. However, the bottom 15 has openings 16 through which the crystals 14 can escape from the centrifuge drum 10 due to its gravity. These openings 16 are closed during the centrifuging process and are only then opened. In order to remove the adhering to the inner wall of the shell 13 crystallizate 14 from there, a Ausräumer 20 is provided. The scraper 20 has a scraper bar 21 and an element 22 arranged on the scraper bar 21, for example a paring knife 22 or a razor. The paring knife 22 or the Räumpflug are pivotable relative to the raking bar about the axis formed by the raking bar 21.

The peeling blade 22 and the Räumpflug parallel to the axis of the centrifuge drum 10 and thus vertically. They extend over the whole or almost the entire height of the shell 13th This pivotal movement causes the paring knife 22 can move into the crystals 14 and successively peels off the layers of the crystals 14 there. After the peeling process, the sugar crystals of the crystallizate fall 14 due to their gravity within the centrifuge drum 1 1 down in the direction of the bottom 15 and there through the now no longer sealed openings 16. In Figure 2, we see now the same situation of the same centrifuge drum 10th in a section perpendicular to the drum axis and thus perpendicular to the drive spindle 1 1.

It can be clearly seen here that the scraper 20 is supplemented with its clearing bar 21 by an element 22 in the form of a paring knife or Räumflugs. In the position shown, this element 22 does not reach into the crystallizate 14. This position of Figure 1 and Figure 2 is thus taken during centrifugation. The jacket 13 is provided with a larger number of holes 50. These holes 50 are so small in proportion that they do not appear separately in the illustration in Figures 1 and 2.

Syrup, which escapes from the sugar crystal suspension during the centrifuging operation and leaves the crystallizate 14, can escape from the centrifuge drum 10 with the casing 13 to the outside through these holes 50. The crystals 14 themselves remain hanging on a screen (not shown) which is placed on the inside of the jacket 13. FIG. 3 shows a jacket sheet which would be suitable for producing a jacket 13 from FIGS. 1 and 2.

It can be seen that a large number of elliptical holes 50 are provided in the jacket 13. The elliptical holes 50 are over that for the jacket 13th provided jacket sheet distributed. Here are a variety of possibilities conceivable.

The holes 50 are thereby introduced by means of water jet cutting in the jacket plate for the jacket 13.

FIG. 4 shows a first embodiment of a hole 50 at the top in section and at the bottom in a plan view. In the figure 4, the jacket plate for the jacket 13 in section and at the bottom of the region of the hole 50 in plan view can be seen above.

It can be seen here that the hole 50 has an elliptical shape and is introduced into the jacket sheet by abrasive processes perpendicular to the plane of the sheet.

If now the jacket sheet is bent in a cylindrical shape for the production of the shell 13, then it can be well imagined in FIG. 4 that the hole 50 on the upper side is then compressed and bent on the lower side, for instance in the case of a bend upwards. This process is uniform, so that only by this curvature results in a continuous shape of the hole 50, which is open in the figure 4 down. Further explanations on this can be found in connection with the description of FIG. 7 below.

FIG. 5 shows a second embodiment of a hole 50 at the top in the section and at the bottom in a plan view. The hole 50 is here composed of two individual regions 50a and 50b, which together form an elliptical shape with an intermediate web 51.

In the cross section, which is shown at the top in FIG. 5, it can be seen that this embodiment too is introduced by vertical water cutting into the jacket plate for the jacket 13.

In the case of a bending of this sheet for producing the cylindrical shell 13, a deformation of the elliptical structure, which may be approximately conical in one dimension, results in turn, as in FIG. 4. The web is advantageously already slightly obliquely made (viewed in plan view) and although to the outside in the direction of rotation steadily sloping.

FIG. 6 shows a third embodiment of a hole 50 at the top in the section and at the bottom in a plan view. The hole 50 is in turn here elliptical and divided by two webs 51 a and 51 b, so that form three partial holes 50 a, 50 b and 50 c.

FIG. 7 shows a plan view of an embodiment of a hole 50, which initially resembles the illustration in FIG.

However, this presentation focuses on another aspect. The hole 50 has a total of three dimensions. A first dimension runs on the circumference of the cylinder drum and can be seen in the sheet plane from left to right in FIG.

A second dimension runs on the cylinder drum parallel to the drum axis and is shown in the sheet plane in Figure 7 from top to bottom.

A third dimension runs perpendicular to the jacket 13 of the centrifuge drum 10 and thus stands perpendicular to the plane of the sheet in FIG. 7.

The jacket 13 of the centrifuge drum has a finite dimension. He has an inside, which faces the drum axis, and a Au ßenseite, which faces the environment.

The hole 50 now has a cross section, which is constructed elliptical in each case. The elliptical cross-section thus has a usually smaller diameter, which in the illustrated embodiment is parallel to the drum axis, in Figure 7 from top to bottom. In this case, the diameter of the ellipse-like cross section on the outside of the jacket 13 is designated by ai and with a ₂ the diameter of the ellipse-like cross section on the inside of the jacket 13. As can be seen, both diameters and a _{2 are} equal and also coincide. The second, in the majority of embodiments and in the illustrated embodiment larger diameter is perpendicular to the first diameters ai and a ₂ in the circumferential direction of the shell 13 and thus in Figure 7 from left to right. Here, the Au on the outside of the drum shell located cross-section of the ellipse-like hole 50 is denoted by, located on the inside of the shell 13 diameter of the elliptical cross-section in this dimension is denoted by l ₂ . It can be seen that greater than l ₂ . Since the hole wall, the elliptical cross-sections au Shen on the shell 13 and inside the shell 13 continuously connects with each other, it follows that the hole wall in Figure 7 on the sides, which are in the illustration above or below, perpendicular to the page plane, while they are in the areas that are located to the left or right of the hole 50, obliquely to the leaf level.

