A mechanism for autonomously controlling the liquid level in plastic recycling methods.

Abstract

The present invention relates to a mechanism for autonomously controlling liquid levels in a plastic recycling method, comprising at least one compensation vessel and at least one stirring vessel, wherein the compensation vessel and the stirring vessel are filled with process water, whereby the compensation vessel has a first liquid level and the stirring vessel has a second liquid level, and the at least one compensation vessel is fluidly connected to the stirring vessel, whereby process water can flow freely between the compensation vessel and the stirring vessel, whereby the first and second liquid levels in the at least one compensation vessel and the at least one stirring vessel are equal.

Description

Technical Field

[0001] The present invention relates to a mechanism for autonomously controlling the liquid level in a plastic recycling method.

Background Art

[0002] The continuously increasing amount of plastic waste will pose a severe challenge to our society in the future. In 2019, the post-consumer plastic waste in Germany amounted to approximately 5.35 million tons. Among them, only 1.33 million tons were materially recycled in the reprocessing facilities in Germany. Furthermore, only 1.03 million tons were output with a quality suitable for reuse in the plastic processing industry. This corresponds to a ratio of just over 19%. The facts regarding Germany's ability in plastic recycling and the use of recycled materials are in a situation that should be viewed frankly.

[0003] As the current situation, Germany does not have the recycling infrastructure necessary to reprocess the amount of plastic waste generated there economically, technically, and into high-quality recycled materials. Many reprocessing facilities do not meet the current technical level, are aging, and are based on an economically very vulnerable foundation.

[0004] Domestic and international legislation that is becoming stricter regarding the continuously increasing amount of plastic waste, regarding the approval procedures, and regarding the increase in the recycling rate and the use of recycled materials, as well as restrictions on the import and export of waste, will pose severe challenges to EU member states and especially to plastic recycling companies in the future. Investment in reprocessing capacity, and especially investment in the development of new reprocessing methods to solve the above-mentioned challenges and problems, is urgently needed.

[0005] One of the biggest challenges for plastic recyclers is heavily soiled plastic waste mixtures. Existing recycling processes and equipment can currently only reprocess such fractions to a very limited extent. Therefore, the majority of such waste currently ends up being recycled thermally. Furthermore, the majority of recycled materials produced, due to their qualitative defects, do not enable stable plastic processing processes and therefore rarely serve as a sustainable replacement for new plastic products with high technical requirements.

[0006] Modern plastic waste reprocessing processes involve numerous individual process steps, in which a heavily contaminated mixture of plastic waste, which can contain a wide variety of plastic types in various compositions, is washed or purified, crushed, and finally separated with high precision into distinct plastic types. High process reliability and stability are essential for the efficient and, as accurately as possible, separation of each different plastic fraction. One aspect of this is the continuous provision, as much as possible, of a specific volumetric flow rate of plastic waste, process water, and mixture, which is necessary for the separation of individual plastic fractions, for example, by hydrocyclone. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Therefore, the object of the present invention is to provide a mechanism for controlling liquid levels in different containers using a plastic recycling method, which has relatively low technical costs and can operate reliably and without maintenance. [Means for solving the problem]

[0008] This problem is solved by the features of the independent claim. Other preferred embodiments are described in the dependent claims, respectively.

[0009] According to this, the mechanism is intended to have at least one compensating vessel and at least one stirring vessel, the compensating vessel and the stirring vessel being filled with process water, so that the compensating vessel has a first liquid level and the stirring vessel has a second liquid level, and at least one compensating vessel being fluidly connected to the stirring vessel, so that the process water can flow freely between the compensating vessel and the stirring vessel, thereby equalizing the first and second liquid levels of at least one compensating vessel and at least one stirring vessel.

[0010] The compensating vessel may be one, meaningfully more than one intermediate reservoir into which process water is collected before being discharged into the subsequent stirring vessel. Accordingly, the compensating vessel may have a larger volume, and in particular a larger average area, than the stirring vessel. The cross-section of the stirring vessel and / or the compensating vessel may be circular. The liquid level may be adjusted to be above half, preferably above two-thirds, of the height of the compensating vessel and / or the stirring vessel. The compensating vessel may be fluidly connected to at least one stirring vessel so that water can flow freely, i.e., unobstructed, between these vessels. Since the process water is a substantially homogeneous liquid and gravity and ambient air pressure are equal in both vessels, the level position in both vessels always rises and falls to the same height.

