Methods and systems for metal recycling from mixed plastic waste

Abstract

Provided here are methods and systems for recovering metal from metal-containing mixed plastic waste. One such method for metal recovery includes pyrolyzing a metal-containing mixed plastic feedstock to produce a char containing a first fraction of a metal and a pyoil containing a second fraction of the metal, treating the char to remove the first fraction of the metal and produce an activated coal, contacting the pyoil with the activated coal to produce a purified pyoil and a spent coal containing the second fraction of the metal, and treating the spent coal to remove the second fraction of the metal and produce the activated coal.

Description

METHODS AND SYSTEMS FOR METAL RECYCLING FROM MIXED PLASTIC WASTETECHNICAL FIELD

[0001] The present disclosure generally relates to methods and systems for metal recovery from metal-containing mixed plastic waste. More specifically, the present disclosure relates to methods and systems for recovering metal from metal-containing mixed plastic waste and recycling the recovered metal to produce metal-containing products.BACKGROUND

[0002] Plastic waste contains several components that are sent to waste management locations, such as landfills. Efforts have been implemented to recycle plastics containing hydrocarbon molecules, such as like polyethylene or polypropylene. However, Applicant has recognized metal is continuously disposed of as prior recovery efforts have been costly for metal recovery from metalcontaining mixed plastic waste. As such, Applicant has recognized there remains a need to for enhanced and cost-effective processes to recover metal from metal-containing mixed plastic waste to produce new products from the recovery process.SUMMARY

[0003] Examples set forth herein include methods and systems for recovering metal from metalcontaining mixed plastic waste. One such method for metal recovery includes pyrolyzing a metalcontaining mixed plastic feedstock to produce a char containing a first fraction of a metal and a pyoil containing a second fraction of the metal, and treating the char to remove the first fraction of the metal and produce an activated coal. The method further includes contacting the pyoil with the activated coal to produce a purified pyoil and a spent coal containing the second fraction of the metal, and treating the spent coal to remove the second fraction of the metal and produce the activated coal.

[0004] In another embodiment, a system to recover metal includes a pyrolysis unit configured to receive a to metal-containing mixed plastic feedstock and to produce a char containing a first fraction of a metal and a pyoil containing a second fraction of the metal, a char treating unit in fluid communication with the pyrolysis unit and having an acid or base supply, and a pyoil purification unit in fluid communication with the pyrolysis unit and the char treating unit. In some embodiments the char treating unit is configured to receive the char and to produce an activated coal, separate thefirst fraction of the metal from the char, and regenerate a spent coal. In some embodiments, the pyoil purification unit is configured to receive and contact the pyoil with the activated coal to extract the second fraction of the metal from the pyoil using the activated coal and to produce a purified pyoil and the spent coal containing the second fraction of the metal.

[0005] In another embodiments, a system for recovering a metal from a metal-containing mixed plastic feedstock includes a pyrolysis unit configured to receive a metal-containing mixed plastic feedstock and to produce a char containing a first fraction of the metal and a pyoil containing a second fraction of the metal, and a pyoil purification unit in fluid communication with the pyrolysis unit and configured to separate the second fraction of the metal from the pyoil by contact with an activated coal. The system further include a char treating unit in fluid communication with the pyrolysis unit and the pyoil purification unit, a steam cracker / polymer unit in fluid communication with the pyoil purification unit and configured to produce a polymer, an additive unit in fluid communication with the char treating unit and configured to receive the first fraction of the metal extracted from the char, and a conversion unit in fluid communication with the steam cracker / polymer unit and the additive unit. In some embodiments, the char treating unit is configured to extract the first fraction of the metal from the char, produce the activated coal, and regenerate a spent activated coal containing the second fraction of the metal. In some embodiments, the conversion unit is configured to receive the polymer and the first fraction of the metal and to produce a recycled metal-and-polymer product from the polymer and the first fraction of the metal.

[0006] Aspects and advantages of these exemplary examples and other examples, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and examples, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and examples. Accordingly, these and other objects, along with advantages and features of the present disclosure, will become apparent through reference to the following description and the accompanying drawings. Furthermore, it is to be understood that the features of the various examples described herein are not mutually exclusive and may exist in various combinations and permutations.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are included to provide a further understanding of the examples of the present disclosure, are incorporated in and constitute a part of this specification, illustrate examples of the present disclosure, and together with the detailed description, serve to explain principles of the examples discussed herein. No attempt is made to show structural details of this disclosure in more detail than may be necessary for a fundamental understanding of the examples discussed herein and the various ways in which they may be practiced. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate examples of the disclosure.

