The invention relates to an apparatus for slushing and sorting fibrous material, in which apparatus the actual slushing is conducted in a rotat¬ ing defibration drum or in another defibration apparatus using defibra¬ tion and disintegration fluids. The apparatus is intended particularly for treatment of unsorted fibre material containing foreign components, such as waste paper containing packing material coated with plastic.

In several known applications for slushing and sorting of fibrous mate¬ rial, a rotating drum is used, as mentioned above, which is usually pro¬ vided with elongated lifting blades fixed inside the housing of the drum, intended for lifting the material to be treated from the lowermost part of the drum housing towards the uppermost part of the housing when the drum rotates around its longitudinal axis. From the uppermost part of the housing, the material is thrown against the lower part of the hous¬ ing, wherein the material is worked and disintegrated. In said embodi¬ ments, the material to be treated is wetted with a defibration and dis- integration fluid containing the required chemicals and being supplied to the drum.

For example in the embodiment known from Finnish Published Specifi¬ cation No. 63075, the housing of said drum is divided in two parts by a partition wall. The part of the housing on the side of the inlet end of the drum, where the material to be treated is supplied, is non-perforated and used for wetting of the material, treatment with chemicals and slushing. The partition wall is provided with an opening, through which the slushed material flows to the housing part on the side of the dis- charge end of the drum, which is perforated and used for sorting of the material. The material to be treated is dry when supplied to the inlet end of the drum and wetted there with the defibration and disintegration fluid which is supplied to the drum e.g. via a spray pipe system led in¬ side the drum. The sorting takes place at the perforated discharge end of the drum by flushing the slushed material with a fluid which is passed through the housing and the material. The purpose of the sorting is to separate the usable part of the mass completely from the unusable part. After this, the usable material is transported for further processing,

for example for refining into recycled paper. Further, corresponding ap¬ paratuses are also known from European Application Publications No. 164 428 and No. 194 332. In these publications, water and the waste paper to be defibred are supplied via a feeder trough to a de- fibration drum for softening and defibration.

The most important disadvantage of the embodiments in use and de¬ scribed above is the fact that the treatment of the material particularly in the actual slushing phase — i.e. for example in the non-perforated part of the drum described above — takes a lot of time. Because the mate¬ rial to be slushed is supplied to the drum in dry state, particularly the absorption of defibration and disintegration fluids to the material in¬ creases the duration of the slushing phase. Thus a relatively high ki¬ netic energy supplied per mass unit of material for slushing is wasted when water is first absorbed in the material to be slushed and brought to a fast movement. This drawback will tend to reduce the degree of utilisation of the apparatus, which will further impair the economy of use.

The above-mentioned drawback related to known embodiments can be eliminated and the prior art in the field improved by an apparatus ac¬ cording to the present invention, which is primarily characterized in what is presented in the characterizing part of claim 1. A pre-treatment device placed upstream of the defibration drum makes it possible to wet the material to have a required moisture content before the actual defibration. The purpose of the pre-treatment device is not to be in¬ volved with defibration but to bring the material to be treated in a suffi¬ cient contact with water, and it is a controllable process separate from the defibration process.

An important advantage of the apparatus according to the invention is the fact that the retention time of the material to be treated in the de¬ fibration drum can be substantially reduced, thus making defibration more effective and raising the degree of utilisation of the apparatus used for it.

As for the other advantageous embodiments of the invention, reference is made to the dependent claims 2 — 7 and to the description.

In the following description, the invention and some embodiments will be described in detail with reference to the appended drawings, in which

Figure 1 shows an embodiment of the invention in a longitudinal sec¬ tion,

Figure 2 shows a section along the line A — A of Fig. 1 ,

Figure 3 shows a second embodiment of the invention in a longitudi¬ nal section, and

Figure 4 shows a third embodiment of the invention in a longitudinal section.

In the embodiments presented in this description, the defibration drum used may be one of different solutions, known as such, where the ma¬ terial to be treated is slushed by impregnating it with defibration and disintegration fluids and by working the material in a rotating defibration drum and further by sorting the actual waste apart from the usable ma¬ terial for further refining. Such a defibration drum will be indicated in this description and in the drawings with the reference numeral 1. Fur¬ ther, it is possible to use also other types of defibration devices, where the material to be treated can be defibred in a sufficient water content by mechanical working.

