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THERMAL DEPOLYMERIZATION OF POSTCONSUMER PLASTICS
Citation:
Aulich, T. R. AND R. O. Ness Jr. THERMAL DEPOLYMERIZATION OF POSTCONSUMER PLASTICS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-99/114 (NTIS PB2000-101976 A08), 2000.
Description:
The University of North Dakota Energy & Environmental Research Center (EERC) performed two series of tests to evaluate process conditions for thermal depolymerization of postconsumer plastics. The objective of the first test series was to provide data for optimization of reaction temperature and gas residence time in maximizing production of light olefins -- specifically, ethylene, propylene, and butylenes (including 1-butene, isobutylene, 1,3-butadiene, and cis- and trans-2-butene). The feedstock used for the olefin tests was a postconsumer plastics mix obtained from a Minneapolis-area commercial recycling facilty. The objective of the second test series was to provide data for optimization of reaction temperature, gas residence time, and process water requirement to maximize production of terephthalic acid (TA). PET is the plastic from which TA is yielded as a partial depolymerization product. The feedstock for the TA tests was the Minneapolis-area postconsumer mix, to which a sufficient amount of PET was added to provide a PET feedstock concentration of about 50%
Olefin tests were run at gas residence times of 6 and 14 seconds, and temperatures from 637 to 707oC. The olefin test data indicate that gas residence time, which is the amount of time required for a "plug" of fluidization gas to travel through the reactor (a function of gas flow rate), is at least as important as temperature in maximizing olefin yields.
Findings from the TA tests indicate that maximum PET-to-TA conversions of about 26% were achieved with a water:PET ratio of 10:1 (grams water/grams PET). Based on the TA tests results, it appears that for maximizing PET -to-TA conversion over a temperature range of about 500o to 550oC, a eater:PET ratop pf 10:1 is significantly more effective than a ratio of 5:1.
This Project Summary was developed by EPA's National Risk Mangement Research Laboratory, Cincinnati, OH to announce key findings ofthe research project that is fully documented in a separate report of the same title (see Project Report ordering information at back).