FI56416C - FRAMEWORK FOR THE CLASSIFICATION OF CLASSIFICATIONS OF FIBERS - Google Patents

Description

> rftl M1. ANNOUNCEMENT CCA4C

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Sven-Olof Sandberg, Vaggeryd, Sweden-Sverige (SE) (7U) Berggren Oy Ab (5U) Method and apparatus for pulping and sorting fibers - Förfarande och anordning för upplösning och klassificering av fibrer

The present invention relates to a method for pulping and sorting fibers and to an apparatus for applying the method. The method and apparatus are especially intended for treating unsorted fibrous material containing foreign substances, for example waste paper containing plastic-coated packaging material.

As a result of increased paper consumption, the use of waste paper as a raw material in the manufacture of paper and board has become increasingly important. One of the difficulties in using this raw material is that the waste paper is very heterogeneous. Unsorted waste paper may contain e.g. water-insoluble and difficult-to-break paper, plastic film, metal wire or cords to be removed. Although some foreign matter can be separated during the collection of waste paper, some of them and impurities can only be removed during defibering or at a later stage of treatment.

Until now, pulper has generally been used in the defibering of waste paper, i.e.

a device consisting of a tank in which a rotor with blades moves the liquid in which the defibering takes place. The fibrous material of the waste paper is decomposed in the pulper as follows:

Due to the suction of the rotor, the paper material flows towards its middle part. As the material moves toward the circumference of the rotor, the rotor blades tear the paper material into small pieces. Pieces of paper are ejected from the rotor at high speed. Due to the speed difference between the material flowing from the rotor and the surrounding material, the pieces of paper are exposed to frictional forces that detach the fibers.

In order to achieve complete decomposition of the fibrous material in a pulper operating as described above, the waste paper has to be treated for a long time. The decomposition usually takes place at a consistency of 2-3%, as a result of which the amount of liquid circulating in the pulper and the power required become large. Therefore, the defibering is not usually complete in the pulper, but can only be carried out to such an extent that a pumpable mass is obtained which is passed to a defiberer where the decomposition of the fibrous material is completed.

The hitherto used method for breaking up waste paper, i.e. with the help of pulp, there are certain disadvantages. When handling unsorted waste paper, for example containing plastic-coated paper, the stream of material fed to the fiberizer contains pieces of paper which are difficult to break down and from which the plastic has not been removed. In the fiberizer, the plastic is torn into small pieces that are difficult to remove from the system in subsequent processing steps. In the pulper, the waste paper tears into pieces, breaking the fibers. It is difficult to remove all the foreign matter that is separated there from the continuous pulper. The pulper screen is provided with relatively large openings, 6-25 mm, so that, for example, paper rivets or other metal parts can pass through them.

The object of the present invention is to provide pulping and sorting of waste paper so that the separation of foreign matter is possible before the fibrous material is introduced into the fiberizer for further processing. In this case, waste paper can be used, which contains e.g. plastic-coated packaging materials, without pre-sorting.

The main features of the invention appear from the appended claim 1.

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According to the invention, the waste paper is defibered in a rotating drum provided with a torn sheath and mainly longitudinal inner lifting plates. The lifting plates move the fed material as shown in more detail below. The invention can be applied to either continuous or intermittent treatment of waste paper.

As the drum rotates, the fed paper material enters with it, and the drum lift plates lift it above the center axis of the drum, from where it falls down toward the bottom of the jacket. By selecting the rotational speed of the drum appropriately in relation to its diameter, the material is made to follow close to the highest point of the drum. The fluid required to defiber the paper is continuously added to the drum and excess fluid exits through holes in the drum casing. Once the paper is fed into the drum, it is moistened, forming flexible balls of paper as the drum rotates. When the moistened paper falls down and hits the bottom of the drum jacket, the fibrous bonds break, while foreign matter remains indestructible. The detached fibers and bundles of fibers that pass through the holes in the jacket exit with the defibering fluid into a tank located below the drum.

Peat raised from the bog contains 85-95% water as well as rocks, roots and root fibers. In order to bring the peat into a pumpable form, it has hitherto usually been diluted in a pulper to a suspension with a dry matter content of less than 5%, from which water has subsequently been removed. Because it is difficult to remove water from peat, it is desirable to add as little water as possible. To prevent the pulper rotor from breaking, the peat must be roughly cleaned before disintegration.

It has been found that the decomposition of wet peat and the separation of dry matter from coarse particles takes place very efficiently in a aiming, torn drum without the need for coarse cleaning.

