Methods and Equipment for Breaking Down Gold-Containing Concentrates from Lean Ores and Mining Industry Waste

Exhaustion of rich or readily enriched precious metal ores leads to involvement in operation of stubborn ores from which effective extraction of precious metals by traditional methods is impossible. Within stubborn ores, a considerable part of gold is finely associated with sulphide minerals, generally with arsenopyrite and pyrite, and remains inaccessible for leaching even with fi ne comminution. Presence of an active carbonaceous agent occluding cyanide complexes of gold from solutions is another reason for stubbornness of gold-bearing ores. The joint negative effect of both factors on enrichment gives rise to doubly stubborn ores. A reduction in gold extraction indicators during hydrometallurgical processing for ores and concentrates with sorption and active organic carbon is overcome in most cases by using ion-exchange resins and activated carbon, whereas recovery of gold bonded in sulfides requires breakdown of the mineral crystal lattice. For this purpose, oxidizing roasting, and autoclave or bacterial oxidation of sulfides in a pulp are usually applied. The last two methods are now the most widespread. At the same time, roasting gold ores and concentrates is applied at a number of the overseas enterprises. This shows that hightemperature processes remain the main methods for preparing gold-bearing ores and concentrates for leaching. On the basis of results of calculations, research, and design and engineering development, and industrial tests the authors conclude that it is possible to increase extraction of gold and silver in products from the Mai and Badran fields after pyrolysis in a rotary drum furnace. Compared with oxidizing roasting environmental protection issues are resolved. Procedures and production equipment schemes are developed.