WO2014135335A1

WO2014135335A1 - Fibrous material preparation

Info

Publication number: WO2014135335A1
Application number: PCT/EP2014/052508
Authority: WO
Inventors: Werner Brettschneider; Albrecht FALK; Alexander Peschl; Fanny Balke
Original assignee: Voith Patent Gmbh
Priority date: 2013-03-07
Filing date: 2014-02-10
Publication date: 2014-09-12

Abstract

The invention relates to a method for forming and treating a fibrous material suspension that is suitable for the production of paper for graphical or hygiene purposes, or cover layers for boxboard or packaging papers, in which said fibrous material suspension is at least partially conducted from a dissolution stage (3) to a dewatering stage (9) via a plurality of treatment stages. The overheads involved in treating the fibrous material suspension should be reduced as a result of the material density of the fibrous material suspension lying at at least 2% between the outlet of the dissolution stage (3) and the inlet of the dewatering stage (9).

Description

Fiber Preparation

The invention relates to a process for the formation and treatment of a pulp suspension suitable for the production of graphic or hygiene papers, special papers or cover layers for cardboard or packaging papers, wherein the pulp suspension from a dissolving stage over a plurality of treatment stages at least partially results in a dewatering process. Stage is performed. In the dissolution stage, the separation and separation of the fibers and the waste paper and the detachment of the printing inks. This is followed by several process steps for the treatment of the pulp suspension until the pulp suspension meets the required parameters and can be transferred to a machine for producing a fibrous web.

In the recycling of waste paper for graphic papers, the entire pulp stream is usually passed through several treatment stages together.

The pulp suspension before a full or partial flow flotation usually passes through a hole sorting and a heavy-particle cleaning.

This is also relatively expensive because of the large volume flows to be processed.

The object of the invention is therefore to reduce the effort for the treatment of the pulp suspension without significantly affecting the quality of the finished material produced.

According to the invention, this object is achieved in that the consistency of the pulp suspension between the outlet of the dissolving stage and the inlet of the first dewatering stage of the total flow or a partial flow of the pulp suspension is at least 2%. Due to this relatively high consistency, the amount of pulp suspension to be treated decreases considerably, which is why the corresponding treatment units can be made smaller and require less energy. It is deliberately accepted that some treatment units work somewhat less efficiently at these high densities, especially hydrocyclones for cleaning the pulp suspension.

If only a partial stream of the pulp suspension is fed to a dewatering stage, this partial stream should be as large as possible in the interests of a broad utilization of the advantages and preferably comprise more than 50% of the pulp suspension to be treated.

Since dilution generally occurs in the treatment of the pulp suspension, the consistency of the pulp suspension at the outlet of the dissolution stage should be at least 4%, preferably at least 4.5%, and in particular between 4.5 and 5%.

In particular, HC pulpers are suitable for this purpose. In this case, the container should have one or more interconnected truncated cones, the largest diameter of which adjoins the side wall of the container and which are arranged so that their inner diameter decreases from top to bottom. The pulper can advantageously be supplemented by flow barriers on the side wall of the container, which brake the circumferential flow and guide the pulp suspension to the center and thus support the dissolution.

In this case, the purification of the pulp suspension between the outlet of the dissolution stage and a first sorting or fractionating stage to form a clean fine fraction with a high proportion of short fibers and a coarse fraction with a high proportion of long fibers exclusively via one or more Hydrocyclones take place.

The first hydrocyclone acts as a heavy duty cleaner, the consistency of the Fibrous suspension in the first hydrocyclone between 4 and 5%, preferably between 4.3 and 4.7%.

For hydrocyclones, purification, i. in particular the discharge of heavy parts using a centrifugal field. This cleaning already sufficiently relieves and protects the following fractionation stage.

In order to improve the efficiency of the cleaning of the hydrocyclones, especially at high material densities, its inner surface has a polygonal cross section in the area of the heavy part outlet.

The sorting or fractionating stages which are generally used here already work with relatively high overflow or reject rates. Therefore, they can also easily cope with the increased by the omission of the hole or slot sorting (gross sorting) increased Störstofffracht. Because of operational safety, the first or only fractionating stage should be formed by a slot sorter having a sieve element with sieve openings in the form of slots having a slot width of at most 0.2 mm, which is rotationally symmetrical about a sieve axis.

Accordingly, the pulp suspension is passed through slots for the first time during this fractionation.

After cleaning the pulp suspension, at least the coarse fraction is passed through a dewatering step. As a result, the higher consistency at the treatment stages leads to improved efficiency.

In the production of tissue paper, a scrubber is usually used as the dewatering stage, which simultaneously serves for deashing. Depending on the type and quality of the pulp suspension, it may be advantageous when the coarse and fine fractions are passed together through at least one dewatering stage or via separate dewatering stages.

