Device for recycling mixed plastic waste, a blade system for said device and a method for recycling mixed plastic waste

Abstract

A blade system for device for recycling mixed plastic is disclosed. Furthermore, a device and a method for recycling unidentified, unclean, and unsorted mixed plastic into reusable plastic mixture is disclose. The present solution allows the recycling of mixed plastic waste outdoors, both in warm and cold climate conditions. In the course recycling mixed plastic waste the mixed plastic waste is taken to a melting temperature, at which the mixed plastic waste is mixed in a molten state, and the organic and bacterial material is destroyed during the thermal processing. After the melting, mixing and thermal processing of the mixed plastic waste, the compaction process of the molten mixed plastic waste is performed. Volume compacting is performed, and the mass of mixed plastic waste in a molten state is rapidly cooled down, crushed, after-cooled and homogenized.

Claims

1. A device for recycling mixed plastic, said device comprising: an agglomeration chamber base; an agglomeration chamber attached to the agglomeration chamber base, wherein the agglomeration chamber comprises a bottom and a double wall; an observation and service opening in the double wall of the agglomeration chamber; an outlet port in the double wall of the agglomeration chamber; a loading chamber attached to the agglomeration chamber, wherein the loading chamber is equipped with a loading port, an upper observation opening, and an exhaust fan for water vapor; a collar attached to the bottom of the agglomeration chamber; a blade system at the bottom of the agglomeration chamber, wherein the blade system comprises a blade holder, two material exit guides, two inner blades, two outer blades, two blade mounting plates with fastening holes, and fasteners; a motor, capable of rotating the blade system, wherein the motor is connected to the blade system through a shaft; a cooling system equipped with a cooling inlet, and a cooling outlet; a transmission and lubricating chamber with a preheater equipped lubricating pump; and a switchboard capable of operating the device; wherein: the shaft comprises a bearing pedestal with closed bearings and pressure seals, and cutting angle α of the blade mounting plates and cutting angle β of the inner and outer blades are approximately 28° to 32°, and angle γ between cutting edge of the inner blades, and edge on side of the material exit guides is approximately 50°.

2. The device according to claim 1, wherein the double wall of the agglomeration chamber comprises at least three replaceable parts with their height greater than thickness of belt of mixed plastic waste being recycled in the agglomeration chamber, and height to which mixed plastic waste particles can be thrown in course of crushing process.

3. The device according to claim 1, wherein the blade system is capable of rotating at approximately 1200 rpm, the motor is capable of operating at amperage approximately 600 A, and temperature in the agglomeration chamber being approximately 140 to 160° C. during recycling process.

4. The device according to claim 1, wherein distance between the outer blades of the blade system and the double wall of the agglomeration chamber is approximately equal to thickness of the blades.

5. A device according to claim 1, wherein: the blades are attached to the blade holder with cutting surface of the blades towards the bottom of the agglomeration chamber, and bottom surface of the blades upwards, and wherein the blades and the blade mounting plates of the blade system form an even surface, with the fasteners tightened.

6. The device according to claim 1, wherein cutting surface of the blades has been hardfaced, and cutting edge of the blades has been blunted by hardfacing.

7. The device according to claim 1, wherein cutting surface of the blade mounting plates of the blade system has been hardfaced, and hardfacing has been provided in front of the fastening holes of the blade mounting plates in rotating direction.

