Method and system for separating plastics using a covered screen bed

Abstract

The invention includes a method and system for separating materials using a combination of a screen bed and a gravity separator. The material is collected from a waste stream and passes through a screen. Larger collected materials are then directed to a first gravity separator with a specific gravity. Plastics are recovered, and residual metals are recovered.

Description

Technical Field

[0001] The present disclosure relates to systems and methods for separating plastics in waste streams. More particularly, the present disclosure relates to systems and methods using a coated screen bed for separating materials in recycling or waste recovery operations.

Background Art

[0002] Recycling of waste materials is important for several reasons, particularly from an environmental and economic perspective. Properly sorted recyclable materials can yield significant financial benefits by being sold for profit. Additionally, many valuable recyclable materials are not biodegradable within a short time frame, and thus recycling them helps reduce pressure on local landfill sites and mitigate environmental impact. This reduces pollution, decreases resource depletion, and makes carbon dioxide emissions smaller.

[0003] Waste flows typically consist of various types of materials that can be recycled to produce aggregates and recover valuable metals. These aggregates have substantial value, especially if they are relatively clean. Examples of waste flows come from the recycling of automobiles, heavy machinery, or electrical appliances. Automobiles are shredded at the end of their lifespan, and the resulting materials are processed to recover ferrous and non-ferrous metals. The remaining waste, known as automobile shredder residue (ASR), still contains valuable ferrous and non-ferrous metals such as copper, along with other recyclable materials such as plastics. Generally, ASR is disposed of in landfills, but efforts continue to recover non-ferrous metals and plastics from these waste flows. A similar process applies to whitegood shredder residue (WSR), which includes waste generated after recovering ferrous metals from shredded machinery or heavy equipment. Other types of waste flows containing recoverable materials include electronic components ("e-waste" or waste electrical and electronic equipment, WEEE), building components, recovered landfill materials, and other industrial waste flows. For example, U.S. Patent No. 6,024,226 (A) describes a system and process for separating and recovering materials from solid waste flows, while International Publication No. 2012 / 146974 (A1) details apparatus and methods for separating shredder fractions.

[0004] A given waste stream may contain various plastics, some of which are suitable for recycling and can be melted and mixed to produce new materials with different properties. Common types of plastics found in waste streams include polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS) (including high-impact polystyrene (HIPS)), and polyvinyl chloride (PVC). The value of these plastics increases when they are separated into "light" plastics (PP and PE) and "heavy" plastics (ABS and PS). However, certain types of plastics, such as PVC and certain types of PP (including those filled with talc or glass fibers), are considered undesirable. To maximize the value of recycled plastics, it is important to remove undesirable plastics from the mixture to obtain a more uniform and higher-quality material.

[0005] Therefore, there is always a need for improved methods and systems for separating materials. This application relates, in particular, to this need. [Overview of the project]

[0006] One aspect of this application includes a method and system for separating plastics from waste material using a covered screen bed. A particular embodiment includes separating the plastics through a series of processing steps, which include screening to create separate flows of light plastics, heavy plastics, or sized plastics. These methods enable the efficient removal of undesirable and non-plastic materials, ultimately producing a single-type plastic flow. The system is designed to process waste flows resulting from recycling processes, including common plastics such as polypropylene (PP), polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), and polystyrene (PS).

[0007] Another embodiment is a method of separating materials by feeding a waste stream through a screen of a specific size, allowing smaller materials to pass through and collecting larger materials for further processing. These larger materials are directed to a first gravity separator having a specific gravity of 0.95–1.05, where they can be separated into denser materials that settle and lighter materials that float. The lighter materials from this gravity separator are transferred to a second gravity separator having a specific gravity range of 1.05–1.25, where they are further separated into a second set of lighter materials and a second set of heavier materials. This method includes recovering the second set of heavier materials from the second gravity separator for subsequent processing or use. The specific gravity of the first separator may be set to 1.0 and the specific gravity of the second separator to 1.2. The lighter plastics recovered from the second gravity separator may include polyethylene (PE) and polypropylene (PP), while the heavier plastics may include acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS).