[0011] In particular, process water may be intended to contain pulverized plastic waste mixtures having non-uniform bulk densities. For example, 2D materials such as films made of LD-PE have, on average, lower bulk weights than 3D materials such as plastic hollow bodies made of HD-PE. That is, bulk density correlates with the proportion of 2D or 3D materials in the plastic waste mixture. The bulk density is, for example, between 10 grams / liter under a very high proportion of 2D materials and 475 grams / liter under a very high proportion of 3D materials.

[0012] At least one compensatory vessel and at least one stirring vessel may be intended to have at least one ventilation opening above their respective liquid levels. For example, both vessels may each open upwards.

[0013] The compensation vessel may further have an intake port through which process water flows into the compensation vessel, and the stirring vessel may have an outlet port through which process water flows out of the stirring vessel.

[0014] Furthermore, this mechanism may be intended to have at least two or more stirring vessels fluid-connected to the compensating vessel, the second, and optionally yet another, stirring vessels having liquid levels equal to the first and second liquid levels, respectively. An advantage of the present invention is that it eliminates the need to separately intend for costly filling water level monitoring, which involves connecting control circuits with controls, piping, and valves, to each stirring vessel. Instead, filling water level monitoring can be limited to the compensating vessel only. The more stirring vessels connected to the compensating vessel, the greater the savings.

[0015] In particular, at least two stirring vessels may be fluidly connected to a compensating vessel via their respective piping. Alternatively, the stirring vessels may be connected to each other via piping located below level.

[0016] In order for the first and second fluid levels in at least one compensating vessel and at least one stirring vessel to be equal, it is clear that the piping connections communicate with each vessel below the first and / or second predetermined liquid levels.

[0017] Each vessel, i.e., the stirring vessel and the compensating vessel, may have the same vessel height, and the connections may be intended to communicate with each vessel at a height between half and two-thirds of the vessel height. Furthermore, the piping may be flanged tangentially to the stirring vessels via the connections on the stirring vessel side. This allows process water to flow into each stirring vessel without generating backflow in the stirring direction when the stirring direction is appropriately selected. For this purpose, each stirring vessel may have a stirring device that rotates about a substantially vertical axis. The stirring direction may be intended to be selected to coincide with the inflow direction of process water flowing into the compensating vessel.

[0018] The compensation vessel may be intended to have a level detection device and a control device set up to maintain the filling water level of the compensation vessel at a constant level. The level detection device may be embodied, for example, by a float or overflow. The control device may be connected to the level detection device via a data connection and can actuate an actuator of a valve located at the intake, thereby controlling the liquid level of the compensation vessel.

[0019] In addition, at least one centrifugal separator, such as a hydrocyclone, may be process-engineered and retrofitted to the agitated vessel. This may have an inlet that is fluidly linked to the outlet of the agitated vessel. At least one hydrocyclone may be set up to separate the pulverized material of the plastic waste mixture depending on a predetermined density separation segment. For this purpose, the hydrocyclone may have the aforementioned inlet for process water and may further have a first outlet for the light fraction and a second outlet for the heavy fraction.

[0020] Density-based separation of plastic waste mixtures can be repeated multiple times to concentrate the desired material fraction. Therefore, it may be further intended that process water containing the plastic mixture passes sequentially through multiple hydrocyclones. The concentration of the pulverized material will be higher at the hydrocyclone outlet for particles with relatively high specific gravity than at the outlet for particles with relatively low specific gravity. Thus, the density of the second stage of the hydrocyclone can be adjusted to be progressively lower or higher than the density of the first stage. The hydrocyclone has an upper cylindrical segment with a tangential outflow and a lower conical segment with an underflow or apex nozzle. Furthermore, the hydrocyclone may have a vortex finder or overflow nozzle in the form of an immersion tube that enters the cyclone interior from above in the axial direction and ends inside the tangential outflow. Entering tangentially into the cylindrical segment forces the liquid to follow a circular orbit, flowing downward as a downward-facing vortex. The tapering of the conical segments causes volume to be pushed downwards, and a damming occurs in the lower region of the taper. This leads to the formation of an upward-facing inner vortex, which escapes through the vortex finder or overflow opening. The purpose is to separate inherently heavier fractions (e.g., solids) at the cyclone wall and discharge them through the underflow, while allowing inherently lighter fractions to escape through the overflow. A hydrocyclone can have vertical flow, directed downwards in the outer region (primary vortex) and upwards in the inner region (secondary vortex). That is, particles collected in these flow are supplied to either the overflow or underflow opening.

