The present invention relates to a method and an apparatus for cleaning of a pulp suspension from heavy as well as light contaminate particles, the cleaned suspension is accepted without any fiber losses. ^j

The object of the present invention is to provide a method and an apparatus by which is maintained a high cleaning efficiency of a pulp suspension with respect of both heavy and ligth contaminate particles. The distinguishing features characterizing for the invention are disclosed in the following claims.

The invention will now be described in detail with re¬ ference to the accompanying drawings, on which

Fig. 1 schematically illustrates in a side view and partly in a cross section a preferred em- bodiment of a fiber reclaimer according to the present invention and with respect to a separation of heavy contaminate particles.

Fig. 2 schematically illustrates in a side view and partly in a cross section an embodiment of a fiber reclaimer according to the present invention and with respect to a separation of light contaminate particles such as polymer, stickles.

Referring to Fig. 1 the fiber reclaimer according to the present invention consists of a connection arrangement including a cone 1 which is terminating in a conical housing 2, a suction pipe 3, vessels 4,5 and at least one connection pipe 6 if there are at least two vessels 4,5. A cyclone not illustrated in the drawings is with its lower cone and flange connected to the cone 1 with its flange 7.

A fibre or pulp suspension which is to be cleaned is in¬ jected tangentially through a inlet of the cyclone with a determinated pressure. In the cyclone the suspension is divided into accept (cleaner suspension) and into reject c (suspension uncleaned with heavy and even light contaminate particles) . With known technics of today it is almost impossible to recycle and save all fibres from cleaning operations and therefore some fibres get into the sea. According to the present invention all fibres are to the 0 contrary recycles and saved e.g. in the last stage of a cleaner installation.

The cleaning or separation according to the etod of the present invention is achieved by pressing the reject through the cone 1 and against and through its outlet 13 5 having a diameter d. After that the reject is expanding in the conical housing 2 and flows into the vessel 4 through an opening gap 17 between the vessel 4 and the suction pipe 3. In the vessels 4,5, the hight H of which determinates the time of delay in the fiber reclaimer, the heavy con- 0 taminate particles are separated (e.g. sand from the sus¬ pension) . The pulp suspension is filling up the vessel 5 through the connecting pipe 6 and get in this way a further opportunity to be free from fine sand. Heavy contaminate particles are sinking to the bottom of the vessels and 5 where they can be emptied manually or automatically.

When the suspension flows into the vessel 4 through the opening gap 17 a vacuum zone is created between the dia¬ meter d of the cone 1 and an opening end 16 having a dia¬ meter D resulting in that all suspension which reaches the 0 level of a second tail end 18 of the suction pipe 3, will be resucked through the cone 1 into the cyclone. The im¬ portance of the diameter of the cone 1 of the outlet 13 and of the diameter D of the suction pipe 3 of the opening end 16 is as follows. For cyclones or cleaners with low capa- 5 city e.g. 100 1/min it is characteristic that the outlet

diameter d of the cone 1 is small (e.g. some mm). The opening end or mouth 16 of the suction pipe 3 may not be of the same order of magnitude or size because the suction pipe 3 is more susceptible to be plugged up with fibres than the outlet 13 of the cone 1 having the diameter d.

The diameter D of the suction pipe 3 of the opening end 16 must be much greater than the diameter d. Only when the diameter d of the cone 1 reaches about 30-40 mm the dia¬ meter D also can reach to 40 mm. When using large dimen- sions of d, the diameter D can be smaller than the diameter d and the distance A in Fig. 1 can be reduced to zero. The geometry around the cone 1 and the suction pipe 3, the distance A between the outlet 13 of the cone 1 having the diameter d and the opening end 16 of the suction pipe 3 having the diameter D, the time of delay of the suspension in the vessels (depending on the hight H) and the number of vessels, all these are affecting or determinating the cleaning efficiency of the fiber reclaimer.

Fiber reclaimers also can include only one vessel 4 with suction pipe 3 or also include a plurality of vessels connected to each other by connecting pipes 6. On the vessel 4 there is a valve 8 for waterfeed if delution is required. The cleaning efficiency is increased when the fiber consistency is decreased.

The separation of light contaminant particles, e.g. ad¬ hesive substances (stickies), which can be present in some pulp suspensions, ccould be achieved by means of an arrangement illustrated in Fig. 2. These stickies occur i.a. in fibres which are recycled from secondary paper and are descended from envelopes (glue), backs of books etc. In order to be able to separate the fibres in the reject fraction from stickies and bring the cleaned fibres back to the accept this is done in the same way as described above, but with a modification. A connection pipe 9 is ended in

the upper part of the connected vessel or vessels. This arrangement is done because of the fact that the stickies are gathering (collecting) on the surface in the upper part of the vessels. A suction pipe 10 is provided on a rela- tively low level near the bottom of the vessel with the aim to suck the pulp suspension free from stickies. Close below the upper part of the connection pipe 9 a valve 11 is placed for discharging suspension having concentrated stickies. Light contaminate particles can be supplied from outside to the connection 12 of the vessel 5 in Fig. 2, e.g. from the cyclone which is separating light contaminate particles but is retaining a lot of good fibres.