In iron ore sintering, the properties of the flame front are clearly critical as they determine the heat imparted to the particulate bed and, hence, the strength of the formed sinter. This study explores the factors that influence flame front temperature and also the speed at which it descends down a bed. These two properties are dependent on post-ignition airflow rate and the properties of the sinter mix. Post-ignition airflow rate is a strong function of the pre-ignition airflow rate and the flow resistance of the flame front. This study reiterates the strong dependence of flame front resistance on gas flow velocity, flame front temperature and applied suction. Dense ores produce higher bulk density and lower porosity beds and, as a consequence, they have the effect of slowing down and broadening the flame front. The influence of flame front speed on flame front properties for different ores was also established. For comparable flame front properties results show that sinter basicity has a large influence on sinter strength and yield. Studies of coke combustion efficiency show decreasing values with increasing flame front speed and values increased significantly when sintering YANDI ore. Many of the obtained quantitative dependences will be used to verify a sintering mathematical model that is under development.

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Ash residues from fires of radiata pine timber, both untreated and treated with chromated copper arsenate (CCA), were analyzed for the presence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F). Fire conditions were simulated using a cone calorimeter. The sensitivity of the magnitude and profile of PCDD/F in the ash under controlled experimental conditions were examined to gain an insight into the formation of PCDD/F in a system containing CCA. The total amount of PCDD/F increased from 2.0 ng/kg of ash (0.05 ng of TE/kg of ash, using WHO-TEF) for untreated radiata pine to a maximum of 2700 ng/kg of ash (78 ng of TE/kg of ash) for 0.94% CCA. Ash containing CCA showed a distinct preference for formation of PCDFs, particularly the tetrachloro homologue. It is concluded that PCDD/F formation predominantly occurred via de novo synthesis during smoldering of the char rather than during the initial flaming and pyrolysis. Furthermore, the composition of the CCA constituents present in the timber was controlled to assess whether the physical presence of Cu, a known catalyst in PCDD/F production, was sufficient to account for the formation of PCDD/F in fires of timber impregnated with CCA.

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This article demonstrates that biocidal organochlorines such as tebuconazole and permethrin, employed in formulations of wood preservatives, produce significant quantities of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) when subjected to thermal decomposition under oxidative conditions. Both tebuconazole and permethrin form PCDD/F during gas-phase oxidation, but much greater yields occurred in the presence of surrogate ash corresponding to wood treated with copper-based fungicides. The significant yields have implications for the increased toxicity of PCDD/F emissions during fires of wood impregnated by combination of organic and copper-based preservatives. The oxidative pyrolysis of tebuconazole and permethrin over simulated wood ash generated amounts of PCDD/F exceeding those of untreated wood by 3 orders of magnitude. We obtained yields of 1000 ng WHO97-TEQ/g tebuconazole and 5500 ng WHO97-TEQ/g permethrin when reacting the organochlorines in an oxidizing atmosphere over surrogate wood ash. Gas-phase oxidation also produce measurable quantities of PCDD/F, corresponding to 1 ng WH097-TEQ/g tebuconazole and 36 ng WHO97-TEQ/g permethrin. In the case of tebuconazole, the present measurements correlate well with those obtained from oxidative pyrolysis of CBA-treated wood in the cone calorimeter. It appears that permethrin and tebuconazole provide phenyl and diphenyl precursors to formation of PCDD/F and both constitute a source of chlorine upon fragmentation.