Patent Publication Number: US-2019168422-A1

Title: Device and method for the joint feeding of plastic particles and a liquid into a purification device

Description:
CROSS REFERENCE TO RELATED INVENTION 
     This application is a national stage application pursuant to 35 U.S.C. § 371 of International Application No. PCT/EP2017/054006, filed on Feb. 22, 2017, which claims priority to, and benefit of, German Patent Application No. 10 2016 103 781.8, filed Mar. 3, 2016, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The invention relates to a device for jointly delivering plastic particles and a liquid to a cleaning device to remove impurities from the plastic particles. The invention also relates to a method for jointly delivering plastic particles and a liquid to a cleaning device to remove impurities from the plastic particles. 
     Cleaning devices for removing impurities from plastic particles, in particular from plastic flakes, are for example known from WO 2013/010654 A2 or WO 2014/111412 A1. To clean the plastic particles, they are introduced together with a liquid, generally water, into the processing region of the cleaning device. 
     There are basically two versions of known delivery methods. On the one hand, it is known to stir the plastic particles into water in a separate container and pump the suspension through the cleaning device by means of a solids pump. A disadvantage in this context is that a comparatively large stirring container with a correspondingly involved agitator is needed. Moreover, the produced suspension must be pumpable so that a comparatively large amount of water is necessary. This in turn eventuates in a high energy requirement by the cleaning device since a large amount of water must be accelerated. Moreover, a solids pump between the stirring tank and cleaning device is necessary. It is alternatively known to add the plastic particles by means of a stuffing screw and supply water, either to the stuffing screw or to the cleaning device. However, it is revealed in practice that at present, no satisfactory technical solution exists for delivering film particles (plastic flakes) to the cleaning device. Screw deliveries have a natural output limit due to the low bulk density of plastic flakes and the geometric boundary conditions. This output limit lies below the potential capacity of the cleaning devices so that they cannot be optimally exploited. Moreover, continuously supplying plastic particles to the stuffing screw, and hence to continuously supplying the cleaning devices is difficult in practice. 
     BRIEF SUMMARY OF THE INVENTION 
     Proceeding from the described prior art, the object of the invention is therefore to provide a device and a method of the aforementioned type by means of which the cleaning device can be supplied a precisely-dosed mixture of plastic particles and liquid in an easy and energy-efficient manner. 
     The invention achieves the object for a device of the aforementioned type by means of a delivery funnel whose inlet is connected to a supply for the plastic particles, and whose outlet is connected via a supply line to an inlet of the cleaning device, wherein at least one delivery nozzle connected to a liquid supply is arranged on the delivery funnel and through which at least one liquid jet is discharged into the delivery funnel, wherein the at least one delivery nozzle is arranged such that a mixture occurs in the delivery funnel of the plastic particles supplied to the delivery funnel with the liquid. 
     For a method of the aforementioned type, the invention achieves the object in that plastic particles are supplied to the inlet of a delivery funnel, wherein by means of at least one delivery nozzle connected to a liquid supply, at least one liquid jet is discharged into the delivery funnel such that a mixture occurs in the delivery funnel of the plastic particles supplied to the delivery funnel with the liquid, and wherein the mixture of the plastic particles and the liquid is supplied via an outlet of the delivery funnel to an inlet of the cleaning device. 
     The plastic particles are cleaned in the cleaning device during a recycling process. They can for example be comminuted plastic beverage bottles, or other comminuted plastic products. The plastic particles can for example be PET plastic particles. Other materials are also possible. In the cleaning device, impurities are removed from the plastic particles. The cleaning device can be a so-called refiner in which the impurities are rubbed off of the plastic particles. The refiner can be a disk refiner with two cleaning discs that oppose each other, between which the plastic particles are cleaned, in particular by friction. It can however also be a drum, or respectively ball refiner. The impurities are in particular adhesions to the plastic particles such as cellulose residue, adhesive residue, label residue or organic contaminants. The plastic particles can be plastic particles with a low bulk density, in particular shredded plastic, or respectively flat pieces of film (plastic flakes). The plastic particles can however also be plastic particles with a greater bulk density such as granulate plastic, in particular granular hard plastics. 
     The device according to the invention comprises a delivery funnel with an inlet that is supplied with the plastic particles, in particular separately. At least one delivery nozzle is provided on the delivery funnel. The at least one delivery nozzle is connected to a liquid supply, for example via a pump. The liquid to be supplied to the cleaning device together with the plastic particles is conducted into the delivery funnel through the at least one delivery nozzle. The liquid discharged into the delivery funnel can for example be water. Correspondingly, the liquid supply can be a water supply. The plastic particles fall from above, in particular under gravity, into the delivery funnel and are captured by the liquid discharged by the at least one delivery nozzle. The outlet of the delivery funnel is for example connected via a pipeline to an inlet of the cleaning device, such as a refiner. 
