Apparatus and method for repulping used paper

Abstract

The invention relates to a device (100) and a method for processing used paper bags, which are shredded into pieces of paper on a shredder (130), wherein the pieces of paper are separated according to size and freed from impurities on a tensioned wave screen machine (220), and wherein the screen overflow is compressed into product bales on a press (430).

Description

AREA OF INVENTION

[0001] The invention relates to a device and a method for processing, in particular, used, emptied paper bags from industry and commerce. TECHNICAL BACKGROUND OF THE INVENTION

[0002] One aspect of the circular economy, established in the German Packaging Ordinance and later in the Circular Economy Act and the Packaging Act, is the material recycling of used paper bags. Due to their composition (kraft paper) and construction (multi-layered with plastic barrier layers), these bags, which are regularly collected in the general paper and cardboard recycling stream and taken to paper mills, cannot be recycled untreated. A large proportion of them are rejected as so-called rejects from the pulping process of paper production and are thermally recycled.

[0003] The basic requirement for material recycling is the return of used paper bags as a mono-collection fraction, the shredding of the material, its cleaning of residual contents and contaminants, and the return of the processed bag paper as secondary fiber to paper manufacturers specializing in recycled kraft paper.

[0004] As part of the processing, it is known to shred the paper bags, sieve the paper pieces, and then compress the sieved paper pieces again. However, the individual processes differ significantly in terms of the quality of cleaning and the degree of recovery. SUMMARY OF THE INVENTION

[0005] The object of the invention is to provide a device and a method for processing used paper, in particular used paper bags, which achieves improved results with regard to the quality of cleaning and the degree of recovery.

[0006] Against this background, the invention relates to a method for processing used paper, in particular used paper bags, wherein the used paper is shredded, the resulting paper pieces are separated by size by screen separation and cleaned of impurities, and the screen overflow in the form of larger paper pieces is pressed into product bales. According to the invention, the screen separation takes place in a tensioned screen machine. Furthermore, according to the invention, the screen overflow is drawn through a shredder fan, with a block separator being installed upstream of the shredder fan.

[0007] The invention further relates to a device for carrying out such a method, comprising a shredder, a tension shaft screening machine and a press.

[0008] The operating principle of the tension wave screen machine is based on the use of vibrations to separate materials. The machine consists of one or more screen mats that are set into vibration by tension waves. The vibrations cause paper pieces of different sizes to be transported across the screen mat. Finer paper pieces and impurities, such as residual contents from paper bags, fall through the screen openings, while larger paper pieces remain on the screen. The tension wave screen machine enables intensive loosening and segregation of the paper pieces and impurities, which makes the inventive method particularly efficient compared to existing methods. This is achieved through high acceleration values ​​accompanied by a trampoline effect. The frequency and amplitude of the waves can be adjusted to optimize the separation efficiency for different feed materials.

[0009] In one embodiment, it is provided that the tension shaft screening machine used in the device according to the invention comprises several screen mats, in particular more than 5, preferably more than 10 or particularly preferably more than 20 screen mats.

[0010] In one embodiment, the screen mat(s) of the tensioned shaft screening machine have a mesh size of between 5 and 30 mm, preferably between 7 and 20 mm, and particularly preferably between 8 and 15 mm. These mesh sizes have proven to be particularly suitable in the context of the feed material in the process according to the invention.

[0011] The method according to the invention is preferably a purely dry mechanical method.

[0012] In one embodiment, the paper or paper bags processed in a method or with a device according to the invention meet certain requirements.

[0013] In one embodiment, the residual contents of the paper bags are a maximum of 20% by weight of the bag's empty weight. The bags should have a residual moisture content of no more than 30% by weight.

