GB2064612A

GB2064612A - Treating waste paper

Info

Publication number: GB2064612A
Application number: GB8035824A
Authority: GB
Original assignee: Hermann Finckh Maschinenfabrik GmbH and Co
Current assignee: Voith Finckh Fiber Systems GmbH and Co KG
Priority date: 1979-11-08
Filing date: 1980-11-07
Publication date: 1981-06-17
Also published as: EP0028658A1; GB2064612B; DE3040998C2; ATA547980A; FR2469496B1; AT382649B; FR2469496A1; DE3040998A1

Description

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GB 2 064 612 A 1 .DTD:

SPECIFICATION Method and device for treating waste paper .DTD:

In the known methods which are used for treating waste paper the procedure is such that the paper is placed together with water in a so called pulper comprising a receptacle which is open at the top and whose bottom is penetrated by the drive shaft of a pulper wheel arranged inside the receptacle. A filter is disposed above the receptacle bottom and beneath the pulper wheel and the receptacle bottom comprises an outlet. In these known pulpers the quantity of water added to the waste paper is such that they operate in a consistency range of two to six per cent. The pulper is operated until the waste paper is largely dissolved and the filter above the receptacle bottom serves to retain insoluble material such as metal fragments, wood, glass and plastics material (as far as this is possible). While the waste paper is being dissolved in the pulper ' 85 however the pulper wheel inevitably also breaks up plastic constituents such as plastic coatings of paper and cardboard, plastic bags and sacks and so forth, so that a considerable portion of the plastics can pass through the filter of the pulper and can subsequently only be separated with difficulty from the fibre suspension produced in the pulper. Further disadvantages of the known method are a high degree of wear on the pulper wheel and on the filter, caused particularly by the metal fragments contained in the waste paper and the long operating time of the pulper, which is necessary to dissolve the waste paper, standstill periods on account of the necessary cleaning, carried out at intervals, of the filter disposed above 100 the receptacle bottom and the high energy requirement for dissolving the waste paper in the pulper. In this connection it should be noted that the degree of impurities in waste paper increases from year to year.

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On the whole, the recently disclosed use of a conventional pulper comprising a filter with larger holes, in connection with a so-called after-pulper of the same design, but whose filter comprises essentially smaller holes, does not prove any 1 10 better. According to this method, part of the dissolving work is effected by the after-pulper, and metal and wood fragments, together with other light-weight dirt such as, for example foam plastic material are removed from the fibre suspension in 1 15 the after-pulper. Although, on account of the larger holes in the filter of the first pulper, the latter need not be cleaned so often, i.e. the cleaning intervals are longer, particles of dirt and particularly plastics are reduced to such a small size in this known method that their subsequent sorting involves further disproportionately high costs and results in considerable losses in the quality of the fibre material produced.

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Furthermore, this kind of treatment also requires a 125 relatively large amount of energy.

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The general object of the invention is to provide a method for treating waste paper, in which the latter is more carefully dissolved, which requires less energy and by means of which the abovementioned disadvantages of the known methods can be at least partly avoided.

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Based on a method for treating waste paper, in which the latter, while being constantly moved and rearranged, is steeped, possibly treated with chemicals, and dissolved, the resulting fibre suspension then being sorted, it is proposed according to the invention that the steeped material should be put into intermediate storage directly after the steeping operation in order to swell. With a relatively shorter steeping time, it is therefore possible for the material to be dissolved in a more careful manner, without the necessity of tolerating a comminution of useless constituents such as plastics material sheet. Furthermore, the dissolution can be accomplished with a far smaller energy expenditure, as no energy need be expended during the intermediate storage period, so that this period, and therefore that available for selling the waste paper, can be of almost any desired duration.

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A considerable amount of energy can be saved if the material is left to swell for a considerable time and the fibre material is soaked in a more satisfactory manner than was previously the case. In the method according to the invention the steeping time can therefore be up to 2 hours (in the case of waste paper which is difficult to dissolve) and the intermediate storage period up to 4 hours.