If the coarse and fine fractions pass through a common dehydration step, they should have separate chambers for the thickening of both fractions, but preferably the filtrate is removed together.

To minimize the effort but only the coarse fraction, but not the fine fraction can be performed on a dewatering stage. However, the fractions can also be reunited and pass through one or more drainage stages together.

In order to be able to remove the hydrophobic impurities from at least part of the pulp suspension stream, the fine and / or coarse fraction should pass through at least one flotation stage.

Since the fine fraction often already meets the required qualities, it is not absolutely necessary that this passes through a further sorting through holes or slots or even a treatment stage in the form of a sorter or a hydrocyclone or a flotation stage. However, this does not preclude joint treatment of any recombined fractions with such aggregates.

However, a separate treatment of the fine fraction by means of flotation can be advantageous for achieving the highest purities and the overall quality increase, whereby the corresponding flotation units can be made smaller and thus more cost-effective.

Irrespective of this, at least one treatment stage of the coarse fraction should be formed by a disperser or kneader or refiner in order to replace the To ensure printing inks and dirt particles from the fibers.

Because of the high consistency, the drainage stages are advantageously formed by screw presses, disc thickeners or scrubbers.

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

In the accompanying drawing, Figures 1 to 4 show different

Plant schemes for pulp treatment.

The pulp suspension should be at least partially formed from waste paper and be suitable for the production of graphic papers or tissue papers or specialty papers or upper layers (white blanket) of cardboard and packaging papers.

Common to the four different versions that the stock preparation a dissolution level 3 for the dissolution of the waste paper and possibly other fibers in the form of a pulp or similar. and at least one of the following sorting / fractionating stage 5 for forming a long fiber-enriched coarse 1 and a short fiber-enriched fine fraction 2, wherein at least the coarse fraction 1 is fed to a dewatering stage 9 and the consistency of the pulp suspension between the spout the dissolution stage 3 and the inlet of the first dewatering stage 9 is at least 2%. This high consistency reduces the effort and energy for the treatment of the pulp suspension considerably, even if it can affect the effectiveness of certain treatment units, such as the hydrocyclones.

In addition, no further sorting stage with hole or slot sorting is arranged before the first fractionating stage 5. In order to be able to ensure this high consistency throughout, is the Density of the pulp suspension at the outlet of the dissolution stage 3 between 4.5 and 5%.

In particular, dissolving drums or HC pulpers are suitable for this purpose. The cleaning of the pulp suspension stream between dissolution stage 3 and first fractionation stage 5 takes place exclusively via one or more purification stages 4 in the form of one hydrocyclone each. These cleaning stages 4 may be, for example, a high consistency cleaning stage or a heavy cleaning stage, which are passed through successively.

The consistency of the pulp suspension in the first hydrocyclone is between 4.3 and 4.7%.

Hydrocyclones are capable of concentrating and extracting heavy particles in pulp suspension by centrifugal forces. For this purpose, the pulp suspension is pumped tangentially into the interior of the hydrocyclone via an inlet and rotated in the downwardly conical interior. While the purified pulp suspension is discharged as accepts via the centrally arranged overhead spout, the heavy parts reach the Schwerteilauslass via a connecting part whose inner surface forms a polygon.

This shape of the connecting part, the rotation can be reduced towards Schwerteilauslass, which in turn reduces wear.

The fractionation stage 5 is designed as a slot pressure sorter and separates the pulp suspension stream into a coarse fraction 1 with a high proportion of long fibers and / or high impurity content and a fine fraction 2 with a small proportion of longer fibers and / or a lower impurity content.

Since the first fractionation stage 5 is already operated at a relatively high reject rate (preferably 20-50%), it can easily process the higher amount of contaminant due to the lack of hole sorting prior to fractionation. After the fractionation, the coarse fraction 1 is passed by way of example according to FIG. 1 through one or more sorting stages 7, one or more dewatering stages 9, a disperser 10 and / or refiner and, in the case of high brightness requirements, also a bleaching stage 11 and then again merged with the fine fraction 2.

Subsequently, the pulp suspension then passes through a flotation stage 8 and, if necessary, also one or more dewatering stages 9 and a bleaching stage 1 1. In contrast, the coarse fraction 1 in Figure 2 passes through only one or more sorting stages 7 before both fractions 1, 2 are reunited.

Subsequently, the pulp suspension can be treated according to the requirements.

Here, the pulp suspension successively passes through a flotation stage 8, possibly a sorting stage 7, one or more dewatering stages 9, a disperser 10, possibly a bleaching stage 1 1, if necessary, a flotation stage 8 and possibly even one or several dewatering stages 9 and a bleaching stage 1 1. In FIG. 3, the coarse 1 and the fine fraction 2 are treated separately, with only the coarse fraction 1 passing through a disperser 10.

