EP0886001B1 - Process and apparatus to disperse a paper fibers slurry - Google Patents

Abstract

Process for dispersing a fibrous paper web which comprises a substantially consistent fibrous paper material. The process includes loosening and pulverizing a fibrous paper material into a fine, friable fibrous material; guiding the fine, friable fibrous material into a vapor chamber in which at least one of a gaseous and vaporous heating medium mixes, calefies, and disperses the fine, friable fibrous material; and dispersing the fine, friable fibrous material in a disperser zone, the disperser zone and the vapor chamber being located in one device. A device for dispersing a fibrous paper web which comprises a substantially consistent fibrous paper material. The device includes an inlet for fibrous paper material, a stationary stator, and at least one rotatable rotor. The stator and the at least one rotor form a pulverizing zone including a pulverizing element located near the inlet for the fibrous paper material, the pulverizing element including least one of scrapers and knives for pulverizing the fibrous material into a fine, friable material; a vapor chamber forming a ring about the pulverizing zone, the vapor chamber being for calefying the fine, friable material formed by the pulverizing element; and a dispersing zone including at least one row of teeth on the stator and at least one row of teeth on the at least one rotor which can be moved relative to the at least one row of teeth of the stator.

Description

The invention relates to a method for dispersing paper pulp according to the Preamble of claim 1.

Procedure of the above Be e.g. needed to improve the quality of fiber, which was obtained from waste paper. It is known that pulp by Dispersing can be homogenized and thereby significantly improved. there in many cases a fiber material is used that has a dry content between 15 and has 35% and has been brought to a temperature far above that Ambient temperature. It makes sense to heat up when the Fibrous material already has the consistency required for dispersion. With this Thickening process becomes a considerable part of what was previously in the pulp Water depressed, which firstly makes its viscosity essential when dispersing increases and secondly less water needs to be heated. The most important Thickening machines are screw presses and screen presses.

In the case of a screen press, the fibrous suspension is introduced and pressed between a screen and a roller or between two screens so that the water emerges. This creates a moist fibrous web. Depending on the operating parameters, this membrane has a weight per unit area of between 500 and 2000 g / m ² , although values that differ from this can also be useful. The wet web is removed from the area of the screen or screens and must then be torn into flat pieces. Although these can easily be brought to the desired temperature, a relatively long heating-up time is required. For example, warm-up times of several minutes have to be accepted, especially if a temperature above 90 ° C is desired. The hot crumb is then fed to the disperser. The whole requires a fairly complex system.

In a screw press, the fiber suspension is between one Conveyor screw and a perforated jacket surrounding it, the Water leaks through the jacket. The resulting compact or graft expressed from the snail and breaks into pieces. These can only be in a relatively long heating-up time to the desired temperature. Another Shredding can e.g. in a shredder screw or a system with counter rotating Rotors are made, which is very expensive.

A device is already known from WO 96/18769 A1, in which a device with "pulp" specified substance introduced into a screw conveyor and then in a Disk disperser is dispersed. To support the dispersion is in the Center of the disc disperser steam added. The fiber-vapor mixture then travels radially outwards from the center into the actual, between machining zone located on the disperger discs. The substance should be steam can be mixed and crushed and dispersed at the same time. With this known Device should only be able to heat the substance to a limited extent.

It is therefore an object of the invention to provide a method with which the Shorten heating times and at the same time the equipment and space to reduce considerable construction effort.

This object is achieved by the features mentioned in the characterizing part of claim 1 completely solved. Claim 15 defines an apparatus for performing the method. Preferred embodiments are defined in the dependent claims.

With the help of the method it is possible, firstly, with little effort to produce enough fine crumbs that heat up quickly lets and secondly, the expenditure on equipment is relatively low, since the processes Shredding, heating and dispersing in a single device have it carried out.

The highly consistent paper pulp can either be used as a plug or in the form of a loose, just pre-shredded high consistency fabric directly into the clothing of one Dispergers can be entered. The fabric is then seen from the direction of flow the first crushing stage of the disperser is detected, crushed and swirled, whereby the fine fiber crumbs arise. By feeding steam into that of the first Crushing stage downstream of the following zone, the material is then cut to the necessary Temperature warmed up, due to the previous intensive comminution a relatively short heating-up time is sufficient The actual dispersion, i.e. The material properties change in the dispersion zone, which changes connects downstream.

Fig. 1

die grundsätzlichen Verfahrensschritte anhand eines erfindungsgemäß ausgestalteten Dispergers;

Fig. 2a+b

ein Zerkleinerungselement in 2 Ansichten;

Fig. 3

eine Variante mit geänderter Stoffzuführung und geändertem Dampfraum;

Fig. 4

Teil des Dampfraumes in Draufsicht, schematisch.

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

Fig. 1

the basic method steps using a disperger designed according to the invention;

2a + b

a shredding element in 2 views;

Fig. 3

a variant with a modified material feed and a modified steam chamber;

Fig. 4

Part of the steam room in top view, schematic.