LIST OF REFERENCE NUMBERS

10 centrifuge drum

1 1 drive spindle of the centrifuge drum 10th

12 direction of rotation of the centrifuge drum 10th

13 coat

14 crystals on the inside of the jacket 13

15 floor

16 openings

20 cleaners

21 Scraper of the scraper 20

22 element, in particular paring knife or Räumpflug the Ausräumers 20 23 pivoting direction of the element 22 of the Ausräumers 20th

24 transducer for force and / or torque in the pivotal movement of the element 22nd

50 holes

50a partial hole

50b partial hole

50c partial hole

51 footbridge

51 a first footbridge

51 b second bridge

Diameter of the hole 50 in the vertical direction on the outside of the shell 13th

Diameter of the hole 50 in the vertical direction on the inside of the shell thirteenth

Diameter of the hole 50 in the horizontal direction on the Au ßenseite the shell thirteenth

Diameter of the hole 50 in the horizontal direction on the inside of the shell thirteenth

Claims

claims

1 . Discontinuous centrifuge

with a centrifuge drum (10) which can be rotated about a drum axis and has a jacket (13),

in which the cylindrical centrifuge casing (13) is provided with holes (50) for the discharge of a liquid produced by centrifuging, which holes (50) have a cross-section with an elliptical shape,

characterized,

that the cross-section of the holes (50) is continuous from the inside to the outside, that the diameter (a ₂ ) of the cross-sections of the holes (50) parallel to the drum axis on the inside of the shell (13) is equal or nearly equal to the diameter (a ^ the cross-sections of the holes (50) parallel to the drum axis on the Au ßenseite the holes (50), and

that the diameter (l ₂ ) of the cross-sections of the holes (50) in the circumferential direction on the inside of the shell (13) is smaller than the diameter (15) of the cross-sections of the holes (50) in the circumferential direction on the outside of the shell (13) so that the cross sections of the holes (50) expand outward.

2. Discontinuous centrifuge according to claim 1,

characterized,

that the outwardly widening elliptical cross sections of the holes (50) hole walls at an angle relative to the perpendicular to the jacket (13) at the outer ends of the diameter (\ l ₂ ) in the circumferential direction of more than 0.1 ° and less than 10 °, preferably more than 0.2 ° and less than 3 °. 3. Discontinuous centrifuge according to claim 1 or 2,

characterized,

the hole walls of the holes (50) are also continuous in the circumferential direction.

4. Discontinuous centrifuge according to one of the preceding claims, characterized

the holes (50) are introduced by means of a water jet cut before the rounding of the sheet to form the cylindrical centrifuge casing (13) as openings in a jacket sheet.

5. Discontinuous centrifuge according to one of the preceding claims, characterized

that the diameter (\ l ₂ ) of the cross sections of the elliptical holes (50) in the circumferential direction is greater than the diameter (ai, a ₂ ), the

Holes (50) parallel to the drum axis, and

the half-axis ratio of the ellipses is between 1: 2.5 and 1: 7.5, preferably between 1: 4.5 and 1: 5.5.

Discontinuous centrifuge according to one of the preceding claims, characterized

that the open area of each ellipse lies between 80 mm ² and 50 mm ² , preferably between 95 mm ² and 1 05 mm ² .

7. Discontinuous centrifuge according to one of the preceding claims, characterized

in that the holes (50) in the jacket (13) of the centrifuge drum (10) have a different opening cross-section over the height of the drum.

8. Discontinuous centrifuge according to one of the preceding claims, characterized

in that the holes (50) in the jacket (13) of the centrifuge drum (10) have different distances from each other over the height of the drum.

9. Discontinuous centrifuge according to one of the preceding claims, characterized

the material thickness of the jacket plate of the jacket (13) of the centrifuge drum (10) is between 8 mm and 25 mm, preferably between 10 mm and 17 mm.

10. Discontinuous centrifuge according to one of the preceding claims, characterized

in that one, several or all ellipses of the holes (50) in the jacket (13) of the centrifuge drum (10) have at least one central web (51) running parallel to the drum axis which preferably divides the ellipse into two halves symmetrical to each other. 1 1. Discontinuous centrifuge according to claim 10,

characterized,

that the cross-sectional area of the webs (51) is designed to decrease outwardly, and

that the hole wall is also continuous in the region of the webs (51).

12. Discontinuous centrifuge according to claim 10 or 1 1,

characterized,

the ellipse has a plurality of webs (51 a, 51 b), preferably at least two and at most five.

13. A process for producing a discontinuous centrifuge with a centrifuge drum (10) and a jacket (13) according to one of the preceding claims,

characterized,

that the jacket (13) before the rounding of the jacket sheet by means

Water jet section is provided with openings in elliptical shape, from which after rounding the holes (50) are formed with the elliptical cross-section.

14. A process for producing a discontinuous centrifuge according to claim 13,

characterized,

that the openings in elliptical shape obtained before the rounding of the jacket plate by means of water jet cutting a conical shape.

15. A process for producing a discontinuous centrifuge with a centrifuge drum (10) and a jacket (13) according to one of claims 1 to 12,

characterized,

that the jacket (13) is provided after the rounding of the jacket plate by means of water jet cutting with holes (50) with a cross-section in elliptical shape,

that the walls of the holes (50) are formed from the inside to the outside and in the circumferential direction continuously, and

that the diameter (l ₂ ) of the cross-sections of the holes (50) in the circumferential direction on the inside of the shell (13) is formed smaller than the diameter (12) of the cross-sections of the holes (50) in the circumferential direction on the outside of the shell (13), so that the cross sections of the holes (50) widen outward.