Chemistry of hydrocarbon compounds – Production of hydrocarbon mixture from refuse or vegetation – From synthetic resin or rubber
Reexamination Certificate
2000-06-07
2002-09-03
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Production of hydrocarbon mixture from refuse or vegetation
From synthetic resin or rubber
C585S648000
Reexamination Certificate
active
06444864
ABSTRACT:
BACKGROUND OF THE INVENTION
Today's society uses and quickly discards a large volume of an increasingly diverse range of polymeric materials. According to a recent EPA report, in 1997 “plastics” accounted for 9.4% by weight (19.8×10
6
tons) of the total municipal solid waste (MSW) generated in the United States (Environmental Protection Agency, “Characterization of Municipal Waste: 1997 update, EPA Report 530-R-98-007, Franklin Assoc. Ltd., Prairie Village, Kans., May (1998)). Of this, only 5.3% (1.1×10
6
tons) is recycled into low-grade applications such as synthetic lumber for park benches. The rest is either incinerated or landfilled. However, incineration is generally associated with the generation of NO
x
and other hazardous emissions while the cost of landfilling in many areas now exceeds $100/ton due to tighter federal and state regulations and decreases in the available land. Further, polymers from petrochemical sources have a very slow rate of biodegradation. Thus, the need to recycle MSW plastics is becoming increasingly important.
Most conventional chemical methods cannot deal with MSW due to the diversity of its composition, which ranges from single thermoplastics to complex thermosets and composites.
Thermal plasma processing of mixed industrial waste streams containing metallic, inorganic or organic components have been reported (Montgomery, R. W. Proc. 11th Intl. Symp. Plasma Chem. (ISPC-11), IUPAC, Loughborough, UK, August 22-27, Vol. 2, 526-530 (1993); Taylor, P. R. and Pirzada, S. A. Adv. Performance Mater. 1, 35-50 (1994); and Hoffelner, W. and Funfschilling, M. R. Proc. Workshop on Ind. Appl. of Plasma Chem., 12th Intl Symp. Plasma Chem. (ISPC-12), IUPAC, Minneapolis, Minn., August 25-26, Vol. B. Thermal Plastic Applications, 3-7 (1995)). These processes generate both solid (metal +slag) and gaseous product streams. Gaseous product streams are typically in the form of “syn-gas” which is a mixture of CO and H
2
usable as a fuel or as a precursor for organic syntheses. The thermal plasma gasification of particulate coal and processing of methane gas have also been reported for the synthesis of acetylene (Gannon, R. E. Ind. Eng. Chem. Prod. Res. Develop. 9(3), 343-347 (1970)). Further, thermal plasma destruction of toxic chemicals such as PCBs and CCl
4
have been disclosed (Smith et al. Proc. 3rd Euro. Cong. Thermal Plasma Process (TPP-3), VDI, Aachen, Germany, September 19-21, 667-674 (1994); Tock, R. W. and Ethington, D. Chem. Eng. Comm. 71, 177-187 (1988); Han et al. J. Mater. Synth. Process 1(1), 25-32 (1993); Lachmann et al. Proc. 3rd Euro. Cong. Thermal Plasma Process (TPP-3), VDI, Aachen, Germany, September 19-21, 591-597 (1994); Mosse, A. and Kusnetov, G. Proc. 3rd Euro Cong. Thermal Plasma Process (TPP-3), VDI, Aachen, Germany, September 19-21, 651-657 (1994); Breitbarch et al. Plasma Chem. Plasma Proc. 17(1), 39-57 (1997); and Sekiguchi et al. Plasma Chem. Plasma Process 13(3), 463-478 (1993)). In addition, thermal plasma vitrification of high and low level nuclear waste has been reported as a means of reducing the volume of the waste and of encapsulating it in a non-leachable matrix prior to burial/storage (Hoffelner, W. and Funfschilling, M. R. Proc.
Workshop on Ind. Appl. of Plasma Chem., 12th Intl Symp. Plasma Chem. (ISPC-12), IUPAC, Minneapolis, Minn., August 25-26, Vol. B. Thermal Plastic Applications, 3-7 (1995)); Girold et al. Thermal Plasma for Hazardous Waste Treatment, Benocci et al. eds. World Scientific, Singapore, 160-168 (1996); Munz, R. J and Chen, G. Q. J. Nucl. Mater. 161, 140-147 (1989); and Hoffelner et al. Thermal Plasmas for Hazardous Waste Treatment, Benocci et al. eds. World Scientific, Singapore, 126-145 (1996)). The primary advantage of thermal plasma processes over other technologies is their ability to process solid, liquid and gaseous materials, rapid thermal response and quenching, and low off-gas emission compared with combustion-driven incinerators.
