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In our lab, we have been studying the emissions of different pollutants during pyrolysis and combustion of wastes under different conditions for the last three decades. These studies have focused on the effect of temperature and presence of oxygen on the production of different pollutants. Waste decomposition has been studied in a horizontal laboratory scale reactor, but no estimate has been made of the actual emissions in a conventional thermal decomposition system. In the present study, emissions during these wastes’ thermal decomposition were estimated using Aspen HYSYS. In the simulation software, the waste composition (elemental analysis) was given as an input parameter, as well as the gas flow rate used as atmosphere during the decomposition. The emitted hydrocarbons measured in the laboratory were equated to the emission of a single compound (propylene). The simulation permitted calculating the percentage of oxygen in the emitted gas, and the pollutant emissions were then recalculated under standard conditions. The emission of dioxins and furans were estimated under different conditions of decomposition, and an adequate approximation of the waste decomposition in actual incineration systems could be obtained.

In order to reduce the calculation effort during the simulation of the emission of polychlorinated dibenzo-p-dioxins and furans (PCDD/F) during municipal solid waste incineration, minimizing the number of simulated components is mandatory. For this purpose, two new multilinear regression models capable of determining the dioxins total amount and toxicity of an atmospheric emission have been adjusted based on previously published ones. The new source of data used (almost 200 PCDD/F analyses) provides a wider range of application to the models, increasing also the diversity of the emission sources, from industrial and laboratory scale thermal processes. Only three of the 17 toxic congeners (1,2,3,6,7,2,3,7,, whose formation was found to be linearly independent, were necessary as inputs for the models. All model parameters have been statistically validated and their confidence intervals have been calculated using the Bootstrap method. The resulting coefficients of determination (R 2 ) for the models are 0.9711 ± 0.0056 and 0.9583 ± 0.0085; its root mean square errors (RMSE) are 0.2115 and 0.2424, and its mean absolute errors (MAE) are 0.1541 and 0.1733 respectively.Energies 2019, 12, 4434 2 of 11 eight chlorine atoms in eight different places on the molecule. This combination of number of chlorines and places results in an extensive family of molecules, where each molecule is called a congener.Combustion processes emit PCDD/Fs as a mixture of up to 210 congeners, of which only 10 dioxins and 7 furans are considered to be toxic and thus most frequently analysed. In order to evaluate the impact of atmospheric emissions, the most common approach is to calculate the amount of toxic equivalents (TEQs) according to NATO/CCMS (North Atlantic Treaty Organization/Committee on the Challenges of Modern Society) [5]. This criterion uses toxic equivalency factors (TEFs) that proportionally modify the amount of each congener considering the most toxic one (2,3,7,8-TCDD) as the reference (unity factor). Despite the fact that TEFs have been questioned [6,7] and updated [8], the International Toxicity Equivalency Factors (I-TEFs) [9] prevail internationally, since most regulations for atmospheric emissions refer to them [10].Despite the fact that the emission of PCDD/F has been related to industrial processes and human activity, some authors highlight the contribution of forest fires to the total emission of PCDD/Fs [11]. Several studies have been published on the formation of PCDD/F during the combustion of biomass and e-waste [12], demolition and construction wood [13], viscoelastic memory foam [14], furniture [15] and many other different residues. A publication addressing the emissions of a cement production plant [16] determined that, focusing on the distribution of the congeners of their samples, no big differences were observed among their emissions despite the fuel used in the kiln. The formation of PCDD/Fs from MSW incineration showed a strong interdependence with phenols, chlorinated benzenes and other precursors [17]. Thi...