Abstract
The SO2/Air cyanide destruction process is the most common method used to destroy cyanide in the gold extraction sector globally. It was developed in an era when typical requirements were based on relatively steady concentrations of 150 to 200 mg/L of weak acid dissociable cyanide (WAD CN-) in the feed and a discharge limit of less than 50 mg/L. However, as industry develops more metallurgically complex deposits and environmental regulations become more stringent, the demands and performance expectations for cyanide destruction have changed. Feeds to the SO2/Air in some cases have increased to more than 650 mg/L of WAD CN- that are subject to large variations depending on the mill feed while discharge limits are well below 1 mg/L are not uncommon. Adding further complexity is that more often than ever, solutions contain elevated levels of thiosalts and/or thiocyanate (SCN-) which can interfere with cyanide destruction and other constituents that can affect either the ability to recycle process water or the overall site environmental compliance. Additionally, the industry is embracing reductions in carbon footprint and pursuing increases in resiliency. This paper will look at the future of the SO2/Air process, from its interconnection between metallurgical and environmental issues to changes in design and operations strategies that will be needed to meet the requirements of modern gold extraction projects.