COMPARISON OF THE MMS CN-D~(TM) CYANIDE DESTRUCTION PROCESS WITH CARO'S ACID, SMBS/AIR AND HYDROGEN PEROXIDE OPTIONS

摘要

Modern gold plants are under increasing pressure to adopt world-class cyanide management practices due to escalating environmental pressures, particularly for signatories to the International Cyanide Management Code. Operations are lowering the levels of weak-acid dissociable (WAD) cyanide reporting to spigot discharge and to any eventual discharges from the tailings storage facility (TSF). Gold operations are increasingly adopting the inclusion of cyanide oxidation processes into their circuits, particularly for greenfields projects. These processes predominantly use sodium metabisulfite (SMBS, or SO_2) with air, Caro's acid (H_2SO_5), or hydrogen peroxide (H_2O_2).Maelgwyn Mineral Services (MMS) has developed the MMS CN-D~(TM) process, which utilizes the Aachen Reactor~(TM), a high-energy mass-transfer superoxygenation system, in conjunction with an activated carbon-based catalyst, to increase the rate of cyanide oxidation to cyanate, the thermody-namically more stable form. These four processes are compared with respect to stoichiometric reagent costs, chemical reaction efficiencies and risks, as well as logistical, operability, safety and environmental issues, for both remote sites and those close to urban areas. Considerable potential upside benefit is demonstrated for MMS CN-D~(TM) compared with the alternative cyanide destruction processes. Additional potential features of the MMS CN-D~(TM) process are also considered, such as the potential to recover additional gold otherwise lost to tailings, to de-risk implementation and lower capital costs via staged integration of Aachen Reactors~(TM) into existing oxygenation and SO_2/Air equipment and to modify existing plant tankage in CIL trains to become part of the MMS CN-D~(TM) cyanide destruction plant component. P^169