8. The device according to claim 1, wherein the material exit guides have been hardfaced.

9. A method for recycling mixed plastic waste comprising the steps of: obtaining pre-processed mixed plastic waste by preliminary processing of the mixed plastic waste; routing 60-150 kg of the pre-processed mixed plastic waste to the agglomeration chamber of the device according to claim 1; utilizing the device to: achieve amperage of approximately 400 A for the motor of the device; rotate the blade system of the device at an approximate speed of 1200 rpm; crush and simultaneously mix the pre-processed mixed plastic waste by rotating blade system; allow temperature of the agglomeration chamber to rise to 140-150° C., wherein the temperature rises due to mechanical friction while crushing of the pre-processed mixed plastic waste; heat and melt the pre-processed mixed plastic waste to obtain molten plastic mass; increase amperage of the motor to approximately 600 A; allow temperature of the agglomeration chamber to rise to 150-160° C.; harden the molten plastic mass by rapid cooling to obtain a hardened mass; crush the hardened mass by rotating blade system to obtain crushed mixed plastic; allow temperature of the agglomeration chamber to rise again to 100-110° C.; open the outlet port of the device; and routing the crushed mixed plastic from the agglomeration chamber to an after-cooler chamber, wherein the after-cooler chamber is designed to preserve plastic properties and fraction of the crushed mixed plastic; routing the crushed mixed plastic from the after-cooler chamber to a homogenizing device; and homogenizing the crushed mixed plastic to obtain recycled mixed plastic.

10. The method according to claim 9, wherein the rapid cooling is achieved through spraying water at temperature of 4° C.-10° C., and in quantity of 2 to 3 liters decreasing temperature of the agglomeration chamber instantly to approximately 80° C.

11. The method according to claim 9, wherein the recycled mixed plastic has uniform size between 3-10 mm, and moisture content below 1%.

12. The method according to claim 9, wherein a cycle from preliminary processing to obtaining recycled mixed plastic lasts for 5-15 minutes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained more precisely with references to figures added, where:

(2) FIG. 1 presents the general diagram of the system for recycling mixed plastic waste, including the device for recycling mixed plastic waste according to the present invention;

(3) FIG. 2 presents the device for recycling mixed plastic waste according to the present invention with the location of the blade system shown;

(4) FIG. 3 presents the perspective view of the parts of the blade system according to the present invention;

(5) FIG. 4 presents the perspective view of the blade system according to the present invention;

(6) FIG. 5 presents the top view of the blade system depicted on FIG. 4;

(7) FIG. 6 presents the side view of the blade system depicted on FIG. 4;

(8) FIG. 7 presents the end view of the blade system depicted on FIG. 4;

(9) FIG. 8 presents the perspective view of the mounting plate of the blade system blades;

(10) FIGS. 9a to 9c present the outer blades of the blade system in case of various implementation examples;

(11) FIGS. 10a to 10c present the inner blades of the blade system in case of various implementation examples.

DETAILED DESCRIPTION OF THE INVENTION

(12) The system for recycling unsorted mixed plastic waste into homogenized raw material mass of unidentified, unclean, and unsorted mixed plastic waste of different densities and low volume weight, presented in FIG. 1 comprises input 1 for the mixed plastic waste, waste crusher 3, connected with the input 1 via a feed conveyor 2, metal separator 4 connected with the waste crusher 3, air separator 6 and collecting container 7 connected with the metal separator 4 via the first conveyer 5, device for recycling mixed plastic waste 9 according to the present invention, connected with the collecting container 7 via the second conveyor 8, after-cooler 11 connected with the device for recycling mixed plastic waste 9 via the third conveyor 10, homogenization device 13 connected with the after-cooler 13 via the fourth conveyor 12, and an outlet conveyor 14.

(13) The system presented in FIG. 1 performs the preliminary processing of mixed plastic waste, the method for recycling mixed plastic waste according to the present invention, and after-cooling of the granulated mass created from the mixed plastic waste in the course of recycling. An alternative solution of the method for recycling mixed plastic waste according to the present invention performs the preliminary processing of the mixed plastic waste outside the system presented in FIG. 1, and they are routed directly to the device for recycling mixed plastic waste 9.

(14) The device for recycling mixed plastic waste 9 according to the present invention presented in FIG. 2 comprises an agglomeration chamber base 15, agglomeration chamber 16, equipped with a double wall 17, observation and service opening 18 (for visual inspection by technical/maintenance personnel, and replacing of the blade system parts and double walls), and recycled plastic mixture outlet port 19, loading chamber 20 equipped with a loading port 21 and an upper observation opening 22, cooling system 23 equipped with the cooling inlet 24 and cooling outlet 25, motor 26, transmission and lubricating chamber 27, pre-heated lubricating pump 28, switchboard 29, collar 31 attached to the bottom 30 of the agglomeration chamber 16, shaft 32 running through the bottom 30 and collar 31, and connected with the motor 26, blade system 33 according to the present invention attached to the shaft 32, and exhaust fan for water vapor 52.