[0008] FIG. 1 is a schematic representation of an embodiment of a metal recycling processing system for recovering metal from plastic waste to produce new products from the recovered metal, according to an example.

[0009] FIG. 2 is a schematic representation of another embodiment of a metal recycling processing system for recovering metal from plastic waste to produce new products from the recovered metal, according to an example.

[0010] FIG. 3 is a flow chart of a method in which metal is recovered metal from plastic waste, according to an example.

[0011] FIG. 4 is a diagrammatic representation of experimental results from recovery of the metal from plastic waste, according to an example.

[0012] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other embodiments without further recitation.DETAILED DESCRIPTION

[0013] The present disclosure describes various examples related to methods and systems for recovering metal from metal-containing mixed plastic waste and recycling the recovered metal to produce new metal-containing products. Efforts to recover valuable compounds, such as metals, from metal-containing mixed plastic waste, is overlooked as it may be costly to implement. Applicant has recognized that present facilities that recycle hydrocarbons, such as polypropylene or polyethylene, may benefit from integration from the present disclosure to beneficially recover another valuablecompound in efforts to reduce waste, and / or carbon footprints, increase product yield, and reduce cost of recycling implementation. In some embodiments, facilities may create a closed-loop process of recovering metals from the metal-containing mixed plastic waste. Stated differently, these facilities, through implementation of the present disclosure, may not dispose of valuable metals in large quantities to disposal sites, but rather will be able to recover a substantial amount of the metal present in the metal-containing mixed plastic waste for use in new products. For example, but not limited to, chip packaging and hydrocarbon-coated aluminum pipes each contain metals capable of recycling indefinitely with an enhanced recycling process.

[0014] Therefore, the present disclosure benefits existing hydrocarbon recycling processes and new recycling processes for recycling metal from metal-containing mixed plastic waste to reduce overall waste, including landfill waste, thereby reducing dependency on raw metallic material, and to increase efficiency in metal recycling, and further to introduce new recycled metal-containing products valuable to a market space.

[0015] The description may use the phrases “in certain examples,” “in various examples,” “in an example,” or “in examples,” which may each refer to one or more of the same or different examples. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to examples of the present disclosure, are synonymous. The term “plurality” as used herein refers to two or more items or components. The terms “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting example, these terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0016] The terms “removing,” “removed,” “reducing,” “reduced,” or any variation thereof, when used in the claims and / or the specification includes any measurable decrease of one or more components in a mixture to achieve a desired result. The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The terms “wt. %”, “vol. %”, or “mol. %” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, which includes the component. In a non-limiting example, 10 grams of a component in 100 grams of the material is 10 wt. % of the component.

[0017] FIG. 1 is a schematic representation of an embodiment of a metal recycling processing system 100 for recovering metal from plastic waste to produce new products from the recoveredmetal, according to an example. The metal recycling processing system 100 includes various units, such as, a pyrolysis unit 102, a char treatment unit 104, a pyoil purification unit 106, a steam cracker / polymer unit 108, an additive unit 112, a conversion unit 110, and a metal oxide processing unit 114. The metal recycling processing system 100 further includes various streams such as streams 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, and 138.

[0018] The metal recycling processing system 100 may begin with metal-containing mixed plastic waste feed. The metal-containing mixed plastic waste may include used plastic products containing small portions of metal and / or large metallic waste objects having a plastic additive or a plastic coating. In some embodiments, the metal-containing mixed plastic waste includes polypropylene, or polyethylene, having metal layers or metallic additives therein or thereon. The metal-containing mixed plastic waste may be collected to a waste collection site (not shown) to be stored and then used as a feedstock to the pyrolysis unit 102 via stream 120. In some embodiments, the stream 120 may be transported via a conveyer track or other like devices to feed the metal-containing mixed plastic feedstock to the pyrolysis unit 102.

