Hao Ke Ruici northwestern Nevada gold mine ore mix of quartz and clay, gold grade greater than 0.5g / t. The mine uses the heap leaching method to process 1 million tons of ore and produce 1.71 tons of gold.
The mine is open-pit mining with a stripping ratio of 1:1.1. The ore was crushed to -38 mm in two stages, and a small NaCN solution was sprayed into a drum of 3 m in a crucible, and was continuously sent to a heap immersion field by a belt conveyor.
After the yard is flattened, a layer of plastic plate is laid, and a layer of thick -0.3 m is covered to remove the ore of the lump ore to protect the plastic plate. The built mine has a length of 600m, a width of 360m and a height of no more than 7.5m.
The normal leaching time of a heap is 60d. Since the heap leaching is carried out in the open air, the operation should be stopped in the winter. This intermittent leaching sometimes extends the leaching time of one ore heap to one year or longer, which depends on the leaching recovery rate of gold in the ore. If the heap is 250,000 tons of ore, the dilute NaCN solution used for heap leaching must be guaranteed to be not less than 2.27 m 3 (600 US·gal) per minute for leaching operations to proceed normally.
The precious liquid (about 600 gal) flowing out of the heap was continuously passed through 4 carbon columns connected in series. Each column is packed with coconut shell activated carbon 2t, which can absorb about 9.33kg of gold. The desorption of gold-loaded carbon is carried out by high-temperature desorption of NaOH plus ethanol, and the desorption process takes 24 hours. The desorbed precious liquid is extracted by steel cathode electrolysis, and the molten gold ingot with a purity of 95% is obtained by fire method, and then purified into a pure gold ingot containing 99.99% of gold.
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