[0014] In one embodiment, the contents of the paper bags are selected from the group of building materials, for example cement or lime, or from the following chemical products: alkaline inorganic compounds, acidic inorganic compounds, inert inorganic compounds, mutually unreactive organic compounds, organic polymer compounds other than PVC, or PVC. Conversely, it is preferably provided that the contents of the paper bags do not contain carbon black, color pigments, seeds, food or feed, or materials containing pollutants as defined in Section 15 of the German Packaging Act 2019 (VerpackG), with the exception of cement and lime. The paper is preferably free of metals and, in particular, aluminum.

[0015] In one embodiment, the used paper undergoes a sensory incoming inspection for residual moisture and / or impurities. This ensures that the aforementioned parameters for the paper are met.

[0016] In one embodiment, the used paper is fed in in the form of paper bales and, preferably under a suction device, is freed from the bale wire.

[0017] In one embodiment, the paper is shredded in a shredder with a shaft and multiple shredding tools, to which the paper is fed via a feed chute. The feed chute can be equipped with a suction device. Furthermore, the feed chute can be equipped with a slide for conveying material. Additionally, the feed chute can be equipped with a fill level sensor. The amount of paper fed into the shredder can be regulated by the fill level sensor. The shredder can have a drive power of, for example, between 50 and 300 kW. The rotational speed of the shaft can, for example, be between 50 and 200 rpm. It should be designed and operated in such a way that the paper is shredded into pieces approximately the size of a hand.

[0018] In one embodiment, the paper pieces are transported away from the shredder by means of a conveyor belt. The conveyor belt is preferably fully enclosed and equipped with a suction device. In one embodiment, it can be inclined.

[0019] In one embodiment, the paper pieces fall from above into a feed hopper of the tensioned-shaft screening machine. The discharge height can be between 2 and 10 meters, particularly between 4 and 8 meters. The discharge can occur at the end of the conveyor belt. The feed hopper can be equipped with a fill level sensor. The quantity of paper pieces fed into the tensioned-shaft screening machine can be controlled by the fill level sensor.

[0020] In one embodiment, it is provided that the sieve overflow is drawn in horizontally or substantially horizontally by a chopper fan.

[0021] The block separator, positioned upstream of the shredder fan, removes heavy particles such as metals, wood, stones, etc., which are present as contaminants in the paper bales. This increases the service life of the shredder fan, prevents malfunctions, and reduces the risk of dust explosions. The block separator's separation mechanism can, for example, involve flow deflection, causing heavy particles to settle due to their inertia.

[0022] A paper separator is preferably arranged after the chopper fan, in which the conveying air is separated from the pieces of paper.

[0023] The sequence of the shredder fan and the paper separator achieves a final cleaning of the paper. A rotary valve for the screen overflow can be installed upstream of the suction section leading to the shredder fan to ensure transport and a constant and appropriate flow rate.

[0024] In one embodiment, a spark extinguishing system is arranged downstream of the shredder fan, specifically between the shredder fan and the paper separator. This system comprises optical sensors for spark detection and an extinguishing nozzle through which high-pressure water is sprayed into the pipeline in the event of spark detection. This serves to prevent dust explosions, as sparks can occur if metal parts are present in the shredder fan, which is not entirely avoidable.

[0025] In one embodiment, dust-laden air, which is extracted in one or more process steps, particularly at the paper separator, is conveyed through an extraction line to a filter system and filtered there. The filter system preferably comprises a bag filter and, more preferably, a jet filter. To protect against dust explosions, the filter system can be equipped with pressure relief vents.

[0026] In one embodiment, it is provided that dust retained in the filter system is combined with impurities separated in the tension shaft screening machine and pieces of paper sorted according to their size.

[0027] In one embodiment, impurities separated in the tensioned-shaft screening machine and paper pieces sorted according to size, possibly along with any dust retained in the filter system, are transported to a filling station and filled into bags there. The filling station is preferably fully enclosed and has a suction device for extracting air, which can then be directed to the filter system.

