Removal of zinc from submerged arc furnace flue gas wash water using steel slag with polyacrylamide

The aim of this research was to investigate zinc removal from submerged arc furnace flue gas wash water with steel slag and polymer treatment. The current treatment for the submerged arc furnace flue gas wash water is treatment with polymer only which aids in the settling of particulate zinc. However, in this research enhanced removal of zinc by also precipitating soluble zinc using steel slag was studied. The zinc removal results were compared with the results using commercial neutralizing agents NaOH, Mg(OH)₂, and Ca(OH)₂ together with polymer. The precipitation conditions were simulated with MINEQL + software and the calculated results were compared with the results from laboratory jar test experiments. Zinc was removed to less than the target concentration 2 mg/l with steel slag and polymer treatment at pH 9. Additionally, turbidity of the treated water decreased to 20 NTU compared to the initial 860 NTU. However, the amount of steel slag needed in the treatment was significantly higher than the amounts of NaOH and Ca(OH)_2. The main zinc removal mechanism of steel slag was precipitation as zinc oxide. Calculated zinc removal was higher than the experimental which indicates that equilibrium was not reached in the precipitation experiments which could be due to relatively short contact time chosen to simulate the actual process conditions at the plant.