GB2087266A

GB2087266A - Method for the separation of mixed waste paper

Info

Publication number: GB2087266A
Application number: GB8131869A
Authority: GB
Original assignee: Babcock Krauss Maffei Industrieanlagen GmbH; BKMI Industrieanlagen GmbH
Current assignee: BKMI Industrieanlagen GmbH
Priority date: 1980-11-13
Filing date: 1981-10-22
Publication date: 1982-05-26
Also published as: ES507064A0; NL8104952A; IT8149697A0; BE891090A; DE3042849A1; ES8300158A1

Abstract

A method for the separation of mixed waste paper comprises the steps of: a) Coarse comminution of the waste paper while preserving its natural distinguishing features, b) Screening-out of a coarse fraction which substantially contains uncomminuted papers, c) Sucking-off of the light components from the coarse fraction separated in step b), d) Return to the comminutor of the heavy components of the coarse fraction separated in step b), e) Classification of the fine fraction obtained in step b) in a gas stream into at least two fractions of different density. s

Description

SPECIFICATION Method for the separation of mixed waste paper The invention relates to a method for the separation of mixed waste paper into different grades of paper, during which process the paper is comminuted, screened and classified.

Methods of this kind are known, for example from DE AS 2542 571. For the recovery of waste-paper grades which have a relatively high value deagglomeration units are used following the comminution thereof and prior to their separation into grades with the aid of an air classifier. However, the separation into grades brought about with the known methods does not satisfy the paper industry requirements which have to be fulfilled by relatively high-value waste-paper grades with respect to their yield and purity.

Accordingly, the task underlying the invention is to improve the known methods in such a way that there can be separated from mixed waste-paper grades high-quality grades giving higher yields and having a higher degree of purity.

According to the invention there is provided a method for separation of mixed waste paper in which the paper is comminuted, screened and classified, characterised in that the waste paper undergoes the procedural steps set forth hereinafter: (a) Coarse comminution of the waste paper while preserving its natural distinguishing features, (b) Screening-out of a coarse fraction which substantially contains uncomminuted papers, (c) Sucking-off ofthe light components from the coarse fraction separated in step b), (d) Return to the comminutor of the heavy components of the coarse fraction separated in step b) (e) Classification of the fine fraction obtained in step b) in a gas stream into at least two fractions of different density.

The waste paper is initially subjected to a course comminution. As is known, such a measure ensures that the natural distinguishing features of the individual grades of paper are largely preserved. This coarse comminution, which is preferably effected by a cutting operation, generally causes a wide grainsize range to be formed. Above all flat material, such as paper, is limited to a very small extent, at least in one dimension.

The mixed waste paper coming from the comminutor is loaded on a screen. Here, there is effected a separation into a fine fraction, that is to say into parts which pass through the screen, and into a coarse fraction, that is to say oversize parts. The coarse fraction is composed of uncomminuted individual papers as well as uncomminuted folded papers. During the classifying process, the uncomminuted folded papers, e.g. daily newspapers and magazines, would not be separated in accordance with their specific paper weight (g/cm2), that is to say the paper quality, but would be separated according to the shape in which they happen to be folded. They therefore have to be returned to the comminutor.By contrast, a proportion of the individual papers contained in the coarse fraction already has, with the larger grain size, the corresponding separation characteristic so as to allow them to be separated as a separate light paper grade in a classifying operation.

According to the invention, this light-paper proportion is therefore sucked from the coarse fraction (for example with the aid of a known 'per se' stone selector). By this means, the quantity to be returned to the comminutor is considerably reduced. It is advantageous if the light fraction is already sucked off during the classifying operation.

The sucking-off operation simultaneously loosens the light fraction, whereby a subsequent separation of the plastics film material that is partly contained in the mixed waste paper is facilitated. In order to intensify the loosening process, it is advantageous if the sucked-off light fraction is segregated from the delivery air downwstream of the suction fan.

As the material passes through the fan itself, for which a conventional hay fan is suitable, most of the folds are removed by the high shear flows in the air and by the mechanical action of the fan vanes. The separation of the sucked-off fraction into paper and plastics film material is preferably effected directly during the segregation of the light fraction from the delivery air. However, it is also conceivable to load the light fraction on the classifier together with the delivery air or else to seggregate the light fraction and to load it once more on the classifier for the separation thereof into paper and plastics film material.

If the paper separated from the mixed waste paper is to be utilised for paper making, it is advantageous if the ferromagnetic scrap components are magnetically separated prior to the comminution process and, if necessary, once more following the comminution process.

To explain the invention, a preferred embodiment of the method for the separation of mixed waste paper will be described hereinafter with reference to a flow diagram shown in the drawing.

The mixed waste paper is continuously loaded on a cutting-roll comminutor 1. Thereafter, it passes on a screen 2. The fine proportion of the screened material is loaded on a zig-zag classifier 4, which divides it into a light fraction and a heavy fraction.

The light fraction may consist, for example, of thin papers of daily newspapers, whereas the heavy fraction is composed of cardboard boxes. That portion of the screened coarse fraction that is readily capable of flying, again mainly newspapers, is separated with the aid of a suction device 3 and the remainder is returned to the comminutor 1.

