GB2096661A

GB2096661A - A process for preparing waste paper

Info

Publication number: GB2096661A
Application number: GB8205777A
Authority: GB
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1981-04-10
Filing date: 1982-02-26
Publication date: 1982-10-20
Also published as: ATA44082A; AT381124B; GB2096661B; FR2503748A1; FR2503748B1; FI821272L; FI73748C; JPS57183485A; DE3114527C1; FI821272A0; FI73748B

Abstract

In order to save energy and to economise on plant components, in the process for preparing relatively clean, pre-sorted waste paper the following preparation steps are carried out: a) Pulping in the breaker (1) to a stock consistency of more than 15%, b) Delivery from the breaker (1) with the pulp stock at the consistency level established therein, c) Sorting of the pulpy paper stock by conducting it past a metal-seeking device (5), d) Introduction into a dispersion appliance (4) with an operating range which lies within the pulp stock consistency established in the breaker (1), e) Dispersion of the pulp stock in the dispersion appliance (4), f) Ensuing thinning of the pulp stock, g) Further preparation of the pulp by fine sorting and fine cleansing for the purpose of supplying it to the paper or cardboard machine. <IMAGE>

Description

SPECIFICATION A process for preparing waste paper The invention relates to a process for preparing relatively clean, pre-sorted waste paper, particularly paper rejected during the manufacture of paper.

Until now, waste paper has either been pulped to a low consistency in a breaker and then delivered to the further processing stages such as cleansing, sorting and thickening, or the waste paper has been pulped in a breaker to a higher consistency of more than 20%, for example, and then either thinned while still in the breaker or delivered from the breaker to the further processing stages, thinned to a consistency which can easily be pumped and sorted. In all cases when following this procedure a thickener was required, which made the whole process more expensive and also required more space.

An object of the present invention is to provide a simplified process which is particularly intended for the preparation of relatively clean papers, i.e.

either pre-sorted waste paper or papers which have been rejected during the manufacture of paper, such as waterproof portions, for example.

According to the invention, such a process is characterised by the features set out in Patent

Claim 1.

In accordance with the invention a quick and easy preparation process is achieved, which is greatly simplified compared with the known process.

It is particularly advantageous when waste paper containing few contraries is to be prepared, where specifically heavy items such as screws, stones, wires, etc. and large-surface are elements such as foils, pieces of wood, textiles, etc. are meant by the term "contraries", since in this case a very rapid preparation method is obtained for the waste paper up to re-use in the paper machine; in this case any printing inks contained are not removed but are finely dispersed in the subsequent process.

A very advantageous development of the process is realised by using a disc grinder, since the operating characteristic and effect of this can be adapted to the pulp stock consistency involved by adjusting the gap between the discs, and this leaves the choice of pulp stock consistency in the breaker relatively free.

The invention will now be explained in more detail in the following description of one embodiment example of the process, with reference to the accompanying drawing, which is a schematic view of said process.

It will be seen from the drawing that the path of the fibrous pulp from the breaker passes via a shut-off device 10, a screw conveyor 2 and a conveyor belt 3 to the disc grinder 4 in which the suspension is dispersed. Above the conveyor belt 3 there is a metal-seeking device 5 to ensure that metal parts such as screws or staples or suchlike contained in the suspension cannot reach the subsequent sorting equipment or even the paper machine. In the disc grinder the lumps are removed to bring the pulp to the necessary degree of fineness, i.e. it is broken down into individual fibres and any printing inks, for example, which may be contained are dispersed. In this process the pulp stock consistency amounts to approximately 20%, and in particular to more than 20%, and is maintained throughout without change, from the breaker up to the disc grinder.

The most favourable pulp stock consistency, which may also be less than 20%, will be chosen either according to the operating method of the breaker alone, or by also taking into account the possible range of the disc grinder, i.e. its possible spacing. Generally, however, it will be found that the operating characteristic of the disc grinder can be adapted to the consistency which is most favourable for the breaker, by adjusting its operating gap.

Naturally, instead of the disc grinder another dispersion appliance may be selected, and particularly, for example, a single-shaft grinder, which does not have an adjustable operating gap so that in this case the choice of the pulp stock consistency in the breaker may not be made freely, but must be made according to the best possible operating characteristics of the singleshaft grinder.

After the disc grinder the pulp is delivered via a continuousiy operating conveyor belt with reversible conveying direction into an intermediate tank in which thinning is carried out. This is necessary in order to meet the requirements with regard to being sorted, for the subsequent fine sorting and cleansing of the pulp stock. Extraction from the intermediate tank 8 is effected by means of a pump 9. After this, very varied sorting equipment such as strainer sorters, particularly vertical sifters, and also flotation devices may follow. Flotation devices are not necessary, of course, if unprinted waste papers and/or only offcuts (rejects) from the paper manufacturing process are used as the waste paper.When the plant is being run up the conveyor belt can run in the opposite direction and deliver the pulp leaving the disc grinder back into the breaker again via a return conveyor screw 11, as a certain amount of transition time is necessary when the plant is being run up before the pulp has the required properties when it leaves the disc grinder.

The figures also shows that the fibrous pulp is supplied onto the disc grinder 4 by a feed screw 12. If a single-shaft grinder is used a very high pulp stock consistency of, for example, possibly around 30%, and in exceptional cases up to 35%, is necessary in the breaker; however, this is quite within the capabilities of the latter. In the case of the disc grinder the consistencies are lower and, as stated, may vary within a wide range.

