EP0992624A1 - Apparatus for removing rotating flows - Google Patents

Abstract

At the vessel (10) outlet and/or in the following pipework (11, 12) there is a flow-straightener, which reduces or preferably eliminates secondary swirling flows which develop around the main flow direction. An Independent claim is included for the corresponding method.

Description

The invention relates to the constant part of a paper or Cardboard machine according to the preamble of claim 1 and a Procedure for avoiding pulsation in the constant part of a Paper or board machine.

The quality of a finished paper is next to the basic properties, which differ according to the Change the area of application of the paper, essentially through the Uniformity of these properties over the entire area determined away. This includes the same as possible Mass distribution over the paper surface and with the same mass per area also the uniformity of the distribution of the Ingredients (e.g. fibers, ash) and the spatial Orientation of the fibers (formation or Fiber orientation cross profile). To achieve this, one is endeavors to achieve a material suspension flow that is as uniform as possible lead to the headbox of the paper machine. This Material flow must with regard to its volume and mass flow be as constant as possible - i.e. free of pulsations.

To achieve these boundary conditions, intensive Efforts to dampen pulsations in the Stock suspension flow undertaken. For example, are out patent applications DE 42 37 308, DE 41 14 668 or DE 44 10 556 Measures to dampen pulsations in the Stock suspension stream known.

In addition, it should also be noted that in the Flow lines no dirt, deposits or Form fiber wipes so that they are not as chunks or other errors appear in the paper.

Furthermore, the post-published patent application the applicant DE 198 19 330 A1 pointed out in the Possibilities to combat pulsation in pipes general and in particular in the area of spatial manifolds be described before entering double-flow pumps.

Despite these known measures has been in operation emphasized that pulsations in the Stock suspension flow occur, which also leads to a Reduce paper quality.

It is therefore an object of the invention to take a further measure in Finding a constant part of a paper or board machine that leads to equalization of the stock suspension flow.

This object is achieved by the features of claim 1 and of claim 33 solved.

The inventors have recognized that another cause for the Development of pulsations in the constant part of a Paper machine, especially in the feed lines to Headbox, is that in the outlet area of suspension-bearing containers swirl flows (vortex), mostly in the outlet area of the containers.

These swirl flows can be due to the Coriolis forces or also due to unfavorable, one-sided flows arise. Such effects are generally known from the daily life at the water outlet of a bathtub, in the corresponding vortex forms when it runs out. At these processes cause secondary flows that overlap with the main flow and a kind helical vector profile of the total flow cause. Such effects occur particularly strongly in Outlet area of ventilation containers.

It has been found in operation that these swirl flows not just when introducing double-flow pumps like it is described in DE 198 19 330 A1, for pulsations lead, but also without the involvement of pumps, probably due to the smallest disturbances and Instabilities in the flow of the pipes, too Cause pulsations. Ultimately, this will make the Paper quality adversely affected because of pulsations Fluctuations in the basis weight cross profile and Longitudinal basis weight profile of the resulting paper web to lead.

It also creates the rotational component in the flow due to the different specific weights of the Solids in the stock suspension segregation of the Ingredients. This causes an uneven distribution the fibers and the ash in the flow cross section, whereby also an uneven distribution of fibers and ash over the width of the paper web can be the result.

At the same time, the rotational component of the flow, especially if it occurs in the headbox, a unwanted alignment of the fibers are caused, the unfavorable on the uniformity of the formation and on affects the fiber orientation cross profile.

The inventors therefore propose to avoid pulsations before using the swirl component of the flow Swirl crushers as close as possible to the point of origin or at possible place of origin itself, namely at the outlet area a suspension-carrying container and / or in the subsequent pipeline, to reduce, respectively completely wiped out. It is advantageous to To design swirl breakers in a special way to fiber-containing suspensions no interference Fiber wiping, dirt or mucilage to evoke.

Positioning is particularly advantageous and effective of a swirl breaker on or in a deculator (Ventilation tank), because this is due to only a small amount Built-in components and large flow spaces are particularly susceptible to is the formation of swirl currents.

The run-out area has a special form of training of the container has an, at least partially conical, Transition area to a pipeline.

In general, this can cause the formation of swirl currents be reduced that in addition to the outer wall of the pipeline or additional surfaces in contact with the flow be provided. This will make an additional one Frictional resistance creates the emergence of larger ones Secondary flows difficult.

A particularly advantageous design of a swirl breaker may consist of forming a tube bundle. Since the individual pipes have a smaller diameter than that single large pipe and possibly between the Pipes only have smaller passage areas this measure strongly the formation of swirl currents reduced.