[0008] Another embodiment includes a screen which is a covered screen bed having a stirring bed.

[0009] Another embodiment relates to a screen having a variable screening size. The screen has a screening capability of 6 mm to 12 mm and can separate materials at 6 mm.

[0010] Another embodiment includes a method in which the first gravity separator is a floating gravity separator that separates materials based on specific gravity, such that denser materials sink and lighter materials float.

[0011] Another embodiment describes using a dewatering screen to remove excess moisture from the separated material.

[0012] Another embodiment is a system for separating materials using a screen bed and gravity separators, the covered screen bed being designed to separate materials based on size and including a first gravity separator set to a specific gravity of 0.95–1.05 to separate the material into denser materials that settle and lighter materials that float, and a second gravity separator set to a specific gravity of 1.05–1.25 to further separate the lighter materials from the heavier materials. An extruder and pelletizer can process the concentrated plastic fraction and pelletize it for further use. The system is designed to process waste streams containing organic matter, textiles, foams, fiber scraps, and pre-sorted metals.

[0013] In another embodiment, the first gravity separator or the second gravity separator may include at least one of the following: a liquid sedimentation / flotation tank, a sand flow separator, or a hydrocyclone.

[0014] Another embodiment is a method for separating material using a screen bed and gravity separators, wherein a waste flow is fed into a screen bed having a specific mesh size to facilitate separation, larger material is collected and smaller material passes through the screen, the larger material is directed to a first gravity separator having a specific gravity of 0.95–1.05, where it is separated into denser material that settles and lighter material that floats, the lighter material is then transferred to a second gravity separator having a specific gravity of 1.05–1.25 to further separate the lighter material from the heavier material. The second set of recovered heavier material can then be processed for further use. The system may be characterized in that the first or second gravity separator includes at least one of the following: a liquid settling / floating tank, a sand flow separator, or a hydrocyclone. [Brief explanation of the drawing]

[0015] [Figure 1] An exemplary system is shown, featuring a covered screen bed operably connected to a gravity separator. [Figure 2] An exemplary cover, which is part of the screen bed shown in Figure 1, is provided. [Figure 3] Figure 2 provides a side cross-sectional view of the cover on the screen bed. [Figure 4] Figure 1 provides a top view of the agitation bed within the screen bed. [Figure 5] Figure 4 shows an exemplary agitator that may be used in the agitated bed shown. [Figure 6] An exemplary method for screening materials is shown. [Modes for carrying out the invention]

[0016] This application describes a method and system for separating plastics from waste materials using a covered screen bed. Certain embodiments involve separating plastics through multiple processing steps, which include a covered screen bed for creating separate flows of light and heavy plastics. These methods enable the efficient removal of undesirable plastics and non-plastics, ultimately producing a single-type plastic flow. The system is designed to process waste flows from recycling processes, including common plastics such as polypropylene (PP), polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), and polystyrene (PS). By efficiently separating plastics, these methods aim to maximize revenue recovery while minimizing landfill waste.

[0017] Initial waste streams often contain a variety of non-plastic materials such as rubber, wood, metal, wire, circuit boards, foam, and glass. The described methods use a size reduction system to sort these waste streams, resulting in multiple product and by-product streams. These processes are applicable to a variety of plastic-rich waste sources, including office automation equipment (printers, computers, copiers, etc.), white goods (refrigerators, washing machines, etc.), household appliances (televisions, stereos, etc.), automotive shredder residues, packaging waste, household waste, construction waste, and plastics from industrial molding and extrusion scrap. In some embodiments, the initial waste stream or material is treated in a process for recovering metals.

