GB2109260A

GB2109260A - Sorting fibre suspensions

Info

Publication number: GB2109260A
Application number: GB08227740A
Authority: GB
Inventors: Josef Tra; Werner Witek
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1981-10-13
Filing date: 1982-09-29
Publication date: 1983-06-02
Also published as: IT1153904B; JPS58122012A; DE3140549A1; ATA343082A; IT8223140V0; DE3140549C2; IT8223694A0; FR2514384A1; AT384253B; GB2109260B; CH657395A5

Abstract

A device for sorting fibre suspensions in the paper industry, the sorter having a separate outlet for a relatively lighter stuff fraction (light fraction), comprising a substantially rotational flow of the fibre suspension can be produced, means for introducing a proportion of the stuff for the purpose of after-cleaning in the proximity of the axis of rotation of the rotational flow, while. an outlet connection 8, coaxial to the axis of rotation, is disposed for the light fraction in an end wall of the sorter casing. A proportion of stuff which has undergone intermediate sorting is returned to the sorter casing through a casing extension 11 which is disposed around the light stuff outlet connection and forms an annular chamber. The fibre suspension is fed tangentially into the device through pipe 6, accepted stuff passes out via sieve 10 through pipe 19 and heavy dirt passes out through pipe 7. Another embodiment utilises a cylindrical screen, and a further embodiment, Figure 4, comprises a hydrocyclone. <IMAGE>

Description

SPECIFICATION A device for sorting fibre suspensions, particularly in the paper industry The invention relates to a sorter comprising a substantially rotationally symmetric casing in which a rotational flow of the fibre suspension can be produced, for example by means of a rotor.

A sorter of this kind is known from DE-OS 2514 162. In this machine, which also serves as a pulper, a predetermined proportion of the stuff, which has undergpne intermediate cleaning, is returned to the pulper. A particularly suitable location for this purpose is a point in the pulper where the pressure is relatively low and which lies substantially in the axis of the rotor, which in practice is also the axis of rotation of the substantially rotationally symmetrical main body of the pulper casing.

The problem underlying the invention is that of so developing a sorter that this proportion of stuff is returned in such a manner that it entails substantially no disturbance of the flow in the pulper casing, so that the discharge of the different fractions is also not disturbed and that as much light dirt as possible can be separated through a light dirt outlet.

The invention provides a device for sorting fibre suspensions in the paper industry, the sorter having a separate outlet for a relatively lightstufffraction (light fraction), comprising a substantially rotationally symmetrical casing in which a rotational flow of the fibre suspension can be produced, means for introducing a proportion of the stuffforthe purpose of after-cleaning in the proximity of the axis of rotation of the rotational flow, an end wall of the sorter casing having the outlet pipe connection for the light fraction disposed coaxially to the axis of rotation, and there being an annular chamber which is formed concentrically with respect to the outlet pipe connection for the light fraction in a casing extension and into which a feed pipe for the said proportion of the stuff leads, the said annular chamber opening into the casing substantially in the direction of the axis of rotation.

It has been found that through this arrangement a sorter of this form can be operated without disturbance, particularly a sorter of the previously known type, while very effective separation of light dirt can be achieved.

In so-called disc sorters and vertical sifters, the latter having a rotationally symmetrical sieve in front of which blades or sorting arms of a rotor also rotate, the same effect can likewise be achieved.

The solution provided by the invention can also be adopted in so-called hydrocyclones.

In a sorter allowing the separate discharge of fractions predominantly containing light dirt in the one case and heavy dirt in the other another advantage is gained if the proportion returned to the sorter, as mentioned above, consists of the heavy fraction, after it has been cleaned in a hydocyclone. If it is considered that the material discharged, which is diluted by the after-cleaning in the cyclone, in leaving the sorter in accordance with the invention entails no additional load on the other equipment of the entire plant (as, for example, in the case of DE-OS 2514162), particularly the pumps, the separation of heavy dirt from the plant will in fact be improved by the greater possible volume of this fraction which is discharged.

By way of example, specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which: Figure 1 is a basic sketch, in longitudinal section, of an embodiment of sorter according to the invention; Figure 2 is a basic end elevation of the sorter shown in Figure 1; Figure 3 is a longitudinal section of an embodiment of sorter in the form of a sifter according to the invention; and Figure 4 shows schematically in section an embodiment of sorter in the form of a hydrocyclone according to the invention.