In a possible, advantageous training of such A variety of tubes can be selected from the tube bundle have at least two different diameters. Likewise, the arrangement of the tubes can be chosen so that the center lines of several tubes of the tube bundle on one - imaginary - cylinder jacket or cone jacket.

If the pipes are connected to each other with webs, then the effect of the swirl breaker is increased. Can also in the Central axis of the cylinder or cone is another tube be arranged concentrically to further decrease of the individual flow cross sections.

In another, special version, the Swirl breaker from at least one flat plane with finite Thickness d, which is parallel to the main flow direction. Preferably, the thickness d of the plane should be greater than that Length of the longest fibers in the stock suspension, or still better larger than twice the length of the longest fiber in of the stock suspension.

In a special embodiment, this level can be defined by a flat sheet metal or formed by a flat plastic element become.

An improvement in the effect is achieved, if not only one level, but several levels in the pipeline are provided, which are at an angle of, for example, 90 ° stand with each other and in this way a kind of rectangular Form a cross with four quadrants in the pipeline. It is but also possible to get three levels at an angle of 120 ° to be cut so that the planes have a cross-section Form kind of star.

It can be advantageous here if one side of the level is at a distance from the nearest wall, wherein these are preferably at least twice the middle Correspond to the fiber length of the fibers in the stock suspension should. With the nearest wall it can be both around the wall of the pipeline as well as the next one act flat level. If the levels are only on one their sides attached to the wall of the pipeline, so there can be a free passage area in the center of the pipeline are maintained for the current in which there is none Levels of the swirl breaker. In a special one Design of the only one-sided attached levels Distance from the not attached side of the level to the next Wall maximum 2/3 of the diameter of the pipeline correspond. With such a configuration several in the main flow direction within the pipeline running, possibly narrow strips with the Inner wall of the pipeline connected.

In a further, special embodiment to avoid of fiber wiping and deposits on the swirl breaker proposed the level of the swirl breaker - in cross section seen the pipeline - at the connection to the wall of the Pipe to give a curvature that is continuously in the curvature of the pipe wall passes. In a another embodiment, the level in the area of Connection to the wall of the pipeline on both sides a kink on its surface so that the surface on both sides with an angle α that is significantly greater than 90 ° is on the curvature or on the surface of the Wall abuts. Another advantageous embodiment of the Twist breaker according to the invention is that the upstream narrow edge of the plane to the Flow direction - at least in the edge area to the wall of the Pipeline - has an angle γ greater than 90 °, preferably greater than 135 °.

It is also advantageous to in the area of the swirl breaker provide at least one plaster cover for the pipeline the possibly necessary cleaning of the Swirl breaker can be performed. It is advantageous even if at least two cleaning covers are provided, the are arranged on both sides of the swirl breaker.

According to the inventive concept described above, the Inventor also proposed to avoid pulsations in the Constant part of a paper or board machine, in Outflow area of a fluid-carrying container and / or in the subsequent pipeline swirl flows, so Rotational flows around a main flow direction avoid.

For example, to avoid swirl flows Ratio of area flowed through to flow contacted Walls opposite a single pipeline or one single inner cross section of a container can be reduced. This measure on the one hand prevents the emergence of Rotational currents more difficult, as well as existing ones Rotational currents are dampened and even extinguished.

Preferably, in addition to the outer walls surfaces in contact with the flow in the flow cross-section be introduced. It is particularly advantageous if the Alignment of the surfaces parallel to the main flow direction runs. In this way the rotational component is the Flow directed against these surfaces and is caused by the Surface destroyed or redirected.

There is also the possibility that the flow resistance increased in the direction of rotation around the main flow direction or that flow resistance increasing elements in the Flow cross section are introduced.

It is understood that the above and Features of the invention not yet to be explained below only in the specified combination, but also in other combinations or used alone, without leaving the scope of the invention.

Further features and advantages of the invention result from the subclaims and the description below preferred embodiments with reference to the Drawings.

Figur 1a - 1c:

Drei Ansichten eines Drallbrechers;

Figur 2a:

Drallbrecher mit zwei Ebenen;

Figur 2b:

Drallbrecher mit drei Ebenen;

Figur 3a + 3b:

Drallbrecher mit zentraler Lücke;

Figur 4:

Konstanter Teil mit Deculator;

Figur 5:

Drallbrecher mit Rohrbündel;

Figur 5a:

Drallbrecher mit Rohrbündel mit geschlossenen Zwischenkanälen;

Figur 6:

Querschnitt durch weitere Form eines Drallbrechers;

Figur 7:

Längsschnitt durch Drallbrecher nach Figur 6.

