Precipitated gold and silver are refined in an induction furnace to produce dore bullion. The crushing plant will operate independently of the mill. In addition, whereas the mill will be primarily run from local start/stop stations, the crusher is designed to be run from its control panel.
The hashing stage is a little more complex for gold ores, as the optimal process flowsheet selection choice is heavily dependent on a good understanding of two fundamental geometallurgical parameters, the gold mineralogical associations, and the gold particle size and liberation characteristics.
Traditional gold processing methods generally use the toxic chemicals cyanide or mercury as reagents to extract gold particles from ore, exposing miners and the environment to toxic waste and gases. In contrast, Clean Mining offers an environmentally sound gold processing technology that uses an inorganic compound, thiosulphate, in the place of toxic chemicals.
A gold processing plant in Song County, Henan Province adopts flotation + cyanide leaching + carbon slurry adsorption process. The final product is gold loaded carbon, and cyanide tailings are directly discharged after pressure filtration.
The Miller process uses gaseous chlorine to extract impurities when gold is at melting point; impurities separate into a layer on the surface of the molten purified gold. The Miller process is rapid and simple, but it produces gold of only about 99.5 percent purity. The Wohlwill process increases purity to about 99.99 percent by electrolysis.