[0018] Figure 1 shows an embodiment of a system for separating materials using a covered screen bed 110 with a cover 160 and gravity separators 120. The screen bed or particle size separator 110 is a large rectangular industrial structure with a sturdy frame, resembling a horizontal conveyor system with a slightly upward slope leading to the screening area. As can be seen from the figure, the material flows from the feeder 120 to the screen bed 110 using a conveyor 125. In the screen bed 110, the material is released and separated / screened without substantial dust and debris floating in the surrounding environment. As the material passes over the screen bed 110, smaller materials (e.g., fibrous waste, textiles, foam, wood) may be further processed using, for example, a high-frequency screen 130. Larger materials are then processed using one or more gravity separators 120. At this point, materials such as wood or fibrous waste are removed and fall through the agitated bed. Larger materials, or for example, materials exceeding 6 mm in size, can be moved to a second screening bed having a fluidization chamber, thereby encapsulating lighter, denser materials in an airflow, while heavier materials (e.g., plastics) remain on the screening bed for further screening through the process or system. Lighter materials (e.g., fibrous waste) may be carried by the airflow into the fluidization chamber, and further into an expansion chamber or cyclone. Smaller materials may be concentrated and discarded. A purifier 150 and a water supply device 151 may also be present.

[0019] Figure 2 shows one embodiment of a cover 160 which is part of a screen bed 110. As can be seen from the figure, the cover 160 has side panels 170 which help prevent the material from separating from the mixing bed 190. The cover may have a top panel to prevent dust-containing material from entering the surrounding environment. A curtain or flap 162 helps to hold the material against the bed and helps to prevent the material from being aerosolized or becoming particulate. The curtain 162 provides an opening for the material to flow across the bed 110. A protective casing surrounds the bed and covers 80% to 99% or 85% to 95% of its surface, providing a barrier against dust and debris while shielding the system from external elements. The cover has varying zones (A, B, C).

[0020] Figure 3 shows a side cross-sectional view of the cover 160. As can be seen from the figure, the curtain 162 is suspended above the mixing bed 190 such that there is a distance between the curtain 162 and the mixing bed 190. This allows the material to flow across the mixing bed. In some examples, the height of the cover may be lower to allow the material to bounce off the cover and improve separation.

[0021] Figure 4 shows a top view of the floor showing the agitated bed 190, which shows the dispersed star shape or agitator 192. The platform includes a series of screening spaces having either a predetermined spacing or a variable spacing. The material placed on the upper side of the platform is agitated by the rotating shaft / star shape 192 (shown in a later figure), resulting in a dynamic screening process. As the shaft rotates, smaller materials pass through the screening spaces, while larger materials remain on the surface of the platform. Constant agitation and rotation ensure effective sorting and prevent material accumulation. The screen can be a coated screen bed having an agitated bed with a screening capacity of 6 mm to 12 mm (for example, 6 mm). The larger the screen size, the more material can fall, but this may reduce the final product. The material that falls to the bottom through the space S having the screen size is sorted or discarded based on both its size and weight.

[0022] Figure 5 shows an exemplary view of the material that leaves the screen bed 120 and does not fall through the screen bed. In this embodiment, the system uses a coated screen bed for the initial separation and then two gravity separators having specific gravity settings of 1.0 and 1.2, respectively. The method is initiated by feeding the waste stream to the coated screen bed, which sorts the material based on size and initial density. Larger and denser materials are retained on the screen bed, while smaller or lighter materials pass through the screen and reach the collection area.

[0023] The heavier material from the screen bed can be directed towards the first gravity separator set at a specific gravity of 1.0. This flotation device uses a liquid medium to separate the material based on density. In this process, materials with a high density such as certain types of plastics and rubber sink to the bottom, while lighter materials float on the surface. The floating materials can be polyethylene (PE) and polypropylene (PP), which are collected, while the sedimented materials are either transferred to the second gravity separator or discarded.

[0024] The second gravity separator set at a specific gravity of 1.2 further separates the materials. This stage is designed to recover plastics such as acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS). The floating materials in the second separator are typically the lighter plastics (ABS and HIPS), while the sedimented materials can be heavier plastics, residual metals, glass, or other denser materials.

[0025] This two-stage gravity separation method of this embodiment enables efficient and flexible sorting of materials in combination with a coated screen bed. It can accommodate various waste streams, is suitable for recycling processes that require separation of different densities, and facilitates a thorough and effective separation process.

[0026] Additional sorting processes can further purify the plastics by removing unwanted plastics and non-plastics. These methods can accommodate mixtures of plastics from multiple sources, resulting in a stream of purified plastics ready for extrusion and pelletization. This system can efficiently sort plastics such as ABS, high impact polystyrene (HIPS), polystyrene (PS), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyamide (PA), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC).