Specifically, here is the coarse fraction 1 via one or more sorting stages 7, one or more dewatering stages 9, the disperser, possibly a bleaching stage 1 1, a flotation stage 8, possibly a cleaning stage 4 and one or several dewatering stages 9 and the fine fraction 2 via a flotation stage 8, a sorting stage 7, possibly a cleaning stage 4 and one or more dewatering stages 9 passed.

Thereafter, the combination of both fractions 1, 2 and a common treatment of the pulp suspension, for example in a dewatering stage 9 (not shown) and / or a bleaching stage 1 1 takes place here, too. The plant shown in FIG. 4 has two fractionating stages 5, 6. In this case, the coarse fraction 1 of the first fractionating stage 5 is passed through one or more sorting stages 7 and, after being brought together with the corresponding fine fraction 2, passed via a flotation stage 8 to the second fractionating stage 6.

The coarse fraction 1 of the second fractionating stage 6 then passes through a sorting stage 7, one or more dewatering stages 9, a disperser 10, possibly a bleaching stage 11 and a flotation stage 8 before both fractions 1, 2 are reunited become. This is followed by the common running through possibly a cleaning stage 4, one or more dewatering stages 9 and possibly also a bleaching stage 1 1 at.

In order to increase the fiber yield, the heavy-particle cleaning stage 4 between the dissolution-3 and the first fractionation stage 5 can also be formed by a plurality of hydrocyclones. Advantageously, the reject of the first hydrocyclone enters a second hydrocyclone. While the Accept this second hydrocyclone is recycled to the inlet of the first hydrocyclone, the reject of the second hydrocyclone passes into a third hydrocyclone, the Accept of the coarse fraction 1 is mixed. As drainage stages 9 are particularly suitable screw extruder, disc filter or scrubber because of the high density.

As a result, the consistency of the entire process is set to a higher level in all versions, which considerably reduces the volume flows of pulp suspension to be treated. This in turn allows smaller aggregates to treat the pulp suspension and lowers the energy required for this.

A deterioration in efficiency due to the higher consistency, especially in the case of deinking flotation, may be due to a higher number of Ventilation points and / or the inclusion of, the ventilation assisting devices are compensated. The higher investment costs are quickly compensated by the greatly reduced energy costs for plant operation.

Claims

Claims 1. Process for the formation and treatment of a pulp suspension suitable for the production of graphic or hygienic papers or cover layers for board or packaging papers, wherein the pulp suspension from a dissolving stage (3) over several treatment stages at least partially to a dewatering stage (9 ), characterized in that the consistency of the pulp suspension between the outlet of the dissolving stage (3) and the inlet of the first dewatering stage (9) is at least 2%.

2. The method according to claim 1, characterized in that the consistency of the pulp suspension at the outlet of the dissolving stage (3) is at least 4%, preferably at least 4.5% and in particular between 4.5 and 5%.

3. The method according to claim 1 or 2, characterized in that the cleaning of the pulp suspension between the outlet of the dissolution stage (3) and a first fractionation stage (5) to form a fine fraction (2) with a high

Share of short fibers and a coarse fraction (1) with a high proportion of long fibers exclusively via one or more hydrocyclones.

4. The method according to claim 3, characterized in that the consistency of the pulp suspension in the first hydrocyclone between 4 and 5%,

preferably between 4.3 and 4.7%.

5. The method according to any one of claims 3 to 4, characterized in that the

Fractionation stage (5) is formed by a slot sorter.

6. The method according to any one of claims 3 to 5, characterized in that at least the major part of the pulp suspension by a

Drainage stage (9) is performed.

7. The method according to any one of claims 3 to 6, characterized in that the coarse (1) and the fine fraction (2) together over at least one

Drainage stage (9) are performed.

8. The method according to any one of claims 3 to 6, characterized in that the coarse (1) and the fine fraction (2) via separate dewatering stages (9) are guided.

9. The method according to any one of claims 3 to 6, characterized in that only the coarse fraction (1) via a dewatering stage (9) is guided.

10. The method according to any one of claims 3 to 9, characterized in that the

Fine (2) and / or the coarse fraction (1) passes through at least one flotation stage (8).

1 1 .Verfahren according to one of claims 3 to 10, characterized in that only the coarse fraction (1) is passed through at least one treatment stage in the form of a sorter or hydrocyclone or a flotation stage (8).

12.Verfahren according to any one of the preceding claims, characterized

characterized in that the dewatering steps (9) are formed by screw presses or disc thickeners or scrubbers.