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It was previously thought advisable to carry out the steeping operation at the highest possible temperatures, as it was considered that the effectiveness of the steeping procedure increased with the temperature. The inventor has now surprisingly found that optimum results are obtained with steeping temperatures of approximately 40 C and the higher temperatures provide no advantages. On the contrary, they represent an energy waste and entail the disadvantage of an irreversible hornification of the fibres, thus damaging the latter. In a preferred embodiment of the method according to the invention steeping is therefore performed out at a temperature of approximately 40 C, thus allowing more energy to be saved.

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As industrial waste water is generally relatively warm and is introduced into the fibre suspensions by mechanical method steps in the treatment of waste paper, thus heating the fibre suspensions, so that the waste water of such treatment methods has a high temperature with respect to the ambient temperature, although high temperatures of industrial waste water are not only undesirable, but also represent an energy waste, it is also proposed to draw heat from the waste water of the entire factory, particularly from the waste water of the treatment method, and to feed this to the steeping water, preferably by using a heat pump appliance.

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In order to promote dissolution of the fibre material, it has also proved advisable to scrape the material out of the material mass in intermediate storage in small portions.

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2 The inventor has recognised that it is advisble to maintain quite specific consistencies or consistency ranges during all the steps of such a treatment method. It is therefore proposed, for a preferred embodiment of the method according to the invention in which the waste paper is steeped in batches, to weigh the waste paper which is to be steeped and to calculate and measure out the quantity of water to be added in accordance with the consistency which is favourable for the steeping operation.

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For the desired, careful dissolution of the fibre material, it is advisable for the material which has been steeped and put into intermediate storage to obtain a consistency of at least approximately 8%, preferably of 8-12%, to be diluted with water. and mixed with the latter by setting the material and the water together in rapid circulation for several minutes. In the method according to the invention the operation is therefore performed with a distinctly higher consistency than with known pulpers (2-6% in the latter case), so that a high degree of dissolution can also be achieved in a relatively short time.

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Whereas the known pulpers also include sorting devices on account of the filter which is installed, it is recommended when carrying out the method according to the invention, not to sort the material until the completion of the rapid circulation, i.e. the mixing procedure.

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The method according to the invention is advantageously performed with a device which comprises a steeping vessel -which can be made to rotate and which has an opening and a servo-controlled closure for the latter- as well as 100 a weighing device for the waste paper which is to be steeped, a metering device for the steeping water and a computer, which can be acted upon by the two latter devices, for controlling the closure. The steeping procedure can therefore be automatically controlled and the obtaining of an optimum consistency is also guaranteed. A bunker is then appropriately provided directly beneath the steeping vessel for the intermediate storage of the steeped material. In order to promote the dissolution procedure and to move the swollen material onto a conveyor belt or similar in a uniform manner, it is advisable to provide the bottom of the bunker with a bunker emptying and distributing device which comprises several material, conveying elements distributed over at least the greater part of the cross-section of the bunker bottom.

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To ensure automatic control of the steeping procedure, it is advisable to provide a weighing device, associated with a mixer for carrying out the mixing procedure, for weighing the amount of material to be put into the mixer, a computer connected to the weighing device in order to determine the amount of water to be put into the mixer, as well as a computer-controlled metering device for the amount of water, as a result of which the above-mentioned, favourable consistency is also reliably maintained for the mixing procedure.

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GB 2 064 612 A 2 Further characteristic features, advantages and details of the invention should become apparent from the following description and the accompanying diagrammatic representation of a preferred embodiment of device according to the invention for treating waste paper. In the drawing:

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Figure 1 is a schematic representation of the entire device; Figure 2 is an enlarged view of the bunker of the device according to Figure 1; and Figure 3 is a front view of the bunker.