[0027] In one embodiment, heavier material from a first screen bed undergoes further separation using a buoyancy process that separates the material based on its specific gravity. This process works by immersing the material in a fluid, where denser materials sink and less dense materials float. In plastic recycling, plastics with higher densities sink, while those with lower densities float. The first buoyancy apparatus includes multiple chambers with adjustable specific gravity, enabling precise separation. The specific gravity (SG) range is typically 1.0 to 1.2, with sub-ranges varying depending on the plastic being processed.

[0028] The material that settles in the first buoyancy process typically consists of rubber or less desirable plastics. The floating material is then transferred to a second buoyancy device that uses a similar separation principle but has a different specific gravity range. The SG range of the second device is typically between 0.95 and 1.05, allowing for the efficient separation of lighter plastics such as PP and PE from heavier materials such as ABS and PS. The sorting process involves recovering the lighter plastics, such as PP and PE, from the heavier ones. By controlling the specific gravity of the liquid, these systems can effectively separate different plastics. The general specific gravity of plastics varies considerably, providing flexibility to the sorting process.

[0029] As can be seen in Figure 4, an exemplary embodiment of the system uses a screening bed with a cover, which includes a series of shafts with adjustable agitators to facilitate sorting of materials as they move through the screening device. The system uses a combination of airflow and a screening bed to separate materials based on size and density. Lighter materials, such as wood and fiber scraps, are removed through the airflow, while heavier materials remain on the screening bed for further processing.

[0030] A typical screen bed is a large industrial structure consisting of multiple screens arranged at an angle, often enclosed to contain dust and debris. It features a vibration mechanism to facilitate material movement and prevent clogging. These mechanisms, such as a rotating shaft or vibration motor, ensure efficient sorting. The bed includes a discharge chute that directs the separated material towards a collection bin or conveyor belt. An access panel provides maintenance capabilities, while safety rails, industrial lighting, and a control panel offer additional functionality.

[0031] In certain embodiments, a star-shaped scraper / agitator with flexible star-shaped fingers is used to separate the material. Some star-shaped fingers have scrapers for removing material from adjacent shafts. A dewatering screen can be used to further separate the solid from the liquid. This configuration ensures effective and durable sorting while minimizing maintenance requirements. The star-shaped or aagitator may vary in size. In certain embodiments, the star-shaped may range in diameter from 4 inches to 16 inches. An exemplary star-shaped is shown in Figure 5.

[0032] A specific embodiment of the system can handle waste streams containing high concentrations of plastic, typically 15% or more. This system is designed to handle materials from various sources, such as household waste, that have been pre-sorted into plastic and non-plastic streams. This flexibility allows the system to adapt to different waste sources and plastic concentrations, ensuring effective and efficient sorting.

[0033] Exemplary embodiments of the present invention provide a method and system for separating plastics from waste materials using a covered screen bed. Such embodiments provide a process and system for separating plastics in multiple processing steps, which may result in flows of light and heavy plastics using a covered screen bed. The method includes specifying arrangements for preparing recycled plastic products. Furthermore, certain methods and systems may enable the removal of undesirable plastics and non-plastics from a flow to produce a product of a single plastic type. Certain embodiments provide a cost-effective and efficient method and system for recovering plastics from waste flows, such as materials found in recycling processes, including polypropylene (PP), polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), and polystyrene (PS), in a way that reduces landfill requirements while facilitating revenue recovery.

[0034] Initial waste flows include certain rubber, wood, metal, wire, circuit boards, foam, glass, and other non-plastics. Size reduction methods and systems have been developed to carry out this treatment, enabling the separation of plastic-rich feed flows into multiple product flows and by-product flows. These methods and systems can be applied to a variety of plastic-rich flows originating from industrial and consumer waste. These flows may include plastics from office automation equipment (printers, computers, copiers, etc.), white goods (refrigerators, washing machines, etc.), home appliances (televisions, video / cassette / recorders, stereos, etc.), automotive shredder residue, packaging waste, household waste, construction waste, and industrial molding and extrusion scrap.

