XXVI Congresso Nazionale della Società Chimica Italiana XXX Y000
Analysis of the products and wastes of a pyrolysis plant powered by residual
plastic materials for energy’s production
Giulia Costamagna a, Marco Ginepro b, Janeth Tafur Marinos c,
Vincenzo Zelano d, Giuseppe Benzi e
a ,b, c, d. Dipartimento di Chimica, Università di Torino Via Pietro Giura 5; e. MECTRA s.r.l. C.so Genova 19 Carbonata Scrivia (AL); [email protected]
Alternative and renewable energy sources are going to play an increasingly strategic role in the global landscape. Among them, the waste of plastic materials produced by our society are remarkable, establishing a potential renewable source for excellence. However, it’s known that recovery and recycling technologies of waste are very often expensive. When these technologies aren’t workable or economically convenient, it’s useful to regain the energy in the so-called “quaternary recycling”, using the plastic materials as alternative fuel. In fact, the average HHV of a mixture of plastics is about 35 MJ/kg. Actually, waste of plastic materials coming from automotive industry are transferred to landfills or to incinerators, but it should evaluate the high risk of formation of oxygenated heterocyclic compounds (e.g. dioxins) as well as of all the polluting substances (e.g. polycyclic aromatic hydrocarbons) during the combustion process. Taking into account these compounds, the research has been pointed on pyrolysis equipment where a syngas is formed in an oxygen-free environment with very low emissions from the plant in the atmosphere during the process. In collaboration with MECTRA s. r. l., equipped with an innovative pyrolysis plant, it was possible to propose an analysis of its products and by-products, in order to respect its good working and to achieve a minor environmental impact according to the limits of law. Synthetically, the process allows plastic materials coming from automotive industry to be transformed into combustible gas through a slow pyrolysis at temperatures between 400 to 700 °C. Thanks to a heating induction’s system, the frequency can be calibrated according to the raw material chosen. At the end of the process, a gas with high HHV is produced and used to generate electricity by an alternator linked to an endothermic engine. The aim of the research, therefore, is
the physical-chemical characterization of the input materials, the syngas produced, the emission
fumes from the engine, the by-products formed during the process such as carbon black, ashes, hydrocarbons in both liquid and bituminous form, and washing waters. Concerning the parameters to be monitored on input materials, it is chosen to analyze ashes, HHV, moisture content, volatile heavy metals and the presence of sulfur and chlorine. Regarding the syngas, the analysis is focused in particular on the amount of methane gas, of higher volatile hydrocarbons and eventually of HCl and CO. About the emission of pollutants from the engine the study is mainly directed to the presence of toxic compounds such as dioxins and PAHs, in order to test the actual environmental impact eventually due to the choice of raw material. In the end, the analysis of by-products is based
to understand their possible toxicity and their possible reuse, analyzing the presence of numerous
metals and compounds such as PAHs and PCBs. In conclusion, the analytical characterization of the above mentioned parameters is particularly important, in order to verify the versatility of the pyrolysis process in its industrial application. This characterization, in addiction, could be a starting point of future legislative measures on the environment and on the potential of residual plastics as a
renewable energy resource. For future perspectives, during the testing phase, the plant is going to be
fed with biomass, such as rice straw, walnut shell etc., with electrical cables, composite packaging and tire coverings.
