EP1069234B1 - Method and device for removing impurities from a hydrocyclone - Google Patents

Abstract

A hydrocyclone (2) having a feed suspension inlet (2), clarified liquid outlet (3), and a separator section (1,6) with a bottom outlet (7,17) for discharge of concentrated slurry, is additionally provided with at least one inlet (5) allowing addition of a diluent liquid. The diluent inlet is located at a point in the radial interior of the hydrocyclone. The diluent addition point is positioned so that the diluent exits, essentially along the axis of the separator, with the clarified liquor (3). Preferably the diluent liquid is caused to rotate, and the inlet is located at a height 'a', not more than 30% of the hydrocyclone body height (L), and may be adjustable.

Description

The invention relates to a method according to the preamble of claim 1.

As is well known, hydrocyclones are well suited to removing heavy parts by centrifugal forces or concentrate light parts in fiber suspensions and by using one to lead the intended discharge opening out of the hydrocyclone. Usually serve the removal of small metal parts, broken glass and sand and / or Styrofoam and lightweight plastics. In addition to achieving a high separation effect is the operational safety, especially the freedom from clogging of such hydrocyclones particularly important. Blockages can occur if the contaminants, e.g. in the area of the discharge opening provided for them, so collect and concentrate that there is a blockage. In many cases, a A compromise can be found between operational safety, i.e. avoiding Blockages, on the one hand, and the highest possible effectiveness of the machine (Throughput, separation effect), on the other hand. A known way to To reduce the risk of constipation on heavy-duty hydrocyclones is that a dilution liquid is supplied. For this purpose, a water supply line opens into the Edge area of the hydrocyclone e.g. through slots in the circumferential direction in the Cyclone wall. The dilution liquid then whirls up the outer layers and must penetrate the heavy dirt already concentrated in it, resulting in a Backwashing heavy parts in the accept stream can result.

Other solutions use a central tube to add the dilution liquid radially outward openings. An example is shown in CA 1 138 378 A. Also here the dilution liquid quickly reaches the wall of the hydrocyclone with the harmful effects already described. Because of the short distance and the flow of the dilution liquid directed directly onto the cyclone wall undesirable rebound effects occur. There is also increased Risk of clogging of the openings, which are to be kept relatively small. The proposed one Swirl flow leads to further disturbing eddies.

Another variant is shown in US 3,785,489. There is an axial one here Outflow ahead, however, through a number of vanes at the central Inlet of the dilution water a rotational flow can be generated Dilution water quickly expels to the outside. In addition to the disadvantages already mentioned the effect of this flow is increased even with such wings Clogging.

The invention is based on the object of a method for applying To create contaminants from hydrocyclones, with which both a reliable Removal of the contaminants is possible, as well as a good separation effect.

This object is achieved by the features mentioned in the characterizing part of claim 1 solved.

According to the invention, the dilution liquid is therefore not introduced into the Edge of the hydrocyclone, where blockage is expected, but in the middle, with axial Direction, and thus mainly in the core flow. With a sufficiently large one Inflow velocity the dilution liquid reaches the conical area of the separating room and mixes through the effect of the ones prevailing there Gradually shear flow with the surrounding pulp suspension. The kind of Dilution leads to a gentle backwashing of the fibers in the accepted fabric without that the same thing happens with already concentrated heavy parts, since these are on the wall and are not affected by the dilution water addition. Without the measures according to the invention, some of those that have already been concentrated would be concentrated Heavy parts whirled up and get into the middle of the hydrocyclone. From there then discharged with the accepted material.

Fig. 1

die Durchführung des Verfahrens an Hand eines Schwerteil-Hydrozyklons in Seitenansicht, geschnitten;

Fig. 2 - 4

Varianten zur Zugabe der Verdünnungsflüssigkeit;

Fig. 5

ein Vektordiagramm von speziellen Geschwindigkeiten am Strahlrand der Verdünnungsflüssigkeit;

Fig. 6

eine perspektivische Ansicht eines erfindungsgemäßen Hydrozyklons;

Fig. 7 und 8

jeweils eine weitere Variante des unteren Teils des erfindungsgemäßen Hydrozyklons.

The invention and its advantages are explained with reference to drawings. Show:

Fig. 1

the implementation of the method using a heavy-duty hydrocyclone in side view, cut;

Figs. 2-4

Variants for adding the dilution liquid;

Fig. 5

a vector diagram of special velocities at the jet edge of the dilution liquid;

Fig. 6

a perspective view of a hydrocyclone according to the invention;

7 and 8

each a further variant of the lower part of the hydrocyclone according to the invention.