The individual shows:

Figure 1a - 1c:

Three views of a swirl breaker;

Figure 2a:

Swirl crusher with two levels;

Figure 2b:

Swirl breaker with three levels;

Figure 3a + 3b:

Swirl breaker with a central gap;

Figure 4:

Constant part with deculator;

Figure 5:

Swirl crusher with tube bundle;

Figure 5a:

Swirl crusher with tube bundle with closed intermediate channels;

Figure 6:

Cross section through another shape of a swirl breaker;

Figure 7:

Longitudinal section through swirl crusher according to Figure 6.

Figures 1a, 1b and 1c show three views of one swirl breaker according to the invention in a pipeline. In the Figure 1 a is the longitudinal section through an inventive Swirl breaker 1 shown in a pipeline 2. The Swirl breaker 1 consists of one in the main flow direction trending flat level 3 that has an upstream edge 6 has. The connection between level 3 and the Wall 7 of the pipeline 2 is through a transition fitting 4 created, which in the edge areas of level 3 Thickening of the plane creates. Due to the design of the Transition fitting 4 form the wall 7 of the pipeline 2 and the transition surfaces of the transition molding 4 upstream an angle γ that is significantly greater than 90 ° is. Because of this angle γ and the gap-free connection with the wall 7 of the pipe 2 is achieved, that none Fiber wiping occurs in this area.

FIG. 1b shows the section B-B from FIG. 1a shown. In addition to FIG. 1a, they are on both sides the level 3 attached cleaning cover 5 can be seen. The level 3 has a thickness d which is greater than the greatest length of the Fibers is in the stock suspension through the pipeline 2 can be transported. This prevents fix individual fibers at edge 6 of level 3. Furthermore, Figure 1 b shows the contour of the Transition fitting 4 into the wall 7 of the pipeline 2.

1c is the section B-B from FIG. 1a shown. This view shows how the Level 3, with the help of the connected transition fitting 4, with a curvature 8 continuously into the curvature of the Wall 7 of the pipeline 2 merges. According to the invention this transition even without curvature with a straight surface occur. Such a situation is in the Enlarged section shown at bottom right. Here points the transition fitting has no curvature, but forms a straight surface with an angle α that is essential is greater than 90 ° to the wall 7 of the pipeline 2 connects.

FIG. 2a shows an example of a swirl breaker 1 with two Levels 3 that intersect at an angle β = 90 °. in the Connection area of the two levels 3 to the wall 7 of the Tube 2 are also provided here transition fittings 4, the with a curvature continuously into the curvature of the wall 7 of pipeline 2. For an easy one The possibility of cleaning the surfaces of levels 3 are in each of the quadrants created by levels 3 Plaster cover 5 provided through which all the walls become easily accessible.

FIG. 2b shows a further embodiment of a Swirl breaker shown. Cut in this embodiment the three levels 3 with an angle β = 120 °. In each the resulting pipe segment is in turn for cleaning a cleaning cover 5 is provided. The levels 3 meet in this Embodiment without a special transition directly against the outer wall 7 of the pipeline 2. Such Execution can be selected where there is a risk of Pollution is low.

Another embodiment of the swirl breaker is in the Figures 3a and 3b shown. The execution of the The twist breaker of Figure 3a corresponds in principle to the Figure 2a. However, levels 3 do not reach Center of the tube and are only on one side connected to the tube wall 7. At the transition to the pipe wall shown a curvature that is in the curvature of the Pipe wall runs. The distance a of the free edges 9 of the Levels 3 is chosen so that there is between them cannot form fiber bridges. According to the invention, this can Distance a be up to 2/3 of the pipe diameter.

3b is the section B-B through FIG. 3a shown, the upstream edges of level 3 such are curved that they form without a paragraph in the Pass over wall 7 of tube 2.

It goes without saying that, for example, the Execution of Figure 2b with three swirl-breaking levels 3 with free edges 9 and a gap in the center corresponding to the Figure 3 is possible.

Figure 4 shows a highly schematic excerpt from the Constant part of a paper machine with a deculator 10, that with stock suspension via a feed 20 from one not shown cleaner system is loaded and from which the Stock suspension via a pipeline 12 by a pump 14 is conveyed to a vertical classifier 15. The pipeline 12 indicates at the transition from deculator 10 to pipeline 12 conical transition piece 11. From the vertical sifter 15 the stock suspension passes through a further pipeline 13 to a density-controlled headbox 16.

