Influence of temperature on PCDD/PCDF desorption from waste incineration flyash under nitrogen.
A municipal solid waste incinerator flyash was heated to between 200 and 400 degrees C under nitrogen in a bench-scale, static bed reactor for 4 days soak time. The influence of temperature on the levels of PCDD and PCDF remaining in and desorbed from the ash were investigated using GC-MS/MS. PCDD and especially PCDF formation was seen on the flyash between 225 and 300 degrees C. Large increases in the I-TEQ of the treated ash relative to the increase in its overall PCDD/PCDF content indicated that the formation of 2378-substituted congeners was favoured over that of other substitution patterns. In the absence of a source of gaseous oxygen, formation was mainly attributed to de novo reactions involving solid phase oxygen. Dechlorination of the PCDD/PCDF in flyash became increasingly important above 275 degrees C. Maximum desorption was seen at 325 degrees C, with the equivalent of 35 wt% of the PCDD/F in the original flyash being recovered from the exhaust traps at this temperature. The desorbed species were mainly M(1)CDD/CDDF-T(3)CDD/CDDF resulting from dechlorination of higher chlorinated PCDD/PCDF, with consequently low I-TEQ values.
Cunliffe
Adrian M
AM
Energy and Resources Research Institute, University of Leeds, Leeds LS2 9JT, UK.
Williams
Paul T
PT
D001572:Benzofurans / Q000032:analysis*; D000072338:Dibenzofurans, Polychlorinated; D017745:Incineration / Q000592:standards*; D009584:Nitrogen; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis; D013696:Temperature
D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D000072317:Polychlorinated Dibenzodioxins; D009584:Nitrogen