1. A method for the separation of mixed waste paper in which the paper is comminuted, screened and classified, characterised in that the waste paper undergoes the procedural steps set forth hereinafter:- a) Coarse comminution ofthewaste paper while preserving its natural distinguishing features.

b) Screening-out of a coarse fraction which substantially contains uncomminuted papers.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method for the separation of mixed waste paper The invention relates to a method for the separation of mixed waste paper into different grades of paper, during which process the paper is comminuted, screened and classified. Methods of this kind are known, for example from DE AS 2542 571. For the recovery of waste-paper grades which have a relatively high value deagglomeration units are used following the comminution thereof and prior to their separation into grades with the aid of an air classifier. However, the separation into grades brought about with the known methods does not satisfy the paper industry requirements which have to be fulfilled by relatively high-value waste-paper grades with respect to their yield and purity. Accordingly, the task underlying the invention is to improve the known methods in such a way that there can be separated from mixed waste-paper grades high-quality grades giving higher yields and having a higher degree of purity. According to the invention there is provided a method for separation of mixed waste paper in which the paper is comminuted, screened and classified, characterised in that the waste paper undergoes the procedural steps set forth hereinafter: (a) Coarse comminution of the waste paper while preserving its natural distinguishing features, (b) Screening-out of a coarse fraction which substantially contains uncomminuted papers, (c) Sucking-off ofthe light components from the coarse fraction separated in step b), (d) Return to the comminutor of the heavy components of the coarse fraction separated in step b) (e) Classification of the fine fraction obtained in step b) in a gas stream into at least two fractions of different density. The waste paper is initially subjected to a course comminution. As is known, such a measure ensures that the natural distinguishing features of the individual grades of paper are largely preserved. This coarse comminution, which is preferably effected by a cutting operation, generally causes a wide grainsize range to be formed. Above all flat material, such as paper, is limited to a very small extent, at least in one dimension. The mixed waste paper coming from the comminutor is loaded on a screen. Here, there is effected a separation into a fine fraction, that is to say into parts which pass through the screen, and into a coarse fraction, that is to say oversize parts. The coarse fraction is composed of uncomminuted individual papers as well as uncomminuted folded papers. During the classifying process, the uncomminuted folded papers, e.g. daily newspapers and magazines, would not be separated in accordance with their specific paper weight (g/cm2), that is to say the paper quality, but would be separated according to the shape in which they happen to be folded. They therefore have to be returned to the comminutor.By contrast, a proportion of the individual papers contained in the coarse fraction already has, with the larger grain size, the corresponding separation characteristic so as to allow them to be separated as a separate light paper grade in a classifying operation. According to the invention, this light-paper proportion is therefore sucked from the coarse fraction (for example with the aid of a known 'per se' stone selector). By this means, the quantity to be returned to the comminutor is considerably reduced. It is advantageous if the light fraction is already sucked off during the classifying operation. The sucking-off operation simultaneously loosens the light fraction, whereby a subsequent separation of the plastics film material that is partly contained in the mixed waste paper is facilitated. In order to intensify the loosening process, it is advantageous if the sucked-off light fraction is segregated from the delivery air downwstream of the suction fan. As the material passes through the fan itself, for which a conventional hay fan is suitable, most of the folds are removed by the high shear flows in the air and by the mechanical action of the fan vanes. The separation of the sucked-off fraction into paper and plastics film material is preferably effected directly during the segregation of the light fraction from the delivery air. However, it is also conceivable to load the light fraction on the classifier together with the delivery air or else to seggregate the light fraction and to load it once more on the classifier for the separation thereof into paper and plastics film material. If the paper separated from the mixed waste paper is to be utilised for paper making, it is advantageous if the ferromagnetic scrap components are magnetically separated prior to the comminution process and, if necessary, once more following the comminution process. To explain the invention, a preferred embodiment of the method for the separation of mixed waste paper will be described hereinafter with reference to a flow diagram shown in the drawing. The mixed waste paper is continuously loaded on a cutting-roll comminutor 1. Thereafter, it passes on a screen 2. The fine proportion of the screened material is loaded on a zig-zag classifier 4, which divides it into a light fraction and a heavy fraction. The light fraction may consist, for example, of thin papers of daily newspapers, whereas the heavy fraction is composed of cardboard boxes. That portion of the screened coarse fraction that is readily capable of flying, again mainly newspapers, is separated with the aid of a suction device 3 and the remainder is returned to the comminutor 1. CLAIMS

c) Sucking-off of the light components from the coarse fraction separated in step b).

d) Return to the comminutor of the heavy components of the coarse fraction separated in step b).

e) Classification of the fine fraction obtained in step b) in a gas stream into at least two fractions of different density.

2. A method as claimed in Claim 1, characterised in that the communition is substantially effected by means of a cutting operation.

3. A method as claimed in Claim 1, characterised in that the light fraction sucked off in the procedural step c) is separated from the delivery air downstream of the suction fan.

4. A method as claimed in Claim 1, characterised in that during the segregation of the light fraction of step d) from the delivery air there is effected a division into a paper fraction and a plastics film fraction.

5. A method as claimed in Claim 1, characterised in that the steps b) and c) occur simultaneously.

6. A method as claimed in Claim 1, characterised in that the light fraction of step c) is combined with the fine fraction of step b) and that this combination is loaded on the classifier.

7. A method as claimed in Claim 1, characterised in that any ferromagnetic scrap components which may be contained in the waste paper are magnetically separated upstream of the comminuton

8. A method as claimed in Claim 1, characterised in that prior to the screening of the coarse fraction according to step b) there occurs another screening which separates a fine fraction in a grain size which is 30 to 70 % below the separation size of step b).

9. A method as claimed in Claim 1, characterised in that a pneumatic conveyor system is used for the transportation of the fine material from thescreening (according to step b)) to the classifying thereof (step e)), the material to be conveyed being sucked through the fan.

10. A method for the separation of mixed waste paper substantially as described herein with reference to the accompanying drawings.