Inhibition of PCDD/F by adding sulphur compounds to the feed of a hazardous waste incinerator
State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, Hangzhou, Zhejiang Province 310027, China. Chemosphere
(Impact Factor: 3.34).
11/2011; 86(4):361-7. DOI: 10.1016/j.chemosphere.2011.10.016
Sulphur compounds, including (NH(4))(2)SO(4) and pyrite, were tested as suppressants in a hazardous waste incineration facility. The test results suggested that adding sulphur compounds only slightly reduced PCDD/F stack emissions; this restricted effect was attributed to the release of fly ash in large amounts during the sulphur adding experiments, i.e., it was due to a malfunctioning of the baghouse filter. Nevertheless, for the combined flow of flue gas+fly ash a reduction of more than 50% was achieved for the total PCDD/F concentrations and the total toxic concentrations, and an even higher inhibition capability was observed for PCDD. Also, a simulation of the thermodynamic equilibrium conditions by sulphur dioxide was conducted in the domain of experimental interest. Deactivation of catalysts, which promote PCDD/F formation, was found to be the dominant inhibition mechanism in low temperature PCDD/F formation. SO(2) could also inhibit the formation of molecular Cl(2) via the Deacon reaction, but that was not the main reason for inhibition.
Available from: aaqr.org
- "Remarkably, during the two tests with a joint injection of 500 ppm NH 3 and 500 ppm SO 2 a negative reduction for the sum PCDD/Fs was observed. Although a clear decrease in the concentrations of PCDD/Fs occurred when either 500 ppm NH 3 or 500 ppm SO 2 was injected (Ruokojärvi et al., 1998; Ke et al., 2010; Wu et al., 2012), only 0.3% of PCDD/Fs reduction was achieved in these experiments when they were injected together. The experiments were conducted in duplicate and the results were well reproducible, with values for the standard variation of 11% for PCDD, 8%% for PCDF and 16% for I-TEQ. "
Available from: Paul-Marie Marquaire
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ABSTRACT: “Dioxins” (or PCDD/F) are persistent organic pollutants (POP) which are emitted in the atmosphere by several combustion and thermal processes. Many studies concern the formation of dioxins, but very few thermal destruction. The present study concerns the oxidation and the pyrolysis of dibenzofuran which is chosen as a model molecule of “PCDF” (polychrorodibenzofurans). The reaction is studied at very low concentration of dibenzofuran (i.e. near 2 ppm) in a continuous perfectly stirred reactor, at atmospheric pressure. The residence time is varying between 3 s and 5 s, whereas the temperature is ranging from 500 to 950 °C. Dibenzofuran is a solid compound in standard conditions, so a difficulty of this study is to realize a continuous gas flow of this species.
During dibenzofuran decomposition, the conversion can be close to 100% and several intermediary species are formed. These species are identified by GC/MS and then quantified by GC/FID. The main byproducts are derivatives of benzofuran, polyaromatic hydrocarbons and other volatile organic compounds. These experimental data are used to improve a kinetic mechanism and previously validated with experimental data obtained with higher ranges of DBF concentration.
Available from: Stina Jansson
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ABSTRACT: The use of waste wood as an energy carrier has increased during the last decade. However, elevated levels of alkali metals and chlorine in waste wood compared to virgin biomass can cause increased deposit formation and higher concentrations of organic pollutants. In this study, we investigated the effect of the ChlorOut technique on concentrations of organic pollutants. Ammonium sulfate was injected into the combustion system to inhibit formation of KCl (which causes deposits) and persistent organic pollutants, namely polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs). The results showed that concentrations of the toxic congeners of PCDD, PCDF and PCB decreased in the presence of ammonium sulfate.
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