Hydraulic separator for plastic materials

Abstract

A hydraulic separator for separating a mixture of two plastics comprises two opposing horizontal plates formed by a plurality of contiguous half-cylinders so as to form a plurality of chambers (C1-C7) parallel and contiguous, provided with collecting ducts (R1-R7) extending from the bottom of the chambers (C1-C7), with a plurality of inlet ducts (11-18) and outlet ducts (01-08) regularly distributed at the ends of the separator in a symmetrical and aligned position. The axis (A) of the chambers (C1-C7) forms an angle (B) of about 70° with a line (C) joining an inlet duct (I) with the corresponding outlet duct (O), so that plastic particles settling in the separator will accumulate at the side wall (P) adjacent to the collection ducts (R1-R7).

Description

[0001] “HYDRAULIC SEPARATOR FOR PLASTIC MATERIALS”

[0002] The present invention concerns separators used for recycling waste materials, and in particular a hydraulic separator for separating two different types of plastics.

[0003] It is well known that, in order to reduce waste disposal in landfills and the use of energy and virgin raw materials, numerous processes have been developed to separate materials in waste so as to obtain high-quality secondary raw materials that can replace all or part of virgin raw materials. For the separation of plastics, in particular, traditional plants use processes that are based on the different physical properties of the polymers and can be broadly divided into dry processes (air, electrostatic, sensor-based separators) and wet processes (hydraulic, hydrocyclonic, flotation separators). Most of these processes require rather complex equipment and / or specific operating conditions that make separation expensive and / or difficult.

[0004] The hydraulic separator, on the other hand, is a rather simple device into which a mixture of two polymers is introduced with water to separate it into two products, one collected inside the separator and the other ejected with water through the outlet pipes, with high accuracy and completeness of recovery. More specifically, the hydraulic separator of the present invention is a so-called Multidune separator as described in the following published papers:

[0005] - La Marca F., Moroni M., Cherubini L., Lupo E., Cenedese A. (2012) “Separation of plastic waste via the hydraulic separator Multidune under different geometric configurations”. Waste Management, 32, 1306-1315;

[0006] - Moroni M., Lupo E., Della Pelle V., Pomponi A., La Marca F. (2018). “Experimental Investigation of the Productivity of a Wet Separation Process of Traditional and Bio-Plastics.” Separations 5(2), 26;

[0007] - Moroni M., Lupo E., La Marca F. (2017) “Hydraulic separation of plastic wastes: Analysis of liquid-solid interaction”. Waste Management, 66, 13-22; and

[0008] - De Sena G. et al. (2008) “The hydraulic separator Multi dune: Preliminary test on fluid-dynamic features and plastic separation feasibility”. Waste Management, 28, 1560- 1571.

[0009] Briefly, as shown in Figures 1 and 2, this type of hydraulic separator is a channel made by combining two opposing horizontal plates each consisting of 8 contiguous halfcylinders, so as to form 8 parallel chambers C1-C8 with an axis orthogonal to the main flow direction. Water is introduced into the separator through eight inlet ducts 11-18 regularly distributed along the front wall from the side of the first chamber Cl, with axes normal to the axes of the chambers, and is discharged through eight outlet ducts 01-08 regularly distributed along the back wall from the side of the last chamber C8, symmetrically aligned with respect to the inlet ducts 11-18. The mixture of the two plastics to be separated is introduced through one or more of the inlet ducts, typically duct 14 or 15. There is a collection duct R1-R8 at the bottom of each C1-C8 chamber to extract the material deposited in each chamber at the end of the separation process, and all the above ducts are equipped with taps to be disconnected from the flow circulation if necessary.

[0010] The shape of the chambers can be changed by moving the two plates relative to each other in the direction of flow, i.e., along the line joining the inlet ducts with the corresponding outlet ducts, and it has been found that the separation efficiency is greatest when the relative position of the two plates is such that the inlet width LI in the halfcylinders of the bottom plate is greater than the outlet width L2, i.e., L1 / L2>1, as shown in Fig.2 (LI and L2 being measured along the above-mentioned joining line).

[0011] However, this known type of separator has a serious drawback that makes it unsuitable for industrial use since, as mentioned above, the extraction of the material deposited in the separator requires the interruption of the separation process and thus adversely affects the productivity of the process. In fact, since the material remaining in the separator spontaneously distributes itself along the entire axis of each Cl -C8 chamber while the R1-R8 collection ducts are arranged at one end of said chambers, extraction requires stopping the flow and tilting the separator transversely so that all the separated material slides toward the collection ducts.

[0012] This not only slows down separation operations, but also requires a special tilting mechanism that makes the separator more complex and expensive, possibly including a vibrator to ensure that all the material detaches from the bottom of the chamber and slides toward the end. Furthermore, additional time is required when the process is resumed for the proper flow to be re-established for effective separation.