1 shows the method according to the invention using a method that can be used for this purpose Contraption. In this solution, the highly consistent paper pulp S is used as a plug 1, coming from the thickening press 15, directly into the area of the disperser set pressed. The version shown here is a disperger set with a radial flow of material, with a stator 2 and a rotor 4. In principle, could an axial disperger or kneader can also be used. The Disperger 3 shown here is loaded radially inside, for which a first in the center of the rotor 4 Comminution element 5 is attached, which e.g. wing-shaped or cross-shaped Crushing strips 6 can carry. The stopper 1 pressed here becomes peeled off or grated and thereby broken up into fine crumbs, but here are not drawn. Primary stator teeth 7 brake the fabric and lengthen it thereby its dwell time in the radially outer steam chamber 8 Impact of the fiber material thrown off by the comminution element 5 becomes this further divided. Crushing down to the size of the speck is advantageous Keep heating time low.

The vapor space 8 is essentially ring-shaped and does not contain any of the mechanical ones Dispersion teeth. As is known, dispersion is brought about by the fact that Teeth are moved relatively close together at a relatively high speed and the fiber between them is subjected to strong shear forces. This function only has that which adjoins the steam chamber 8 radially further outside Dispersing zone 9. There are then high peripheral speeds of the dispersing teeth possible and advantageous, while those lying radially further inside Crushing bars 6 are slower and therefore the incoming stopper 1 shred gently. The substance is therefore not within the vapor space 8 mechanically dispersed. If necessary, internals 18 (FIG. 4) can be present be that slow down the movement of the circulating fabric and loosen the fabric. The will be explained later. Heating steam ST is added via the steam pipes 11 brought into contact with the fiber. He is swirled in the steam room 8 or at least kept loosened so that it is well penetrated by the steam can. The heating is essentially achieved by condensation of the steam, i.e. Steam is constantly replenished. The make-up improves the swirl and the loosening of the fiber crumbs. After the dispersion, the dispersed falls Fibrous material S 'through outlet 13.

The vapor space 8 is light due to the plug 1 and the substance in the dispersion zone 9 to seal against the outside world. The closure of the dispersion zone 9 is also advantageous by a throttle ring 10 because this controls the degree of filling of the set leaves. In connection with the invention is a high and uniform degree of filling particularly advantageous in the dispersion zone 9, because otherwise the outer diameter of the Disperger set should be chosen very large to the specific desired To be able to transfer work to the pulp. Such a throttle ring is e.g. by DE 195 23 704 A1 is known.

Considered overall, this results in a procedure according to the invention high impact in the smallest space, which is why very compact devices are possible. The size of the steam room 8 must of course be determined so that the crumbs in it have the residence time required for heating. Approximately 1 to 2 seconds of dwell time are required; this time depends on the desired temperature and the fineness of the crumb.

2a and 2b show a possible embodiment of the comminution element 5 in the Side view (2a) or top view (2b). You can see the radially aligned Crushing bars 6. Their effect is on the required crushing task matched, in particular a fiber damage especially when the fibers are still cold is to be avoided as far as possible. But they also have the task of producing the fine one Loosen up and throw off crumbs.

3 shows a further solution according to the invention with the main one The difference is that the highly consistent paper pulp is not as compact Grafting, but pre-shredded into a more or less loose form Dispersing device is entered. Such a pre-shredded material falls e.g. when the thickening has been carried out on a screen press, from which the Thickened paper pulp runs out as a wet web. By subsequent Crushing, e.g. in a snail, the fabric becomes so wide pre-crushed that it can be conveyed in screw systems. The pre-shredded material is then before entering the Disperger 3 '- as shown here in Fig. 3 - by a feed screw 16 detects and directly into the central inlet of the disperser 3 'performed. This feed screw 16 can have a stuffing effect, that is but not necessary to carry out the method according to the invention. Much more it can also be designed as a band screw, which is only on the outside diameter has a helical band 17 and comparatively promotes. With Advantage, the fabric in it can already be preheated, possibly for what existing steam lines 11 'serve. Then the crushing step gentler on fibers and later heating to dispersion temperature is faster. If the fabric is relatively loosely fed into the central inlet of the disperser, it does not offer the support of a solid plug, as shown in Fig. 1. The However, fine comminution is possible because the material is less Radial speed has than the shredding bars 6, which on the Crushing element 5 are attached. Often the primary stator teeth 7 in addition to their slowing effect, they promote comminution.

In the embodiment shown in FIG. 3, the heating steam ST is added on radially outer edge of the steam chamber 8 and thus different than in Fig.1. This is supposed to Countercurrent heating can be achieved, which of course is a corresponding Centrifugal field in the steam room 8 provided. Depending on the fed - and condensed - amount of steam, the steam swirls the crumb in the steam room additionally on. Similar considerations regarding the optimal dam addition locations are also in other configurations, e.g. to start according to FIG. 1.

To ensure sufficient loosening of the fine fiber crumbs in the steam chamber 8 ensure, further installations can be provided in this area, which exert a braking and / or loosening effect on the fiber. The can be pins or small wings, which are to be designed so that they have the volume the steam room 8 does not significantly reduce. Conceivable internals 18 and 18 'are 4, according to which the internals are anchored on the stator side. Such Baffles 18, 18 'can e.g. round, rounded or with baffle edges Be pens.

