Device and method for separating a liquid from a feedstock

Abstract

The invention relates to a device and a method for separating a liquid from a feedstock, in particular from a ground material composed of plastics material. The device comprises a rotor (1) having paddles (3) for swirling the feedstock. The paddles (3) are arranged on a peripherally extending wall (5) of a core (2) of the rotor between the core (2) and a perforated inner wall (4) of a screening drum (1), and a chamber is formed between the core (2) and the outer wall (4). The core (2) is hollow, has openings (6) in the peripherally extending side wall (5), and has, at an axial end, a feed (7) for an air flow, in particular for a warm or hot air flow. The feed (7) and the openings (6) are connected by the interior of the hollow core (2) in such a way that the air flow introduced through the feed (7) is conducted through the openings (6) into the chamber in order to separate the liquid from the feedstock.

Description

[0001] DEVICE AND METHOD FOR SEPARATING A LIQUID FROM A MATTER

[0002] The invention relates to a device and a method for separating a liquid from a feed material, in particular from a ground material made of plastic.

[0003] Devices and methods of the type in question have been known in practice for years. In many cases, two separate units are used to dry plastic regrind. In the first machine, the feed material is accelerated to high peripheral speed using mechanical energy and conveyed through a perforated metal chamber. Any free water present is separated during this process. Such a dryer is known, for example, from DE 102016 010 377 A1. In the subsequent machine, this pre-dried regrind is aerated using an airflow, particularly a hot airflow, both aerated and thermally. By injecting air, especially cold air, the water can be blown off the surface of the regrind and drained through the screen drum. This presents several challenges.Firstly, mechanical dryers must be operated at high speeds to achieve the required drying levels, resulting in significant product losses due to abrasion and comminution. Furthermore, this necessitates high drive power and thus high energy consumption per unit mass of material being ground. This also leads to high wear and tear on the machine. The requirement for two separate machines also results in a large footprint for these installations. Additionally, the thermal stress on the product in conventional thermal dryers is very high, sometimes exceeding the softening point of the polymers in order to achieve the required drying levels.

[0004] The present invention is therefore based on the objective of designing and further developing a device and a method for separating a liquid from a feed material in such a way that at least some of the existing challenges are solved.

[0005] According to the invention, the aforementioned problem is solved by the features of claim 1. The device in question for separating a liquid from a feed material, in particular regrind made of plastic, comprises a rotor with paddles for swirling the feed material. The paddles are arranged on a circumferential wall of a core of the rotor between the core and a perforated inner wall of a sieve drum. A chamber is formed between the core and the outer wall. The core is hollow. The core also has openings on its circumferential side wall. The openings and a hollow interior of the core are fluidically connected in such a way that when an airflow is directed into the hollow interior of the chamber, the airflow is guided through the openings into the chamber to separate the liquid from the feed material and / or to heat the regrind and the chamber and cause the liquid to evaporate.

[0006] According to the invention, it has first been recognized that the mechanical dryer can be operated at a lower rotational speed if, in addition to drying by turbulence and centrifugal forces, an airflow is used to further dry the material in the mechanical dryer. The result is a machine in which the two processes of "mechanical drying" and "thermal drying" can be carried out in combination in a single machine. The device according to the invention therefore provides a machine in which warm / hot air can be introduced into the process through the rotor drum of the mechanical dryer. This makes it possible to generate a hot airflow transverse to the product's transport direction, in addition to the mechanical turbulence of the material by the rotor paddles.This results in an additional drying effect, as the hot air can act on the product in a cross-flow. The invention thus relates to a combination of a mechanical paddle dryer and thermal drying in a single machine, particularly for use in processing plants for plastics recycling. The resulting more humid air can, for example, be discharged (and optionally extracted) outside the rotor and, depending on the residual energy, fed into a heat recovery system. The device according to the invention (and the corresponding method) enables lower energy consumption per unit mass of the produced product, reduced equipment complexity, a smaller footprint with lower total installed power, reduced product losses due to fine abrasion, less wear on the device components compared to conventional mechanical dryers, and a lower generation of microplastic particles.

[0007] In the present invention, the openings and a hollow interior of the core are fluidically connected such that when an airflow is introduced into the hollow interior of the chamber, the airflow is directed through the openings into the chamber. This can be achieved by the hollow rotor having an inlet for an airflow, in particular for a warm or hot airflow, at one axial end. The inlet and the openings are connected through the interior of the hollow core in such a way that the airflow introduced through the inlet is directed through the openings into the chamber to separate the liquid from the feed material and / or to heat the material being ground and the chamber and to evaporate the liquid.