(15) Due to the abrasiveness and high temperatures of the mixed plastic waste, an additional double wall 17, manufactured of at least three parts has been provided for the inner wall of the agglomeration chamber 16 for higher wear resistance and durability, with its height greater than the thickness of belt of the mixed plastic waste being recycled, and the height to which the mixed plastic waste particles can be flown in the course of being crushed. To achieve better wear resistance, the double wall 17 has been manufactured of abrasion resistant material with a hardness of at least 450 HBW.

(16) In the course of the melting process of the device for recycling mixed plastic waste 9 unsorted, unidentified, and unclean mixed plastic waste is taken to melting temperature, at which the mixed plastic waste is mixed in a molten state, and the organic and bacterial material is destroyed during thermal processing. After the melting, mixing and thermal processing of the mixed plastic waste, the compaction process of the molten mixed plastic waste is performed. The compaction of the volume of up to approximately ten times is performed. The mass of mixed plastic waste taken to a molten state in the course of the melting process is rapidly cooled down by the spraying of approximately 2 to 3 liters of water, preferably to approximately 4° C. to 10° C., causing the molten mass to harden. The blade system blades of the device for recycling mixed plastic waste that were initially mixing the molten mass now start to crush the hardened mass.

(17) FIGS. 3 to 7 present the blade system 33 of the device for recycling mixed plastic waste 9 according to the present invention, comprising a blade holder 34, two material exit guides 35, two inner blades 36, two outer blades 37, two blade mounting plates 38, and fasteners (e.g. bolts) of the blade holder 34, material exit guide 35, blades 36 and 37 and mounting plate 38. To achieve better wear resistance, the parts of the blade system 33 have been manufactured of abrasion resistant material with a hardness of at least 450 HBW.

(18) The blade systems used by known solutions are not able to withstand the friction, high temperatures, vibration and high power; they quickly grow blunt and worn, and break. To solve this problem the parts of the blade system according to the present invention have been designed to be more durable; this has been achieved by using thicker blades with their cutting angles and construction different from the ones used by known solutions.

(19) FIG. 3 depicts the length L1 of the outer blade 37 of the blade system according to the present invention, and the side length L2 of the inner blade at the side towards the holder 34, that according to the preferred embodiment are approximately equal, L1≈L2. If L1>L2, the outer blade 37 would wear more quickly and more extensively, because according to the preferred representation the outer blade 37 works more intensively. If L1<L2, partial uneven wearing of the inner blade 36 would occur. The fraction size decreases due to worn blades. The alternative representation of the invention has the same volume of the agglomeration chamber 16, but the quantity of the mixed plastic waste input for recycling has been increased, the length L1 has been increased, and the length L12 decreased, and L1>L2; or the quantity of the mixed plastic waste input for recycling has been decreased, and in that case a blade system with L1<L2 has been used.

(20) FIGS. 4 to 7 present various views of the assembled blade system according to the present invention. According to the preferred representation of the blade system the cutting surface of the blade mounting plates 38 has been hardfaced 39 to ensure melting and wear resistance. Welded strips of hard metal 41 have been provided in front of the fastening holes 40 of the mounting plate 38 in the direction of rotation, preferably e.g. crescent-shaped. In contrast to the known solutions, to achieve larger impact forces, the inner blades 36 and outer blades 37 of the blade system have been attached to the blade holder 34 reversed, with the cutting surface of the blades 42 downwards toward the agglomeration chamber 16 bottom 30, and the bottom surface 43 of the blades upwards as depicted in FIGS. 3 to 7. The material guides 35 are hardfaced 44. The material guides 35 have been attached to the blade holder 34 e.g. by welding and/or using a bolted connection 45. The blade system 33 has been attached to the shaft with bolts 46. The collar 31 has been attached to the bottom, and also welded in addition to the bolted connection.

