GB2121703A

GB2121703A - Waste paper processing apparatus

Info

Publication number: GB2121703A
Application number: GB08315531A
Authority: GB
Inventors: Theodor Bahr; Wilfried Keck; Helmut Konecsny
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1982-06-11
Filing date: 1983-06-07
Publication date: 1984-01-04
Also published as: FR2528460B1; FI832106A7; GB2121703B; FI832106L; FR2528460A1; GB8315531D0; DE3221932A1; FI832106A0; ATA160583A

Abstract

Apparatus for the processing of waste paper comprises a pulper (1) in which the waste paper is pulped, and a perforated filter drum (8) located immediately downstream of the pulper and rotatable about a horizontal axis, in which the fibrous suspension leaving the pulper is sorted, the suspension being introduced at one end and the reject material discharged at the other end of the filter drum. For sorting purposes, where the material density is greater than 12%, the diameter of the perforations of the filter drum, at least in a region adjacent to the inlet (5) is at least 20 mm. The filter openings may be kept clear by means of air blown through air lines (18) onto the drum casing. The apparatus allows a relatively small filter drum to be used at a high material content. Further sorting may be effected in a second drum 12 having smaller perforations than the drum 8. Alternatively, a single drum having larger perforations adjacent the inlet and smaller perforations adjacent the outlet may be used. <IMAGE>

Description

SPECIFICATION Waste paper processing apparatus The present invention relates to waste paper processing apparatus comprising a pulper for pulping the waste paper and a perforated filter drum located immediately downstream of the pulper and rotatable about a horizontal axis for sorting the fibrous suspension leaving the pulper.

A problem in regard to the processing of waste paper resides in the large quantities to be processed in the initial stage when the fibrous suspension is still very thick and, in particular, is mixed with large, rough-surfaced impurities.

In order to keep the size of the apparatus required small, efforts have recently been made to carry out the first processing steps at a very high consistency of about 14 to 18%.

An example of such a process is described in "Wochenblatt fuer Papierfabrikation", 1981, pages 927 to 930. However, in the systems described, the high material concentration of 16% in this case is maintained only in the pulper. In the succeeding filter drum, which is rotatable about a horizontal axis, the material consistency is substantiaily reduced to, in fact, 4 to 6%. This means that the volume of the filter drum must be correspondingly large. However, in contrast to other systems described in the prior art, this system at least has the advantage that the need for the conventionai "ragger" is avoided and, consequently, the system operates more reliably.

It is an object of the present invention to provide waste paper processing apparatus which, in addition to ensuring operating reliability, permits the devices used in the first stages to be as small as possible in size.

In accordance with the invention, there is provided apparatus for processing waste paper comprising a pulper for pulping the waste paper and a perforated filter drum, located immediately downstream of the pulper and rotatable about a horizontal axis, for sorting the fibrous suspension leaving said pulper, said filter drum having an inlet for the fibrous suspension from said pulper at one end face thereof and an outlet for rejected material at the other end face thereof, wherein, for use with a material consistency of above 12% in said pulper and said filter drum, the perforations of said filter drum, at least in a region thereof adjacent to said inlet, have a diameter of at least 20 mm.

In order to overcome possible clogging of the perforations of the filter drum, at least one air line may be arranged outside the drum having air outlet openings directed towards the outer peripheral surface of the drum.

Preferably, the filter drum is followed by a further filter drum, the perforations of which are smaller than those of the first-mentioned filter drum, the further filter drum serving to further sort reject material from the first-mentioned drum after it has been converted to a highly diluted state.

Alternatively, the filter drum may be in two parts, a first part adjacent to the inlet having perforations of diameter at least 20 mm, whilst the second part has perforations of smaller diameter, the second part serving to further sort reject material leaving the first part of the drum after it has been highlydiluted. The two parts of the drum preferably form a single structural unit having a continuous peripheral surface, the parts being sepa rated by an annular partition wall, the outer periphery of which abuts against the inner peripheral surface of the drum, and which is preferably inclined relative to the peripheral direction of the drum.

Preferably, the lowest part of the filter drum is spaced at a considerable distance below the base of the pulper, the outlet of the latter being connected to the inlet of the filter drum by means of a chute.

The invention will now be further described with reference to the drawing, in which: Figure 1 is a schematic side sectional view of one form of apparatus according to the invention; and Figure 2 is a schematic side sectional view of a modified form of filter drum for use in the invention.