[0008] In principle, the device according to the invention can be operated with various types of airflow. A distinction can be made between passive and active air supply, and between cold and warm or hot airflow. With active air supply, a blower is used. Accordingly, the device can further comprise a means for supplying the airflow, in particular a blower, especially a warm air or hot air blower, or a blower in combination with an air heater, which is configured to supply the airflow to be directed through the supply. Alternatively, in the case of passive air supply, the air supply can be effected by the high-speed rotor, which draws the air through the process chamber by means of a suction effect. In this case, a warm or hot airflow can be generated with the aid of an air heater.The hot air blower or air heater is designed to provide an airflow with a temperature of at least 70°C (or at least 80°C, or at least 90°C, or at least 100°C) or to heat an airflow to at least 70°C (or at least 80°C, or at least 90°C, or at least 100°C) in order to thermally separate the liquid from the feed material. Consequently, the warm or hot airflow can also have a temperature of at least 70°C (or at least 80°C, or at least 90°C, or at least 100°C). At the same time, it is important to ensure that the air temperature does not soften the feed material. Depending on the type of polymers used, the air temperature can be a maximum of 130°C (or at most 120°C, or at most 110°C, or at most 100°C). Accordingly, the warm air or hot air blower can be designed to provide the airflow with an air temperature of no more than 130° (or no more than 120°, or no more than 110°, or no more than 100°).

[0009] The present invention is based on the combination of a mechanical paddle dryer with an airflow dryer. The rotor is designed to separate the liquid from the feed material by mechanically agitating the feed material with the paddles. In addition, some of the liquid can be separated by the centrifugal forces of the rotating rotor acting on the feed material. This occurs in addition to the fluidic drying effect of the airflow.

[0010] A particularly effective thermal drying process can be achieved when the air flows in a cross-flow pattern onto the material being processed. Therefore, the openings can be arranged and shaped so that the airflow is directed perpendicular to the material's transport direction. "Perpendicular" in this context means that the airflow is directed onto the material essentially perpendicular to the transport direction, with only a slight deviation from this perpendicular axis. The transport direction can be parallel to the rotor's axis of rotation. For example, the openings can be arranged and shaped so that the airflow enters the chamber perpendicular to the rotor's axis of rotation, or so that the airflow is inclined by a few degrees towards a material discharge opening of the rotor, thus creating a cross-flow pattern onto the material.To increase the airflow velocity and control its direction, the openings can also be designed as nozzles. Nozzles serve primarily to convert pressure into velocity or to shape the air jet. Accordingly, a nozzle is a component suitable for selectively influencing the airflow velocity and / or direction. This allows the drying effect of the airflow to be increased, at least in specific areas.

[0011] To further enhance the drying effect, the air moistened by thermal drying can be rapidly extracted. For this purpose, a suction device, such as a suction blower, can be used in conjunction with the blower. However, this is often unnecessary, as the airflow is sufficient to automatically extract the moistened air. For example, the device can comprise a housing, with the rotor and the screen drum located inside. The housing can have at least one outlet opening, such as one or more extraction openings, for removing or extracting air escaping from the chamber through the perforated wall. In particular, the outlet openings can be located on the top of the housing, since the separated water drains downwards.At least one suction fan can now be connected to the outlet openings, which can also be designed as extraction openings, to extract the air, and in particular the air escaping from the chamber through the perforated wall. For example, this suction fan can be separate from the described device. Alternatively, the device can include the suction fan(s).

[0012] To increase energy efficiency, i.e., to further reduce the energy required per unit mass of the produced product, heat can be recovered from the exhaust air by feeding it into a heat recovery system. Specifically, a pipe or hose connection can be used to convey the exhaust air to the heat recovery system. In many cases, the airflow will be designed to escape on its own, without the need for extraction. Alternatively, a suction fan and a corresponding pipe or hose connection can be used to convey the exhaust air to the heat recovery system. For example, the exhaust air can be fed into a heat exchanger to transfer its heat to the supply air. A heat pump can also be used to utilize the heat contained in the exhaust air for the supply air.

[0013] Preferably, in the device according to the invention, the feed material is guided through the device parallel to the base surface, i.e., horizontally. Accordingly, the axis of rotation of the rotor can be guided parallel to a base surface of the device. Alternatively, the axis of rotation can be guided obliquely or orthogonally to the base surface of the device.

[0014] The invention relates not only to the device according to the invention but also to a corresponding method for separating a liquid, such as water or a cleaning fluid, from a feed material, in particular for separating the liquid from a regrind made of plastic. The method comprises swirling the feed material by means of a rotor with paddles for swirling the feed material. The method includes directing an airflow through a hollow core of the rotor and openings in a surrounding wall of the hollow core onto the feed material in order to separate the liquid (fluidically) from the feed material.