[0019] The pyrolysis unit 102 is configured to receive the metal-containing mixed plastic feedstock and produce a pyrolysis oil (“pyoil”), a pyrolysis char (“char”), and a non-condensable gas configured to exhaust via stream 118. In some embodiments, the non-condensable gas may advantageously be recycled as a fuel source for energy production within an industrial plant. In some embodiments, the pyrolysis unit 102 includes an incinerator configured to bum any organic material within the metalcontaining mixed plastic feedstock. The pyrolysis unit 102 may pyrolyze the metal -containing mixed plastic feedstock up to temperatures of up to about 250 degrees Celsius to about 800 degrees Celsius to produce the pyoil and the char. In some embodiments, pyrolysis unit 102 may have various collection bins (not shown) to temporarily store the pyoil and / or the char produced from the pyrolysis process. The produced char contains a first fraction of the metal found in the metal-containing mixed plastic feedstock. The first fraction of metal within the char may include a total metal concentration of about 1 wt. % to about 20 wt. %. For example, individual metal concentrations can range from at least about 0.1 wt. % to about 10 wt. % iron, at least about 0.1 wt. % to about 10 wt. % aluminum, and / or 0.1 wt. % to about 10 wt. % titanium. The produced pyoil contains a second fraction of the metal found within the metal-containing mixed plastic feedstock. The second fraction of metal may include a total metal concentration of at least about 1 part per million (“ppm”). For example, individual metal concentrations can range from at least about 0.5 ppm to about 20 ppm iron, at least about 0.5 ppm to about 200 ppm aluminum, and / or at least about 0.5 ppm to about 150 ppm titanium.The produced pyoil from the pyrolysis unit 102 is transferred to the pyoil purification unit 106 via stream 122. The pyrolysis unit 102 is in fluid communication with the pyoil purification unit 106. In some embodiments, stream 122 may be transported through a pipe, an open channel such as a trench, or transported via an auger-type device to provide metered, or measured, flow of the pyoil from the pyrolysis unit 102, or similar transfer device.

[0020] The pyoil purification unit 106 is configured to receive the pyoil from the pyrolysis unit 102 and to produce a purified pyoil. In some embodiments, the pyoil purification unit 106 includes guard beds configured to physically contact the pyoil with a catalyst designed to capture contaminants, such as the second fraction of the metal found within pyoil. In some embodiments, the catalyst, for at least a metal-contaminant capture, is an activated charcoal (“activated coal”). The activated coal is configured to extract at least a portion of the second fraction of the metal found within pyoil. In some embodiments, the activated coal adsorbs impurities from the pyoil. After the activated coal has adsorbed the capacity of the activated charcoal molecule, or substantially adsorbed the capacity, the activated coal is deactivated (also referred to as “spent activated coal” or “spent coal”) rendering the spent activated coal molecule substantially unable or ineffectively able to adsorb more metalcontaminant. In some embodiments, various cycles of activated coal purification are used to purify and / or cleanse the pyoil within the pyoil purification unit 106. Each cycle of activated coal purification produces spent activated coal. In some embodiments, the pyoil purification unit 106 may receive a constant flow, or stead-state flow, of activated coal from a char treatment unit 104 via stream 126. In some embodiments, the pyoil purification unit 106 may receive a batch supply of activated coal from the char treatment unit 104. In some embodiments, the pyoil purification unit 106 may receive a hybrid supply of activated coal, including a mixed process of constant flow and alternating batch flow from the char treatment unit 104.

[0021] Purified pyoil is provided to the steam cracker / polymer unit 108 via stream 132. In some embodiments, stream 132 may be transported via a pipe, tubing, that may include an auger-type device to provide metered, or measured, flow of the purified pyoil from the pyoil purification unit 106 to the steam cracker / polymer unit 108. The steam cracker (not shown) benefits from a purified pyoil feed as any purities within the pyoil are known to scale and / or coat the interior of the steam cracker thereby increasing the frequency of cleaning cycles for the steam cracker and reducing productivity. The steam cracker / polymer unit 108 is configured to receive the purified pyoil from the pyoil purification unit 106 and to produce a polymer. In some embodiments, the polymer may include polypropylene and / or polyethylene. In some embodiments, the polymer produced from the steamcracker / polymer unit 108 may be in the form of a polymer pellet, granule, brick, clay, and / or liquid, for transport to a conversion unit 110 via stream 134. The steam cracker / polymer unit 108 is in fluid communication with the conversion unit 110. In some embodiments, stream 134 may be transported via a conveyor belt, pipe, an auger-type device to provide metered, or measured, polymer product to the conversion unit 110, or similar transfer device.

[0022] Referring back to the pyrolysis unit 102, the produced char is transported to the char treatment unit 104 via stream 124. The pyrolysis unit 102 is in fluid communication with the conversion unit 110. In some embodiments, stream 124 may be transported via a conveyor belt, or a pipe with an auger-type device to provide metered, or measured, polymer product to the conversion unit 110, or similar transfer device. Further, stream 124 may utilize a blower (not shown) to transport the produced char includes a carbon ash and the first fraction of the metal from the metal-containing mixed plastic feedstock. The char treatment unit 104 is configured to receive the char from the pyrolysis unit 102 and the spent activated coal from the pyoil purification unit 106 via stream 128. The char treatment unit 104 is also configured to produce the activated coal from the spent activated coal and the produced char for use in the pyoil purification unit 106 via stream 126 and to further produce substantially pure metal, including metal ions, and metal oxides from the char and from the spent activated coal. The substantially pure metal is transported to an additive unit 112 via stream 130. The char treatment unit 104 is in fluid communication with the additive unit 112. In some embodiments, stream 130 may be transported via a conveyor belt, or a pipe with an auger-type device to provide metered, or measured, metal to the additive unit 112, or similar transfer device. The produced metal oxides are transported to the metal oxide processing unit 114 via stream 116. The char treatment unit 104 is in fluid communication with the metal oxide processing unit 114. In some embodiments, stream 130 may be transported through a pipe with an auger-type device to provide metered, or measured, metal oxide to the metal oxide processing unit 114, or similar transfer device.