From the longitudinal section shown in Figure 1 can be seen the tangential connection of a pipe connection 6, through which the fibre suspension is fed, substantially in the direction of rotation of a rotor 2, into the pulper casing 1,which is under pressure. The rotor 2 further breaks up the fibre lumps. The longitudinal section also shows the pipe connections discharging the various fractions from the casing 1, namely the connection 7 for the fraction carrying heavy concentrations of heavy dirt and the connection 8 for the fraction carrying heavy concentrations of light dirt. The heavy dirt connection 7 is connected substantially tangentially to the periphery of the casing 1.The light stuff outlet connection 8 lies in an end wall 20 of the casing, at the opposite end to a sieve 10, and is disposed coaxiaily with respect to the axis of rotation of the rotor 2 rotating in front of the sieve 10. This rotor produces a turbulent flow in the casing 1, which is here in the form of a circular cylinder, with very low pressure around the axis of rotation. The sieve 10 is disposed in front of the accepted stuff outlet chamber 3, to which an accepted stuff pipe connection 19 is connected. The rotor is driven by means of a shaft 4 and coupling flange 5. Owing to the fact that the light stuff collects predominantly at the axis of rotation, that is to say in the zone of lowest pressure, a fraction with a heavy accumulation of light stuff is discharged through the light stuff outlet connection 8.However, it is naturally not possible to achieve here the best possible necessary separation of light stuff, with only a single passage of the stuff being sorted. A proportion of the stuff, which has predominantly been freed of heavy and coarse dirt but still contains large proportions of light dirt, that is to say particularly films of smaller dimensions, is therefore fed back through a connection 9, this proportion advantageously consisting of the material which is discharged from the heavy dirt connection 7 and has already undergone intermediate sorting. The intermediate sorting is in fact effected by means of a hydrocyclone which, although it can separate heavy dirt, cannot adequately further separate light dirt.

Through the construction of the casing extension 16 in accordance with the invention, so that it forms an annular chamber concentric with the outlet connection 8, it is possible to introduce without disturbance into the pulper the proportion of stuff which has undergone intermediate sorting, so that the operation of the pulper and the discharge of the various fractions are not disturbed, but on the contrary the amount of light stuff discharged is substantially increased.

A still further improved action is achieved if the funnel-shaped guide wall 13 shown in Figure 1 is provided for this purpose. The outside diameter of the annular chamber 11 for this proportion can be selected so that the cross-sections of the outlet connection 8 and of the annular chamber 11 are substantially equal. The annular chamber may however also have a smaller or larger area than the outlet connection 8, depending on existing circumstances. The length of the annular chamber 11 can be so selected that this length is slightly larger or smaller than the outside diameter of the annular chamber. It will naturally be ensured that the length of this chamber is not made too great, in order to limit the length of the pulper.The pipe connection 9 for the aforesaid proportion of stuff is best connected, as illustrated, in such a manner that it extends radially and obliquely in relation to the interior of the casing. An inclined connection, which in addition is substantially tangential, as shown in dash-dot lines in Figure 2, is also possible but not necessary.

For the sake of better accessibility of the pipes, the casing extension 16, which forms the annular chamber in conjunction with the light stuff outlet pipe connection 8, is disposed outside the casing 1. The best possible mode of operation of the arrangement is achieved, because of the turbulence assisting action, if the casing extension projects into the interior of the sorter.

Amongst other items, valves (not shown) are also provided in the individual pipe connections and serve to adjust optimum flow.

Figure 3 shows in longitudinal section a sorter 21 operated undersuperatmospheric pressure, known for short as a vertical sifter. Here the inlet pipe connection is designated 26, the outlet pipe connection for accepted stuff is designated 29, the outlet connection for the fraction containing the heavy dirt is designated 27, and the outlet connection for the fraction containing the light dirt is designated 28.