[0021] Furthermore, the predeterminable density for separating plastic waste mixtures is 1 to 1.05 kg / dm³. 3 It may be intended to be adjustable between these two values.

[0022] Furthermore, the separation into two fractions may be intended to include concentration of the light fraction in at least one first hydrocyclone and concentration of the heavy fraction in at least one second hydrocyclone. These hydrocyclones may be connected in series. For example, the first hydrocyclone may perform a first separation section into a light fraction and a heavy fraction, and another light fraction hydrocyclone for accommodating and further concentrating the light fraction may be provided, and / or another heavy fraction hydrocyclone for accommodating and further concentrating the heavy fraction may be provided. The heavy fraction hydrocyclone may be a flat-bottom hydrocyclone.

Brief Description of the Drawings

[0023] Further details of the present invention will be described with reference to the following drawings. The drawings show the following: FIG. 1 is a schematic plan view showing an embodiment of the mechanism according to the present invention.

[0024] FIG. 2 is a schematic side view showing an embodiment of the mechanism according to the present invention.

Embodiments for Carrying Out the Invention

[0025] Figure 1 shows a schematic plan view of an embodiment of the mechanism according to the present invention. This mechanism has a compensating vessel 10 having an intake port 11 that can be controlled via a valve 13. The compensating vessel 10 has a level detection device 12 for continuous level monitoring. This is linked to a control unit 14 via a data connection, which is further set up to activate an actuator of the valve 13 to open or close it depending on whether the level P1 of the process water W in the compensating vessel 10 is above or below a target value. The compensating vessel 10 is open upward and therefore has an opening 5 through which the process water W in the compensating vessel 10 comes into contact with the ambient air. In the illustrated embodiment, two stirring vessels 20 are connected to the compensating vessel, which are fluidly connected to the compensating vessel 10 via piping 30. These pipes have a first connection 31 on the compensating vessel side and a second connection 32 on the stirring vessel side, and both connection 31, 32 are located below the liquid levels P1, P2 of the compensating vessel 10 and the stirring vessels 20. The connection parts 31 and 32 are flange-jointed laterally and tangentially to the compensation container 10 or the stirring container 20, respectively. The stirring container 20 is also filled with process water W, and the water levels P1 and P2 are equal. The stirring container 20 is also open upwards and has an opening 5 accordingly. Furthermore, each stirring container 20 has an agitator 21 having a vertical rotation axis. The rotation direction of the agitator 20 is selected so that the process water W flowing from the piping 30 into each stirring container 20 flows in the agitation direction. Furthermore, each stirring container 20 has an outlet 22 to which a hydrocyclone 40 is located, for separating the plastic mixture contained in the process water into a light fraction 42 and a heavy fraction 43 along predetermined density separation divisions. The process water W flows into the hydrocyclone through the intake port 41.

[0026] Figure 2 shows a schematic side view of the mechanism in Figure 1. It can be seen that the liquid level P1 of the compensation container 10 and the liquid level P2 of the stirring container 20 are equal. This is caused by the fact that the connection part 31 of the connecting pipe 30 to the compensation container 10 and the connection part 32 to the stirring container 20 communicate with each container below the liquid levels P1 and P2, and furthermore, that the containers 10 and 20 are open upward or have openings 5. In the illustrated embodiment, the containers 10 and 20 each have the same height H1. The intake port 11 of the compensation container 10 is located above the connecting pipe 30, and the outlet port 22 of the stirring container 20 is located below the connecting pipe 30. The process water W flows into the compensation container 10 first through the intake port 11, depending on the position of the valve 13. The process water W flows from the compensation container 10 into one or more stirring containers 20 through the connecting pipe 30. The process water is then stirred by the agitator 21 and flows out of the agitator 20 from the outlet 22 towards the hydrocyclone 40. The hydrocyclone 40, which is used to obtain polymers in the process of density-based separation of the plastic waste mixture, is located behind the agitator 20 and connected to it at least indirectly. A mixture of process water W and the plastic waste mixture is supplied to the hydrocyclone 40, which contains components such as PE, PP, PS, PET, PP-T, ABS, and other materials. The hydrocyclone 40 is a conical hydrocyclone in the illustrated example and separates the plastic waste mixture into a light fraction 42 and a heavy fraction 43. The hydrocyclone 40 has a flow rate of, for example, 1 kg / dm 3 The light fraction 41 and the heavy fraction 43 are separated under the density classification. Thus, the light fraction 41 contains, for example, PE and PP. Accordingly, the heavy fraction 43 contains the remainder of the plastic waste mixture, namely PS, PET, PP-T, ABS, and other components. The light fraction 41 is then fed to another (not shown) step of the process, while the heavy fraction 43 is fed to a second (not shown) hydrocyclone, which may be configured as a flat-bottom hydrocyclone, in which a maximum of 1.05 kg / dm³ is passed. 3Under this condition, density separation can be performed, and in the second hydrocyclone, the second light fraction can be separated from the second heavy fraction. At this time, the second light fraction can contain PS, PP-T, and ABS, and the second heavy fraction can contain PET and other components. Then all the fractions can be supplied separately to the next process step after passing through the hydrocyclone.