Referring to Fig. 1, the apparatus comprises a pulper 1 and a perforated filter drum 8 which is arranged immediately downstream of the pulper 1 and rotates about a horizontal axis. The perforations of the filter drum 8 have a diameter of at least 20 mm. The filter drum 8 is arranged below the base of the pulper 1 at a sufficient distance therefrom to allow the fibrous suspension to pass from the pulper through a chute 3, into an inlet opening 5, in one end wall of the filter drum under the influence of gravity. The processing consistency is about 14 to 1 8%, both in the pulper 1 and in the immediately following filter drum 8. The outlet opening of the pulper can be closed by a sliding member 16.As shown in Fig. 1, air lines 1 8 provided with outlet openings which are directed towards the casing of the drum are provided at the outer periphery of the filter drum 8. The emerging air streams clean the perforations in the upper part of the drum. This is necessary since the danger exists that the partially spinning impurities of large surface area may rapidly obstruct the holes. For the circulation of the suspension in the filter drum, rotating ribs 9 are arranged on the interior of the periphery of the drum parallel to the axis of rotation of the drum. The suspension which passes out through the perforations of the filter drums has an unaltered high consistence and can be transported onwards by means of a conveyor belt 4. At the outlet end 6 of the drum the reject material is discharged into a trough 20.In the example apparatus illustrated in Fig. 1, it is then fed in diluted form by means of a pump 25 to a further filter drum 1 2 which has very much finer perforations than those of the first drum. In this further drum 12, the diameter of the perforations is between 1 2 and 20 mm. The ac cepted material which passes out through the perforations of the second drum is fed by way of a thickening device 21, as described, for example, in German Utility Model No. 79 33 250, to the conveyor belt 4 of the first filter drum and together with the accepted material which has been sorted in the first drum is passed onwards for further processing.Spray water lines 22 and 23 are provided in order to improve the separation of the fibres from the reject material in the further drum 1 2 and to protect the perforations therein from becoming obstructed.

In the form of filter drum illustrated in Fig.

2, the two filter drums 8 and 1 2 of Fig. 1 having different types of perforation, are combined in one structural unit 8', the parts of which are separated from one another by a partition wall 10 in the form of a ring abutting against the interior of the drum casing. In this case, the second part 8" of the drum which has the finer perforations, is supplied with sprayed water by means of a water line 22'.

Additional water is sprayed onto the exterior of the drum casing by means of a water line 23'. The fibrous suspension discharged through the perforations of the second drum part 8" is now in diluted form and is fed by means of a pump 26' to a thickening device (not illustrated) corresponding to the device 21 of Fig. 1, where it is again thickened and fed to a conveyor belt 4' which receives the discharge from the first part of the drum 8'.

The same processing stage has now been reached as in Fig. 1.

As Fig. 2 shows, the partition wall 10 is slightly inclined in relation to the peripheral direction of the drum casing. In association with rotating ribs 9' on the inside of the drum which serve to lift the fibrous material, this ensures that the fibrous material is lifted over into the other part 8" of the drum when that part of the partition wall which is closest to the inlet opening 5' is located in the lower part of the drum. In addition, this also ensures that the relatively thick fibrous material (which possesses a consistency of about 16%) remains for an adequate length of time in the first part of the drum so as to allow sufficient sorting time for the accepted material. On the other hand, dilution of this material by the diluted fibrous suspension from the second part 8" of the drum is ayoided.

Claims

1. Apparatus for processing waste paper comprising a pulper for pulping the waste paper and a perforated filter drum, located immediately downstream of the pulper and rotatable about a horizontal axis, for sorting the fibrous suspension leaving said pulper, said filer drum having an inlet for the fibrous suspension from said pulper at one end face thereof and an outlet for rejected material at the other end face thereof, wherein, for use with a material consistency of above 1 2% in said pulper and said filter drum, the perforations of said filter drum, at least in a region thereof adjacent to said inlet, have a diameter of at least 20 mm.

2. Apparatus as claimed in Claim 1, wherein at least at that part of the filter drum adjacent to said input, at least one air line is arranged outside the drum and close to its periphery, the or each said air line having air outlet openings directed towards the outside peripheral surface of the drum.

3. Apparatus as claimed in Claim 1 or Claim 2, wherein a further filter drum is arranged downstream of said first-mentioned filter drum, said further filter drum having perforations of smaller diameter than those of said first-mentioned filter drum, said further filter drum serving to sort the reject material from said first-mentioned drum after it has been converted to a highly diluted state.

4. Apparatus as claimed in Claim 1 or Claim 2, wherein said filter drum is formed in two parts, a first part adjacent the inlet having periorations of diameter at least 20 mm and a second part adjacent the outlet having perforations of smaller diameter than those of said first part, said second part serving to further sort reject material leaving said first part after said material has been highly diluted.

5. Apparatus as claimed in Claim 4, wherein said first and second drum parts form a single structural unit having a continuous peripheral surface, said parts being separated by an annuiar partition wall abutting at its outer periphery against the peripheral inner face of said drum.

6. Apparatus as claimed in Claim 5, wherein said partition wall is inclined relative to the peripheral direction of said filter drum.

7. Apparatus as claimed in any one of the preceding Claims, wherein the lowest part of said filter drum spaced at a considerable distance below the base of said pulper and that the outlet of said puiper and the inlet of the filter drum are connected to one another by means of a chute.

8. Apparatus for processing waste paper substantially as hereinbefore described with reference to and as shown in Fig. 1, or Fig. 2, of the drawing.