[0013] It is therefore the purpose of the present invention to provide a separator that overcomes this drawback. Said purpose is achieved by means of a separator in which the axes of the chambers are not orthogonal to the main direction of flow, i.e., to the line joining each inlet conduit with the corresponding outlet conduit, but present an angle of between 60° and 80° with respect to that direction, with the collecting conduits located at the most forward ends of the chambers with respect to the direction of flow. Other advantageous features of the present separator are specified in the dependent claims.

[0014] The main advantage of the separator according to the present invention is to allow the extraction of the separated material present in the chambers without having to interrupt the separation process. In fact, this new geometry results in a helical motion of the plastic particles intended to settle inside the chambers, so that these particles will accumulate at the side wall of the hydraulic separator near the collection ducts. In this way, it is sufficient to open the taps of the collection ducts to suck out the separated material without interfering with the continuation of the separation process nor significantly disrupting the flow.

[0015] A second important advantage of this separator comes from its simple design, as it does not require any tilting or vibrating mechanism, making it more compact and economical.

[0016] These and other advantages and features of the separator according to the present invention will be apparent those skilled in the art from the following detailed description of an embodiment thereof with reference to the attached drawings in which:

[0017] Fig.l is a top view in transparency of a traditional separator as described above;

[0018] Fig, 2 is a side view in transparency of the separator of Fig.1;

[0019] Fig, 3 is a top view of a separator according to the invention;

[0020] Fig, 4 is a side perspective view of the separator of Fig.3; and

[0021] Fig, 5 is a view similar to Fig.4 but in transparency.

[0022] Referring to figures 3 to 5, it can be seen that a separator according to the invention differs from the prior art separator illustrated in figures 1 and 2 in that the A-axis of each chamber forms an angle B less than 90° with the flow direction represented by line C, which joins an inlet duct I with the corresponding outlet duct O (e.g., 14-04 in Fig.3). More specifically, the angle B is between 60° and 80°, preferably about 70°.

[0023] Another difference with the separator of figures 1 and 2 is the presence of only 7 chambers C1-C7, with the corresponding collecting ducts R1-R7 shown schematically but not illustrated in figures 3 to 5. Note that this difference is present only with the same size of the separator, since the slope of the chambers implies a lack of space for the eighth chamber, but it would be possible to maintain the 8 chambers by slightly increasing the length of the separator.

[0024] The novel aspect of the separator according to the present invention, as mentioned above, lies in the fact that the arrangement of the C1-C7 chambers with the A-axis tilted by the aforementioned angle B generates a flow pattern within the separator whereby the separating plastic particles are not distributed along the entire length of the A-axis, but spontaneously collect against the side wall P formed by the forward ends of the C1-C7 chambers. Thus, by opening the collection ducts R1-R7 formed near that side wall P, it is possible to extract the separated material easily and without interfering with the separation process, which can be continuous, so as to achieve the productivity levels required for the industrial application of the present separator.

[0025] To achieve this, it is advantageous for the L1 / L2 ratio, as defined above, to be between 1.8 and 2, preferably about 1.9.

[0026] It is clear that the embodiment of the separator according to the invention described and illustrated above is only an example susceptible to many variations. In particular, the number and size of the chambers and their collection ducts, as well as that of the inlet and outlet ducts, could be varied according to specific construction requirements, realizing further variations that are within the reach of a person skilled in the art based on the above description.

Claims

CLAIMS1. A hydraulic separator comprising two opposing horizontal plates each of which comprises a plurality of contiguous half-cylinders so as to form a plurality of parallel and contiguous chambers (C1-C7), a plurality of inlet ducts (11-18) regularly distributed along a front wall on the side of the first chamber (Cl), a plurality of outlet ducts (01-08) regularly distributed along a back wall on the side of the last chamber (C7) symmetrically aligned with respect to said inlet ducts (11-18), and a plurality of recovery ducts (R1-R7) each extending from the bottom of one of said chambers (C1-C7) near a side wall, the relative position of said opposing horizontal plates being such that the inlet width (LI) in the half-cylinders of the bottom plate is greater than the outlet width (L2), characterized in that the axis (A) of each of the chambers (C1-C7) forms an angle (B) between 60° and 80°, preferably about 70°, with a line (C) joining an inlet duct (I) with the corresponding outlet duct (O), and in that the side wall near which said recovery ducts (R1-R7) are formed is the side wall (P) formed by the forward ends of the chambers (C1-C7).

2. A hydraulic separator according to claim 1, characterized in that the ratio of the inlet width (LI) in the half-cylinders of the bottom plate to the outlet width (L2) is between 1.8 and 2, preferably about 1.9.

3. A hydraulic separator according to claim 1 or 2, characterized in that it comprises seven chambers (C1-C7) with associated recovery ducts (R1-R7), eight inlet ducts (11-18) and eight outlet ducts (01-08).

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