[0028] In one embodiment, dust retained in the filter system and / or impurities separated in the tensioned-shaft screen machine, along with paper pieces sorted according to size, are fed to a further screening stage, and the overflow from this further screening stage is also fed to the shredder fan. This additional screening step can increase the yield. Suitable screening devices for this further screening stage include, for example, a gyratory screen.

[0029] Further details and advantages of the invention will become apparent from the following description of an exemplary embodiment. BRIEF DESCRIPTION OF THE FIGURES

[0030] Fig. 1 a schematic representation of a system according to the invention in an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] The in Fig. 1The plant marked with reference number 100 is used for the processing of used paper bags, which includes cleaning and shredding.

[0032] The paper bags are delivered in bales by truck. After an initial inspection, which may include measuring the moisture content of each bale and performing a sensory or visual check for markings, contaminants, or other foreign materials, the bales are transferred to receiving warehouse 110. Storage until processing takes place separately according to delivery.

[0033] The bales 10 are removed from the receiving storage area 110, unwrapped from the baling wire using suitable tools, opened, and placed onto a bale storage conveyor 120. The bale storage conveyor 120 is equipped with extraction devices 512 that can draw any released dust upwards.

[0034] The bale storage conveyor 120 throws the opened paper bales 10 into the feed chute of a shredder 130. The conveying capacity of the bale storage conveyor 120 is regulated by a level sensor in the feed chute of the shredder 130 to ensure a consistent feed and prevent overfilling. The level sensor can include one or more radar sensors. An additional extraction device 513 and a plastic louvered curtain at the feed opening of the feed chute prevent dust from escaping.

[0035] In the exemplary embodiment, the shredder 130 is an electrically driven single-shaft shredder. Depending on the size of the system 100, the shredder 130 can have a drive power of, for example, between 50 and 300 kW. A pusher, which can be hydraulically driven, pushes the opened paper bales 10 in the feed chute in front of the rotor, which is equipped with a larger number of shredding tools. The rotational speed of the rotor can, for example, be between 50 and 200 rpm.

[0036] The paper, shredded into palm-sized pieces, falls from the shredder 130 onto a conveyor belt 140. The conveyor belt 140 is fully enclosed and equipped with a suction device 514. It rises at an angle to a discharge height, which, depending on the dimensions of the system 100, can be between 2 and 10 meters, for example.

[0037] The shredded paper enters a tension-shaft screen 220 installed below it via a feed hopper (not shown separately in the figure). The conveying capacity of the conveyor belt 140 is regulated by a level sensor in the feed hopper to ensure regular feeding and prevent blockages. The level sensor may include a microwave barrier.

[0038] The tensioned wave screening machine 220 is a core element of the device 100 according to the invention. It preferably comprises several screening mats, for example about 30 screening mats, wherein the mesh size can be, for example, 10 mm. The tensioned wave screening machine 220 enables intensive loosening and segregation of the material being screened. This is achieved through high acceleration values ​​accompanied by a trampoline effect.

[0039] The screen overflow, i.e., the cleaned pieces of paper, falls into a rotary valve 310 at the end of the tensioned-shaft screen machine 220. Contaminants, which may consist in particular of residues of the filling materials from the bags, so-called residual filling materials, as well as fine pieces of paper with a size that is below the mesh size, fall through the screen mats of the tensioned-shaft screen machine 220 into a screen trough 221.

[0040] The paper pieces are drawn into a shredder fan 320, essentially horizontally, from the rotary valve 310. In addition to transporting the paper, the mechanical action as it passes the impeller of the shredder fan 320 also provides a final cleaning of the paper.

[0041] A block separator 315 is installed between the rotary valve 310 and the shredder fan 320. Heavy particles, such as metals, wood, stones, etc., which are present as contaminants in the paper bales, are separated at the block separator 315, while the lighter paper passes into the shredder fan 320. The separation mechanism of the block separator 315 can, for example, include flow deflection, where heavier particles settle due to their inertia. The block separator 315 increases the service life of the shredder fan 320 and process safety with regard to potential dust explosions.

