Polychlorinated dibenzo-p-dioxin and dibenzofuran and polychlorinated biphenyl emissions from different smelting stages in secondary copper metallurgy. 
Secondary copper production has received much attention for its high emissions of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) reported in previous studies.  These studies focused on the estimation of total PCDD/F and polychlorinated biphenyl (PCB) emissions from secondary copper smelters.  However, large variations in PCDD/F and PCB emissions reported in these studies were not analyzed and discussed further.  In this study, stack gas samples at different smelting stages (feeding-fusion, oxidation and deoxidization) were collected from four plants to investigate variations in PCDD/F and PCB emissions and characteristics during the secondary copper smelting process.  The results indicate that PCDD/F emissions occur mainly at the feeding-fusion stage and these emissions contribute to 54-88% of the total emissions from the secondary copper smelting process.  The variation in feed material and operating conditions at different smelting stages leads to the variation in PCDD/F emissions during the secondary copper smelting process.  The total PCDD/F and PCB discharge (stack gas emission+fly ash discharge) is consistent with the copper scrap content in the raw material in the secondary copper smelters investigated.  On a production basis of 1 ton copper, the total PCDD/F and dl-PCB discharge was 102, 24.8 and 5.88 μg TEQ t(-1) for the three plants that contained 100%, 30% and 0% copper scrap in their raw material feed, respectively.