DE102011079230A1 - pressure screens - Google Patents

Abstract

The invention relates to a pressure sorter for cleaning a fibrous suspension (1) with a sieve element (2) which is rotationally symmetrical about a Siebachse (7) and divides the pressure sorter into an inlet space (3) and an accepts space (4), wherein the inlet space (3) with a suspension inlet (11) and a Rejektauslauf (18) and the Acceptance space (4) with a Gutstoffablauf (13) is in communication and in the inlet chamber (3) is a rotor (5) with rotor blades, the axis of rotation (10) of the Siebachse (7) and rotates relative to the screen element (2). In this case, the energy consumption and possible pulsations are to be reduced by making the distance (15) between the rotation axis (10) and the straight line passing in the flow direction through the centroid (6) of the cross-sectional area of the suspension feed (11) perpendicular to the flow direction (14) smaller than 1.0 times, preferably less than 0.7 times the radius of the sieve element (2).

Description

The invention relates to a pressure sorter for cleaning a pulp suspension with a Siebense rotationally symmetrical trained sieve element, which divides the pressure sorter into a Zulaufraum and a Gutstoffraum, the Zulaufraum with a suspension inlet and a Rejektauslauf and Acceptance space is connected to a Gutstoffablauf in connection and in Zulaufraum a rotor is located with rotor blades whose axis of rotation corresponds to the Siebachse and rotates relative to the screen element.

Pressure screens are used in the processing of paper pulp suspensions, in order to process the pulp suspension in a wet sieving. For this purpose, such a pressure sorter includes a sieve element which is provided with a plurality of openings. The fibers contained in the suspension are to pass through the openings as accept, while the unwanted solid constituents are rejected thereon and discharged as a reject again from the sorter. It is also conceivable to use for the separation of different fiber components, so the shorter of the longer fibers. As sorting holes round holes or slots are usually used. In most cases, pressure sorters of the type considered here are provided with screen scrapers having reaming surfaces moved past the screen. As a result, clogging of the screen openings is prevented in a manner known per se.

From the WO 98/53135 is a Siebräumer become known, which is provided with wing elements for the clearance of the screen. These wing elements have a hydrodynamic profile which extends over the entire length of the screen element of a screen basket. Due to the relative movement to the surrounding suspension, the wing element at the front gives a pressure and behind it a suction pulse onto the sieve to be cleared. Thereby, a part of the suspension, which was rejected on the screen or has already passed through the screen as accepts, sucked back, whereby the screen openings are kept free or cleared.

In contrast, the rotor blades are for example in the DE-OS 3701669 formed by surveys.

Irrespective of the design of the rotor blades, in practice a comprehensive effect of the rotor blades is sought by overlapping them in the circumferential direction. The same design of the rotor blades ensures a homogenization of the effect.

Disadvantages of the known pressure sorters, however, are not only the high energy absorption but also pulsations, which in the case of sorters in the constant part can lead to fluctuations in the basis weight of the fibrous web. The pulsations essentially start from the rotor.

The attenuation of these pulsations is associated with considerable effort and has been done either via a Pulsationsdämpfertank before the headbox or a special design of Gutstoffablaufs.

The object of the invention is therefore to reduce energy consumption and pulsations.

According to the invention, this object is achieved in that the distance between the axis of rotation and in the flow direction through the centroid of the perpendicular to the flow direction extending cross-sectional area of the suspension inlet going straight line is less than 1.0 times, preferably less than 0.7 times the radius of the screen element.

Since the suspension is not injected tangentially, it also has no or at least a reduced rotational flow when entering the inlet space. Consequently, exclusively or predominantly the rotor is responsible for generating the rotational flow in the inlet space.

This in turn makes it possible to reduce the speed of the rotor, which has a correspondingly positive effect on energy consumption and pulsations.

This makes the machine easier. In addition, the effect of the rotor is optimized.

It has proved to be advantageous if the flow direction forms an angle of at least 10 °, preferably at least 20 ° and in particular at least 35 ° with all tangents on the screen element in the region of the suspension feed.

In order to change the position of the centroid of the perpendicular to the flow direction extending cross-sectional area of the suspension inlet, the suspension inlet should have a flow cross section influencing, preferably adjustable aperture.

For optimal mixing of the suspension, it is advantageous if the flow direction in the suspension feed runs horizontally or inclined from above directly in front of the feed space, wherein the flow direction with the horizontal one Angle between 0 and 90 °, preferably between 0 and 60 ° forms. Furthermore, the distance between the axis of rotation and the straight line passing in the flow direction through the centroid of the cross-sectional area of the suspension feed running perpendicular to the flow direction can be zero or greater than zero.

In the interest of a uniform distribution of effects, the axis of rotation should be vertical. However, other orientations, for example, lying arrangements are possible.

Further advantages with regard to the design and function of the pressure sorter arise when the rotor is located inside the sieve element and the sieve element is cylindrical.

The invention will be explained in more detail below with reference to several exemplary embodiments.

In the attached drawing shows:

1 a schematic longitudinal section through a pressure sorter;

2 : a partial longitudinal section with inclined suspension feed 11 ;

3 : a cross section with added suspension feed 11 and

4 : a suspension feed 11 with aperture 8th ,

In 1 one recognizes a pressure sorter according to the invention with a sieve element 2 , here in the form of a cylindrical screen basket with vertical Siebachse 10 , which the interior of the pressure sorter in a Zulaufraum 3 and an accepts room 4 divides.

In the Zulaufraum 3 is via a suspension feed 11 the pulp suspension 1 fed.