CLAIMS 1. A process for preparing relatively clean, presorted waste paper, such as paper rejected during the manufacture of paper, characterised by the following features:

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A process for preparing waste paper The invention relates to a process for preparing relatively clean, pre-sorted waste paper, particularly paper rejected during the manufacture of paper. Until now, waste paper has either been pulped to a low consistency in a breaker and then delivered to the further processing stages such as cleansing, sorting and thickening, or the waste paper has been pulped in a breaker to a higher consistency of more than 20%, for example, and then either thinned while still in the breaker or delivered from the breaker to the further processing stages, thinned to a consistency which can easily be pumped and sorted. In all cases when following this procedure a thickener was required, which made the whole process more expensive and also required more space. An object of the present invention is to provide a simplified process which is particularly intended for the preparation of relatively clean papers, i.e. either pre-sorted waste paper or papers which have been rejected during the manufacture of paper, such as waterproof portions, for example. According to the invention, such a process is characterised by the features set out in Patent Claim 1. In accordance with the invention a quick and easy preparation process is achieved, which is greatly simplified compared with the known process. It is particularly advantageous when waste paper containing few contraries is to be prepared, where specifically heavy items such as screws, stones, wires, etc. and large-surface are elements such as foils, pieces of wood, textiles, etc. are meant by the term "contraries", since in this case a very rapid preparation method is obtained for the waste paper up to re-use in the paper machine; in this case any printing inks contained are not removed but are finely dispersed in the subsequent process. A very advantageous development of the process is realised by using a disc grinder, since the operating characteristic and effect of this can be adapted to the pulp stock consistency involved by adjusting the gap between the discs, and this leaves the choice of pulp stock consistency in the breaker relatively free. The invention will now be explained in more detail in the following description of one embodiment example of the process, with reference to the accompanying drawing, which is a schematic view of said process. It will be seen from the drawing that the path of the fibrous pulp from the breaker passes via a shut-off device 10, a screw conveyor 2 and a conveyor belt 3 to the disc grinder 4 in which the suspension is dispersed. Above the conveyor belt 3 there is a metal-seeking device 5 to ensure that metal parts such as screws or staples or suchlike contained in the suspension cannot reach the subsequent sorting equipment or even the paper machine. In the disc grinder the lumps are removed to bring the pulp to the necessary degree of fineness, i.e. it is broken down into individual fibres and any printing inks, for example, which may be contained are dispersed. In this process the pulp stock consistency amounts to approximately 20%, and in particular to more than 20%, and is maintained throughout without change, from the breaker up to the disc grinder. The most favourable pulp stock consistency, which may also be less than 20%, will be chosen either according to the operating method of the breaker alone, or by also taking into account the possible range of the disc grinder, i.e. its possible spacing. Generally, however, it will be found that the operating characteristic of the disc grinder can be adapted to the consistency which is most favourable for the breaker, by adjusting its operating gap. Naturally, instead of the disc grinder another dispersion appliance may be selected, and particularly, for example, a single-shaft grinder, which does not have an adjustable operating gap so that in this case the choice of the pulp stock consistency in the breaker may not be made freely, but must be made according to the best possible operating characteristics of the singleshaft grinder. After the disc grinder the pulp is delivered via a continuousiy operating conveyor belt with reversible conveying direction into an intermediate tank in which thinning is carried out. This is necessary in order to meet the requirements with regard to being sorted, for the subsequent fine sorting and cleansing of the pulp stock. Extraction from the intermediate tank 8 is effected by means of a pump 9. After this, very varied sorting equipment such as strainer sorters, particularly vertical sifters, and also flotation devices may follow. Flotation devices are not necessary, of course, if unprinted waste papers and/or only offcuts (rejects) from the paper manufacturing process are used as the waste paper.When the plant is being run up the conveyor belt can run in the opposite direction and deliver the pulp leaving the disc grinder back into the breaker again via a return conveyor screw 11, as a certain amount of transition time is necessary when the plant is being run up before the pulp has the required properties when it leaves the disc grinder. The figures also shows that the fibrous pulp is supplied onto the disc grinder 4 by a feed screw 12. If a single-shaft grinder is used a very high pulp stock consistency of, for example, possibly around 30%, and in exceptional cases up to 35%, is necessary in the breaker; however, this is quite within the capabilities of the latter. In the case of the disc grinder the consistencies are lower and, as stated, may vary within a wide range. CLAIMS

1. A process for preparing relatively clean, presorted waste paper, such as paper rejected during the manufacture of paper, characterised by the following features: a) pulping in the breaker to a stock consistency of more than 15%, b) delivery from the breaker with the pulp stock at the consistency level established therein, c) sorting of the pulpy paper stock by conducting it past a metal-seeking device, d) introduction into a dispersion appliance with an operating range which lies within the pulp stock consistency established in the breaker, e) dispersion of the pulp stock in the dispersion appliance, f) ensuing thinning of the pulp stock, g) further preparation of the pulp by fine sorting and fine cleansing for the purpose of supplying it to a paper or cardboard machine.

2. A process according to Claim 1, characterised in that the pulp stock consistency in the breaker is established according to the (optimum possible) operating characteristic of the dispersion appliance.

3. A process according to Claim 1 or 2, characterised by the use of a dispersion appliance with an adjustable operating gap (a disc grinder), the operating gap being set according to the pulp consistency, for the optimum operation of the dispersion appliance.

4. A process according to one of Claims 1 to 3, characterised in that delivery from the breaker is carried out by means of a feed screw or a bucket chain conveyor or a belt conveyor.

5. Apparatus for carrying out the process according to one of Claims 1, 2 or 4, characterised in that the dispersion appliance is a single-shaft grinder.

6. Apparatus for carrying out the process according to one of Claims 1, 3 or 4, characterised in that the dispersion appliance is a double disc grinder, with an adjustable operating gap between the discs.

7. A process for preparing relatively clean, presorted waste paper, or apparatus therefor substantially as hereinbefore described with reference to the accompanying schematic drawing.