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

Minerals & Metallurgical Processing , 2010, Vol. 27, No. 2, pp. 60-64

Fernandez, R.R.; Collins, A.; Marczak, E.

ABSTRACT:

The Newmont roasting plant in Carlin, NV, commenced operating in December 1994. Over the years, refractory ores and pyrite concentrates from different gold deposits constituted the feed to the facilities. Historical plant performance indicated that the roasting temperature was the main variable affecting the structural characteristics of the calcine, which in turn affected the recovery of gold by cyanidation. Gold recovery as a function of roaster temperature has been closely monitored since October 2000. The original design temperature was 550° C. Lower roaster temperatures of around 500° C resulted in a gold recovery increase of more than six percent. This increase was directly related to an increase of the surface area of the calcine. The implementation of an “intelligent” process control system helped significantly in achieving steady low roasting temperatures, thus obtaining high gold recoveries of 92 to 93%. Under these conditions, several roasting campaigns with high-arsenic-containing ores were conducted, which resulted in a significant decrease in gold recovery. The reduced gold recovery was caused by the loss of surface area (e.g., porosity) of the calcine as the arsenic content of the roaster feed increased.