[0035] As shown in Figure 6, a particular embodiment includes a method and system for processing the light fraction of a metal separation process. In a metal separation process, the light fraction refers to the portion of the input material that has a lower density than the metal to be recovered. This fraction typically consists of non-metallic materials such as plastics, rubber, glass, and other lightweight materials. Separation of the light fraction from the heavy fraction (the portion of the input material containing the metal to be recovered) is a step in the metal recovery or recycling process. This separation is typically achieved using mechanical and / or pneumatic methods, such as a combination of an air classifier, a vibrating screen, and a cyclone.

[0036] Figure 6 shows an exemplary method according to the present application. Materials that may have been pretreated to remove metals and other undesirable materials are introduced into a covered screen bed or screen 200. The resulting screen pass-through, i.e., smaller materials that pass through the screen, typically consist of fiber scraps, textiles, foams, wood, or other similar materials 210. The screen residue, i.e., larger materials that do not pass through the screen, is sent to a first gravity separator set to a specific gravity 220 of about 1.0 to separate floating materials, generally polyethylene (PE) and polypropylene (PP) 225, from the settling material. These floating materials may optionally be pelletized (227). The settling material from the first gravity separator is processed in a second gravity separator 230 set to a specific gravity of about 1.2, which separates floating materials 232 such as acrylonitrile-butadiene-styrene (ABS) and polystyrene (PS) from the settling material. The settling material 234 at this stage may include glass, rubber, talc-filled plastic, and other residual metals.

[0037] Once the light fraction is separated, it can be further sorted and processed to recover recyclable material and plastic for recycling and retail. Certain embodiments allow for the purification or separation of material from waste streams to remove undesirable plastics and non-plastics from streams of multiple plastic families. Plastics from two or more sources of durable goods may be included in a mixture of materials supplied to a plastic recycling plant. Exemplary plastics include acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (HIPS), polystyrene (PS), polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyamide (PA), polymethyl methacrylate (PMMA), polyvinyl chloride (PCV), polyether ether ketone (PEEK), polysulfone (PSU), and polyoxymethylene (POM). Plastic-containing materials can be separated from heavy plastics to light plastics. After separating the materials, the refined plastic can be concentrated, extruded, and pelletized.

[0038] Heavier material from the second screen bed can be further separated using the first flotation device or the first gravity separator. The flotation device can separate materials with different densities, such as plastics. This process works by taking advantage of the fact that materials with a higher density than the liquid will sink, while materials with a lower density will float. For example, in a flotation system for plastic recycling, plastic pieces are placed in a tank of water. Some plastics have a higher density than water, so they will sink to the bottom, while those with a lower density will float to the top. In this device, the material is placed in a liquid, typically water or a medium, and can sink or float based on its density. This first flotation device may include various units having tanks that allow the fluid to move slowly. The first flotation device may have multiple chambers equipped with augers to aid in the separation of materials. In one embodiment, SG is 1 to 1.2. In another embodiment, SG is 1.05 to 1.15. In yet another embodiment, SG is 1.15 or about 1.15.

[0039] The material sinking from the first buoyancy device may be rubber or a less desirable plastic. The floating material is then transferred to a second buoyancy device, which may have multiple zones and units. In one embodiment, SG is 0.95 to 1.05. In another embodiment, SG is 0.98 to 1.03. In yet another embodiment, SG is 1.0 or about 1.0.

[0040] Lighter or floating materials are generally PP / PE, while heavier materials may be ABS and PS. By controlling the density of the liquid, it is possible to effectively separate materials with different densities.

[0041] The specific gravity of a material is a measure of its density relative to water. Since different plastics have different densities, specific gravity can be used as a way to distinguish between them. Here are some common specific gravities of various types of plastics. Polyethylene (PE): Specific gravity is in the range of 0.92 to 0.96. Polypropylene (PP): Specific gravity is in the range of 0.89 to 0.91. Polyvinyl chloride (PVC): Specific gravity is in the range of 1.38 to 1.59. Polystyrene (PS): Specific gravity is in the range of 1.04 to 1.10. Polyethylene terephthalate (PET): Specific gravity is in the range of 1.38 to 1.40. Acrylonitrile butadiene styrene (ABS): Specific gravity is in the range of 1.03 to 1.06.

