Gold recovery from high-arsenic-containing ores at Newmont´s roasters

The Newmont roasting plant in Carlin, Nevada, which began operations in 1994, has continuously processed refractory ores and pyrite concentrates. This study aimed to assess the influence of roasting temperature on gold recovery through cyanidation, based on historical performance data. A series of experiments were conducted to monitor gold recovery as a function of roaster temperature, originally set at 550°C, which indicated an increase of over six percent in recovery rates when temperatures were lowered to approximately 500°C. This improvement was attributed to a significant increase in the surface area of the calcine produced. The operation of an intelligent process control system contributed to maintaining these optimal low temperatures, achieving gold recoveries consistently between 92 to 93 percent. However, a series of campaigns involving high-arsenic ores revealed a noticeable reduction in gold recovery due to loss of calcine porosity as arsenic content increased. This work highlights the critical relationship between roasting conditions and gold extraction efficiency, particularly in the context of processing challenging high-arsenic feed materials.