[0027] The constituent elements of the present invention disclosed in the above description, drawings, and claims can be the main parts for embodying the present invention either alone or in any combination.

Explanation of Reference Numerals

[0028] 5 Opening 10 Compensation Container 11 Inlet 12 Level Detection Device 13 Valve 14 Control Unit 20 Stirring Container 21 Stirring Device 22 Outlet 30 Connecting Pipe 31 Connection Part of Compensation Container 32 Connection Part of Stirring Container 40 Hydrocyclone 41 Inlet 42 Light Fraction 43 Heavy Fraction P1 Liquid Level of Compensation Container P2 Liquid Level of Stirring Container W Process Water

Claims

1. A mechanism for autonomously controlling liquid levels in a plastic recycling method, comprising at least one compensating vessel (10) and at least one stirring vessel (20) having a stirring device (21) that rotates substantially vertically around an axis, wherein the compensating vessel (10) and the stirring vessel (20) are filled with process water (W), thereby the compensating vessel (10) having a first liquid level (P1) and the stirring vessel (20) having a second liquid level (P2), and at least one of the compensating vessels (10) is fluidly connected to the stirring vessel (20), thereby allowing the process water (W) to flow freely between the compensating vessel (10) and the stirring vessel (20), thereby equalizing the first and second liquid levels (P1, P2) of at least one of the compensating vessels (10) and at least one of the stirring vessels (20), wherein at least one hydrocyclone (40) is process-engineered to follow the stirring vessel (20).

2. The mechanism according to claim 1, wherein the process water (W) contains pulverized plastic waste mixture having a non-uniform bulk density.

3. The mechanism according to claim 1, wherein at least one of the compensating containers (10) and at least one of the stirring containers (20) each have at least one ventilation opening (5) above their respective liquid levels (P1, P2).

4. The mechanism according to claim 1, wherein the compensation container (10) further has an intake port (11) through which process water (W) flows into the compensation container (10), and the stirring container (20) further has an outlet port (22) through which process water (W) flows out of the stirring container (20).

5. The mechanism according to claim 1, comprising at least two or more stirring vessels (20) fluidly connected to the compensation vessel (20), wherein the second and optionally further agitated vessels (20) each have a liquid level equal to the first and second liquid levels (P1, P2).

6. The mechanism according to claim 5, wherein at least two of the stirring vessels (20) are fluidly connected to the compensation vessel (10) via their respective pipes (30).

7. The mechanism according to claim 6, wherein the connection portions (31, 32) of the piping (30) communicate with the respective containers (10, 20) below the first and / or second predetermined liquid levels (P1, P2).

8. The mechanism according to claim 6, wherein each of the containers has the same container height (H1), and the connecting parts (31, 32) communicate with each container (10, 20) at a height between half and two-thirds of the container height (H1).

9. The mechanism according to claim 6, wherein the piping (30) is flange-joined tangentially to the stirring vessel (20) via connection parts (32) on each stirring vessel side.

10. The mechanism according to claim 1, wherein the compensation container (10) comprises a level detection device (12) and a control device (14) set up to maintain the liquid level of the compensation container (10) at a constant level.

11. The mechanism according to claim 10, wherein the control device (14) is connected to the level detection device (12) via a data connection, and acts on an actuator of a valve (13) located at the intake port, thereby controlling the liquid level (P1) of the compensation container (10) via this valve.

12. The mechanism according to claim 1, wherein at least one of the hydrocyclones (40) is set up to separate the pulverized material of the plastic waste mixture in a manner dependent on predetermined density separation segments.

13. The hydrocyclone (40) has an intake (41) for process water (41), a first outlet (42) for the light fraction, and a second outlet (43) for the heavy fraction, according to any one of claims 1 to 12.

Images