[0015] It is evident that the method can be carried out using the device described above. Features described in connection with the device can be adopted analogously into the corresponding method. In particular, the method can include providing an airflow with an air temperature of at least 70°C (or at least 80°C, or at least 90°C, or at least 100°C) and / or at most 130°C (or at most 120°C, or at most 110°C, or at most 100°C). Furthermore, the method can include extracting air discharged through outlet openings in the housing. The method can also include supplying the extracted air to a heat recovery system. There are now various possibilities for advantageously elaborating and further developing the teaching of the present invention.Reference is made, on the one hand, to the claims subordinate to claim 1 and, on the other hand, to the following explanation of preferred embodiments of the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawing, generally preferred configurations and further developments of the teaching are also explained. The drawing shows...

[0016] Fig. 1 shows an isometric view of a rotor and a sieve drum for a device for separating a liquid from a feed material; and

[0017] Fig. 2 shows an isometric view of the device for separating a liquid from a feed material; and

[0018] Fig. 3 shows a flowchart of a process for separating a liquid from a feed material.

[0019] Fig. 1 is a schematic drawing of a rotor 1 for a device for separating a liquid from a feed material. The rotor comprises a hollow core 2. The rotor 1 shown is partially hollow and has sections with different diameters that form the hollow core 2 of the rotor 1. At the end faces are the shaft stubs, which are used for supporting the rotor in the housing and for driving it. A chamber is formed between the core 2 and an inner wall, which can be made, for example, of perforated sheet metal, a screen drum 4, in which the feed material is swirled by paddles 3. The screen drum 4 can also rotate, at a lower speed than the rotor 1. Alternatively, a stationary screen drum can be used. The paddles 3 are attached to a wall 5 of the hollow core 2.The paddles are attached in rows along the rotor's axis of rotation to the wall 5 of the hollow core 2 and can extend over at least 80% (or at least 90%) of the core's dimensions along the rotor's axis of rotation. The rotor's rotation agitates the feed material, such as recycled plastic, and separates it from the liquid through mechanical agitation and centrifugal forces.

[0020] Additionally, openings 6 are provided on the wall 5 of the hollow core 2, which can, for example, be designed as nozzles. Similar to the paddles 3, the openings 6 are also attached in rows along the axis of rotation of the rotor to the wall 5 of the hollow core 2 and extend over at least 80% (or at least 90%) of the core's dimensions along the axis of rotation of the rotor 1. For example, at least four rows of openings 6, each with at least four openings, can be used. The number of openings 6 can depend on the axial length of the rotor. For example, the openings 6 can be arranged at regular intervals within each row along the wall 5. For example, a maximum distance between adjacent openings in a row can be at most 20 cm.

[0021] An airflow is directed through the openings 6 into the chamber between the core 2 and the inner wall of the sieve drum 4. This airflow reaches the openings through the hollow interior of the core 2 and is introduced into the core at an axial end via a feed 7. The feed 7 and the openings 6 are fluidically connected through the interior of the hollow core 2 in such a way that the airflow introduced through the feed 7 is directed through the openings 6 into the chamber to separate the liquid from the feed material by means of flow drying and / or thermal drying. In the case of the rotor 1 of Fig. 1, the feed 7 is a partially open axial end of the core 2. To ensure the stability of the core 2, the hollow core 2 contains a rotor shaft that is connected to the wall 5 of the core 2 in a star-shaped configuration by means of struts.

[0022] In Fig. 1, the openings 6 are designed as nozzles through which the airflow is directed onto the material being processed. In particular, a crossflow is generated by arranging and shaping the nozzles so that the airflow is directed through the openings onto the material perpendicular to its transport direction. This results in particularly efficient mechanical and thermal drying of the material.

[0023] Fig. 2 shows a schematic drawing of the device 8 for separating a liquid from a feed material. The device 8 comprises a housing 9. The rotor 1 shown in Fig. 1 is arranged inside the housing 9. A further feed 7' for the airflow is arranged on the housing and is fluidically connected to the feed 7 on the rotor 1. The device 8 can also include a blower (not shown), in particular a warm air or hot air blower or a blower with an air heater, which is fluidically connected to the further feed 7' and provides the warm or hot airflow.