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Waste paper, either loose or in bales, is loaded onto a conveyor belt 10 by means of a load board (not shown) and the conveyor belt conveys the waste paper to a steeping vessel 12. This is provided on the outside with axle journals (not shown), by which it is mounted in bearing supports 14, so that it can be made to rotate by means of an electric motor (also not shown) about a central axle 16 extending perpendicular to the drawing plane of Figure 1. The vessel 12 has an opening 18, which can be closed by a sliding member 20. The latter is actuated by a pressure medium cylinder 22, so that the opening 18 can be opened and closed.

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At one or both axles of the steeping vessel 12 there is a weighing device 26 for determining the amount of waste paper conveyed from the conveyor belt 10 to the steeping vessel 12. This weighing device 26 is connected to a computer 28 via a lead 26a, this computer also controls the drive motor of the steeping vessel 12 via a lead (not shown), so that the steeping procedure can be terminated after a predetermined period. The computer also controls, via a lead 22a, the pressure medium cylinder 22 for opening or closing the steeping vessel 12. A driving device 30 for the conveyor belt 10 is also controlled by the computer via a lead 30a. Finally, the computer 28 controls via a lead 32a a flowmeter 32 which is disposed in a steeping water conduit 34 and behind which a valve 36 is disposed in the steeping water conduit 34, this valve being controlled via a lead 36a by the flowmeter. The steeping water conduit 34 leads from the valve 36 to the steeping vessel 12, preferably via the hollow rotation axle into the steeping vessel.

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The computer 28 is fed via adjustment elements 28a, 28b and so forth with the steeping 1 15 time, the type and the amount of waste paper of each batch to be steeped and the consistency for the steeping procedure. The computer then opens the sliding member 20, sets the conveyor belt 10 in motion, until the quantity of waste paper which is to be steeped per batch is in the steeping vessel 12, opens the valve 36 via the flowmeter 32 until the quantity of steeping water required for the preselected consistency is in the steeping vessel 12, and then closes this opening 18 and connects the drive for the steeping vessel 12 during the preselected steeping time. The steeping vessel is subsequently stopped in a position in which its opening 18 is pointing downwards, whereupon the sliding member 20 opens and the steeping vessel is emptied. The steeped quantity of waste 3 G B 2 064 612 A 3 paper then reaches a bunker 40 disposed below the steeping vessel 12, for the intermediate storage of the material, so that it can continue to swell.

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As can be seen from Figures 2 and 3, a bunker emptying and distributing device 44 extends over a bunker bottom 42 and is provided with two endless chains 44a, between which removal strips 446, to which driving elements 44c are connected, extend. The chains 44a pass over 75 chain wheels 48 secured to shafts 46, so that they can be caused to rotate by a geared engine 49 driving one of the shafts. As a relatively high consistency of approximately 20-40% is set for the steeping procedure, transverse slots 40b can be provided between the end walls 40a of the bunker and the bunker bottom 42, through which slots the emptying device 44 extracts the swollen material and delivers it to a conveyor belt 50.

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The conveyor belt 50 conveys the steeped and swollen material to a mixer 52 comprising a mixer wheel 52b which disposed directly above the bottom of the mixer and has a vertical axle, the mixer wheel being driven by a motor 52c arranged below the bottom of the mixer. A discharge opening 52d is also provided in the region of the mixer bottom and comprises a drain valve 54.

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A weighing device 56 is arranged in the upper region of the mixer 52 and comprises a chamber 56b which is open at the top and can be closed at the bottom by flaps 56a which can be pivoted upwards in the direction of the arrows. These flaps can be opened and closed by pressure medium cylinders 56c, and weighing elements 56d are provided in order to determine the weight of the material mass which is put into the chamber 566.

