Hunan Longwangshan gold ore iron cap muddy oxidized ore. The ore is deeply oxidized, its appearance is honeycomb structure, and the pores are developed. Natural gold mainly exists in limonite, and the gold content is 2.43~2.7g∕t. After the coarse crushing of the ore, the argillaceous ore of -1mm size accounts for about 40%. Once using flotation treatment, the gold recovery rate is only about 25%. With the direct heap leaching- zinc replacement process after crushing, the recovery rate of gold is only between 40% and 50%. After switching to powder ore granulation heap leaching, the recovery rate of gold is more than 75%, and the consumption of NaCN is also reduced from 1.5kg ∕t to 0.59kg ∕t.
Although the mine has more than 10,000 tons of mines, it is built using mobile belt conveyors and is not subject to crushing by heavy-duty vehicles. Therefore, after the yard is compacted with a bulldozer, the fine soil is filled with fine soil and sprinkled with water. After the inspection site is flat and no broken stone roots emerge, the oil blanket is covered with two layers and a 50 μm plastic film is covered. A 50 mm thick pebble layer was placed on the film. A 400mm×300mm rainwater embankment is built on the outside of the site, and a 350mm×200mm liquid collection ditch is opened at the lower edge.
The ore entering the original mine bin is -200mm, and the 250mm×400mm jaw crusher is automatically fed from the mine bin. After crushing, it is sieved by vibrating screen. The +10mm sieve upper ore is sent to the yard by the belt conveyor. The mine is fed by a belt conveyor into a φ2800mm disc ball machine with cement (11kg∕t), lime (11.7kg∕t) and sprayed with 0.1% NaCN liquid. Due to the high mud content of the powder ore, in addition to the increase in the amount of cement and lime added, it is necessary to increase the amount of water. The inclination angle of the disc granulator is 48°, and the powder ore is rolled on the disc for about 6 minutes to make 12% of water. The pellets of ～15% and φ10～20mm roll onto the belt conveyor, and are sent to the quarry via the moving belt conveyor to be naturally mixed with the lump ore and solidified. The wet pellet strength is 94.7%, the angle of repose is 38°~42°, and the curing time is 24h.
The pile height is about 3.5m. After leveling, a layer of 5~10mm lump with a thickness of 100mm is laid on the surface of the pile to prevent surface slab formation and reduce channeling and segregation. The spray is first sprayed with lime water containing 0.005% to 0.01% of CaO to the pH of the discharge liquid 10-11, and then sprayed with NaCN and CaO liquid. The concentration of NaCN is 0.08%-0.12% in the early stage, 0.05%-0.08% in the middle stage, and 0.03%-0.05% in the later stage. The top of the heap is sprayed with a nozzle, and the four surrounding slopes are sprayed with a φ25mm plastic tube to ensure uniform coverage of the immersion liquid. In order to improve the oxygen supply conditions in the ore heap, the bamboo snorkel is also buried in the mine at a certain interval, and intermittent leaching is adopted, that is, the spray is stopped for 1 hour for 1 hour, and the spray strength is 45-52 L/(d·t). . The leaching period is 30 to 45 days.
The adsorption of gold in the leaching solution is carried out in series using five φ500mm×2000mm adsorption towers, each packed with activated carbon 100kg. The precious liquid contains about 4g∕m 3 of gold and is supplied to the tower at a linear velocity of 25m 3 /h. The adsorption recovery rate of gold is 98%, and the tail liquid returns to the leaching process. The industrial saturated capacity of gold-loaded carbon is controlled at about 10kg/t, and the desorption is carried out by using NaCN 4% to 5%. The 3% solution of NaOH is desorbed at a temperature of 98 ° C for 4 to 5 hours, and then washed with a 1 m 3 washing solution for 8 to 10 hours. The gold-free charcoal contains 100-300 g of gold, and is returned to the adsorption process after pickling. The electrolysis of the desorbed liquid is carried out by using a steel wool cathode and a stainless steel anode, and electrolyzing to a poor liquid containing 1 to 5 g ∕m 3 at a tank voltage of 3.5 V and a current intensity of 120 to 140 A. The gold mud is sent to the fire method for melting.
After the heap leaching was terminated, the heap was washed with clean water for 2 days, drained for 3 days, and then the bleaching powder was sprinkled on the heap by 2 kg ∕t ore. After standing for 3 days, the pile was folded with a bulldozer.
In the whole process, the leaching rate of gold is more than 75%, and the total recovery rate is 63% to 70%. According to the production cost of the workshop (excluding the production cost of raw ore), in 1991, it handled 37,800 tons of raw ore, workshop cost was 948,900 yuan, and gross profit was 1,577.9 thousand yuan. In 1992, it handled 37,100 tons of raw ore, the workshop cost was 855,300 yuan, and the gross profit was 1.38 million yuan.
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