JPS5857560B2 - Method for forming continuous material webs of fibrous particles from highly concentrated suspensions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for the formation of a continuous material web made of fibrous particles from a suspension.

The present invention is designed for highly concentrated pulp suspensions and is suitable for use in paper machine head boxes.
dbox).

The high concentration headbox basically consists of a lateral distribution device, a forming area and an outlet duct from which the pulp suspension is placed on an endless wire,
further processed.

The horizontal distribution device is composed of a horizontal distribution channel, distribution pipes arranged over the entire width of the machine, and a mixing chamber.

When a suspension of water and fibers enters a tube with a sufficiently high fiber concentration, it forms a cohesive fiber network surrounded by a thin boundary layer of water.

The higher the fiber concentration, the stiffer the fiber network.

Therefore, in the paper produced, strands are generated by the water layer formed in the distribution pipe of the horizontal distribution device, and a concentration route and a velocity route are generated and appear after the distribution pipe. .

In order to balance these strands, the suspension and the aqueous layer can be mixed in a mixing chamber after the distribution tube by supplying distributed agitation energy.

To date, although tests have been repeated using distribution pipes of various designs and mixing chambers of various designs (see the Swedish Patent No. 355615, No. 366787
No. 362,458 and No. 385,029), it was not possible to completely solve the problems related to horizontal distribution.

The cross section of the mixing chamber must be large enough to allow effective mixing of the concentration route.

To obtain a satisfactory mixing result, one of the pinches between the distribution tubes must be
A minimum extension of the order of /2 is desirable.

Such a large cross-sectional area makes it difficult to prevent the formation of large debris clusters, and the result is that the paper produced has a somewhat debris-filled texture.

Furthermore, since the outlet from the mixing chamber is referred to, the word "su" is also added when referring to feeding.

In order to reduce the velocity route generated by the distribution pipe, the pressure can be reduced at the outlet of the mixing chamber.

In order to obtain a sufficient effect, it is necessary to limit the size to such a small size that the risk of word bases becomes extremely large.

In accordance with the invention as set forth in the characterizing part of the claims, a rotational flow is produced in the mixing chamber and a deflection of the suspension at an angle between 900 and 180° at the exit from the chamber. By this, the velocity route and the concentration route can be balanced, and at the same time, the swarming by fiber debris at the exit from the mixing chamber is also prevented.

The cross-section of the mixing chamber makes it possible to suppress the formation of fibrous debris regardless of the large dimensions required for satisfactory mixing and the shear stress to which the suspension is subjected in the rotating flow. shape (eg, oval).

The large angular change upon exiting the chamber causes a large contraction in the exit gap.

This allows the pressure drop to be quite large, but the channel dimensions do not have to be unacceptably small.

The shearing forces of the rotating flow release the fibrous debris that settles in front of the outlet, thereby preventing sludge.

An embodiment of the invention for use in a paper machine for forming sheets with high fiber concentrations will now be described in more detail - with reference to the accompanying drawings.

In the accompanying drawings, the head boxes are illustrated very schematically with respect to their shape and construction.

As mentioned above, the head box has a lateral distributor 1 and a flow channel 3, the outer part of which constitutes a damping channel 4.

The assembly of these parts and their construction are well known in the art to those skilled in the art and do not form part of this invention.

Therefore, these parts will not be described in detail here.

According to the invention, the pulp suspension is forced to flow across the machine from the end of the horizontal distributor 1 and is arranged in parallel rows along the width of the horizontal distributor 1. It is distributed into pipes 2 and, as is clear from FIG. 1, from these pipes 2 it flows into slot-shaped channels 5 having a decreasing height.

The channel 5 forms the inlet 5 of the mixing chamber 6.

The channels or inlets 5 and chambers 6 have a width that corresponds to the width of the lateral distributor 1 and the channels 3, 4.

@One side of the entry port 5 has a length dJ as explained below.
3 Deforms and transitions to wall 7.

In FIG. 1, the length of wall 7 is shown to include an angle of approximately 180 degrees.

The outlet 8 of the chamber 6 extends parallel to the inlet 5 and has a width that corresponds to the width of the chamber 6.

The wall 9 of the chamber 6 opposite the wall 7 is also curved, and the exit 8
has been transformed into.

In principle, the chamber 6 can be considered to have an elliptical cross-sectional shape provided with a tangential inlet and an outlet.

In one embodiment of the chamber 6 shown in FIG. 2, the curved wall 7 into which the inlet 5 transitions has an angle of approximately 260°.

The outlet 8 extends substantially perpendicular to the inlet 5.

As can be seen in the drawings, the inlet 5 has a plate or flap 12 on one side thereof.

The plate flap 12 is drawn down into the chamber 6 and extends across the entire width of the chamber 6.

Plate 12 performs essentially the same function as wall 9 in the embodiment shown in FIGS. 1 and 3.