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A flowmeter 62 and a valve 64 are provided in a diluting water pipe 60 leading into the interior of the mixer 52 in order to allow a quite specific quantity of diluting water to be added to a quantity of material measured by the weighing device 56. A computer 66 is also provided and controls a drive device 68 for the conveyor belt 50 via a lead 68a, receives a weight-dependent signal from the weighing elements 56d via a lead 56f, opens and closes the valve 64 via a lead 62a, the flowmeter 62 and a lead 64a, controls the pressure medium cylinder 56c via a lead 56g and opens and closes the drain valve 54 via a lead 54a. Adjustment elements 66a, 66b and so forth allow pre-selection of the quantity of material per batch to be mixed, the consistency of the fibre suspension following the conclusion of the mixing procedure and the duration of the latter. 120 The mixer wheel 52b is constructed so that the material which is put into the mixer 52 and the diluting water can be made to circulate rapidly and be mixed together, the dissolution of the fibre material being simultaneously completed. When the mixing procedure has been concluded, the drain valve 54 opens and is subsequently closed again. With the flaps 56a in the closed position, the conveyor belt 50 then conveys the pre selected amount of material into the weighing device 56, whereupon the flaps 56a are opened, so that the quantity of material falls into the mixer 52, into which the required quantity of diluting water is simultaneously delivered.

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A pipe connection 70 leads from the mixer 52 into a drum sorter which is open at the front and at the back, this sorter being a cylindrical drum driven about a horizontal axle and comprising a jacket 74 constructed as a filter. The drum sorter is driven via a gear ring 76 and a pinion 78 mounted on the axle of a motor 80. A spraying pipe 82 is disposed above the drum sorter 72 and is connected to the diluting water pipe 60 via a pipe 84. A vat 86 is disposed below the drum sorter 72 in order to receive the accepted stock, i.e. the usable fibre material, while the so-called trash, i.e. the part of the waste paper which cannot be used, reaches a trash container 90 via the outlet opening 72b of the drum sorter 72 and a chute 88.

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The fibre suspension conveyed via the pipe connection 70 and the inlet opening 72a of the drum sorter 72 into the latter is sorted there and the nozzles of the spraying pipe 82, which are directed towards the outside of the filter jacket 74, cause the good fibres of the fibre suspension to be washed out of the trash and flushed through the filter openings into the vat 86. The spraying pipe nozzles are also used for the continuous cleansing of the filter jacket 74.

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It is advisable to arrange driving ledges 12' and 72' inside the steeping vessel 12 and the drum sorter 72.

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The pipe 60 supplying the water for the mixer 52 and the steeping vessel 12 is advantageously supplied with the water which is taken from the fibre suspension before the paper machine, which is not shown, via a conventional thickener. A heat exchanger of a heat pump appliance, indicated as a whole by 96, is arranged in the steeping water pipe 34 which branches off from the pipe 60, this appliance being advantageously a gas-heat pump appliance. Heat is drawn from the waste eater in a waste water pipe, which is not shown, of the treatment plant via this appliance and fed to the steeping water. As such heat pump appliances are known, it is unnecessary to describe them in detail.

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The treatment time in the steeping vessel 12 is preferably between approximately 20 and 45 minutes, whereupon the material should be stacked in the bunker 40 for approximately 30 to 60 minutes, so that it can swell under the influence of the steeping water. This renders the dissolution process substantially easier and results in a careful dissolution of the fibre material.

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During the operation in the mixer it is advisable to have a relatively high consistency of at least 8%, preferably of approximately 8-12%, as it is then sufficient to treat each batch in the mixer for approximately 2-5 minutes. The sorting filter openings of the drum sorter should have a diameter of approximately between 4 and 12 mm and they are advantageously formed so that they widen outwards from within.

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4 GB 2 064 612 A 4 .CLME:

Claims

CLAIMS .CLME:

1. A method for treating waste paper, in which the latter is initially steeped and dissolved in batches, while being constantly moved and rearranged, the resulting fibre suspension then being sorted, characterised in that the steeped material is put into intermediate storage to swell directly after the first steeping operation, that the material is then diluted with additional water and mixed with the latter by setting the material and the water together in rapid circulation and that, in order to obtain a predetermined consistency of at least 5% for this mixing operation, the material is weighed and the quantity of water which is to be added in accordance with the predetermined consistency is calculated and measured out.

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2. A method according to claim 1, characterised in that the material is kept in intermediate storage for a period which is of at least the same magnitude as the steeping time.

