摘要：De novo tests were conducted on fly ash from Medical Waste Incineration at three set temperatures (250, 350, and 400 °C) and at three distinct oxygen concentrations in the carrier gas flow (0, 10, and 21 Vol. % O2). During a test run of 0.5 h Polychlorinated dibenzo-p-dioxins PCDDs and dibenzofurans PCDFs (P = 4 to 8) are newly formed on the previously extracted fly ash and their amount (ng) is measured both in the carrier gas and the remaining residue. The resulting PCDD/F-formation (and its signature or fingerprint) depends on the two experimental variables (temperature and oxygen) in a complex and uncommon way. The PCDD/Fs formation was highest at the unusually high temperature of 400 °C. The gas phase PCDD/Fs are controlled by low chlorinated PCDDs (mainly TCDD); the solid phase PCDD/Fs, conversely, are richer in higher chlorinated PCDF, yet their distribution depends on both temperature and oxygen content. The ratio PCDD: PCDF varies from 1.76 to 16.6 in the gas phase, yet this same ratio spans from 0.09 to 0.71 in the residue, an unexplained and dramatic difference. The ratio of Gas Phase to the Total PCDD/Fs remains surprisingly low and decreases - unexpectedly - with higher oxygen and partly with higher temperature, yet in a manner that differs between PCDDs and PCDFs and between anoxic and oxygen-present conditions. Presumably, these features are due to the presence of large amounts of spent Activated Carbon in the Fly Ash. Most de novo PCDD/Fs fingerprints strongly deviate from the original fingerprint of the original fly ash. The data is analysed statistically, to identify and confirm these data trends.
关键词：de novo test; oxygen; temperature; dioxins
(PCDD/Fs); Gas/Solid distribution