     The at least one delivery nozzle is arranged according to the invention such that a mixture occurs in the delivery funnel of the plastic particles supplied to the delivery funnel with the liquid. By the even mixture according to the invention of the plastic particles supplied to the delivery funnel with the liquid, an optimum delivery of the plastic particles to the cleaning device occurs. A mixing zone is thus formed in the region of the funnel outlet. A suspension consisting of the liquid and the plastic particles with a nearly constant solid component is consequently supplied to the inlet of the cleaning device. 
     A precise and even dosing of the plastic particles into the liquid is achieved by the invention in a simple and energy-efficient manner. In this context, the plastic component in the liquid/plastic mixture can be increased over the prior art. Especially in a highly consistent mode of operation, fluctuations in the dosing can very quickly lead to clogging and therefore interruptions in operation. Due to the reliably precise adjustment of the solid component according to the invention, this can be avoided. A precise and a targeted supply of liquid to the delivery funnel is enabled by the at least one delivery nozzle. The liquid supply is thereby optimized, possibly while exploiting the kinetic energy of the liquid. A reliable mixing zone of liquid and plastic particles is formed that is also configured for high outputs. The mixing zone can lie particularly close to the inlet of the cleaning device, only spaced by the connecting line between the funnel outlet and the inlet of the cleaning device. In addition, the invention is universally useful, i.e., inter alia for (granular) hard plastics. 
     Since the solid component, as explained, can be increased relative to the prior art, the consumption of liquid is comparatively lowered. Accordingly, less liquid must be recycled after the cleaning process. The energy efficiency is improved. Moreover, the throughput is increased with a sub-proportional increase in required energy. The operational reliability is also increased. 
     The at least one delivery nozzle can also be arranged according to one embodiment such that a swirl that mixes the plastic particles supplied to the delivery funnel with the liquid is formed in the region of the outlet of the delivery funnel. Since a liquid swirl, or respectively liquid vortex is formed in the region of the funnel outlet, the even mixture of the plastic particles with the supplied liquid is further optimized. The dosing of the plastic particles can thereby be further homogenized, and the efficiency and operational reliability of the invention can be further increased. 
     According to another particularly practical embodiment, the liquid jet discharged by the at least one delivery nozzle can be directed toward the inner wall of the delivery funnel, preferably at an angle relative to the axial direction of the delivery funnel. In this manner, a swirl can be very easily generated in the funnel outlet. In this case, the axial direction of the funnel is formed by the middle axis running between the funnel inlet and the funnel outlet. The angle of the liquid jet relative to this axial direction can in particular be greater than 45°. It can for example lie within a range of 50° to 80°, preferably within a range of 60° to 70°. 
     At least one delivery nozzle can be arranged on the edge of the inlet of the delivery funnel according to another embodiment. In this case, the at least one delivery nozzle can penetrate the wall of the delivery funnel in the region of the opening edge of the delivery funnel so that a supply line coming from the liquid supply from the outside can be connected to the at least one delivery nozzle. 
     The alignment of the at least one delivery nozzle can be adjustable according to another embodiment, for example, manually or controlled by an adjusting apparatus. The invention can thereby be adapted to different operating situations. 
     According to another embodiment, a plurality of delivery nozzles connected to a liquid supply can be arranged on the delivery funnel, through which the liquid is supplied to the delivery funnel. The plurality of delivery nozzles can then also be arranged such that a swirl that mixes the plastic particles with the liquid is formed in the region of the outlet of the funnel. Correspondingly, the liquid jets discharged from the plurality of delivery nozzles can then be directed toward the inner wall of the delivery funnel, for example at an angle relative to the axial direction of the delivery funnel as explained above, in particular at the same angle relative to the axial direction of the delivery funnel. The liquid jets discharged by the delivery nozzles can also be directed parallel or at a (in particular the same) slight angle (for example less than 20°, preferably less than 10°) to a tangent touching the opening edge of the funnel inlet in the region of the attachment of the delivery nozzles. The liquid discharged by the delivery nozzles then runs helically downward on the inner wall of the delivery funnel to the outlet and forms a swirl there. Likewise, the plurality of the delivery nozzles can be arranged on the edge of the funnel inlet. The position of the plurality of delivery nozzles can also be adjustable. The number of necessary delivery nozzles according to the invention depends on the respective application. It is in principle conceivable to only use one delivery nozzle. In practice however a plurality of delivery nozzles would probably be useful, for example at least four or more than four delivery nozzles. 
