End of life tires as a possible source of toxic substances emission in the process of combustion

Abstract

Several million tons of end of life tires (ELTs) are piled annually as a result of human activities. Various methods have been proposed for the extraction and recycling of the resource potential of ELTs. The chemical composition of ELTs seems to enable their usage as a fuel after mechanical separation of a steel cord. Indeed, in the rubber of ELTs, up to 90 mass% accounts for carbon and hydrogen. Currently, it is by incineration that a significant proportion of ELTs is utilized. However, ELTs contain not only sulfur, which is used for vulcanization, but also nitrogen-containing additives. The behavior of these heteroatoms during oxidation is poorly investigated. It has been shown that the pyrolysis liquid fuel obtained from ELTs contains such sulfur compounds as mercaptans and nitrogen in the form of hydrocyanic acid and cyanogen. Deep oxidation of ELTs results in the oxidation of sulfur compounds to dioxide, but the oxidation products have been found to contain traces of cyanogen. Taking this into account, one should pay attention to the ways of transforming heteroatoms during the process of ELT oxidation and the products of ELT pyrolysis as potential sources of highly toxic gas emissions.