The apparatus shown in Figs. 1 and 2 comprises a defibration drum 1 and a pre-treatment device 2, which includes a wetting drum 3 and a connecting trough 4. The material to be pre-treated is supplied to the inlet end 6 of the wetting drum 3 together with a fluid, such as water. The wetting drum 3 is provided with elongated interior lifting blades 5 for lifting the material to be treated and the said fluid from the lower¬ most part of the drum upwards when the drum rotates around its longi- tudinal axis. From the upper parts of the drum, the material and the fluid are dropped to the lower part of the drum, and this continuous move¬ ment brings about their mixing and the wetting of the material to be treated simultaneously when the material is moved towards the de-

fibration drum 1. The wetting drum is not an ordinary defibration drum, but the purpose of the movement is to mix the material with water in a way that water is absorbed into the material consisting of fibres adher¬ ing to each other, the material swells and the bonds between the fibres get weaker.

In this embodiment, said wetting drum 3 is placed in an inclined posi¬ tion so that the wetted, treated material flows from the inlet end 6 to the discharge end 7, from which it flows further via the connecting trough 4 to the actual defibration drum 1. At the end of the pre-treatment device, the material has typically absorbed about twice its weight water. The material is not yet defibred, but its dry matter content is still at least 30 %, the rest being absorbed fluid.

The apparatus shown in Fig. 3 comprises a defibration drum 1 and a pre-treatment device 2 directly connected to it, including a wetting drum 3 where the material and the fluid are treated in the same way as in the apparatus shown in Figs. 1 and 2. In this embodiment, the wetting drum 3 rotates together with the actual defibration drum 1 , because it is rigidly attached to it, and its lifting blades 5 are placed in an inclined position so that during rotation of the drum they move the wetted mate¬ rial towards the actual defibration drum 1. Mixing of the material to be treated and the fluid, and in addition, wetting of the material is achieved on the same principle as in the embodiment shown in Figs. 1 and 2.

It is obvious that the wetting drum 3 of the apparatus shown in Fig. 3 can be arranged to operate also separately from the actual defibration drum 1 , whereby a connection trough 4 according to Fig. 1 can be ar¬ ranged between the wetting drum 3 and the defibration drum 1. Further, the wetting drum 3 and the defibration drum 1 can be connected to¬ gether by mechanical power transmission.

The apparatus shown in Fig. 4 comprises an actual defibration drum 1 and a pre-treatment device 2 which comprises: - a wetting basin 8, a conveyor 9 running substantially parallel to the bottom of the wetting basin 8, at least four guide rolls 10 guiding the conveyor 9,

at least one shield plate 11 to prevent the material to be treated from getting into contact with the guide rolls 10, and a connection trough 4 at the end of the conveyor 9 to move the material wetted in the basin into the defibration drum 1.

In this embodiment, the material to be wetted is moved into the wetting basin 8 by a known conveyor, such as a chute, belt, bucket, crane, or the like. Fluid is supplied to the basin preferably by means of a pipe or a pipe system 12. The material is supplied to the inlet end of the con- veyor 9, it is wetted in the wetting basin 8, and it is moved by the con¬ veyor 9 towards the supply trough 4, on which it flows further to the ac¬ tual defibration drum 1. The conveyor 9 can be of any conveyor type suitable for conveying material in water, such as a belt conveyor. The conveyor forms e.g. an endless loop which is led by guide rolls 10 over the rims of the basin 8, thus avoiding problems of sealing the bottom. The phenomena taking place during wetting are the same as those pre¬ sented above in connection with the drum alternatives.

It is obvious that the speed of the conveyor 9 can be adjusted depend- ing on how fast the material to be wetted reaches the respective best wetting degree aimed at. Fluid supply from the pipe 12 is determined according to the need for water in the whole defibration process.

Consequently, the material reaches by pre-wetting a water content which will still require a water addition for the actual defibration. This additional water can be supplied already to the pre-treatment device, whereby primarily the retention time and/or the way of treatment in the pre-treatment device causes that at the discharge end the mass moving towards the actual defibration still contains separately the substantially non-defibred, swollen fibre material impregnated with water, and the water which is required for achieving the final defibration consistency of typically 10—20 %. In the actual defibration, the energy to be supplied to the material is higher than in pre-treatment, and defibration will take place quickly by the action of this additional water and the kinetic en- ergy of the defibration device.

Water is moved together with the wetted material to the actual defibra¬ tion device, and for maintaining a sufficient quantity of water in the pre-

treatment device 2, at the end of its transfer path (the inner part of the drum 3 or the conveyor 9) there can be an overflow threshold 13, as a raised rear wall of the drum 3 indicated by broken lines in Figs. 1 — 3 or a higher rear edge of the basin 8 in the alternative of Fig. 4. Further, the drum 3 can be provided with guides rotatable together with the inner part (not shown), for lifting the wetted material at the rear end over the threshold to the trough 4.

The invention is suitable for treatment of all kinds of fibrous material where cellulose fibres adhering to each other can be separated by the combined action of the water and mechanical working, such as in the case of waste paper. Further, the pre-treatment device 2 can also in¬ volve other operations, such as mechanical tearing or cutting of the material to be impregnated into smaller pieces.