[0042] A technique called buoyancy separation is commonly used to separate plastics based on their specific gravity. This involves placing plastic particles in a liquid medium with specific gravities between those of different plastic types. Plastics with higher specific gravity will sink, while those with lower specific gravity will float. By adjusting the specific gravity of the liquid medium, it is possible to separate different types of plastics from one another.

[0043] In an exemplary embodiment, the method or system uses a covered screening bed having a series of shafts with agitators that are adjustable and / or non-adjustably connected to rails. In this embodiment, the shafts are arranged along rails that help sort the material as it passes through the screening device or bed. As the material passes along the screening bed, it may be sorted by the agitators based on size. Smaller elements (e.g., less than 6 mm) that fall through the star-shaped opening may be transported via a conveyor belt or fall into bins located near or below the screening bed.

[0044] A screen bed incorporates a visible vibration mechanism, such as a frame-mounted rotating shaft or vibration motor, designed to facilitate material movement and prevent clogging. These vibration components ensure a smooth flow of material through the system. A protective casing has curtains or flaps mounted along its length to further contain dust and debris during operation, enhancing both dust control and protection from wind and rain. A screen bed is disclosed in U.S. Patent No. 10363578 of Thomas A. Valerio, incorporated by reference.

[0045] At the bottom or side of the structure, a discharge chute guides the separated material into a designated collection bin or onto a conveyor belt for further processing or disposal. The screen bed is designed with maintenance in mind and features easily accessible panels along the sides of the frame. These panels allow operators to inspect or replace components without dismantling the entire structure. Additional safety features may include safety rails, industrial lighting for visibility, and control panels for operating vibration mechanisms and other mechanical components.

[0046] In one embodiment, the screen bed incorporates a star-shaped scraper or agitator having adjacent shafts. The star-shaped member has a hub with radially projecting star-shaped fingers and an opening for attachment to the shafts of the star-shaped scraper. Some star-shaped fingers may include scrapers at their tips, designed to scrape along the hub on adjacent shafts to prevent material buildup. The star-shaped fingers may be axially flexible to assist this process, ensuring robust and low-maintenance separation.

[0047] Certain embodiments, which include a protective cover enclosing 80% to 95% of the screen bed, along with a curtain or flap, a vibration mechanism, and a robust safety mechanism, provide an effective solution for material separation. Other embodiments may include a cover over more than 15%, or 25%, 45%, 55%, 65%, or 75% or 85% of the bed. This minimizes the leakage of dust and debris while facilitating a clean and safe working environment.

[0048] In one embodiment, multiple screens or screen beds can be used in conjunction with each other, varying in size and rotation speed. For example, one screen bed may have a stirrer rotating at 300 RPM, while another screen bed may rotate at 350 RPM or 450 RPM, enabling customized separation based on different material properties and processing needs.

[0049] Figures 1–3 show an exemplary screening bed 110, a motor-driven platform having a frame 111, and a series of rotatable shafts 192 mounted within the frame 111 using bearings. The frame 111 is designed with rails for supporting the shafts, allowing the shafts to rotate freely while providing stability. A motor (not shown) powers the rotatable shafts, typically via a belt or chain drive system, ensuring smooth and reliable operation. The axes of the rotatable shafts are aligned substantially parallel when fitted into the frame 111. The frame 111 may have grooves along the rails, providing space for adjusting the bearing positions and allowing for variable spacing between the shafts. This flexibility allows the operator to change the distance between the shafts by adjusting the bearings, thereby determining the size of the screening space. This ability to vary the spacing provides versatility when screening different types of materials. The screen may be 8 inches, 16 inches, 24 inches, or 30 inches from the agitated bed.