The dotted area of the deculator 10 is the preferred place for one according to the invention Swirl breaker, which in this example is conical Transition piece 11 is located. Possible designs are both in Figures 1a-3c, and in Figures 5-7 shown.

FIG. 5 shows the design of a swirl breaker (Section A-A from Figure 4) in a pipeline as a built-in Tube bundle. There are interconnected via webs 18 Pipes 17.1, 17.2 and 17.3, each with a different one Diameter shown symmetrical in the actual Pipeline are arranged in the flow direction. The Pipe bundle itself is also via webs 18 with the wall 7 of the pipeline connected. The tubes 17.1 and 17.2 are with their centers symmetrically dashed on a indicated inner circle arranged, the tubes 17.1 alternate with 17.3. Located centrally between the tubes another pipe 17.3. This arrangement creates a variety of channels, both within the pipes themselves, as well as through the outer walls of the tubes 17.1-17.3 and the Webs 18 formed. Due to the shape of these channels and The increased wall friction will create the swirl currents either prevented or an existing one Swirl flow braked with respect to its rotational component.

FIG. 5a shows a variant of the configuration of a Swirl crusher according to Figure 5, wherein the intermediate channels between the individual tubes 17.1, 17.2 and 17.3 closed here are. Thus the suspension flows exclusively through the Pipes 17.1, 17.2 and 17.3 itself. This is advantageous Execution that niches at the junctions of between the webs 18 and the outer walls of the tubes 17.1, 17.2 and 17.3 are avoided, and thus the Soiling tendency is reduced.

Also in the embodiments of the swirl breaker It is advantageous for the wall thicknesses of the tube bundles Choosing tubes thicknesses that get caught in fibers avoid.

Another form of swirl breaker is shown in FIGS. 6 and 7. Figure 6 shows a cross section through a tapered transition piece 11 in which Four levels 3 are arranged in a cross shape, which is general act as additional surfaces in the flow and on which any swirl currents break, or not at all.

FIG. 7 shows the transition piece 11 accordingly Figure 3 in a longitudinal section. Here is in addition to recognize that to avoid pollution and Fiber wiping the upstream edges 6 to Main flow direction 19 are chamfered and thus sticking prevent fibers or dirt.

Overall, the arrangement according to the invention and Execution of a swirl breaker in the constant part of a Paper or board machine achieves that swirl flows and the resulting pulsations in the stock suspension flow avoided, thereby improving the Paper quality is effected.

Reference list

1

Swirl breaker

2nd

Pipeline

3rd

level

4th

Transition fitting

5

Cleaning cover

6

upstream edge of the plane

7

Wall of the pipeline

8th

curvature

9

free edge

10th

Deculator

11

conical transition piece

12th

Pipeline

13

Pipeline

14

pump

15

Vertical classifier 1st stage

16

Headbox

17.1

Tubes of the tube bundle (first diameter)

17.2

Tubes of the tube bundle (second diameter)

17.3

Tube of the tube bundle (third diameter)

18th

web

19th

Main flow direction

20th

Feed

α

Angle between plane and wall

β

Angle between two levels

γ

Angle between the upstream edge of the plane and Wall

Claims (38)