[0024] Outlet openings 10 are arranged on the upper side of the housing 9, through which the moist air can be discharged from the housing 9, or optionally even extracted. For example, the device 8 can optionally include a suction fan or suction device (not shown) that is fluidically connected to the outlet openings and extracts the moist air. The discharged or extracted air can be fed to a heat recovery system. The rotor 1 is driven by a motor 11. In this case, the motor 11 is located on the axial side of the rotor where the product is discharged at an outlet 13. However, this is not mandatory. The feed 12 for the product is located on the opposite axial side of the rotor 1. The paddles 3 are slightly inclined towards the axial side where the outlet 13 is located, so that the feed material moves through the rotor from the feed 12 to the outlet 13.

[0025] The functionality and features of rotor 1 and device 8 of Figures 1 and 2 are also found in the method of Figure 3. Figure 3 shows a flow diagram of a method for separating a liquid from a feed material, in particular from regrind made of plastic. The method comprises swirling 15 the feed material by means of a rotor with paddles for swirling the feed material (e.g., by means of rotor 1, which is shown in Figure 1). The method further comprises directing 16 an airflow through a hollow core of the rotor and openings in a surrounding wall of the hollow core onto the feed material in order to separate the liquid from the feed material. Optionally, the method further comprises providing 14 the airflow, extracting 17 the air from a housing in which the rotor is arranged, and / or supplying 18 the extracted air to a heat recovery system.

[0026] Regarding further advantageous embodiments of the device according to the invention, reference is made to the general part of the description and to the attached claims in order to avoid repetition.

[0027] Finally, it should be expressly pointed out that the exemplary embodiments of the device according to the invention described above serve only to discuss the claimed teaching, but do not limit it to these exemplary embodiments.

[0028] Reference symbol list

[0029] 1 Rotor

[0030] 2 cores

[0031] 3 paddles

[0032] 4 sieve drums with perforated walls

[0033] 5 Wall of the Kems

[0034] 6 openings, nozzles, airflow inlets

[0035] 8 Device for separating a liquid from a feed material, dryer

[0036] 9 cases

[0037] 10 Outlet opening

[0038] 11 Motor for Rotor

[0039] 12 Product feed

[0040] 13 Output Product

[0041] 14. Providing an airflow

[0042] 15. Swirling of the feed material

[0043] 16. Directing an airflow onto the feed material

[0044] 17. Air removal

[0045] 18 Supplying air to a heat recovery system

Claims

Claims 1. Device for separating a liquid from a feed material, in particular regrind of plastic, comprising a rotor with paddles for swirling the feed material, wherein the paddles are arranged on a circumferential wall of a core of the rotor between the core and a perforated inner wall of a sieve drum, wherein a chamber is formed between the core and the inner wall, characterized in that the core is hollow, has openings on the circumferential side wall, and the openings and a hollow interior of the core are fluidically connected in such a way that, when an airflow is directed into the hollow interior of the chamber, the airflow is directed through the openings into the chamber to separate the liquid from the feed material.

2. Device according to claim 1, characterized in that the Kem has a feed opening for the airflow, in particular for a warm or hot airflow, at an axial end, and the feed and the openings are connected through the interior of the hollow Kem in such a way that the airflow introduced through the feed is directed through the openings into the chamber to separate the liquid from the feed material.

3. Device according to claim 1 or 2, comprising a device for providing a heated air stream, in particular a hot air blower or an air heater, wherein the device is configured to provide an air stream with an air temperature of at least 70°C in order to separate the liquid fluidically and thermally from the feed material.

4. Device according to one of claims 1 to 3, characterized in that the rotor is provided to separate the liquid from the feed material by means of mechanical turbulence, centrifugal forces generated by the rotor and by means of the airflow.

5. Device according to one of claims 1 to 4, characterized in that the openings are arranged and shaped such that the airflow is directed through the openings onto the feed material transversely to a transport direction of the feed material.

6. Device according to one of claims 1 to 5, characterized in that the openings are designed as nozzles.

7. Device according to one of claims 1 to 6, characterized in that the device comprises a housing, the rotor and the sieve drum are arranged inside the housing and the housing has at least one outlet opening for removing air that has escaped from the chamber through the perforated wall.

8. Device according to claim 7, comprising a suction blower for extracting air escaping from the chamber through the perforated wall via the at least one outlet opening.

9. Device according to claim 7 or 8, characterized in that the extracted air is supplied to a heat recovery system.

10. Device according to one of claims 1 to 9, characterized in that a rotation axis of the rotor is guided parallel to a base surface of the device.

11. Method for separating a liquid from a feed material, in particular regrind made of plastic, comprising swirling the feed material by means of a rotor with paddles for swirling the feed material, and directing an airflow through a hollow core of the rotor and openings in a surrounding wall of the hollow core onto the feed material in order to separate the liquid from the feed material.

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