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Wu H.-L.,Zhejiang University | Lu S.-Y.,Zhejiang University | Li X.-D.,Zhejiang University | Jiang X.-G.,Zhejiang University | And 3 more authors.
Chemosphere | Year: 2012

Sulphur compounds, including (NH 4) 2SO 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. © 2011 Elsevier Ltd. Source

Lin X.,Zhejiang University | Huang Q.,Zhejiang University | Chen T.,Zhejiang University | Li X.,Zhejiang University | And 5 more authors.
Aerosol and Air Quality Research | Year: 2014

The PCDD/F emissions from incinerator start-up are a major contributor to the total amount of such emissions, as has been reported in studies of numerous municipal solid waste incinerators. However, very few studies have examined the start-up process at hazardous waste incinerators (HWIs). In this work we studied the emissions of PCDD/Fs and other pollutants, such as PCBz, at the stack during start-up and normal operations in a HWI. We found that the PCDD/F emissions during start-up were greater than during normal operations, and were comparable to the annual emissions during the normal combustion regime. The emissions of PCDD/Fs were highest during start-up when the temperature was around 500°C, reaching 59.5 ng/Nm3 (5.49 ng I-TEQ/Nm3) when no APCDs were applied. The emission values of PCDD/Fs during start-up with the application of APCDs and during normal operations were very low, which indicates the importance of APCDs when starting up a HWI, as well as before feeding waste. The chlorination degree, the ratio of PCDFs/PCDDs and the congener profiles were also discussed during start-up and normal operations, with the results suggesting different formation mechanisms of PCDD/Fs. PCBz emissions are two or three orders of magnitude higher than those of PCDD/Fs, and 1,2,4,5-TeCBz was the best correlated PCBz used as a PCDD/F indicator in real HWI flue gas. © Taiwan Association for Aerosol Research. Source

Wang Q.,Zhejiang University | Jin Y.,Zhejiang University | Li X.,Zhejiang University | Chen J.,Zhejiang University | And 5 more authors.
Aerosol and Air Quality Research | Year: 2014

In order to investigate the dioxin emission levels of hazardous waste incinerators (HWIs), and estimate their emission factors to the atmosphere, flue gas samples were collected from 12 HWIs in China, and analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Eleven HWIs are located in the south-eastern coastal areas of China, with rotary kilns being is the most widely used type of incinerator (more than 50% of the units), followed by pyrolysis kilns. Eleven incinerators had their emission levels below the current standards in China, while only four facilities exhibited emission levels below the European Union's limits. The highest concentration of PCDD/Fs, at nearly 1 ng TEQ/Nm3, was in the flue gas collected from an HWI with a waste burning capacity of 5 ton/d. This result was significantly higher than the values found for the other 11 incinerators, and thus was due to the poor performance of air pollution control devices and the influence of memory effects caused by PCDD/Fs emissions related to the start-up of the incinerator. In addition, the high dioxin emissions of this HWI were related to its feeding wastes, which mainly consisted of chemical industry waste residue with high a chlorine content. The emission factors of PCDD/Fs from the HWIs examined in this work were in the range of 0.27-18 μg TEQ/ton hazardous waste, with an average value of 3.74 μg TEQ/ton hazardous waste. It is estimated that 5.0 g TEQ of PCDD/Fs was released from HWIs to the atmosphere in China in 2010, which is less than that seen in 2004. The results of principal component analysis and hierarchical cluster analysis show all the investigated HWIs can be assigned to three groups, as verified by the results of nonparametric statistics. OCDD, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8- HpCDF and OCDF are the main congeners in these three groups. © Taiwan Association for Aerosol Research. Source

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