As a result of the applied pressure gradient between the above drawn suspension feed 11 and the downstream reject outlet 12 of the Zulaufraumes 3 However, a transport flow is generated.

On the way of this transport flow is a large part of the pulp suspension 1 as intended by the sieve 2 as a good 17 in the acreage room 4 derived and from there on the accepts expiration 13 dissipated. At least a large part of this occurs in the pulp suspension 1 contained fibers in the accepts space 4 above.

The from the sieve element 2 rejected part of the pulp suspension 1 is called a reject 18 about the reject outlet 12 from the supply room 3 promoted.

To prevent the openings of the sieve element 2 become clogged, a known Siebräumer is used, which is relative to the screening element 2 emotional.

According to the invention this Siebräumer of one in the sieve 2 rotating rotor 5 formed with attached rotor blades. It has the rotor 5 here the shape of a cylindrical drum, the axis of rotation 7 with the Siebachse 10 matches.

All rotor blades here have the same shape, resulting in a uniform effect on the pulp suspension 1 and the sieve element 2 leads.

In addition, the rotor blades are over several perpendicular to the axis of rotation 7 extending circumferential planes of the rotor 5 arranged distributed.

In 1 are the rotor blades as elevations on the rotor 5 formed, which accordingly no radial distance to the rotor 5 to have. It is in the direction of rotation 16 of the rotor 5 extending cross-sectional area of the rotor blades formed as a rectangle.

However, the rotor blades can also be designed differently, for example with a wing profile.

In the pressure sorter used here receives the pulp suspension 1 no or only a reduced angular momentum. This allows the rotor 5 operate at a lower speed, so that on the one hand less energy is required and on the other hand, lower pulsations of the rotor 5 out. Therefore, it is important that as in 3 to recognize the distance 15 between the axis of rotation 10 and in the flow direction 14 through the centroid 6 the perpendicular to the flow direction 14 extending cross-sectional area of the suspension inlet 11 going straight zero or as here greater than zero and less than 1.0 times, preferably less than 0.7 times the radius of the screen element 2 is. The flow direction forms 14 at the suspension inlet 11 with every tangent on the sieve element 2 an angle 19 of at least 10 °, preferably at least 20 ° and in particular at least 35 °.

To the structure of the suspension feed 11 easy to design, but still the location of the centroid 6 the perpendicular to the flow direction 14 extending cross-sectional area of the suspension inlet 11 can change the suspension feed 11 corresponding 4 a flow cross section changing, preferably adjustable aperture 8th have.

To support the transport flow, the flow direction 14 in the suspension feed 11 immediately in front of the supply room 3 with the horizontal an angle 9 between 0 and 60 °, ie according to 2 be inclined downwards.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 98/53135 [0003]
• DE 3701669 [0004]

Claims (10)

Pressure sorter for cleaning a pulp suspension ( 1 ) with one around a Siebachse ( 7 ) rotationally symmetrical screen element ( 2 ), which places the pressure sorter in an inlet space ( 3 ) and an accepts room ( 4 ), the inlet space ( 3 ) with a suspension feed ( 11 ) as well as a reject rejection ( 12 ) and the accepts room ( 4 ) with an accept flow ( 13 ) and in the supply room ( 3 ) a rotor ( 5 ) is located with rotor blades whose axis of rotation ( 10 ) the Siebachse ( 7 ) and the relative to the sieve element ( 2 ), characterized in that the distance ( 15 ) between the axis of rotation ( 10 ) and in the flow direction ( 14 ) through the centroid ( 6 ) perpendicular to the flow direction ( 14 ) extending cross-sectional area of the suspension feed ( 11 ) straight lines less than 1.0 times, preferably less than 0.7 times the radius of the screen element ( 2 ). Pressure sorter according to claim 1, characterized in that the flow direction ( 14 ) at the suspension feed ( 11 ) with a tangent on the sieve element ( 2 ) an angle ( 19 ) of at least 10 °. Pressure sorter according to claim 1 or 2, characterized in that the flow direction ( 14 ) at the suspension feed ( 11 ) with a tangent on the sieve element ( 2 ) an angle ( 19 ) of at least 20 °, preferably at least 35 °. Pressure sorter according to one of the preceding claims, characterized in that the flow direction ( 14 ) in the suspension feed ( 11 ) immediately in front of the inlet ( 3 ) with the horizontal an angle ( 9 ) between 0 and 90 °, preferably between 0 and 60 °. Pressure sorter according to one of the preceding claims, characterized in that the distance ( 15 ) between the axis of rotation ( 10 ) and in the flow direction ( 14 ) through the centroid ( 6 ) perpendicular to the flow direction ( 14 ) extending cross-sectional area of the suspension feed ( 11 ) going straight is zero. Pressure sorter according to one of claims 1 to 4, characterized in that the distance ( 15 ) between the axis of rotation ( 10 ) and in the flow direction ( 14 ) through the centroid ( 6 ) perpendicular to the flow direction ( 14 ) extending cross-sectional area of the suspension feed ( 11 ) going line is greater than zero. Pressure sorter according to one of the preceding claims, characterized in that the suspension feed ( 11 ) a flow cross-section influencing preferably adjustable aperture ( 8th ) owns. Pressure sorter according to one of the preceding claims, characterized in that the axis of rotation ( 10 ) is vertical. Pressure sorter according to one of the preceding claims, characterized in that the rotor ( 5 ) within the sieve element ( 2 ) is located. Pressure sorter according to one of the preceding claims, characterized in that the sieve element ( 2 ) are cylindrical.

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