It is important that the fine crumb material in the steam room is sufficiently loose to the To allow heating steam to reach all free surfaces.

The inner row of the dispersing teeth 19 shown here belongs to the rotor. The fabric passes between these dispersing teeth and is pressed through the dispersing zone 9. In other cases, it can be advantageous to radially outer the vapor space through a To complete the row of teeth belonging to the stator.

Claims (22)

1. Method of dispersing a paper slurry, which starts off with a highly compact paper slurry (S), converts this in a comminuting stage to a fine crumb, and then mixes and heats it with a gaseous or vaporous heating medium, and disperses it in a dispersing zone (9) lying between the stator (2) and rotor (4) of a disperser, characterised in that the paper slurry (S) is brought to a loosened state, in that it is mixed and heated with the heating medium in an annular steam chamber (8), in that it is then passed into the dispersing zone (9), in which the fibre crumb is dispersed, and in that the same apparatus is used for mixing the paper slurry (S) with the heating medium, for heating and for dispersing.
2. Method according to claim 1, characterised in that the comminuting stage, loosening, heating and dispersion are carried out between the stator (2) and rotor (4) of a disperser, the stator (2) and the rotor (4) each being provided with concentric rows of teeth, and the teeth extending axially into the gaps in the opposite and corresponding fittings.
3. Method according to claim 1 or 2, characterised in that the fine fibre crumbs have a maximum thickness of at most 5-mm.
4. Method according to claim 1, 2 or 3, characterised in that the fine fibre crumbs have a maximum longitudinal extent of at most 10 mm.
5. Method according to claims 1, 2, 3 or 4, characterised in that the fine fibre crumbs are swirled in a heating medium and are in a swirling state at least for most of the necessary heating time.
6. Method according to one of the preceding claims, characterised in that the average dwell time of the fine fibre crumbs in the steam chamber (8) is between 0.5 and 3 sec..
7. Method according to one of the preceding claims, characterised in that the heating medium is heating steam (ST), and is supplied in the radially outer region of the steam chamber (8).
8. Method according to one of claims 1 to 6, characterised in that the heating medium is heating steam (ST), and is supplied in the radially inner region of the steam chamber (8).
9. Method according to one of the preceding claims, characterised in that in the steam chamber (8) means are provided to brake the movement of the fine fibre crumbs located therein.
10. Method according to one of the preceding claims, characterised in that the radial movement of the slurry in the dispersing zone (9) is choked.
11. Method according to one of the preceding claims, characterised in that the maximum speed of the tool triggering the comminution stage is between 10 and 30 m/sec..
12. Method according to one of the preceding claims, characterised in that the comminution stage is carried out with means which act directly on the plug of paper stock emerging from a drainage worm.
13. Method according to one of claims 1 to 11, characterised in that the comminution stage is carried out with means which act on slurry particles, which have been obtained by pre-comminution of a damp slurry web which has run down from a screen head extruder.
14. Method according to one of the preceding claims, characterised in that the highly compact slurry is also heated before the comminution stage.
15. Apparatus for carrying out the method according to one of the preceding claims, having dispersing equipment, which comprises at least a stationary stator (2) and at least one rotating rotor (4), in which in a dispersing zone (9) a plurality of rows of teeth are movable relative to one another with clearance of at most 3 mm, wherein the rotor (4) contains a comminuting tool, which is located in the vicinity of the inlet aperture for the highly compact slurry (S) to be dispersed, characterised in that the comminuting tool is provided with graters or blades, and in that an annular steam chamber (8) is connected upstream, which is for heating the fine crumb material formed in the comminution zone and in that the dispersing zone (9) follows on radially further out.
16. Apparatus according to claim 15, characterised in that the steam chamber (8) is defined upstream by a stator row of teeth, the associated primary stator teeth (7) extending up to a gap of at most 3 mm from the rotor.
17. Apparatus according to claim 18, characterised in that the primary stator teeth (7) have a spacing of at least 50 mm in the circumferential direction.
18. Apparatus according to claim 15, 16 or 17, characterised in that the steam chamber (8) is defined downstream by a rotor row of teeth, wherein the associated primary rotor teeth (7) extend up to a gap of at most 3 mm from the rotor.
19. Apparatus according to claim 15, 16, 17 or 18, characterised in that the steam chamber (8) is connected to a steam supply line by steam ducts (11).
20. Apparatus according to claim 15, 16, 17, 18 or 19, characterised in that the dispersing zone (9) is closed radially externally by a choke which makes the through-flow cross-section adjustable.
21. Apparatus according to claim 20, characterised in that the choke is formed by a choke ring (10) provided with apertures, it being possible to adjust the choke by rotation of the choke ring (10).
22. Apparatus according to claim 20, characterised in that the choke is formed by a choke ring (10), it being possible to adjust the choke by axial displacement of the choke ring (10).

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