     Moreover at least one delivery nozzle can be arranged on the delivery funnel through which a directed liquid jet is discharged directly into the outlet of the delivery funnel. Or a plurality of such delivery nozzles can be provided. The at least one delivery nozzle then functions as at least one rinsing nozzle. It can for example be arranged vertically above the outlet of the delivery funnel so that the discharged liquid jet is directed in an axial direction of the delivery funnel into the funnel outlet. In this manner by exploiting the kinetic energy of the liquid, an acceleration of the suspension toward the inlet of the cleaning device can be effectuated. The liquid discharged by the delivery nozzle(s) directly into the funnel outlet then guides the plastic particles into the funnel outlet. In so doing, a sufficient mixture of the plastic particles with the liquid can be achieved, possibly also without forming a swirl in the region of the mixing zone. This is further supported when the suspension generated in the delivery funnel is drawn by the subsequent cleaning device, for example when the pumping effect of the suspension pumped by the cleaning device generates a vacuum, or respectively suction at the outlet of the delivery funnel. Moreover, any clogs in the region of the funnel outlet can be thereby dissipated. The at least one rinsing nozzle is also connected to the liquid supply, for example via a pump. Of course, a combination of delivery nozzles directed toward the inner wall of the delivery funnel and into the funnel outlet is also possible. 
     At least the edge of the inlet of the delivery funnel can be elliptical according to another embodiment. The funnel itself can also be designed to elliptically taper. A particularly effective swirl formation is thereby achievable. However, other funnel shapes are also conceivable such as a circularly tapering cross-section, in particular when the distance between the funnel outlet and the inlet of the cleaning device is larger. 
     According to another embodiment, the supply for the plastic particles can comprise a supply reservoir containing the plastic particles and connected to the inlet of the delivery funnel, wherein rotatably driven supply brushes are arranged in the supply reservoir by which the plastic particles can be separately supplied to the inlet of the delivery funnel. By the for example two supply brushes that are for example rotatably driven about parallel rotary axes, the plastic particles located in the supply reservoir, that is for example also funnel-shaped, are supplied precisely separately and precisely dosed, in particular supplied like a curtain, to the delivery funnel. This can reliably further increase the throughput of the delivery funnel, even with a high solid consistency. 
     Moreover, a control apparatus can be provided that controls the supply for the plastic particles and/or the liquid supply. The amount of liquid required for the delivery according to the invention depends inter alia on the outlet of the cleaning device. When a pumping effect for an improved cleaning of the plastic particles is to be achieved in the cleaning device and a pump is located at the outlet of cleaning device, a correspondingly larger amount of liquid must be sprayed in so as to generate a pumpable suspension. If in contrast, the suspension is discharged freely from the outlet of the cleaning device, i.e., without a pump, a correspondingly slighter amount of liquid is adjusted so that the expenditure of resources and energy can be optimized. In combination with a jet pump refiner, the amount of liquid can be optimized for the cleaning in the cleaning device (with a minimal energy expenditure), and then a sufficient amount of liquid can be added to the cleaning device for transportation. By means of the control apparatus, the solid consistency supplied to the cleaning device can always be adjusted in the desired manner. 
     Moreover, a regulating apparatus can be provided that controls the supply for the plastic particles and/or the liquid supply on the basis of measured data provided by at least one measuring device. The measuring device can for example comprise a level sensor that measures the fill level in the outlet of the delivery funnel. In this embodiment, for example the fill level in the region of the funnel outlet, the supply of the plastic particles and/or the liquid can be controlled in the manner required depending on relevant measured data. Accordingly for example, a target fill level in the funnel outlet can be regulated that always ensures safe and reliable operation of the device according to the invention. 
     The invention moreover relates to a cleaning device to remove impurities from plastic particles with an inlet for jointly delivering plastic particles and a liquid, comprising a device according to the invention. The cleaning device can for example be designed as described in WO 2013/010654 A2 or WO 2014/111412 A1. 
     The method according to the invention can be carried out by the device according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One exemplary embodiment of the invention is explained below in greater detail with reference to figures. Schematically: 
         FIG. 1  shows a sectional view of an embodiment of a cleaning device for removing impurities from plastic particles configured to jointly deliver plastic particles and a liquid; 
         FIG. 2  shows a perspective view of an embodiment of a delivery funnel of the device shown in  FIG. 1 ; 
         FIG. 3  shows a first side view of the delivery funnel from  FIG. 2 ; 
         FIG. 4  shows a second side view of the delivery funnel from  FIG. 2 ; and 
         FIG. 5  shows a plan view of the delivery funnel from  FIG. 2 . 