(21) To achieve better wear resistance, the cutting surface 42 of the inner blades 36 and outer blades 37 has been hardfaced 47, and the cutting edge 48 of the blades has been blunted by hardfacing. FIGS. 9a to 9c present various preferred representations of the hardfaced cutting surfaces of the outer blades 37, FIGS. 10a to 10c present various preferred representations of the hardfaced cutting surfaces of the inner blades 36; scale-like welding applied on the cutting surface of the blades is the most preferred due to its highest wear resistance (depicted on FIGS. 9c and 10c). To achieve higher durability, also other pattern-shaped hardfacing types are preferred, creating e.g. hardfaced stripes diagonal to the cutting edge 48 on the cutting surfaces of the blades (with its implementation example presented on FIGS. 9a and 9b), or grooves formed by hardfacing, perpendicular to the cutting edge 48, with their implementation examples presented on FIGS. 10a and 10b.

(22) In contrast to the known solutions having the blades cut the material being recycled, the reversed placement of the blades, blunted cutting edge 48 and the cutting surface hardfaced with various patterns of the present invention achieve the effect of making the blades 36 and 37 crush the mixed plastic waste material being recycled instead of cutting it, due to creating an impact effect.

(23) The step of the rhombic weld pattern applied on the blade mounting plate 38, outer blade 37 and inner blade 36, presented in FIGS. 8, 9a and 10a, respectively, is approximately 20 to 30 mm.

(24) This achieves higher durability and wear resistance with respect to temperature and friction. Such design of the blades also ensures uniform fragments when crushing the material being recycled.

(25) In contrast to generally known solutions, where the heads of the fasteners extend out of their holes, and as a result wearing quickly, the blades of the present invention have been thickened, creating deeper fastener holes, and allowing the tightened fastening bolts to remain coplanar to the surface of the blades.

(26) The cutting angle α 49 of the blade mounting plate 38 presented on FIG. 8, and the cutting angle β 50 presented in FIGS. 9a, 9c and FIGS. 10a to 10b are approximately 28-32°. Having the cutting angle within this range achieves the best crushing effect, and at the same time the blades 36, 37 and blade mounting plate 38 last the longest.

(27) The angle γ 51 between the cutting edge of the inner blade 36, and the edge at the side of the material exit guide 35 is preferably approximately 50°. The blades 36 and 37, and the blade mounting plate 38 have shape and dimensions allowing the parts of the blade system 33 to form such a level/even surface by assembly of the blade system 33 that the mixed plastic waste material being crushed would be thrown away from the blade system surface, not slide and rub against it as it does according to the known solutions. Using such a construction achieves higher and better resistance to high temperatures and friction for the blade system and its parts.

(28) In contrast to the known solutions the blades of the blade system of the present invention strike and crush the material instead of cutting it, and create a uniform fragment.

(29) The rotating speed of the blade system 33 generated by the motor 26 is approximately 1200 rpm, and at the amperage of ca 600 A the temperature of approximately 160° C. is achieved in the agglomeration chamber 16 due to friction after the mixed plastic waste has been melted and mixed to a uniform mass at the temperature of approximately 150-160° C.; then the sprinkler is turned on.

(30) To ensure higher productivity (kg/h) when using an agglomeration chamber 16 of the same volume, a more powerful motor 26 is used, enabling larger quantities of material to be input at a time (batch kg) and increasing the productivity (kg/h). The more powerful the motor used, the more durable must be the transmissions, blade system 33, and agglomeration chamber of the device for recycling mixed plastic waste. Different preferred alternative implementation examples for using motors of varying power while the volume of the agglomeration chamber 16 used remains the same are provided below.

(31) TABLE-US-00001 Implementation Implementation Implementation example 1 example 2 example 3 Motor (HP) 540 420-340 270-220 Drum size (mm) 200 1,200 1,200 Batch (kg) 100-150  75-120 60-80 Productivity (kg/h) 1,000-1,500   800-1,000 450-650

(32) One recycling cycle lasts approximately 5-15 minutes. The preferred representation of the solution according to the present invention uses the implementation example 2. When increased productivity is required, the input quantity of mixed plastic waste to be recycled is increased, the capacity of the motor is also increased, and the thickness of the belt of mixed plastic waste being recycled also increases due to centrifugal force; this brings about the need to extend the outer blade and shorten the inner blade. For example, when using an additional quantity of ca 50 kg of mixed plastic waste to be recycled for the alternative representation of the present invention, the length L1 of the outer blade 37 has been increased by 25 mm, and the length L2 of the inner blade 36 has been decreased by 25 mm.