The returned proportion is fed through the connection 19' into the annular chamber 11' formed in the casing extension 16' and disposed coaxially to the connection 28. Here a funnel shaped guide wall 23 adjoining the light stuff outlet connection 28 axially towards the interior of the casing is likewise provided. In this vertical sifter a rotor having blades or sorting arms 25 extending substantially parallel to the axis of rotation 14 rotates in front of a rotationally symmetrical sieve 24. Through this sieve the accepted stuff passes into the accepted stuff outlet connection 29. In this sorter there is also substantially a rotational flow of the fibre suspension inside the chamber formed by the sieve 24. The rotor 22 is driven by means of the shaft 30 by a drive (not shown) which may for example be transmitted through belt pulleys and belts from a motor.The shaft has here an overhung mounting indicated at 50.

It remains to be mentioned that in this sorter, which is inserted at a later stage in the treatment process of the fibre suspension than the previously described sorter, upstream of the paper-making machine, only a scarcely detectable proportion of lightstuffwill in certain circumstances be taken off through the light stuff outlet connection 28. Nevertheless, for reasons of systematics the term "light stuff outlet connection" is selected here. The situation is that at least air contained in the fibre suspension is also taken off here, so that, taking an average over the whole of the constituents of the fibre suspension, a specifically relatively lighter stuff is obtained. Figure 4 shows a hydrocyclone having a tangential inlet 36, this tangential admission giving rise to turbulence in known manner.This turbulent flow is at first directed downwards in the radially outer region of the casing 31, but is then reversed, the heavy particles of dirt being separated through the outlet 37, so that the lighter fraction, which is here the accepted stuff, flows to the accepted stuff outlet connection 38. Here again the annular chamber 11", formed concentrically with respect to the accepted stuff outlet 38, is provided in the casing extension 16" for the admission of a returned proportion entering through the connection 19". This returned proportion may, for example, be at least a part of the accepted stuff passing out through the connection 38, since this material may also in certain circumstances contain relatively large amounts of particles of light dirt, which should really have been discharged through the light dirt outlet pipe 39. As is well known, it has in fact been found that light dirt can still be separated from the accepted stuff directly on or near the axis of rotation 14. However, this is naturally not done absolutely completely.

The invention is not restricted to the details of the foregoing embodiments.

Claims

1. A device for sorting fibre suspensions in the paper industry, the sorter having a separate outlet for a relatively light stuff fraction (light fraction), comprising a substantially rotationally symmetrical casing in which a rotational flow of the fibre suspension can be produced, means for introducing a proportion of the stuff for the purpose of aftercleaning in the proximity of the axis of rotation of the rotational flow, an end wall of the sorter casing having the outlet pipe connection for the light fraction, disposed coaxially to the axis of rotation, and there being an annular chamber which is formed concentrically with respect to the outlet pipe connection for the light fraction in a casing extension and into which a feed pipe for the said proportion of the stuff leads, the said annular chamber opening into the casing substantially in the direction of the axis of rotation.

2. A sorter according to Claim 1, in which the feed pipe for the said proportion of the stuff extends obliquely in the direction of the casing and radially inwards with respect to the axis of rotation and is connected to the casing extension with its centre axis approximately at a distance equal to the outside diameter of the annular chamber from the outlet end of the casing extension.

3. A sorter according to Claim 1 or Claim 2, having a guide wall which widens radially outwards in funnel shape from the annular chamber and which is associated with the outlet connection for the light fraction.

4. A sorter according to Claim 4, in which the guide wall closely adjoins the outlet connection for the light fraction.

5. A sorter according to any one of Claims 1 to 4, provided with separate outlet for light and heavy dirt, the sorter having a rotor which rotates in front of a substantially plane sieve which in conjunction with the end wall of the casing at the opposite end to the outlet connection for the light fraction forms an accepted stuff outlet chamber.

6. A sorter according to any one of Claims 1 to 4, having a rotor which rotates coaxially with the turbulent flow in front of a rotationally symmetrical sieve coaxial to the axis of rotation.

7. A sorter according to any one of Claims 1 to 4, in which turbulent flow is produced solely by the tangential introduction of the suspension into a relatively elongated rotationally symmetrical casing, for example a hydrocyclone, in which the outlet connection for the light fraction is provided on the end wall of the casing at the fibre suspension inlet end.

8. A device for sorting fibre suspensions constructed and arranged substantially as herein described, with reference to Figures 1 and 2, or Figure 3, or Figure 4 of the accompanying drawings.