PCDD and PCDF emissions from scrap metal melting processes at a steel mill

Scrap metal melting processes have been found to be one source for chlorinated dioxins and dibenzofurans in the environment. This study was carried out in a pilot plant with a 10 - ton electric furnace. Feedstocks with varying amounts of chlorinated compounds were charged into the furnace under different operational conditions. The scrap metal was charged either continuously through the furnace or batchwise into the open furnace. Isomer specific analysis show the presence of PCDDs and PCDFs in the range of 0.1 – 1.5 ng TCDD-equivalents/Nm 3 dry gas, according to the Nordic model. The higher value was obtained when melting scrap metal containing chlorine. In the case of batchwise charging the gas collected over the open furnace contained 110 ng TCDD-equivalents/Nm 3 dry gas when using cutting oils containing chlorine. The congener profiles for all flue gas samples show a predomination of dibenzofurans.