Harmony is a signatory to the International Cyanide Management Code for the Manufacture, Transport and Use of Cyanide in the Production of Gold (Cyanide Code). All of our major gold mining operations and most of our metallurgical plants have been certified compliant with the Cyanide Code. Successful recertification audits were conducted at the Joel, Target, Doornkop, Harmony One and Central plants in FY17 – and all plants were recommended for recertification.
Kalgold: The cyanide detox plant was commissioned in July 2015 when the Kalgold plant began to deposit tailings into the D-Zone open pit as part of Kalgold’s open pit closure strategy. The cyanide detox plant will reduce cyanide concentrations in the tailings to acceptable levels. Cyanide concentration levels are monitored at the detox plant, along the tailings and return water pipeline route and at the point of discharge into the pit.
Phoenix retreatment operation (Saaiplaas plant): The plant’s process does not allow for decreases in cyanide dosages as this results in reduced gold recovery and we are therefore unable to reduce the weak acid dissociable concentration of cyanide leaving the plant.
Hidden Valley: Delays in the recertification audit field work and a planned extended mill shutdown for maintenance work, led to Hidden Valley’s cyanide code compliance audit being temporarily postponed. Re-certification procedures have been rescheduled to begin in the third quarter of FY18, once operations have been resumed following the plant shutdown.
Harmony used 21 000t of cyanide during FY17 (FY16: 18 000t). The increase in cyanide consumption was largely due to the greater volume of tonnes treated in FY17 – 19.4Mt compared to 18.1Mt in FY16.
The corresponding intensity usage is 1.08t cyanide/tonne treated for FY17 (FY16: 0.97t cyanide/tonne treated).