[0023] In some embodiments, the life cycle of the char, defined by activating, deactivating, and reactivating, may exhaust or tire the char molecules, as understood by those skilled in the art. Once the char molecules are exhausted and / or rendered inefficient to reactivate, the char may advantageously be sold to interested parties such as, for example but not limited to, a water treatment sector for filtering water and the like. The char volume that is removed from the metal recycling processing system 100 is replaced by the generation of the char from the pyrolysis unit 102. In some embodiments, char is continuously or intermittently removed from metal recycling processing system 100 at a similar rate as char generation from the pyrolysis unit 102.

[0024] The additive unit 112 is configured to receive the substantially pure metal from the char treatment unit 104 and to produce functional metal additives and / or coatings from the substantially pure metal. The metal additives and / or coatings produced from the substantially pure metal are transported to the conversion unit 110 via stream 136. The additive unit 112 is in fluid communication with the conversion unit 110. In some embodiments, stream 136 may be transported via a conveyor belt, a pipe, a trench, or an auger-type device to provide metered, or measured, metal additives and / or coatings to the conversion unit 110.

[0025] The conversion unit 110 is configured to receive the metal additives and / or coatings from additive unit 112 and the polymer produced from the steam cracker / polymer unit 108. The conversion unit 110 produces recycled metal-and-polymer products for consumer use. For example, the recycled metal-and-polymer products may include laminated products such as metalized packages, for example, chip packages or the like, for use in the food industry. In some embodiments, the recycled metal-and-polymer products are used within other units (not shown) within the confines of the industrial plant containing existing hydrocarbon recycling. These recycled metal-and-polymer products, through consumer use, may further create metal-containing mixed plastic waste to be recycled, via stream 138, as a metal-containing mixed plastic feedstock. Stream 138 is an exemplary path to illustrate a consumer using the recycled metal-and-polymer product to create the metalcontaining mixed plastic waste. Thus, the metal-containing mixed plastic feedstock may be again recycled, via stream 120, to create another recycled metal-and-polymer product in a closed-loop process. This closed-loop process for metal recycling reduces metallic waste previously disposed in landfills, for example, and increases the lifecycle of metal within existing and future products.

[0026] FIG. 2 is a schematic representation of another embodiment of a metal recycling processing system 200 for recovering metal from plastic waste to produce new products from the recovered metal, according to an example. Similar to the embodiment of FIG. 1, the metal recycling processing system 200 includes a pyrolysis unit 202, a char treatment unit 204, a pyoil purification unit 206, a steam cracker / polymer unit 208, an additive unit 212, a conversion unit 210, and a metal oxide processing unit 214. The metal recycling processing system 200 further includes streams 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, and 238. Each of the aforementioned, correspond to and include similar components as the units and streams discussed above with respect to FIG. 1. These aforementioned units and streams are similarly labeled, and their descriptions are not repeated in detail for enhanced clarity. The embodiment of FIG. 2 further includes an optional pretreatment unit 240 and streams 242 and 244.

[0027] The pretreatment unit 240 is configured to receive the metal-containing mixed plastic feedstock via stream 244 and to produce a sorted metal stream 242 containing a third fraction of the metal found within the metal-containing mixed plastic feedstock and a second sorted metal stream 220 that feeds the pyrolysis unit 202. In some embodiments, the pretreatment unit 240 is a sorting facility capable of physically separating unwanted materials from the metal-containing mixed plastic feedstock via stream 244 which may include, for example, stones, and / or sand, from large pieces of metal directed to metal stream 242. In some embodiments, the third fraction is produced from a magnetic collection (not shown) of ferrous components within the metal-containing mixed plastic feedstock. In some embodiments, stream 242 from the pretreatment unit 240 is combined with the substantially pure metal stream 230 from the char treatment unit 204 to collectively feed the additive unit 212. In some embodiments, the streams 242 and 244 may be transported via a conveyer belt, or a pipe with an auger-type device to provide metered, or measured, metal to the additive unit 212, or similar transfer device.