1 shows a hydrocyclone according to the invention, roughly schematically an inlet 2 for the paper fiber-containing suspension S and an accept material outlet 3 for the cleaned suspension, i.e. the accepted substance A. The suspension S to be cleaned becomes set in rotation and enters the separating part 6 with a separating cone 1, in which usually increases the speed of rotation again. This will the contained heavy parts ST concentrated on the inner wall of the separating cone 1 and go down into the reject discharge device 17. According to the invention Dilution liquid W in the axial direction in the radially inner area of the Hydrocyclones introduced. The addition point 5 intended for this has the narrowest Position 4 of the separating cone 1 is the distance a, which is preferably in axial Seen direction, is at most a few millimeters. In special cases this can Distance a up to 30% of the length L of the hydrocyclone. Another sensible one The requirement is that the axial distance to the inlet 2 be kept as large as possible e.g. at least 70% of the length L of the hydrocyclone. The heavy parts ST fall, after they have passed the narrowest point 4 of the separating cone 1, into the Discharge chamber 8 from which it, e.g. via a discharge device 17, as reject R be removed. This discharge can take place continuously or intermittently. In the example shown here, the dilution liquid W is replaced by a simple one vertical inlet pipe 9 is added, which is an axial and at the addition point 5 against the discharge direction of the contaminants ST has an opening. This figure is supposed to also schematically illustrate that the added liquid W predominantly Part of it reaches the central core flow of the hydrocyclone. It is important that the sinking interfering substances ST as undisturbed by eddies etc. in the Discharge chamber 8 can fall. On the other hand, by adding the liquid W an undesirable thickening of the heavy fraction can be prevented as a result partial dilution is also possible in the outer areas of the separating cone 1. However, the dilution effect and associated with it weaken Cross currents, eddies, etc. successively towards the cone wall, so that a Impairment of the separation effect is not to be feared. These operations are through dashed arrows 10 indicated. If, in special cases, the rotation of the escaping dilution water flow could not be avoided Circumferential component Vu (see FIG. 5) is so low compared to the axial speed Vax to hold that the angle α between the resultant of the two vectors and the Axis does not exceed 30 °. Overall, with this type of Add dilution water to a much larger volume distributed and is therefore less harmful to the separation effect.

The liquid W is particularly advantageously at a certain axial position in the Hydrocyclone entered. Then there is only one opening at the addition point 5. It may be possible to adjust their position in the axial direction.

FIG. 2 shows a variant for carrying out the method Dilution liquid W via a curved inlet pipe 9 directly in the middle of the entered reject tube 11 below the separating cone 1. It is here the addition point 5 selected so that it is below the narrowest point 4, what but not necessarily so.

3 shows a further possibility for carrying out the method. Here is the Dilution liquid W first placed in a flow insert 16 ', in the Inside there is a central displacement body 12, so that an annular Flow cross section arises. The ring-shaped jet easily penetrates the one above part of the separating cone. It is also indicated here by arrows, like that Heavy parts ST slide down into the discharge chamber 8 near the wall. she can do this without going through the flow of the dilution liquid into the core flow of the Hydrocyclones to be flushed.

The embodiment according to FIG. 4 shows an axial inflow of the Dilution liquid W through the central inlet pipe 9. It opens inside the Flow insert 16 "via an injector 13 into a central tube 14. This allows Parts of the suspension are sucked out of the hydrocyclone and in the middle again be added, which serves the stable operation and the fiber loss minimized.

A hydrocyclone similar to that in FIG. 1 is shown in a perspective view in FIG. 6dargestellt. More constructive details are visible, but also these Drawing is still greatly simplified.

FIG. 7 essentially shows the lower part of FIG. 6 in an enlarged form. you thus recognizes more easily that the inlet pipe 9 is screwed in exactly in the middle and in one circular opening opens here above the narrowest point 4. It's easy too mount and can be adjusted axially. With the help of the axial adjustment is one better adjustment of the hydrocyclone to the existing conditions possible.

The discharge chamber 8 of FIG. 8 has a slightly eccentrically inserted one Inlet pipe 9, but this remains in the radially inner region of the hydrocyclone. The The outlet cross-section of the inlet pipe 9 keeps one from the wall of the hydrocyclone Distance b a, which is at least 10% of the inner diameter of the hydrocyclone on it Digit is. It must be guaranteed that the already concentrated Heavy parts can no longer be washed in by the dilution liquid. The Eccentricity can bring advantages in special cases, e.g. if the hydrocyclone is operated horizontally. It can also be made adjustable.