Due to the design of the wall 7 and the location of the outlet 8, the angles (c) are wider than those in the example according to the drawings.

The plate 12 can be adjustably displaced backwards and forwards and/or rotated towards and away from the center of the chamber 6 in a suitable manner.

Alternatively, plate 12 may be replaced.

The angle (α) is approximately 170° in Fig. 1, and
In the figure, it is approximately 145°.

It has been found that an angle (a) between 90° and 1800° is recommended.

Since the chamber 6 is shaped to promote rotation, the suspension, after entering the chamber 6, is given a rotational or swirling motion.

If fiber debris is present at the inlet 8 leading to the narrow channel 3 and damping channel 4,
If the entrance is blocked, the suspension sliding along the wall 7 by the inlet creates a self-cleaning action, thereby releasing the fiber debris.

Fragments consisting of fibrous debris can also occur in the event of an accidental shutdown.

The base tendency does not increase at the start.

The reason is that there are no flow components directed directly towards the inlet 8.

To prevent the machine from creating an uneven or sloping material web that would result if the suspension vortex moved from one end of chamber 6 to the other, the suspension was Before reaching it, it must be divided and guided.

This is made possible by the distribution pipe 2, which divides the suspension into several sub-streams, which sub-streams are
Several small vortices are generated in the chamber 6 instead of a large vortex that can be tilted very easily.

As shown in FIG. 3, the distribution pipe 2 is arranged to reach straight into the chamber 6 and terminate tangentially therein.

Each distribution pipe 2 then terminates in a curved shape and forms part of a chamber 6 by its orifice.

Such a mechanism lends itself to efficient mixing of highly concentrated pipe suspensions.

The vortex formed in the chamber 6 serves, apart from cleaning, the entry, mixing and fluidization of the pulp suspension into the outlet 8 (disintegration of the fiber waste).

The degree of fluidization and mixing is influenced by the cross-sectional shape of the chamber 6.

The oval cross-sectional shape allows better fluidization compared to the circular one.

Due to the strong deflection of the flow along the chamber wall γ and around the edge to the outlet 8, the core shrinks considerably at the beginning of the channel 3.

This causes a pressure drop, which compensates for irregularities in the flow profile from the mixing chamber.

The pressure drop and energy conversion occurring in chamber 6 is thus utilized not only for the fluidization of the suspension, but also for velocity and concentration equilibration across the width of the machine, which is directly related to the paper quality. used for.

Within the scope of the invention, it is of course possible to connect one or more chambers 6 in series after the first chamber to intensify the effect, or alternatively to connect several chambers in parallel. It is also possible to form a plurality of layers at the same time by connecting them.

Furthermore, it is also possible to change the shape of the chamber walls 7 and 9, respectively, in the same machine or chamber by assembling the chamber 6 in the form of disassembly and replaceable parts (not shown).

The turning edge between the wall 7 and the outlet 8, i.e. the deformation, can also be made adjustable by constructing the wall by a rotating sleeve which can be made to project more or less on turning towards the opposite wall 9. Conceivable.

These means as well as the technical solution of the adjustment of the plate 12 do not represent any technical difficulty for a person skilled in the art and are therefore not included as part of the invention.

[Brief explanation of the drawing]

1 is a sectional view of a first embodiment of the device according to the invention in one type of head box, FIG. 2 is a sectional view of a second embodiment of the device in a head box of one type, and FIG. FIG. 6 is a cross-sectional view of a third embodiment of one type of head box; In the drawing, 1 is a horizontal distributor, 2 is a pipe, 3 is a flow path, 4 is a damping flow path, 5 is an inlet, 6 is a mixing chamber, 7 is a curved wall, 8 is an outlet, 9
indicates a wall, and 12 indicates a board.

Claims (1)

Claims: 1. In a method for forming a continuous web of material filled with fibrous particles from a highly concentrated suspension: a suspension in the form of several parallel sub-streams is rotated. The suspension is guided tangentially into a chamber with a promoting cross-section and rotated therein, after which the suspension is rotated between 90° and 1
A method for forming a continuous web of material consisting of fibrous particles from a highly concentrated suspension, characterized in that it is guided out of said chamber with its direction of motion deflected by an angle of between 800 and 800 degrees. 2. A method according to claim 1, characterized in that the suspension is forced to leave the chamber in a substantially tangential direction. Method of forming a material web 0 3 A method according to claim 1 or 2, characterized in that a chamber is arranged between the transverse distribution device and the outlet channel of a headbox of a paper machine. A method for forming a continuous material web of fibrous particles from a highly concentrated suspension. 4. A method according to any one of claims 1 to 3, characterized in that the suspension is highly concentrated as it flows out of the chamber. A method of forming a continuous material web of fibrous particles from a liquid suspension.