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3. A method according to claim 1 or 2, characterised in that the material for steeping and swelling is brought to a consistency of approximately 20-40%.

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4. A method according to claims 1, 2 or 3, 90 characterised in that steeping is carried out at a temperature of approximately 40 C.

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5. A method according to any of claims 1 to 4, characterised in that the steeping time is up to approximately 2 hours.

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6. A method according to any of claims 1 to 5, characterised in that the intermediate storage time is up to approximately 4 hours.

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7. A method according to any of claims 1 to 6, characterised in that the steeping time and the 100 intermediate storage time are in each case approximately 20 to 60 minutes.

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8. A method according to claim 7, characterised in that the steeping time is approximately 20 to 45 minutes.

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9. A method according to claim 7, characterised in that the intermediate storage time is approximately 30 to 60 minutes.

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10. A method according to any of the preceding claims, characterised in that heat is drawn from 110 waste water of the treatment process and fed to the steeping water.

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11. A method according to any of the preceding claims, characterised in that the material is scraped out of the material mass in intermediate 1 1 storage in small portions.

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12. A method according to any of the preceding claims, in which the waste paper is steeped in batches, characterised in that the waste paper to be steeped is weighed and the quantity of water to 120 be added for steeping and swelling is calculated and measured out in accordance with a predetermined consistency.

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13. A method according to any of the preceding claims, characterised in that a consistency of at 125 least 8% is set for the mixing operation.

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14. A method according to claim 13, characterised in that a consistency of between 8% and 12% is set for the mixing operation.

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15. A method according to any of the preceding 130 claims, characterised in that the material and the water are set in rapid circulation for approximately 2 to 5 minutes for mixing.

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16. A method according to any of the preceding claims, characterised in that the material is not sorted until the mixing operation has been concluded.

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17. Apparatus for performing the method according to any of the preceding claims, characterised in that a steeping vessel which can be made to rotate and comprises an opening and a servo-controlled closure for the latter, a weighing device for the waste paper which is to be steeped, a metering device for the steeping water, as well as a computer, which can be acted upon by the two latter devices, for controlling the closure, are provided.

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18. Apparatus according to claim 17, characterised in that a bunker is provided below the steeping vessel for the intermediate storage of the steeped material.

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19. Apparatus according to claim 18, characterised in that a bunker emptying and distributing device is provided at the bottom of the bunker and comprises several material carrying elements distributed over at least the greater part of the cross-section of the bunker bottom.

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20. Apparatus according to any of claims 17 to 19, characterised in that a mixer with a container and a drivable mixer wheel, arranged above the container bottom, is provided for mixing with waterthe material which has been put into intermediate storage.

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21. Apparatus according to claim 20, characterised in that the mixer wheel is arranged directly above the container bottom.

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22. Apparatus according to claim 20 or claim 21, characterised by a weighing device, associated with the mixer, for weighing the quantity of material to be put into the mixer, a computer connected to the weighing device for determining the quantity of water to be put into the mixer, and by a computer-controlled metering_ device for the quantity of water to be put into the mixer.

23. Apparatus according to any of claims 20 to 22, characterised in that the mixer comprises an outlet with a time-controlled drain valve in the region of the container bottom. 5

24. Apparatus according to any of claims 20 to 23, characterised in that an open sorter is arranged after the mixer.

25. Apparatus according to claim 24, characterised in that the sorter comprises a horizontal drum which is rotatable about its longitudinal axis and has filter openings, spray water nozzles being directed towards the drum from outside.

26. Apparatus according to claim 25, characterised in that the spray water nozzles are disposed above the drum.

27. Apparatus according to any of claims 17 to 24, characterised in that a heat pump appliance for heating the steeping water is provided between a waste water pipe and a steeping water GB 2 064 612 A 5 pipe leading to the steeping vessel.

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28. A method for treating waste paper substantially as hereinbefore described.

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29. Apparatus for treating waste paper and constructed substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

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Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.

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