Abstract:
A method and apparatus for separating non-biogenic plastic from biogenic waste. A stream of waste materials is delivered through an inlet into a conduit in which the biogenic waste drops out the bottom. The non-biogenic plastic is drawn upwardly by a separator in the form of pressurized gas fed tangentially through two ports in an opposite direction with each other to create a vacuum in the conduit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 61/136,348, filed on Aug. 29, 2008, the content of which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present invention is generally related to capturing carbon contained in plastics that would otherwise be burned or buried in a landfill. The present invention is also generally related to sequestering the carbon that is captured from plastics into a durable solid. 
     BACKGROUND 
     Household solid waste currently ends up in land fills or is burned in an incinerator in what is commonly known as an energy-from-waste (EFW) process. While many municipalities have recycling facilities to capture certain mainstream recyclable plastics, such as polyethylene terephthalate (recycle code 1) and high density polyethylene (HDPE, recycle code 2), other plastics that are not considered to be mainstream recyclable plastics (recycle codes 3-7) end up with the rest of the municipal solid waste. Burning plastics that contain carbon releases carbon dioxide. 
     It is estimated that plastics comprise 16% of waste discards, yet account for 66% of CO 2  emissions from EFW processes. EFW processes currently dispose of about 20% of the waste stream. It is desirable to isolate and sequester post-consumer plastic discards that are currently going to landfills and incinerators, so that CO 2  emissions may be reduced, and the carbon contained in the plastics may be used in a durable building material, rather than sit in a landfill. 
     SUMMARY 
     In an embodiment of the present invention, there is provided a method for capturing and sequestering carbon contained in plastic. The method includes feeding a waste stream that includes at least non-biogenic plastic and biogenic waste into an apparatus configured to separate the non-biogenic plastic from the biogenic waste. The method also includes feeding a pressurized gas to the apparatus via a first tangential port that is configured to create a first flow of the gas in the apparatus in a first direction and via a second tangential port that is configured to create a second flow of the gas in the apparatus in a second direction that is opposite the first direction so that the first flow and the second flow create a vacuum in the apparatus, and separating the non-biogenic plastic from the biogenic waste by conveying the non-biogenic plastic through the apparatus with the vacuum while dropping the biogenic waste out of the apparatus. The method also includes collecting the separated non-biogenic plastic. 
     In an embodiment, the method also includes modifying the non-biogenic plastic for use as a modified polymer aggregate. 
     In an embodiment, the method also includes incorporating the modified polymer aggregate into a mix for formation of concrete. 
     In an embodiment of the present invention, there is provided a method for sequestering carbon contained in waste plastic. The method includes separating the waste plastic from the waste stream prior to incineration, gasification, landfill, or any other method of final disposal of waste, modifying the plastic for use as a modified polymer aggregate, and using the modified polymer aggregate as a constituent ingredient in a durable building material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic diagram of an apparatus in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an apparatus  10  according to an embodiment of the invention. The apparatus  10  generally includes a conduit  12 , which may be in the form of a pipe, and an inlet  14  that is configured to allow plastic and other waste materials to enter the apparatus  10 . In an embodiment, the material that is fed into the apparatus  10  through the inlet  14  may be reduced in size, i.e. ground down, to a 6″ or less particle size via known comminuting methods. In an embodiment, the waste material may be macerated prior to entering the apparatus. In an embodiment, the plastics may be ground after separation curbside, and/or RDF ground (one of the current processes used in WTE plants). 
     The apparatus also includes a first outlet  16  that is configured to allow biogenic waste and other waste materials that are to be separated from the non-biogenic plastic to drop out of the apparatus via gravity. It is possible for some of the non-biogenic plastic to also drop out of the apparatus via the first outlet  16 . A second outlet  18  is configured to allow the non-biogenic plastic that has been separated from the biogenic waste and other waste material to exit the apparatus at a location that is away from the location where the biogenic waste and other waste materials are collected. 
     Pneumatic pressure energy, which may be in the form of a pressurized gas, such as air, may be tangentially injected through a first tangential nozzle array  20  that is constructed and arranged to direct a first flow of the gas in a first tangential direction (e.g. clockwise) into the conduit  12 , and a second tangential nozzle array  22  that is located downstream from the first tangential nozzle array  20  with respect to the direction of flow of the non-biogenic plastic within the conduit  12 . The second tangential nozzle array  22  may be constructed and arranged to direct a second flow of the pressurized gas into the conduit in a second tangential direction (e.g., counterclockwise) that is substantially opposite that of the first tangential direction so as to create pneumatic shear within the conduit. 
     The first and second tangential nozzle arrays may be constructed and arranged to be of the same or substantially the same configuration as the annular chambers and inlet ports of the fluid handling device that is described in U.S. Pat. No. 6,042,340, which is incorporated herein by reference in its entirety. The pressure and flow of the gas being supplied to the pipe via the first and second tangential ports may be controlled so that a vacuum is created within the conduit  12 . The vacuum allows the kinetic energy that is supplied via the ports  20 ,  22  to convey the materials that enter the inlet  14  upward and towards the ports  20 ,  22 . Once the materials are sheared by the counterflows that are provided by the ports  20 ,  22 , the heavier, biogenic waste and some of the non-biogenic plastic that has not fully separated from the waste will drop out of the conduit  12  via the first outlet  16 , and the lighter, non-biogenic plastic will be blown out of the conduit  12  via the second outlet  18 . 
     The biogenic waste (and any non-biogenic plastic) that has dropped out of the conduit  12  via the first outlet  16  may be collected and/or conveyed to an incinerator or gasification process so that energy may be generated from the waste. In an embodiment, the material that has dropped out of the conduit  12  via the first outlet  16  may be conveyed back to the inlet  14  so that additional non-biogenic plastic may be recovered, i.e., separated in the apparatus  10  and blown out of the conduit  12  via the second outlet  18 . 
     The non-biogenic plastic that is separated by the apparatus may be further processed so that any dust or other non-plastic material that exited the outlet  18  of the apparatus  10  may be separated from the non-biogenic plastic. Any such dust or other non-plastic material that is separated by further processing may be conveyed to an incinerator or gasification process so that energy may be generated from the waste. 
     The non-biogenic plastic may then be modified for use as a modified polymer aggregate by the methods described in U.S. Pat. No. 6,488,766, which is incorporated herein by reference in its entirety. The modified polymer aggregate may be used in formation of concrete, thereby sequestering in perpetuity the carbon contained in the plastic. 
     Embodiments of the invention provide a method to capture and sequester accountable carbon dioxide that is otherwise formed in the thermal processing of carbon-containing waste plastics, a non-biogenic. In an embodiment, the method includes separating the carbon-containing plastic from the municipal solid waste (MSW) stream prior to incineration, gasification, or other thermal method of ultimate disposal of the waste discards. In an embodiment, the method includes separating non-mainstream recyclable curbside “other” plastics from the mainstream recyclable plastics and/or from the MSW stream. 
     In an embodiment, a method to sequester accountable carbon contained in waste plastics includes separating the plastic from the waste stream prior to incineration, gasification, landfill, or and other method of final disposal of the waste discards; modifying the plastic for use as a modified polymer aggregate by the methods described in U.S. Pat. No. 6,488,766, which is incorporated herein by reference in its entirety, and using the modified polymer aggregate as a constituent ingredient in durable building materials including but not limited to concrete, stucco, plaster, and adobe, thereby sequestering the carbon contained in the plastic in perpetuity. 
     While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.