[0042] Due to the unavoidable presence of metal parts, even in the shredder fan 320, sparks can occur. To prevent a dust explosion, the pipeline between the shredder fan 330 and the paper separator 330 is equipped with a spark extinguishing system, comprising optical sensors for spark detection and an extinguishing nozzle through which high-pressure water is sprayed into the pipeline in the event of spark detection.

[0043] In the paper separator 330, the cleaned paper is separated from the dust-laden conveying air. The separated air is discharged via the extraction line 500. The paper falls through a chute into a baling press 340. Again, suitable sensors and feedback control of the upstream equipment prevent the chute from overfilling. Suitable sensors include, for example, one or more light barriers.

[0044] The baler 340 compacts the cleaned paper shreds into product bales 30 weighing approximately 1,250 kg, which can be roughly 2 x 1 x 1 meters in size and weigh just over 1 ton. The product bales 30 are then transferred to a product storage unit 350. After weighing, they are transported away, for example, by truck.

[0045] In one variant, the baling press 340 can also be equipped with an additional feed conveyor (not shown in the figure) to allow the pressing of paper that has not been previously processed. This allows, for example, bales that have fallen apart to be re-pressed for further transport or handling.

[0046] The dust-laden air separated in the paper separator 330 is combined in the extraction line 500 with other extracted process air from the extraction devices 512, 513, 514, and 542 (the latter described later) and drawn through a central filter system 520 by a main fan 510. In the filter system 520, the air is cleaned to such an extent that a legally defined maximum dust emission (currently 5 mg / m³ in the EU) is reliably undercut. The filter system 520 can be a bag filter or, in particular, a jet filter, in which the air to be cleaned flows through the fabric tubes from the outside to the inside. The main fan 510 then conveys the cleaned air through an outlet 530, which can be located above the roof. The cleaning of the loaded filter bags 522 is carried out using compressed air 521, depending on the pressure drop of the filter 520.The dust retained by the filter hoses falls downwards, collects in the filter trough 523 and is discharged by a trough conveyor screw 524.

[0047] To mitigate the residual risk of a dust explosion in the filter system 520, it can be equipped with pressure relief openings (not shown in the figure). To enable installation inside a building, quench tubes made of fine metal mesh can be mounted in front of the pressure relief openings. These tubes prevent flame propagation and reduce explosion pressure.

[0048] The dust discharged from the filter system 520 by the trough screw conveyor 524, as well as the residual materials or fine paper pieces collected in the screen trough 221 of the tensioned screen 220, are conveyed via a screw conveyor system 410 to a gyratory screen 415, where any remaining small paper and film fragments are separated from fine-grained and dust-like residual materials. The three-dimensional, elliptical gyratory motion ensures a spiral movement of the material on the screen, large-area utilization of the screen surface, and effective separation. The motion can be generated by an eccentric drive unit below the screen plate, whereby the amplitude and speed of the gyratory motion are preferably adjustable and can be optimized for the specific conditions.

[0049] The screen overflow, consisting of paper and film scraps, is fed to the suction side of the shredder fan 320 by means of a suitable conveying device, in the example shown a trough screw conveyor 416, and thus mixed back into the cleaned paper. This recirculation increases the product yield of cleaned paper. Depending on the application, the feed can take place before or after the block separator 315. Feeding before the block separator 315 does not restrict its capacity and function with regard to the main material flow, while feeding before the block separator 315 allows for the separation of any remaining blocks from the mixed material as well. The use of two separate block separators is also possible in some configurations.

[0050] The remaining contents from the tumbling screen 415 are fed to a bag filling station 420 via further screw conveyors 419 as a sieve pass.