[0050] One embodiment may include a dewatering screen. A dewatering screen is a mechanical device typically used in the context of industrial or mining applications to separate a solid from a liquid. The screen works by applying force to a mixture of solid and liquid, thereby allowing the liquid to pass through the screen while holding the solid material. The dewatering process involves removing excess water from the mixture of solid and liquid, which can be achieved by using a dewatering screen. These screens typically have high-frequency linear vibrations that move the solid material across the screen, while the liquid is separated and collected below.

[0051] Certain embodiments can separate light fractions from metal recovery processes. Light fractions generally consist of non-metallic materials such as plastics, rubber, and glass. This separation is typically achieved using mechanical or pneumatic methods, such as air classifiers, vibrating screens, and cyclones. These methods allow for further processing to recover recyclable materials, including plastics, for recycling and retail purposes.

[0052] Regarding waste flow, certain embodiments can be used to process waste or recyclable materials containing concentrations of plastic higher than 15%, or 25%, 35%, 45%, and / or 50%. This means that as long as the plastic concentration is good (lower than 20%), the system can properly sort the material. Household waste pre-sorted into "plastic and non-plastic" flows is a good example.

[0053] Typically, household waste that does not end up in landfills can be pre-sorted at recycling facilities where plastic separation occurs. This plastic concentrate is an example of "good feed material." Municipal waste containing plastics is an exemplary waste flow material.

[0054] In this context, the terms "heavier" and "lighter" refer to relative specific gravity; "heavier" refers to a material with a higher specific gravity, and "lighter" refers to a material with a lower specific gravity. In fluid-based separators, buoyancy is more important than absolute weight. For example, if the specific gravity of a 1-pound object is lower than that of a 6-ounce object, the 1-pound object may feel lighter than the 6-ounce object.

[0055] A gravity separator is a device or system that uses gravity-based principles to separate materials based on their relative density. These separators work by utilizing the natural tendency for less dense materials to float while denser materials sink when immersed in a liquid or gaseous medium. Commonly used in various industries, gravity separators are effective for sorting and purifying materials, especially when size or magnetic properties cannot be relied upon. One of the most common types of gravity separators is the flotation separator. Dense materials sink to the bottom, while lighter materials float to the surface, allowing for effective separation. This technology is particularly useful for recycling plastics when different types of plastics have different specific gravities. For example, polyvinyl chloride (PVC) has a higher specific gravity than polyethylene (PE), making it possible to separate them using a flotation system.

[0056] Another embodiment is an air classifier that uses airflow to separate materials based on density and shape. The material is introduced into the chamber using a controlled airflow. Heavier or denser particles fall to the bottom, while lighter particles are carried upwards or sideways by the airflow. This method is commonly used to separate fine particles from larger particles or to remove lighter contaminants from a product stream.

[0057] Plastic recycling processes can utilize several separation processes that are sequenced to optimize efficiency and create a valuable combination of products. The sequence may depend on the source, particle size, and properties of the waste plastic material. In certain embodiments, several operations may be repeated if necessary to achieve the desired purity or if operations are required at different stages of the process for different reasons.

[0058] While specific embodiments of the Disclosure have been described in detail above, the description is for illustrative purposes only. Therefore, many aspects of the Disclosure are described above only as examples and should be understood as not intended as necessary or essential elements of the Disclosure unless otherwise expressly stated. Various modifications of the disclosed aspects of the exemplary embodiments, and corresponding equivalent processes, can be made by those skilled in the art without departing from the spirit and scope of the Invention as defined in the following claims, in addition to those described above, and the scope should be given the broadest possible interpretation to encompass such modifications and equivalent structures.

Claims

1. A method for separating materials using a screen and a gravity separator, To facilitate separation, the waste stream is fed into a screen of a specific size, To collect larger material from the waste stream and allow smaller material to pass through the screen, The method involves directing the aforementioned larger material to a first gravity separator having a specific gravity of 0.95 to 1.05, wherein the first gravity separator directs the aforementioned larger material so that it separates it into a first denser material that settles and a first lighter material that floats. The first higher-density material is transferred from the first gravity separator to a second gravity separator set to a specific gravity of 1.05 to 1.25, wherein the second gravity separator separates the first lighter material into a second lighter material and a second heavier material. A method comprising recovering the second heavier material from the second gravity separator.

