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OZONATION FOR DESTRUCTION OF ODORANTS IN ALUMINA REFINERY CONDENSATE

Guan J, Feitz AJ, Wang X, Mullett M, Forster P, Stuetz R

The removal of odorants from alumina refinery condensate using ozonation is reported in this paper. The conditions present in refinery condensate (pH >10, temperature >80°C) mean that many advanced oxidation processes (AOPs) such as UV/H2O2 and Fenton systems are unlikely to perform satisfactorily. However, high pH ozonation could be a suitable technology provided the rate of ozone decomposition into hydroxyl radicals outweighs the increasingly poor solubility of ozone at higher temperatures. Bench scale ozonation tests have indicated that a 85% reduction in odour content of condensate could be achieved at a temperature of 40°C to 60°C, pH of 10 and ozonation dosage of 0.31g/L for 30 minutes. Changes in concentrations of selected odorous organics (aldehydes and ketones) present in condensate were observed, with significant reductions in concentrations obtained for some organics and increases in concentrations obtained for others, presumably due to their formation from oxidation of higher molecular weight organics. A decrease in pH from a desired 10.0 to 7.0 was observed after 30 minutes ozonation which suggested oxidation of organics had occurred to form organic acids. This change in pH would have reduced the efficiency of ozonation since the yield of hydroxyl radicals at the lower pH is significantly reduced. pH control was required to maintain high a yield of hydroxyl radicals during the dosing period.

The findings from this study suggest ozonation has significant potential to be an effective process for reduction in the odour associated with evaporation of condensates that could contribute to further reductions in fugitive odour emissions from alumina refineries.