New Models Used to Determine the Dioxins Total Amount and Toxicity (TEQ) in Atmospheric Emissions from Thermal Processes

Abstract

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...

Kinetics of the formation and destruction of PCDD/Fs in a laboratory tubular furnace

“…Previous work at the Universitat Ramon Llull (URL) (Palmer et al, 2019(Palmer et al, , 2018 showed a dependence on the dioxin and furan emissions from thermal decomposition of different products. This work established three linear regression models that were able to estimate properly the total amount and toxicity of a sample considering only the amount of 1,2,3,6,7,8-HxCDD, OCDF and 2,3,7,8-TCDF in the sample.…”

“…This kinetic study pretends to be simple in order to be used in a future simulation process, where the operational parameters will be selected for simulating total PCDD/F emissions. In order to simplify the kinetics, a correlation between the formation of the PCDD/F congeners previously published will also be taken into consideration (Palmer et al, 2019(Palmer et al, , 2018.…”

Emission Characteristics of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans (PCDD/DFs) in Commercial Bio-SRF and SRF Incineration Plants

“…Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are classified as dioxins [7][8][9][10]. Each PCDD/DFs can include chlorine atoms up to eight in different places on the molecule [11]. These characteristics result in different types of molecules, such as congeners.…”