Example of direct cyanidation of arsenic-containing and carbon-refractory ore

Utah Meck stay (Mecrur) gold mine was founded in 1890, the original use of cyanide leaching of gold, the government ordered the closure of the Second World War. Due to the rise in gold prices, it was decided in 1981 to rebuild mines and plant selection. The gold deposit symbiotic minerals are mainly pyrite, orpiment, realgar and carbon. In order to ascertain the carbonation cyanide performance of the ore, more than 2,200 samples of ore were collected according to the density of the borehole, and the bottle cyanidation test was carried out separately, and the gold leaching rate was lower than 60% as the boundary of the refractory ore. Difficult leaching ore accounts for about 17% of total reserves.

Since the ore is a refractory ore containing carbon, arsenic and calcite , it has been subjected to flotation, roasting and various chemical oxidation and pressure oxidation treatment tests. Among them, the activated carbon pressure oxidation method and roasting method are most effective. The investment in the treatment of all ore by the addition of activated carbon pressure oxidation is large; if cyanidation after roasting, the recovery rate of gold is as high as 90%, but the environmental protection investment is quite high. To this end, the carbon slurry process for the direct cyanidation of ore by activated carbon in stages was studied in detail. The results show that 8-stage leaching is carried out with NaCN 0.45kg/m ³ (t ore consumption of NaCN 1.8～2.3kg), and each section of ore plus activated carbon is not more than 10g, and a small Impeller with a low shear rate is used to reduce carbon. The wear rate of gold is about 80%. According to this process, the refractory ore reserves re-enlined with a gold recovery rate of less than 60% account for only 8% of the total ore reserves.

The use of a stepwise addition of activated carbon to directly cyanide the ore also accelerates the turnover of charcoal and gold in the system and maintains a low level of gold in the lean liquid used. Although this method is 4.5% lower than the recovery rate of activated carbon pressurized oxidation gold, the investment is saved by 25% and the production cost is reduced by 16.3%.

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