[0051] The bag filling station 420 has a speed-controlled metering screw 421, which feeds the remaining material into an enclosure 422. Inside the enclosure 422, the bags 40 are filled according to a preset fill weight. The enclosure 422 is equipped with a suction device 542 that can extract any released dust upwards. A blower inflates the bags 40, ensuring proper filling. An overfill protection device in the filling spout prevents unintentional overfilling. The filled bags 40 are conveyed on a roller conveyor 423 to a discharge station outside the enclosure 422. A small intermediate container, not shown in the figure, is located upstream of the metering screw 421 to serve as a buffer for necessary bag changes.

[0052] The device according to the invention can be designed for an annual throughput of more than 20,000 tons in shift operation or an hourly processing capacity of more than 4 tons of cleaned paper bags. In tests, cleaning of the paper to a residual adhesion of less than 5% was achieved with a proportion of approximately 15-20% of the extracted residual contents.

Claims

1. Method for processing used paper, in particular used paper bags, wherein the used paper is shredded, wherein the resulting pieces of paper are separated by size by screen separation and freed from impurities, and wherein the screen overflow in the form of larger pieces of paper is pressed into bales of product, characterized by that The screen separation takes place in a tension shaft screen machine (220), and the screen overflow of the tension shaft screen machine (220) is sucked through a chipper fan (320), to which a block separator (315) is connected.

2. Method according to claim 1, characterized by the fact that the tension wave screening machine (220) comprises several screening mats, in particular more than 5, preferably more than 10 or particularly preferably more than 20 screening mats.

3. Method according to any of the preceding claims, characterized by the fact thatThe screen mat(s) of the tension shaft screen machine (220) have a mesh size of between 5 and 30 mm, preferably between 7 and 20 mm and particularly preferably between 8 and 15 mm.

4. Method according to any of the preceding claims, characterized by the fact that A spark extinguishing system comprising optical sensors for spark detection and an extinguishing nozzle is arranged after the hacker fan (315).

5. Method according to any of the preceding claims, characterized by the fact that Dust-containing air, which is extracted in one or more process steps, is guided through an extraction line (500) to a filter system (520) and filtered there, wherein the filter system (520) preferably comprises a bag filter and further preferably a jet filter.

6. Method according to claim 5, characterized by the fact thatDust retained in the filter system (520) is combined with impurities separated in the tension shaft screen machine (220) and pieces of paper sorted according to their size and filled into suitable containers (40).

7. Method according to any of the preceding claims, characterized by the fact that Impurities separated in the tensioned wave screen machine and pieces of paper sorted according to their size and / or dust retained in the filter system are fed to a further screen separation, for example in a gyratory screen, and the screen overflow of this further screen separation is also fed to the shredder fan.

8. Method according to any of the preceding claims, characterized by the fact that the residual content of the used paper bags is a maximum of 20% by weight of the empty bag weight and / or the used paper has a residual moisture content of a maximum of 30% by weight. 10.Method according to any of the preceding claims, characterized by the fact that The used paper undergoes a sensory incoming inspection for residual moisture and / or impurities.

11. Method according to any of the preceding claims, characterized by the fact that the used paper is fed in the form of paper bales (10) and is freed from the bale wire after feeding, preferably under a suction device.

12. Method according to any of the preceding claims, characterized by the fact that the shredding of the paper is carried out in a shredder (130), to which the paper is fed through a filling chute, which is preferably equipped with a suction device (513), a slide for conveying material and / or a fill level sensor.

13. Method according to any of the preceding claims, characterized by the fact thatThe pieces of paper are transported away from the shredder by means of a conveyor belt (140), wherein the conveyor belt is preferably encapsulated on all sides, provided with a suction device (514) and / or inclined.

14. Method according to any of the preceding claims, characterized by the fact that the pieces of paper fall from above into a feed hopper of the tension shaft screening machine (220), the drop height preferably being between 2 and 10 meters, and more preferably between 4 and 8 meters.

15. Device (100) for processing used paper, in particular used paper bags, within the framework of a method according to one of the preceding claims, comprising a shredder (130), a tension shaft screen machine (220), a shredder fan (320) with a pre-connected block separator (315), and a press (340).

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