Abstract
Organic waste is generally characterized by high volume-to-weight ratios, requiring implementation of waste minimization processes. In the present study, the decomposition of high-density polyethylene (HDPE), was studied under thermal and catalytic pyrolysis conditions on two experimental systems. Firstly, pyrolytic conditions for HDPE decomposition were optimized in a laboratory-scale batch reactor. In order to maximize gas yields and minimize secondary waste, the effects of aluminosilicate catalysts, catalyst loading, and reaction temperature on decomposition efficiency were examined. Secondly, kinetics and reaction temperatures were studied on a large capacity thermobalance, especially adjusted to perform experiments under pyrolytic conditions at a larger scale (up to 20 g). The addition of catalysts was shown to enhance polymer decomposition, demonstrated by higher gas conversions. Condensable yields could be further minimized by increasing the catalyst to polymer ratio from 0.1 to 0.2. The most prominent reduction in pyrolysis temperature was obtained over ZSM-5 catalysts with low Si/Al ratios; however, this impact was accompanied by a slower reaction rate. Of the zeolites tested, the ZSM-5 catalyst with a Si/Al of 25 was found to be the most efficient catalyst for waste minimization and organic destruction, leading to high gas conversions (~90 wt%.) and a 30-fold reduction in solid waste mass.
Highlights
Organic waste is characterized by high volume to weight ratios, requiring implementation of waste minimization processes
This study demonstrated that the solid waste mass was effectively reduced, additional improvements are required to minimize condensable yields if pyrolysis is to be considered a suitable thermal treatment for the minimization of contaminated solid waste
The present study aims to fill this gap by examining the use of catalytic pyrolysis as a means to optimize product conversions for solid organic waste contaminated with radionuclides
Summary
Organic waste is characterized by high volume to weight ratios, requiring implementation of waste minimization processes. When organic waste is contaminated with radionuclides, it may further pose a hazard due to radiolysis and the generation of combustible and explosive gases. Minimizing waste volume as well as forming a chemically stable and conditioned matrix are of high importance in the treatment of contaminated polymers. Effective volume reduction of solid organic waste can be achieved by thermal treatments, such as incineration, gasification, pyrolysis and plasma treatments. I.e., the process of thermal decomposition of organics in the absence of oxygen, produces three main products: solid char, condensable oils and organic and inorganic gases [3]. Pyrolysis has several key advantages over other thermal processes. It is considered more environmentally compliant than incineration due to the limited carbon dioxide and significantly lower
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