Article

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: 3.14). 11/2011; 86(4):361-7. DOI: 10.1016/j.chemosphere.2011.10.016
Source: PubMed

ABSTRACT 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.

0 Bookmarks
 · 
82 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Flocculants are widely used to improve the properties of sludge dewatering in industrial wastewater treatment. However, there have been no studies conducted on the influence of flocculants on the formation of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) during sewage sludge incineration. This paper selected three typical kinds of flocculants, including polyacrylamide (PAM), poly-ferric chloride (PFC), and polyaluminum chloride (PAC) flocculant, to study their influences on the formation of PCDD/Fs during sewage sludge incineration. The results indicated that PAM flocculant, which is an organic flocculant, inhibited the formation of PCDD/Fs in sewage sludge incineration, while inorganic flocculant, such as PFC and PAC flocculant, promoted the formation. The most probable explanation is that the amino content in the PAM flocculant acted as an inhibitor in the formation of PCDD/Fs, while the chlorine content, especially the metal catalyst in the PFC and PAC flocculants, increased the formation rate. The addition of flocculants nearly did not change the distribution of PCDD/F homologues. The PCDFs contributed the most toxic equivalent (TEQ) value, especially 2, 3, 4, 7, 8-PeCDF. Therefore, the use of inorganic flocculants in industrial wastewater treatment should be further assessed and possibly needs to be strictly regulated if the sludge is incinerated. From this aspect, a priority to the use of organic flocculants should be given.
    Environmental science and pollution research international. 07/2014;
  • Source
    [Show abstract] [Hide abstract]
    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.
    Journal of Environmental Chemical Engineering 01/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are formed during waste incineration and in waste-to-energy boilers. Incomplete combustion, too short residence times at low combustion temperatures (<700°C), incineration of electronic waste and plastic waste containing chlorine are all factors influencing the formation of PCDD/Fs in boilers. The impact of chlorine and catalysing metals (such as copper and iron) in the fuel on PCDD/F formation was studied in a 12MWth circulating fluidised bed (CFB) boiler. The PCDD/F concentrations in the raw gas after the convection pass of the boiler and in the fly ashes were compared. The fuel types were a so-called clean biomass with low content of chlorine, biomass with enhanced content of chlorine from supply of PVC, and solid recovered fuel (SRF) which is a waste fuel containing higher concentrations of both chlorine, and catalysing metals. The PCDD/F formation increased for the biomass with enhanced chlorine content and it was significantly reduced in the raw gas as well as in the fly ashes by injection of ammonium sulphate. A link, the alkali chloride track, is demonstrated between the level of alkali chlorides in the gas phase, the chlorine content in the deposits in the convection pass and finally the PCDD/F formation. The formation of PCDD/Fs was also significantly reduced during co-combustion of SRF with municipal sewage sludge (MSS) compared to when SRF was fired without MSS as additional fuel.
    Waste Management 05/2013; · 3.16 Impact Factor