[0028] FIG. 3 is a flow chart of a method 300 in which metal is recovered metal from plastic waste, according to an example. The method 300 includes operations 302, 304, 306, 308, and operational pathway 310. The following method 300 discussion will reference FIG. 1 numerals for ease of explanation. However, the method 300 is not limited to the embodiment of FIG. 1.

[0029] Operation 302 begins with pyrolyzing a metal-containing mixed plastic feedstock to produce a char containing a first fraction of a metal and a pyoil containing a second fraction of the metal in the pyrolysis unit 102. As discussed above, an incinerator is utilized to destroy the metal-containing mixed plastic feedstock and produce a char with a first fraction of metal within and to produce a pyoil with a second fraction of metal within. The first fraction of metal and the second fraction of metal together substantially account for the total fraction of metal within the metal-containing mixed plastic feedstock. The char is transferred to the char treatment facility 104 via stream 124 of FIG. 1. Similarly, the pyoil is transferred to the pyoil purification unit 106 via stream 122 of FIG. 1.

[0030] Operation 304 treats the produced char from the within char treatment facility 104 to remove the first fraction of the metal and to further produce an activated coal from the treated char. The process within the char treatment unit 104 includes an incineration process and a washing process to purify the char. The char treatment unit 104 also recycles a spent coal further discussed below.

[0031] Chemically, the produced char includes a substantial amount of carbon from the pyrolysis unit 102 incineration. The carbon may be oxidized, via further incineration, to aid in the combinationof metals, or other oxides, within the char, to produce metal oxides. By means of an exemplary process, but not intended to be limiting, the incineration process may proceed as follows.

[0032] By incineration, carbon is oxidized to CO2, see Equation (1), allowing the metal or other oxides to experience combination. As an example, silicon oxide and aluminum oxide, which may exist in the char, are shown to combine, see Equation (2).C + O2-* CO2Equation (1)SiO2(S) + Al2O3(S) -> SiO2—Al2O3(S) Equation (2)

[0033] Upon combination and formation of the metal oxides within the char, the metal oxides are washed to purify the char of the metal oxides and / or metal. The washing process includes an acid or base supply. In some embodiments, the acid or base supply includes oxalic acid, sulfuric acid, and sodium hydroxide. In some embodiments, the acid or base supply is selected from the group consisting of oxalic acid, sulfuric acid, and sodium hydroxide. In some embodiments, the oxalic acid, sulfuric acid, and sodium hydroxide are each 4 weight percent (“wt. %”). In some embodiments, a range of concentration in solution for each of the oxalic acid, sulfuric acid, and sodium hydroxide is 0.5-10 % mass-based. In some embodiments, the washing process may optionally perform an acid wash followed by a basic wash.

[0034] By means of an exemplary process, but not intended to be limiting, the washing process may proceed as follows. In some embodiments, the washing process dissolves the metal oxides into an acid to convert the metal oxides within the char to an ionic form, see Equations (3) and (4). The process of washing the char, purifies the char from the metals to produce an activated coal.SiO2+ acid -> Si2++ H2O Equation (3)Fe2O3+ acid -> Fe3++ H2O Equation (4)The above Equation (3) depicts silicon ions formed from the dissociation of oxygen from silicon oxide with an acid wash. In another similar example, see Equation (4), iron ions formed from the dissociation of oxygen from iron oxide with an acid wash.

[0035] The char may then be separated from the combined metal oxides and metal ions to produce an activated coal. Therefore, the first fraction of metal is substantially recovered in the char treatment unit 104 through the incineration and washing process. The separated metal oxides and the metalions may be each transferred to further processing units, such as, but not limited to, to a metal oxide processing unit 114 for use on other processes or products, such as for pigment production, and to an additive unit 112 to produce additives and / or coatings for future metal / plastic recycling products as discussed above. The activated coal may then be transferred to the pyoil purification unit 106 via stream 126.

[0036] At operation 306, the activated coal physically contacts the pyoil within the pyoil purification unit 106. As discussed above, the pyoil purification unit 106 may utilize guard beds to facilitate the contact between the pyoil, containing the second fraction of metal, and the activated coal from the char treatment unit 104. The contact between the pyoil and the activated coal purifies the pyoil by adsorbing the metal impurities within the pyoil to produce a spent activated coal containing at least a portion of the second fraction of metal.

