The emissions of a blast furnace and the separation efficiency of the top-gas scrubber were investigated for the gaseous components HCl, H 2 S, SO 2 , COS, CS 2 , CH 3 SH, HCN and NH 3. The clean gas emission of sulphur was dominated by COS which accounted for about 85% of the total sulphur emissions. From the hydrogen halides only HCl was present above the detection limit and the concentrations of NH 3 and HCN were also low. The average separation efficiency for HCl, SO 2 and NH 3 was 96%, 81% and 46%, respectively. COS was not separated in the scrubber system. The concentrations of the weak acids HCN and H 2 S were higher in the off-gas after the scrubber compared to the concentration before the scrubber. This phenomenon was explained by the release from the scrubber water into the gas of un-dissociated H 2 S and HCN originating from cyanides and sulphides contained in the separated dust. Separation efficiencies similar to those of the scrubber system are expected to be achieved also by dry sorption gas cleaning processes. However, this has to be verified in experiments. In the case of applying a dry gas cleaning system, the concentrations of H 2 S and HCN in the clean gas would be even less.

In electric arc furnace (EAF) steelmaking significant amounts of dust are generated. The main component in the dust is usually iron.Additionally, increased concentrations of metals which are volatile in the steelmaking process like zinc are found in the dusts. Duringcooling of the off-gas in the off-gas system the volatile metals are deposited on the dust particles. In electric arc furnace dust the zinccan be present in different compounds, for example as zinc oxide and zinc ferrite. Although recycling of EAF dust and utilization forzinc recovery are practiced in several countries approximately 50% of the EAF dust produced worldwide is still goes to landfill. In thisstudy the EAF dust from a mini mill was investigated by chemical fractionation. The experiment was carried out in a sequence of fiveleaching steps, where the residue from a leaching step was treated in the next step. The total zinc content of the EAF dust was approximately 6.4%. In the water-soluble fraction no zinc was found, while the carbonated fraction and the oxide fraction each containedapproximately 25% of the zinc. The reduced fraction contained approximately 8% of the zinc and the majority of the zinc was in theresidual fraction.