If the dry matter content of the peat rises by more than 10%, add the diluent. The treatment in the drum breaks the solid structure of the peat, leaving the peat through the holes in the drum casing, while the stones, roots and root fibers remain in the drum and can be removed from the opening at the end of the drum. In this case, a pumpable mass with a dry content of almost 10% is obtained.

Bagasse obtained when sugar is extracted and pressed from sugar cane can be used to make cellulose. It consists of approx.

2/3 of the fibers (based on dry matter) suitable for the production of cellulose 4,56416 and about 1/3 of the core cells (pith) which are not suitable for this purpose. To remove the core cells, which are mainly in the middle parts of the sugar cane stems, bagasse has been previously treated in energy-absorbing machines such as a hammer mill and pulper. It has been found that the separation of cellulose cells from core cells takes place surprisingly easily in a rotating drum with a torn sheath. The short core cells are rinsed with water through the holes in the drum and the cellulosic fibers are obtained in the form of sticks out of the end of the drum. The drum also wears away epidermal cells, which form a waxy surface layer on the stems and are detrimental to cellulose production. The rinsing liquid is preferably recycled and discharged when its consistency is 2-4%. The cellulose fibers are removed at a dry content of 15-20%. The bagasse is suitably cut shorter and crushed before processing in a drum. The invention is described in more detail below with reference to a few application examples and the accompanying drawings.

Example 1 7.5 kg of magazine paper and a smaller amount of plastic-coated packaging material, aluminum foils, textiles, leather, capsules and book covers were placed in a closed drum with a diameter of 1 m and a length of 0.5 m and equipped with 8 longitudinal inner lifting plates 15 cm high. . The casing of the drum is perforated with 5 mm openings, so that the area of the openings became 40% of the surface area of the casing. The rotation speed of the drum was 25 rpm. 330 l of water to which 200 g of NaOH and 100 g of black liquor had been added were allowed to circulate in the drum at a flow rate of 125 l / min. The temperature of the liquid was 45-50 ° C. The drum was opened after 8 min, at which point it was found that all the magazine paper had defibered and left with the recycled water. The paper in the packaging material was also defibered, but the plastic instead remained unchanged. Aluminum foils, textiles and other foreign matter remained in the drum. The book covers had partially shattered.

Example 2

Figures 1, 2, 3, 4 and 5 show an embodiment for continuous use. Figure 1 schematically shows a process utilizing the method and apparatus according to the invention. Figure 2 shows a section along the line A-A in Figure 1. Figures 3, 4 and 5 illustrate the structure of the device.

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In Figures 1 and 2, reference numeral 1 denotes a drum, 2 and 3 its ends and 4 sheaths. The waste paper is fed by means of a conveyor 5 and slides along the trough 6 into the drum through an opening in its end 2. The drum is provided with longitudinal inner lifting plates 7 which continuously lift the waste paper material from the lower part of the drum casing to a higher level from which it falls down. The defibering liquid to which the necessary chemicals, preferably alkali and surfactants, have been added is added via the spray pipe 8. The fibrous material and liquid disintegrated in the drum flow down to the tank 9, from which part of the formed fiber suspension is returned to the drum via a pipe 10 communicating with the spray pipe 8. Some of the liquid is further pumped to a sorter 11 where coarse and heavy particles are removed. The defiberizer 12 then undergoes defibering so that any bundles of fibers decompose. The fiber suspension is washed and thickened with a washing filter 13, to which washing water 14 is added and from which the liquid is returned to the drum along the pipe 15 and removed along the pipe 16. The fibrous material leaves the filter, after which it can be reused after possible cleaning to make paper and board.

The heavy material sediments in the tank 9 and is removed by means of a screw conveyor 17 placed at the bottom of the tank. In the drum, the paper fibers are separated from the foreign materials, which exit through the opening in the end 3.

To handle 100 t / 24 h of waste paper, which mainly contains magazine and newsprint, the drum must have the following dimensions:

Diameter 2.5 m Length 10 m

Hole diameter 5 mm Hole area 20%

Speed 15 rpm Power 50 kW

The fiber density in the tank is 2-3 JS and after the filter 10-12%.

The defibering water consists of water to which an alkali has been added, e.g. NaOH, which must decompose binders from inks and coatings as well as surfactants such as black liquor, pine soap or other commercial wetting agents in order for the water to penetrate the paper effectively.