[0037] At operation 308, the spent activated coal may then be transferred back to the char treatment unit 104 to regenerate, or treat, and thus reactivate the spent activated coal into activated coal for further purification of the pyoil within the pyoil purification unit 106. In some embodiments, the portion of the second fraction of the metal extracted from the pyoil is recovered by the char treatment unit 104 processes discussed above. In some embodiments, the activated coal is provided to the pyoil purification unit 106 in a continuous flow, or steady state, to continuously extract any remaining second fraction of metal present in the pyoil. In some embodiments, the activated coal is provided to the pyoil purification unit 106 in a batch process or in a mixed, or hybrid, continuous flow and batch process, to extract any remaining second fraction of metal present in the pyoil. The cyclic recycle of the activated coal may be repeated via pathway 310 as the re-activated coal is transferred to the pyoil purification unit 106 for further adsorbing the remaining second fraction of the metal within the pyoil. In some embodiments, the second fraction of metal is substantially captured within the treatment of the spent activated coal within the char treatment unit 104. In some embodiments, stream 124, containing the produced char from the pyrolysis unit 102, and stream 128, containing the spent activated coal from the pyoil purification unit 106, are mixed for recovery of both the first fraction of metal and the second fraction of metal from the mixed plastic feedstock. The first fraction of metal and the second fraction of metal recovered from the char treatment unit 104 together substantially account for the total fraction of metal within the metal-containing mixed plastic feedstock.

[0038] The method 300 discussed above, advantageously facilitates a substantially closed-loop carbon recycle that minimizes the amount of char containing metal sent to a landfill. Stated differently, the substantially closed-loop carbon recycle process of method 300 increases useful charlifecycles before producing carbon waste to increase metal recycling efficiency, efficacy, and reducing operational costs.EXPERIMENTS AND EXAMPLES

[0039] The below experiments are presented to provide experimental data for various examples of operations discussed above.

[0040] Experiment 1: The char treatment unit 104 treats the char obtained from pyrolysis of the metal-containing mixed plastic feedstock. Experimentally, the char was treated by each of the three solvents, listed below, and the char was analyzed for concentration and efficiency of metal capture. These solvents are sulfuric acid (about 4 wt. %), sodium hydroxide (about 4 wt. %), and oxalic acid (about 4 wt. %). Examples 1-3 illustrate the metal recovery efficiency of each of the solvents, respectively. Example 4 illustrates the enhanced quality of the char after metal removal associated with Examples 1-3.

[0041] The experiment is performed with an analysis of the char for metal concentrations as benchmark data reference. The experiment then uses an aforementioned solvent that is absent the presence of metals in liquid phase. The solvent is then utilized to wash the experimental metal containing solute (the char), thereby to define a treatment. After a duration of time, the metal within the char is extracted and is present in the solution. The char is then separated from the solution yielding a concentration of metal in the solution. The char is then evaluated for the effectiveness of metal removal through the treatment. The results show that using any of the aforementioned solvents extract metals from the char to a different extent. The solvents, however, are different in the removal efficiency. Each solvent may be more efficient for some of the metallic elements listed above. For example, aluminum extraction exhibited the highest concentration extraction in a sodium hydroxide solution. However, aluminum may still be recovered by other experimental solvents as discussed above and shown below. Optionally, a combination of an acid wash followed by basic wash may further increase extraction yield. Below are the individual examples of different solvents used to extract the metal from the char. Tables 1-3 below illustrates the concentration of extracted metals through use of about 4 wt. % sulfuric acid, about 4 wt. % sodium hydroxide, and about 4 wt. % oxalic acid from treatment of the char.

[0042] Example 1: In a first example of Experiment 1, a char analysis was performed before and after treatment with about 4 wt. % sulfuric acid (H2SO4) solution and was evaluated for metal extraction yield from the char treatment unit 104 washing process. As previously discussed, the produced char, containing the first fraction of metal of the metal-containing mixed plastic feedstock,and the spent activated coal, containing at least a portion of the second fraction of metal of the metalcontaining mixed plastic feedstock, are washed in the char treatment unit 104 using an acid or a base. Optionally, the spent activated coal may be washed individually from the produced char. Below is the concentration of extracted metals results of washing with an acid, specifically, about 4 wt. % H2SO4. Embodiments also include reduction in metal concentration of one or more of the metals presented in Table 1 and the exact values of these concentrations can differ by the analytical methods or instrumentation used. Furthermore, various values and calculations may be obtained and / or performed from the combination of information presented in the table below. Table 1. Char analysis before and after treatment with solution 4 wt. % H2SO4

[0043] In one example, the removal efficiency of the H2SO4 solvent, as discussed above, includes over 65 percent of aluminum removal from the char. In one example, the removal efficiency of the H2SO4 solvent, includes over 67 percent of iron removal from the char. In another example, the removal efficiency of the H2SO4 solvent, includes over 68 percent of zinc removal from the char.

