Thermodynamic Modeling of PCDD/Fs Formation in Thermal Processes

Tan, Pengfu; Hurtado, I.; Neuschütz, D.; Eriksson, G.

doi:10.1021/es000218l

Cited by 30 publications

(30 citation statements)

References 27 publications

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“…The mechanism of formation of PCDFs is different from that of PCDDs (Cains et al 1997;Luijk et al 1994). The reactions between PCDDs and PCDFs are found to be kinetically inhibited (Tan et al 2001). The PCDD formation occurs by condensation reactions and associated Smile's rearrangements of a small set of chlorophenol precursors (Luijk et al 1994).…”

Section: Polychlorinated Dibenzo-p-dioxin and Dibenzofuran (Pcdd/fs)mentioning

confidence: 94%

Toxic Environmental Releases from Medical Waste Incineration: A Review

Singh

Prakash

2007

Environ Monit Assess

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Toxic releases from medical waste incineration comprising organic emissions such as polychlorinated dibenzo-dioxin/furan (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs), inorganic emissions and ashes containing toxic metals have been reviewed. Attempts made by various investigators to reduce/eliminate emissions have also been included. Legislations concerning emission standards for medical waste incinerators have been discussed.

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Section: Polychlorinated Dibenzo-p-dioxin and Dibenzofuran (Pcdd/fs)mentioning

confidence: 94%

Toxic Environmental Releases from Medical Waste Incineration: A Review

Singh

Prakash

2007

Environ Monit Assess

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“…The same temperature range has also experimentally been found to be favorable for the formation of these compounds. [9][10][11][12][13][14] According to the calculations, the PCDD/F formation requires extremely reducing conditions [6] (Figures 1 and 2). These conditions are most easily realized in direct proximity to carbonaceous matter in the sinter bed and in the dustladen off-gas.…”

Section: Thermodynamic Stability Regions For Pcdd/fsmentioning

confidence: 92%

“…The predictions using the three different databases have been compared, and similar thermodynamic conditions of PCDD/F formation have been found. [6] The isomer distributions of toxic PCDD/Fs have also been predicted by the authors [7] and compared with the measured data from industrial iron ore sinter plants, electrical arc furnaces, waste incinerators, and wood burning furnaces. The calculated isomer fractions of the toxic PCDD/Fs using the database derived from the MNDO method showed the best agreement with the industrial measurements relative to the other databases.…”

Section: Thermodynamic Databases For Pcdd/fsmentioning

confidence: 99%

“…Three thermodynamic databases of PCDD/Fs derived using the Group Additivity approach [3] and two computational molecular modeling methods, Modified Neglect of Diatomic Overlap (MNDO) and Parametrized Model 3 (PM3), respectively, [4,5] combined with the Scientific Group Thermodata Europe (SGTE) database, have been used by the authors [6] to model the formation of PCDD/Fs in thermal processes, such as the iron ore sintering process. The predictions using the three different databases have been compared, and similar thermodynamic conditions of PCDD/F formation have been found.…”

Section: Thermodynamic Databases For Pcdd/fsmentioning

confidence: 99%

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Study on polychlorinated dibenzo-p-dioxin/furan formation in iron ore sintering process

Tan

Neuschütz

2004

Metall Mater Trans B

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In order to understand and control the formation of dioxins and furans (PCDD/Fs) in iron ore sinter plants, a CFD model of iron ore sintering, combined with the kinetic models of 14 relevant chemical reactions and thermodynamic calculations of dioxin formation, has been developed to simulate the concentrations of the gaseous species, temperatures of the gas and solid, velocity of the gas, temperature zones, and residence time of the gas in each temperature zone. The predicted off-gas compositions, the velocities of the gas, and the trends for the gas temperature at the bottom of the bed have been compared with measured data from a sinter plant, and good agreement has been obtained. From the predicted temperature zones of the gas and solid, the predicted residence time of the gas in each zone, and thermodynamic conditions of PCDD/F formation, the PCDD/F formation in sinter plants has been discussed. The dioxins are formed in the critical temperature region of 250°C to 450°C below the combustion zone in the bed, are then carried downward with the gas, and are condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. The dioxins are also formed in the last wind boxes when the hot off-gases cool and reach the critical temperature range. These pathways on PCDD/F formation can explain the industrial observations well. The preceding information may assist in the effective control or elimination of dioxin formation in iron ore sinter plants.

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“…Formation of PCDD/Fs is generally believed to proceed via two major pathways, i.e., condensation reactions of precursors such as polychlorinated phenols (PCPh) (1,2), and de novo synthesis from carbonaceous particulates (3,4) or aromatic entities (5). Additional chlorination/dechlorination of the resulting PCDD/Fs can be of particular importance since the most toxic congeners are chlorinated in the lateral (2,3,7, and 8) positions ( Figure 1). Consequently, detoxification of MSW incineration residues will benefit from elucidating the factors governing chlorine substitution and/or elimination.…”

Section: Introductionmentioning

confidence: 99%

Multivariate Relationships between Molecular Descriptors and Isomer Distribution Patterns of PCDD/Fs Formed during MSW Combustion

Jansson

Antti

Marklund

et al. 2009

Environ. Sci. Technol.

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The isomer distribution patterns of mono- to hepta-chlorinated dibenzo-p-dioxins (PC1-7DD) and dibenzofurans (PC1-7DF) in postcombustion zone flue gas during incineration of an artificial municipal solid waste in a laboratory-scale fluidized-bed reactor were evaluated. Bidirectional orthogonal projections to latent structures (O2PLS) was used to correlate a set of physicochemical properties and chlorine substitution descriptors with the objective to identify parameters correlated with postcombustion zone PCDD and PCDF formation. The most influential variable for the distribution of PCDD congeners was chlorine substitution in positions 1 and 3 (Cl1+3), and overall the chlorine substitution descriptors exerted a larger impact on PCDDs than on PCDFs. For the PCDF, chlorination of the 9-position was the most influential X-variable. Distinct clustering was observed and was most pronounced for PCDFs, dividing mostof the homologues into two or three subgroups of congeners. These subgroups seemed to correspond to the probability of formation by chlorophenol condensation. The sterically crowded dibenzofuran bay-sites (1- and 9-positions) were found to negatively influence PCDF formation, with chlorination of the 9-position having the greatest impact. Since PCDD/F toxicity is related to the lateral positions, elucidating the factors governing chlorination may be of great importance for detoxification of incineration byproducts.

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Thermodynamic Modeling of PCDD/Fs Formation in Thermal Processes

Cited by 30 publications

References 27 publications

Toxic Environmental Releases from Medical Waste Incineration: A Review

Toxic Environmental Releases from Medical Waste Incineration: A Review

Study on polychlorinated dibenzo-p-dioxin/furan formation in iron ore sintering process

Multivariate Relationships between Molecular Descriptors and Isomer Distribution Patterns of PCDD/Fs Formed during MSW Combustion

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