2. The method according to claim 1, wherein the screen is a covered screen bed having a stirring bed.

3. The method according to claim 1, wherein the screen is separated at 6 mm intervals.

4. The method according to claim 1, wherein the screen bed has a screening capability of 6 mm to 12 mm.

5. The method according to claim 1, wherein the first gravity separator is a buoyancy gravity separator for separating materials based on specific gravity, wherein denser materials sink and lighter materials float.

6. The method according to claim 1, further comprising using a dewatering screen to remove excess moisture from the separated material.

7. The method according to claim 1, wherein the first specific gravity is set to 1.

0.

8. The method according to claim 1, wherein the second specific gravity is set to 1.

2.

9. The method according to claim 1, wherein the waste flow includes various non-plastic materials such as rubber, wood, metal, wire, circuit board, foam, and glass.

10. The method according to claim 1, wherein the first gravity separator precedes the second gravity separator.

11. The method according to claim 1, wherein the lighter plastic recovered from the second gravity separator includes polyethylene (PE) and polypropylene (PP), while the heavier plastic includes acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS).

12. The method according to claim 1, further comprising extruding and pelletizing the recovered lighter plastic.

13. The method according to claim 1, wherein the waste material includes automobile shredder residue or white goods shredder residue.

14. The method according to claim 1, wherein the first lighter material is polypropylene (PP) and polyethylene (PE).

15. The method according to claim 1, wherein the second lightweight material is acrylonitrile-butadiene-styrene (ABS) and polystyrene (PS).

16. A system for separating materials using a screen bed and a gravity separator, a. A covered screen bed designed to separate materials based on size, b. A first gravity separator, set to have a first specific gravity of 0.95 to 1.05, which separates the material into a first denser material that settles and a first lighter material that floats. c. A system comprising a second gravity separator set to a specific gravity of 1.05 to 1.25 for separating the first denser material into the second lighter material and the second heavier material.

17. The system according to claim 16, wherein the first specific gravity is set to 1.

0.

18. The system according to claim 16, wherein the second specific gravity is set to 1.

2.

19. The system according to claim 16, wherein the covering screen bed has an adjustable agitator for facilitating the movement of material and preventing clogging.

20. The system according to claim 16, wherein the covering screen bed is equipped with a vibration mechanism to ensure efficient sorting of materials.

21. The system according to claim 16, further comprising a dewatering screen for removing excess moisture from the separated material.

22. The system according to claim 16, wherein the cover contains dust and debris during the sorting process.

23. The system according to claim 16, wherein the first gravity separator uses a buoyancy process to separate materials based on specific gravity, with denser materials sinking and lighter materials floating.

24. The system according to claim 16, further comprising an extruder and a pelletizer for processing a concentrated plastic fraction and pelletizing it for further use.

25. The system according to claim 16, which is designed to process a waste stream passing through organic matter, fibers, foams, and fiber scraps together with pre-sorted metals.

26. The system according to claim 16, which is capable of separating materials in the range of 6 inches to 18 inches in size.

27. The system according to claim 16, which focuses on the effective recovery of plastics from waste materials.

28. The system according to claim 16, wherein the first gravity separator or the second gravity separator comprises at least one of a liquid sedimentation / flotation tank, a sand flow separator, and a hydrocyclone.

29. A method for separating materials using a screen bed and a gravity separator, To facilitate separation, the waste flow is supplied to a screen bed having a specific mesh size, To collect the larger material from the waste stream while allowing smaller material to pass through the screen, The method involves orienting the aforementioned larger material into a first gravity separator set to a specific gravity of 0.95 to 1.05, such that the material is separated into a first denser material that settles and a first lighter material that floats. In order to further separate the first lighter material into a second set of lighter material and a second set of heavier material, the first denser material is transferred from the first gravity separator to a second gravity separator set to a specific gravity of 1.05 to 1.25, A method comprising recovering a second set of heavier material from the second gravity separator.

30. The system according to claim 29, wherein the first gravity separator or the second gravity separator comprises at least one of a liquid sedimentation / flotation tank, a sand flow separator, and a hydrocyclone.

Images