[0044] Example 2: In a second example of Experiment 1, a char analysis was performed before and after treatment with about 4 wt. % sodium hydroxide (NaOH) solution and was evaluated for metal extraction yield from the char treatment unit 104 washing process. Below is the concentration of extracted metals results of washing with a base, specifically, 4 wt. % NaOH. Embodiments also include reduction in metal concentration of one or more of the metals presented in Table 2 and the exact values of these concentrations can differ by the analytical methods or instrumentation used. Furthermore, various values and calculations may be obtained and / or performed from the combination of information presented in the table below. Table 2. Char analysis before and after treatment with solution 4 wt. % NaOH

[0045] In one example, the removal efficiency of the NaOH solvent, as discussed above, includes about 90 percent of aluminum removal from the char. In one example, the removal efficiency of the NaOH solvent, includes over 22 percent of iron removal from the char. In another example, the removal efficiency of the NaOH solvent, includes over 36 percent of zinc removal from the char.

[0046] Example 3: In a third example of Experiment 1, a char analysis was performed before and after treatment with about 4 wt. % oxalic acid (C2H2O4) solution and was evaluated for metal extraction yield from the char treatment unit 104 washing process. As previously discussed, the produced char, containing the first fraction of metal of the metal-containing mixed plastic feedstock, and the spent activated coal, containing at least a portion of the second fraction of metal of the metalcontaining mixed plastic feedstock, are washed in the char treatment unit 104 using an acid or a base. Optionally, the spent activated coal may be washed individually from the produced char. Below is the concentration of extracted metals results of washing with an acid, specifically, 4 wt. % C2H2O4. Embodiments also include reduction in metal concentration of one or more of the metals presented in Table 3 and the exact values of these concentrations can differ by the analytical methods or instrumentation used. Furthermore, various values and calculations may be obtained and / or performed from the combination of information presented in the table below.Table 3. Char analysis before and after treatment with solution 4 wt. % Oxalic acid

[0047] C2H2O4is a weak acid, thus the removal efficiency may be less than that of a stronger acid, such as sulfuric acid, for removal of certain metals, such as aluminum and iron. In certain embodiments, oxalic acid can be used for removal of certain other metals from the char. For example, use of the C2H2O4 solvent results in about 100 percent of manganese removal from the char. In one example, the use of the C2H2O4 solvent results in over 22 percent of iron removal from the char. In another example, the removal efficiency of the C2H2O4 solvent, includes over 21 percent of zinc removal from the char. The analytical method provided above does not increase the amounts of elements, such as aluminum, but rather illustrates an increase in concentration based on the normalization of values.

[0048] Example 4: The treated char becomes better in quality after a wash in the aforementioned solvents. It is understood that activated coal adsorbs impurities. Therefore, a method of enhanced adsorption requires an increase in the surface area of a carbon molecule or an increased porosity thereby increasing the surface area of a carbon molecule. Table 4 below is a comparison of the increased surface area in meters squared / gram (“m2 / g”) or SBET (m2 / g) as a result of each solvent wash, including about 4 wt. % H2SO4, about 4 wt. % NaOH, and about 4 wt. % C2H2O4. Furthermore, various values and calculations may be obtained and / or performed from the combination of information presented in the table below.Table 4. Analysis Results of Treated Char Surface Area from Examples 1-3.

[0049] The char treated with about 4 wt. % C2H2O4 increased the surface area of the char by about 158.1% thereby increasing the adsorption capability of the activated coal produced by the washing process of the char treatment unit 104. The increase in adsorption capability advantageously aids in a more efficient recovery of the second fraction of metal within the pyoil in the pyoil purification unit 106, as discussed above.

[0050] Furthermore, the concentration of any remaining metallic elements within the treated char are illustrated in FIG. 4. FIG. 4 illustrates the reduction of the concentration of any remaining metallic elements in the treated char per solvent using weight percentages of the metals. Therefore, the enhanced char (or activated coal) is effective to increase adsorption of metal impurities from the pyoil and to further release the metal captured from the pyoil into the solution within the char treatment unit 104.

[0047] Experiment 2: The experiment 2 is a collection of information from different oil samples having metal containing oils, such as utilized in the above disclosure. Thus, the collection of information below illustrates the opportunity for a supply of recovered metals using the processes discussed above. Therefore, the extraction of metals from these oils is advantageous to recycle the recovered metals into new products. Table 5 is the max value measured from different oil samples from different technologies. Furthermore, various values and calculations may be obtained and / or performed from the combination of information presented in the table below.Table 5. Analysis Results of Max Value of Metal Compounds in Oils.

