Monitoring and minimisation of HCN(g) emissions from a gold plant

Hydrogen cyanide (HCN(g)) which is emitted from all gold processing operations as part of the normal circuit operation creates a potential occupational, health and safety issue for employees working in the vicinity. An investigation of the hydrogen cyanide detectors based on electrochemical sensors has shown that they are reliable for monitoring ambient HCN(g) concentrations above leach tanks. Strategies to reduce HCN(g) emissions were also investigated and trialled at an operating gold mine with floating barriers being developed that could withstand the aggressive process conditions. These barriers successfully lowered the ambient HCN(g) concentration above a CIL tank by 68%. This enabled the client to run a lower circuit pH whilst maintaining low HCN(g) concentrations above the circuit, potentially saving significant costs through reduced lime and cyanide consumption.