Thermal plasmas can be generated by direct current (DC) or alternating current (AC) arc/plasma systems utilizing either consumable or non-consumable electrodes or by electrodeless radio frequency induction-coupled plasma systems (ICP) (Fauchias et al. in Thermal Plasma for Hazardous Waste Treatment, Benocci et al. eds, World Scientific, Singapore, 1-38 (1996)). The majority of thermal plasma/waste processes developed have used DC plasma generators.
However, DC thermal plasma systems for waste treatment are limited in applicability for several reasons. First, DC plasma systems generally suffer from electrode erosion and product contamination from electrode erosion. Second, scale-up is limited by electrode erosion, and until fairly recently by power supply technology. Finally, the control of the process chemistry is difficult in DC systems since generally only inert, nonoxidizing plasma forming gases can be used. Thus, the importance of ICP systems is beginning to be recognized (Smith et al. Proc. 3rd Euro Cong. Thermal Plasma Process (TPP-3), VDI, Aachen, Germany, September 19-21, 667-674 (1994); Huhn et al. Pract. Period Hazardous Toxic and Radioactive Waste Management , 107-117, July (1997); Boulos Proc. Workshop on Ind. Appl. of Plasma Chem., 12th Intl Symp. on Plasma Chem. (ISPC-12), IUPAC, Minneapolis, Minn., August 25-26, Vol. B, Thermal Plasma Applications, 89-95 (1995); Boulos, M.I. IEEE Trans. Plasma Sci. 19(6), 1078-1089 (1991)).
The focus of thermal plasma technologies has been on destruction of hazardous chemical wastes such as chlorinated and fluorinated hydrocarbons, the extraction of metals from industrial waste, volume reduction/vitrification of nuclear waste and the destruction of military waste.
In the present invention, a method is provided for recovering monomers and high value carbons from polymeric wastes using a thermal plasma treatment process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of recovering monomers and high value carbons such as carbon nanotubes and Fullerenes from polymeric wastes using an RF induction-coupled thermal plasma heated reactor operating close to atmospheric pressure. In this method, powders of polymeric wastes are injected into an induction coupled RF plasma heated reactor wherein the polymeric waste powders are pyrolytically converted to monomers and high value forms of carbons. These monomers and high value forms of carbons are then recovered from the reactor.
DETAILED DESCRIPTION OF THE INVENTION
A significant, valuable percentage of today's municipal solid waste stream is polymeric materials. In fact, typical polymeric municipal solid waste comprises approximately 25.36% polyethylene (LDPE/LLDPE), 20.85% polyethylene (HDPE), 13.06% polypropylene (PP), 10.07% polystyrene, 8.61% polyethylene terepthalate (PET), 6.23% polyvinyl chloride (PVC) and 15.84% other materials. This polymeric waste is generally incinerated, landfilled or recycled via downgraded usage as economic recycling technologies have not been available.
In the present invention, however, an induction coupled RF plasma heated reactor is used for the pyrolytic conversion of olymeric materials to monomers and high value carbon forms including, but not limited to Fullerenes, including carbon nanotubes. It has now been found that a powder of waste polymers can be converted to monomers by injecting the powder axially into the center of a plasma, preferably an argon plasma. Specifically, the methodology of the present invention converts powdered polymeric materials into high levels of ethylene and/or propylene. Analysis of the gaseous product stream of the reactor demonstrated that using the method of the present invention, high levels of ethylene and propylene were obtained, together with lesser amounts of hydrocarbons including, but not limited to, methane, acetylene and 1,3-butadiene. Typically, approximately 50% conversion of the solid feedstock for polyethylene and 75% conversion of the solid feedstock for polypropylene was obtained.
Further, some solid carbonaceous residues were also produc
Grossmann Elihu D.
Guddeti Ravikishan R.
Knight Richard
Dang Thuan D.
Drexel University
Licata & Tyrrell P.C.
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