[0048] As represented in Table 5, there is an opportunity to utilize the processes of the above disclosure in various oil technologies that have recoverable metals. As such, the processes, as discussed above, may be advantageously implemented for recycling metal-containing mixed plastic waste.

[0049] Other objects, features, and advantages of the disclosure will become apparent from the foregoing figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific examples of the disclosure, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from the detailed description. In further examples, features from specific examples may be combined with features from other examples. For example, features from one example may be combined with features from any of the other examples. In further examples, additional features may be added to the specific examples described herein.

Claims

CLAIMSWhat is claimed is:

1. A method for metal recovery, the method comprising:(a) pyrolyzing a metal-containing mixed plastic feedstock to produce a char containing a first fraction of a metal and a pyoil containing a second fraction of the metal;(b) treating the char to remove the first fraction of the metal and produce an activated coal;(c) contacting the pyoil with the activated coal to produce a purified pyoil and a spent coal containing the second fraction of the metal; and(d) treating the spent coal to remove the second fraction of the metal and produce the activated coal.

2. The method of claim 1, further comprising repeating (b), (c), and (d) to extract more of the second fraction of the metal from the pyoil.

3. The method of claim 2, wherein treating the char or the spent coal is performed with an acid or base selected from the group consisting of oxalic acid, sulfuric acid, and sodium hydroxide.

4. The method of claim 3, wherein the oxalic acid is 4 wt. %, the sulfuric acid is 4 wt. %, and the sodium hydroxide is 4 wt. %.

5. The method of claim 1, further comprising forming metal oxides from the first and the second fractions of the metal.

6. A system to recover metal, the system comprising: a pyrolysis unit configured to receive a to metal-containing mixed plastic feedstock and to produce a char containing a first fraction of a metal and a pyoil containing a second fraction of the metal; a char treating unit in fluid communication with the pyrolysis unit and having an acid or base supply, the char treating unit configured to receive the char and to produce an activated coal, separate the first fraction of the metal from the char, and regenerate a spent coal; anda pyoil purification unit in fluid communication with the pyrolysis unit and the char treating unit, the pyoil purification unit configured to receive and contact the pyoil and the activated coal to extract the second fraction of the metal from the pyoil using the activated coal and to produce a purified pyoil and the spent coal containing the second fraction of the metal.

7. The system of claim 6, wherein the acid or base supply is selected from the group consisting of oxalic acid, sulfuric acid, and sodium hydroxide.

8. The system of claim 7, wherein the oxalic acid is 4 wt. %, the sulfuric acid is 4 wt. %, and the sodium hydroxide is 4 wt. %.

9. The system of claim 6, further comprising a steam cracker / polymer unit configured to receive the purified pyoil and to produce polyethylene and polypropylene.

10. The system of claim 9, wherein the first and the second fractions of the metal are combined with the polyethylene and / or the polypropylene to produce a recycled metal-and-polymer product.

11. A system for recovering a metal from a metal-containing mixed plastic feedstock, the system comprising: a pyrolysis unit configured to receive a metal-containing mixed plastic feedstock and to produce a char containing a first fraction of the metal and a pyoil containing a second fraction of the metal; a pyoil purification unit in fluid communication with the pyrolysis unit and configured to separate the second fraction of the metal from the pyoil by contact with an activated coal; a char treating unit in fluid communication with the pyrolysis unit and the pyoil purification unit, the char treating unit configured to extract the first fraction of the metal from the char, produce the activated coal, and regenerate a spent activated coal containing the second fraction of the metal; a steam cracker / polymer unit in fluid communication with the pyoil purification unit and configured to produce a polymer; an additive unit in fluid communication with the char treating unit and configured to receive the first fraction of the metal extracted from the char; anda conversion unit in fluid communication with the steam cracker / polymer unit and the additive unit, the conversion unit configured to receive the polymer and the first fraction of the metal and to produce a recycled metal-and-polymer product from the polymer and the first fraction of the metal.

12. The system of claim 11, wherein the recycled metal-and-polymer product becomes the metalcontaining mixed plastic after use.

13. The system of claim 11, further comprising a pretreatment unit upstream of the pyrolysis unit, the pretreatment unit configured to receive the metal-containing mixed plastic feedstock and to separate a third fraction of the metal from the metal-containing mixed plastic feedstock.

14. The system of claim 11, wherein the system for recovering the metal from the metal-containing mixed plastic feedstock is a closed-loop process.

15. The system of claim 11, wherein the polymer comprises polypropylene or polyethylene.

Images