     
    
    
     If not otherwise specified, the same reference numbers indicate the same objects in the figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 , a cleaning device is shown at reference sign  10  for removing impurities from plastic particles, such as from plastic flakes. In the shown example, the cleaning device is a disk refiner whose cleaning discs are represented at reference signs  12  and  14 . At least one of the cleaning discs  12 ,  14  is rotatably driven by a motor  16 . Such a device is known per se and can for example be designed as shown in WO 2013/010654 A2. Although a disk refiner is portrayed in  FIG. 1 , other cleaning devices are also possible, such as a drum, or respectively ball refiner. 
     A pipeline  20  is connected to the inlet  18  of the cleaning device  10  and is joined to the outlet of a delivery funnel  22 . A supply funnel  24  is arranged above the inlet of the delivery funnel  22  and forms a supply reservoir  26  into which plastic particles to be cleaned are added as illustrated by the arrow  28 . In the portrayed example, two different size supply brushes  30 ,  32  that are rotatably driven about parallel rotary axes are located in the supply funnel  24 . The plastic particles are supplied under gravity from the supply reservoir  26  via guide walls  34 ,  36  to the supply brushes  30 ,  32  and are guided between these into the inlet of the delivery funnel  22 . In so doing, the plastic particles are separated and fall curtain-like evenly into the delivery funnel  22 . A plurality of delivery nozzles  38  are arranged in the delivery funnel  22  as will be explained in greater detail with reference to  FIGS. 2 to 5 . The delivery nozzles  38  are connected by a supply line  39  and a pump  41  to a liquid supply (not shown), in the present case a water supply. Water supplied from this water supply is discharged by the delivery nozzles  38  into the delivery funnel  22 . 
     As in particular discernible in  FIGS. 2 to 5 , the delivery nozzles  38  are arranged distributed at regular intervals on the edge  40  of the inlet of the delivery funnel  22 . In this case, a liquid connection  42  of the delivery nozzles  38  extends outwardly through the wall of the delivery funnel  22 . The supply line  39  is connected to these liquid connections  42 . The liquid jet discharged by the delivery nozzles  38  is directed toward the inner wall of the delivery funnel  22 , in the present case at an angle relative to the axial direction of the delivery funnel that for example runs vertically from top to bottom in  FIG. 3 . The angle can for example lie within a range of 60° to 70° to the axial direction. In addition, the liquid jets discharged by the delivery nozzles  38  are each at a slight angle, for example less than 20°, to an imaginary tangent touching the opening edge  40  of the funnel inlet in the region of the attachment of the delivery nozzles  38 . By means of this arrangement of the delivery nozzles  28 , the sprayed-in water runs down helically on the inner wall of the delivery funnel  22  toward the outlet  44  of the delivery funnel  22 , and a vortex, or respectively a swirling of the sprayed-in water occurs in the region of the outlet  44 . This in turn leads to the formation of a mixing zone in the region of the outlet  44  in which the plastic particles falling under gravity over the supply brushes  30 ,  32  into the delivery funnel  22  are homogeneously mixed with the water and with a precisely defined solid component. The suspension of water and plastic particles formed in this manner is supplied via the supply line  20  to the inlet  18  of the cleaning device  10 , and the plastic particles are freed of impurities in the cleaning device  10 . In particular in  FIGS. 2 and 5 , it is moreover discernible that the edge  40  of the inlet of the delivery funnel  22  is designed elliptically. 
     Although not portrayed in the figures, at least one rinsing nozzle can also be arranged on the delivery funnel  22 , alternatively or in addition to the shown delivery nozzles  38 , through which a directed liquid jet can be discharged directly into the outlet  44  of the delivery funnel  22 . Also, the device according to the invention can comprise a regulating apparatus that, on the basis of measured data from a measuring device, controls the supply for the plastic particles, in particular the rotary speed of the supply brushes  30 ,  32 , and/or the supply of liquid, in particular the pump  41 . The measuring device can for example measure the fill level in the outlet  44  of the delivery funnel  22 . 
     LIST OF REFERENCE SIGNS 
     
         
           10  Cleaning device 
           12  Cleaning disk 
           14  Cleaning disk 
           16  Motor 
           18  Inlet 
           20  Pipeline 
           22  Delivery funnel 
           24  Supply funnel 
           26  Supply reservoir 
           28  Arrow 
           30  Supply brush 
           32  Supply brush 
           34  Guide wall 
           36  Guide wall 
           38  Delivery nozzle 
           39  Supply line 
           40  Edge 
           41  Pump 
           42  Liquid connection 
           44  Outlet