Constant part of a paper or board machine with containers (10) and pipes (2, 11, 12, 13) which carry a suspension containing fibers, the suspension having a main flow direction (19), characterized in that in the outlet area of a container (10 ) and / or in the subsequent pipeline (2, 11, 12) at least one means (swirl breaker) for reducing, preferably for extinguishing swirl flows (= rotational flows around a main flow direction) around the main flow direction (19) is provided. Constant part according to claim 1, characterized in that the container (10) is a deculator (ventilation container). Constant part according to one of claims 1-2, characterized in that the outlet area has an, at least partially conical transition area (11) to a pipeline (12). Constant part according to one of claims 1-3, characterized in that at least one swirl breaker (1) has, in addition to the outer wall (7), additional surfaces or planes (3) in contact with the flow. Constant part according to one of claims 1-4, characterized in that at least one swirl breaker (1) has a tube bundle (17.1, 17.2, 17.3). Constant part according to claim 5, characterized in that the at least one swirl crusher (1) has a plurality of tubes (17.1, 17.2, 17.3) with at least two different diameters. Constant part according to one of claims 5-6, characterized in that the center lines of a plurality of tubes (17.1, 17.2) of the tube bundle (17.1, 17.2, 17.3) lie on a cylinder jacket or cone jacket. Constant part according to claim 7, characterized in that the tubes (17.1, 17.2, 17.3) are connected to one another with webs (18). Constant part according to one of claims 7-8, characterized in that a further tube (17.3) is arranged concentrically in the central axis of the cylinder or cone. Constant part according to one of claims 5-9, characterized in that the walls of the tubes (17.1, 17.2, 17.3) and optionally of the webs (18) have a finite thickness d which is greater than the length of the longest fibers in the stock suspension, is preferably greater than twice the length. Constant part according to claim 10, characterized in that the thickness d of the tubes (17.1, 17.2, 17.3) and / or webs (18) is ≥ 5 mm, preferably ≥ 8 mm. Constant part according to one of Claims 1-4, characterized in that at least one swirl breaker (1) consists of at least one flat plane (3) with a finite thickness d, which runs parallel to the main flow direction (19). Constant part according to claim 12, characterized in that the thickness d is greater than the length of the longest fibers in the stock suspension, preferably greater than twice the length. Constant part according to claim 12, characterized in that the thickness d ≥ 5 mm, preferably ≥ 8 mm. Constant part according to one of claims 12-14, characterized in that at least one plane (3) is a flat sheet or a flat plastic element. Constant part according to one of claims 12-15, characterized in that at least one level (3) is connected on two opposite sides to the wall of the container (10) or the pipeline (2, 11, 12). Constant part according to one of Claims 12-15, characterized in that at least one level (3) is connected to the wall (7) of the container (3) and / or the pipeline (2, 11, 12) only on one side. Constant part according to one of claims 12-17, characterized in that several planes (3) are provided which intersect at an angle of 90 ° or 120 °. Constant part according to one of claims 12-18, characterized in that one side of the at least one plane (3) is at a distance a from the nearest wall. Constant part according to claim 19, characterized in that the distance a corresponds to at least twice the average fiber length of the fibers in the stock suspension. Constant part according to one of claims 19-20, characterized in that the distance a corresponds to a maximum of 2/3 of the inside width of the container (10) or the pipeline (2,11,12). Constant part according to one of claims 12-21, characterized in that at least one plane (3) at the connection to the wall of the container or the pipeline (2, 11, 12) has a curvature which continuously extends into the curvature of the wall (7) transforms. Constant part according to one of claims 12-22, characterized in that at least one plane (3) at the connection to the wall of the container (10) or the pipeline (2, 11, 12) on both sides with an angle α which is substantially smaller than 90 ° is in the curvature or in the surface of the wall. Constant part according to one of claims 12-23, characterized in that at least one level (3) at the connection to the wall of the container (10) or the pipeline (2, 11, 12) has a thickening. Constant part according to claim 24, characterized in that the flow-contacting surface of the thickening has a concave shape. Constant part according to one of claims 12-25, characterized in that the upstream narrow edge (6) of at least one plane (3) to the flow direction at least in the edge region to the wall of the container (10) or the pipeline (2, 11, 12) has an angle γ> 90 °, preferably> 135 °. Constant part according to one of claims 1-26, characterized in that the swirl breaker (1) is clamped and / or welded and / or glued in the container (10) or in the pipeline (2,11,12) without a gap. Constant part according to one of claims 1-27, characterized in that at least one cleaning cover (5) is provided in the region of the swirl breaker (1). Constant part according to claim 28, characterized in that at least one cleaning cover (5) is provided on each side of the plane (3) of the swirl breaker (1). Constant part according to one of claims 1-29, characterized in that a swirl breaker (1) is located in the high-consistency strand to the headbox (16). Constant part according to one of claims 1-30, characterized in that a swirl breaker is located in the low-consistency strand to the headbox (16). Constant part according to one of claims 1-31, characterized in that the headbox (16) is an aperture-controlled and / or material density-controlled headbox. Method for avoiding pulsations in the constant part of a paper or board machine, characterized in that (10) and / or in the subsequent pipe (2,11,12) swirl flows (= rotational flows to a main flow direction) can be avoided in the outlet region of a fluid-carrying vessel . A method according to claim 33, characterized in that, in order to avoid swirl flows, the ratio of the area flowed through to walls in contact with the flow is reduced compared to a single pipeline or a single internal cross section of a container. Method according to one of claims 33-34, characterized in that surfaces in contact with flow in addition to the outer walls are introduced into the flow cross-section. A method according to claim 35, characterized in that the orientation of the surfaces is parallel to the main flow direction. A method according to claim 33, characterized in that the flow resistance in the direction of rotation is increased around the main flow direction. A method according to claim 23, characterized in that elements increasing the flow resistance are introduced into the flow cross section.

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