(33) For other alternative representations the diameter of the agglomeration chamber 16 has been changed. For example, when the diameter of the agglomeration chamber 16 is increased or decreased by x percent, the length, thickness, and width of the parts of the blade system 33 are proportionally increased or decreased by x percent, whereas the distance between the outer blade 37 of the blade system 33, and the inner double wall 17 of the agglomeration chamber is approximately equal to the thickness of the blade. The larger this gap the more untreated material will end up inside it. When the distance between the outer blade 37 of the blade system 33, and the inner double wall 17 of the chamber is less than the approximate blade thickness, the blade could come into contact with the casing due to the temperature rising and parts expanding, making the gap smaller.

(34) In contrast to the known solutions, using riveted connections for the inner walls of the agglomeration chamber 16, the inner walls of the agglomeration chamber 16 of the present invention are provided with bolted connections.

(35) The material guides 35 of the blade system 33 route the material to the impact zone of the blades 36 and 37.

(36) Achieving 160° C. depends on the moisture content of the material, the ambient temperature, and the productivity.

(37) The temperature of the material is 180-190° C. at the agglomeration chamber 16 temperature of 160° C.; mostly the mixed plastic waste is melted into a uniform mass at that temperature. The mixed plastic is not yet overheated. Raising the temperature of the agglomeration chamber to 180° C. creates the danger of overheating the plastic, and the properties of the plastic required for subsequent processing of the polymers deteriorate (its elasticity, toughness, and strength are decreased, and it becomes brittle).

(38) In contrast to the known solutions more fasteners, e.g. bolts have been provided for attaching the collar 31, and the collar has been additionally welded for the attachment to endure, to achieve better resistance to the vibration occurring during the recycling process.

(39) The system presented in FIG. 1 performs preliminary crushing 3 of the mixed plastic waste during preliminary processing; after that metal separation with the magnetic separator 4 takes place; then the waste is taken to the air separator 6 with the conveyor 5 for separating non-plastic material; the broken up plastic waste with metals and other non-plastic materials separated from it is subsequently taken to the collecting container 7, and from there to the device for recycling mixed plastic waste 9 on the conveyor 8 for recycling through mixing, melting and crushing, involving disinfection of the bacterial and organic materials, and the compacting process of the mixed plastic waste at their melting temperature; the plastic mass obtained by recycling is taken to the after-cooler 11 from the device for recycling mixed plastic waste 9, and to the homogenisation system 13 following the after-cooling.

(40) The waste crusher 3 or the pre-crushing system ensures efficient preliminary crushing of the mixed plastic waste. The speed of the feed conveyor 2 for transporting the waste to the pre-crusher 3 is appropriately adjusted to maintain uniform input flow to the pre-crusher 3 according to the waste spreading productivity. A magnetic separator separating metals from the crushed mixed plastic waste is used as the metal separator 4. The capacity of the metal separator 4 has been chosen as optimal for the material flow coming from the crusher. The first conveyor line 5 transports the crushed mixed plastic waste to the subsequent stage at the air separator 6. Non-polymer substances mixed with the plastic, for example sand, glass, nonferrous metals (aluminum, copper), minerals etc. are separated using the air separator 6. This does not involve separation of the mixed plastic by polymer types. The air separation stage also involves the initial mixing of the mixed plastic waste. Due to the large cubic content of the mixed plastic waste the crushed mixed plastic waste is transported to the collecting container 7, equipped with automatic conveyors for moving the crushed plastic waste. The purpose of the collecting container 7 is to create a raw material buffer preferably holding 3-4 tons of material. The second conveyor line 8 controls the transportation of the mixed plastic waste to the compacting and sanitation stage of the mixed plastic waste recycling process according to the present invention in the device for recycling mixed plastic waste 9.