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The defibering already takes place at a relatively low temperature, for example 40-60 ° C. The fiberizing power of the drum depends on the diameter of the drum. In a large drum, the drop height becomes higher and thus the disintegration efficiency also becomes higher when the paper hits the surface of the drum. The most preferred diameter size is 2-3 m. The speed of the drum should be (20-30) ^ ^ -, where D denotes the diameter of the drum expressed in meters, preferably 25w ~ to achieve the best possible lifting power.

The lifting member can either be built in one piece and extend from one end of the drum to the other, or it can consist of several parts overlapping in the circumferential direction of the drum, preferably the part closest to the feed end first and each subsequent part spaced from the previous part. In order to provide better feed power, the lifting members can be mounted so that they form an angle with the axis of rotation of the drum. Alternatively, the drum can be constructed inclined. The transport of the material in the drum can also be arranged by means of rinsing water.

Figure 3 shows a longitudinal section of the drum. Fig. 4 shows the drum in its feed direction and Fig. 5 a cross-section along the line BB in Fig. 3 · Figs. 3, 4 and 5 use partly the same reference numerals as in Figs. 1 and 2. The inner lifting plates 7 acting as lifting members are constructed slightly helical so as to deviate the length of the drum. The angle of inclination is preferably 2-10 ° C. Due to the fact that the end of the lifting member closest to the end 2 through which the waste paper is fed is first viewed in the feed direction, the lifting member acts on the material in the drum with an axial force feeding the material against the opposite end 3. Two rotating bearing rollers support the drum at both ends. The drum is driven by a motor 20 by means of a drive chain 21 and sprocket wheels 22 and 23. The separated foreign matter is removed by means of buckets 24 which lift it from the lowest part of the drum casing to the trough 25 located in the opening of the end 3.

Example 3 50 kg of peat with a dry matter content of 10 5 t was treated for 5 min in a rotating drum according to Example 1. When the drum was opened, it was found that 0.5 kg of stones, roots and root fibers had remained in the drum. The tank below the drum contained most of the dry matter in the form of a pumpable suspension containing about 8% peat. No diluent was added.

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Example 4 15 kg of bagasse having a dry content of 50% and previously pretreated in a manner not further described herein, with the number of core cells reduced to $ 25, was treated in a rotating drum according to Example 1. The treatment was performed in two steps.

Initially, the drum was allowed to spin for 10 min, allowing 300 l of recycled water to flow through the bagasse. The water was then exchanged for an equal volume of circulating rinsing water, which flowed through the bagass while the drum was rotating for another 5 min. When the drum was opened, 80% of the dry matter remained in the drum and the core cell content was reduced to about 10 JK, which is a very satisfactory result.

Within the scope of the invention, it is also possible to use the drum for peeling small wood and branches, as well as for breaking up insoluble chips and separating the bundles in the pulp after cooking.

The size of the holes in the drum casing is adjusted according to the desired separation power. Suitable sizes for waste paper, peat and bagasse are 4-6 or 8-15 or 3-5 mm.

Claims (8)

A method for dissolving and classifying fibrous material, characterized in that the fiber structure is dissolved in the wet state and any foreign material is removed such that the material in a rotating drum is subjected to repeated lifting and falling movement, the material being divided into two fractions, the fine fraction settles via the heel of the drum's mantle and the coarse fraction through an opening in one of the drum's end. Process according to claim 1, characterized in that the fibrous material is wetted with an alkaline liquid, which preferably contains surface tension reducing agents. 3. A process according to claim 2, characterized in that the liquid is made alkaline by the addition of sodium hydroxide, and that black liquor is added as a surface tension reducing agent. Method according to any of the preceding claims, characterized in that part of the liquid with dissolved fiber material is fed back to the drum. Method according to any of the preceding claims, characterized in that fiber material is continuously fed into the drum and foreign material is continuously discharged from the drum. Method according to claim 1, characterized in that the drum rotational frequency is (20-30), preferably 25, where D is the drum diameter expressed in meters. Apparatus for carrying out the method according to any of the preceding claims for the recovery of fibers from fibrous material, characterized by a rotating drum (1), which is provided with a perforated sheath (4) and serves as a lifting member, mainly in the drum of the drum. longitudinally extending lifting discs or strips (7) and with a pipe (8) for supply of defibrating and dissolving fluid. Device according to claim 7, characterized by. that one end (2) of the drum (1) is provided with an opening (5) through which the fibrous material is supplied to the drum, and that the other of the drum