Depending on how the flow insert 16, 16 'or 16 "is designed, there are different effects when the method is carried out. This different effects are generally quite desirable. Because it is - ever according to the application, i.e. throughput, consistency, and dirt load, to just this to name - a special optimization of the process possible. In practice results a major advantage if the various flow operations are carried out in this way that they are interchangeable. Then without much effort, namely through simply exchange the differently designed flow inserts Vote. For practical reasons, one becomes anyway make sure that the flow inserts are easily removable because despite of all efforts to avoid constipation, which is not always successful.

The flow inserts shown should only show the principle. More usable Flow applications are conceivable. In particular, their dimensions can be determined by Invoice and simple tests tailored to the respective purpose become.

Claims (17)

1. Method for removing impurities from a suspension (S) containing paper fibres, by the use of a hydrocyclone with a separator cone (1), in which method a dilution liquid (W) is added to the suspension (S) in the radially inner area of the hydrocyclone, this being done at an axial distance (a) from the narrowest point of the separator cone (1) which is, at most, 30 % of the length (L) of the hydrocyclone,
   characterised in that
   the dilution liquid (W) is added with a flow direction which is directed against the axial discharge direction of the impurities out of the hydrocyclone, this being done without any spin or only with a spin whose resulting flow rate vector of the circumferential speed (Vu) and axial speed (Vax) has an angle (α) of, at most, 30° to the axis.
2. Method as in Claim 1,
   characterised in that
   the dilution liquid (W) is added with a flat jet.
3. Method as in Claim 1 or 2,
   characterised in that
   the dilution liquid (W) is added in a round jet.
4. Method as in Claim 1 or 2,
   characterised in that
   the dilution liquid (W) is added in a ring-shaped jet.
5. Method as in one of the preceding Claims,
   characterised in that
   the dilution liquid (W) is added into the centre with the aid of an injector (13), and that the injector (13) draws in from the ring-shaped area around the addition point (5).
6. Method as in one of the preceding Claims,
   characterised in that
   the dilution liquid (W) is added at an axial speed of at least 4 m/s.
7. Method as in one of the preceding Claims,
   characterised in that
   a light fraction is formed, as accepted stock (A), from a suspension (S) containing paper fibres, and that heavy particles (ST) are separated out in the form of a heavy fraction.
8. Hydrocyclone for implementing the method as in one of Claims 1 to 5, having an inlet (2) for the suspension (S) which is to be cleaned, an outlet (3) for the cleaned suspension, and a separator section (6) to which is connected, directly or indirectly, a reject discharge device (17) for the heavy particles, the hydrocyclone having at least one connection for the addition of a dilution liquid (W), the addition point (5) being located in the radially internal area of the hydrocyclone,
   characterised in that
   the addition point (5) has at least one opening, the outflow direction of which is directed axially and opposite to the discharge direction of the impurities.
9. Hydrocyclone as in Claim 8,
   characterised in that
   the addition point (5) is located at a point which is at a distance, in the axial direction, from the inlet (2) for the suspension (S) into the hydrocyclone of at least 70 % of the length (L) of the hydrocyclone.
10. Hydrocyclone as in Claim 9,
    characterised in that
    the separator section (6) contains a separator cone (1).
11. Hydrocyclone as in Claim 8, 9 or 10,
    characterised in that
    the addition point (5) is part of a flow insert (16, 16', 16") which is inserted into the hydrocyclone.
12. Hydrocyclone as in Claim 11,
    characterised in that
    the flow insert (16, 16', 16") can be replaced by a different flow insert which is arranged differently in respect of its flow action.
13. Hydrocyclone as in Claim 8, 9, 10, 11 or 12,
    characterised in that
    the cross-section of the opening is adjustable.
14. Hydrocyclone as in one of Claims 8 to 13,
    characterised in that
    the position of the opening is adjustable.
15. Hydrocyclone as in one of Claims 8 to 14,
    characterised in that
    the addition point (5) is positioned concentrically to the centre of the hydrocyclone.
16. Hydrocyclone as in one of Claims 8 to 14,
    characterised in that
    the addition point (5) is positioned eccentrically to the centre of the hydrocyclone and at a distance (b) from the inner wall of the hydrocyclone which is at least 10 % of the internal diameter of the hydrocyclone at that point.
17. Hydrocyclone as in one of Claims 8 to 16,
    characterised in that
    the addition point (5) is formed by the outlet opening of a supply pipe (9) which is introduced into the hydrocyclone below the narrowest cross-section of the separator section (6).

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