(41) The method for recycling mixed plastic waste according to the present invention includes preliminary processing of the mixed plastic waste, routing of the pre-processed mixed plastic waste to the device for recycling mixed plastic waste 9, recycling of the mixed plastic waste in the device 9 by heating, melting, mixing, reducing the cubic content of the recycled material, rapid cooling with tempering, crushing, and additional after-cooling and homogenisation. The device for recycling mixed plastic waste 9 performs thermal processing of the material, the melting process and finally crushing of the material recycled from the mixed plastic waste into granules. The device for recycling mixed plastic waste 9 reduces the cubic content of the mixed plastic waste, increases their density, processes the mixed plastic waste mechanically and thermally until melted, and mixes the mixed plastic waste in a molten state, thereat also eliminating the organic and bacterial input, rapidly cools down the plastic mass obtained by melting and mixing until it hardens, crushes the hardened plastic mass into particles, and routes it to after-cooling and homogenisation. The recycled plastic mixture obtained has a fragment size of approximately 3-10 mm, moisture content below 1%, and is stable raw material for the subsequent production process characterized by its melt flow index, melting temperature, density, and granule size.

(42) Then the granules are transported to the after-cooling system 11 using the cyclone conveyor 10, as the material is output from the production process at a temperature exceeding 100 degrees due to high temperatures generated by the production process of the device for recycling mixed plastic waste. The known solutions route the compacted clean materials recycled from single-type plastic to subsequent regranulate production; according to the present invention the material passes through an additional several-hour cooling cycle in the cooling tower. The after-cooler 11 is designed to preserve the plastic properties and fraction of the material. Following the after-cooling, the material is taken to the homogenisation system 13 on the conveyor 12 where mixing of the material takes place. The homogenisation system 13 comprises a container mixer of at least 28 m.sup.3, enabling the mixing of the materials with each other and the homogenisation of the raw material mixture by batches of at least 10 to 15 tons. Unlike known container mixers, an inflow of warm air has been added to the container mixer of the present solution, to also achieve efficient drying along with the mixing.

(43) As a result of the high temperature created in the course of the mixed plastic waste recycling process, the plastic mass recycled from mixed plastic waste is output at the temperature of approximately 115° C. to 165° C. Unlike the generally known processes that route the compacted clean single-type plastics to subsequent regranulate production, according to the present invention the material passes through an additional several-hour cooling cycle in the cooling tower 11, during which the material is mixed, and gradually cooled, this way stabilising the properties of the recycled polymer mixture for the subsequent production cycle. The material is after-cooled to the temperature of approximately 30-40° C.

(44) During the recycling stage the blade system 33 of the device for recycling mixed plastic waste is started in the device 9 with the help of the motor 26 at the approximate rotation speed of 1200 rpm. The mixed plastic waste to be recycled in a quantity of 60-150 kg is taken in the agglomeration chamber 16 via the inlet opening 21. The mixed plastic waste is crushed by the blade system 33, at the same time mixing it; the mixed plastic waste starts to heat and melt due to friction. The mixed plastic waste starts to melt at the temperature of approximately 140-150° C., the amperage of the motor 26 is approximately 400 A. The temperature rises to approximately 160° C. in the agglomeration chamber, and the amperage increases to 600 A. Upon achieving this, about 2-3 liters of cold water is sprayed, instantly lowering the temperature to about 80° C. The blade system 33 continues to rotate at the same time.

(45) The exhaust fan for water vapor 52 is started before spraying the water. The molten mass hardens as the water is sprayed, and the blades still rotating start to crush the hardened mass. The temperature starts to rise again, and the outlet port 19 is opened at the temperature of 100-110° C. The amperage starts to rise as well and will increase to 600 amperes. The crushed fragments of the recycled mixed plastic waste are taken from the agglomeration chamber 16 of the device for recycling mixed plastic waste 9 to cool down in the cyclone of the after-cooler 9 by using centrifugal force, to make the material release heat into the air, not coming in contact with any other materials.