Acid leaching-precipitation-flotation process

This method is applied in our country is still not widespread, mainly due to the nature of copper oxide ore mine in our country with the most suitable for acid leaching, but in individual mines or mine, there is still the possibility of this method should be. Some mines have been tested and have achieved certain results. This method has been successfully applied in many foreign countries, such as the US Butte acid leaching plant, Zimbabwe Mangula heap leaching plant.
I. Butte acid leaching plant (USA)
Butte (Butte) processing plant put into operation in 1964, initially with gold ore, 330 million tons of ore has been mined, as well as the current reserves of 300 million tons. The ore produced around the parent rock and the fault contains copper sulfate, and the average content is 0.18% Cu. An acid leaching-precipitation-flotation workshop was established for the recovery of this part of copper. The process flow is shown in Figure 1.

Figure 1 US Butte acid leaching - sedimentation - flotation process
The ore coming out of the mine bin enters a drum type squeezing machine lined with an acid-resistant material, and the fine mud and oxide in the gangue become dispersed due to the friction pulverization of the mill. About 1.5 kg/ton of sulfuric acid was added to the grinder to make pH=2. In the process of grinding, 70% of the copper oxide is transferred into the solution, and the concentration of copper ions in the solution reaches 1.1 g/L. After the de-grinding, the ore is further subjected to two-stage grinding and flotation with double xanthate; copper sponge iron precipitation stream; then dixanthogen, pine oil, and an alcohol frother flotation of copper precipitation. Sponge iron is recycled and recycled by magnetic separation. The final concentrate grade of the ore portion is 15% Cu. In addition to the double xanthate, a small amount of mercaptan, foaming agent and lime milk were added to the flotation.
In the rough selection of precipitated copper, 14 g/ton of double xanthate and 90 g/ton of foaming agent (50% pine oil and 50% alcohol) were added, and a certain amount of collector was added to the sweeping operation. An acid plant and a sponge iron plant were established near the plant. Sulfuric acid is prepared from sulfur dioxide produced by roasting of chalcopyrite concentrate, and sponge iron is processed by burning slag produced by pyrite roasting.
2. Mangula Heap Leaching Plant (Zimbabwe)
Mangula is one of the large mines in Zimbabwe. The bed is covered by dolomite sandstone , feldspar schist and chlorite. The surface is more than 24 meters oxidized ore, and the following is sulfide ore. Copper oxide minerals include malachite, chrysocolla, pseudo malachite, azurite, and occasionally a small amount of blue- phosphorus copper ore and copper. Copper sulphide minerals are porphyrite, chalcopyrite and a small amount of chalcopyrite. Metal minerals include pyrite, magnetite, mirror iron or molybdenite . All metal minerals are fine-grained inlays. Important positive gangue minerals feldspar, quartz, calcite, sericite, chlorite and minor amounts of anhydrite, tourmaline.
In 1957, a sulphuric ore dressing plant with a daily processing capacity of 3,000 tons was built. In 1965, an oxidized ore heap leaching plant with a daily processing capacity of 2,000 tons was built. The heap leaching plant mainly deals with the upper part of the ore body in the open pit mining of copper oxide ore. The ore contains 1.13% copper.
The process and equipment used in the heap leaching plant are shown in Figure 2. The ore heap leaching site is 380 m × 60 m, which is impervious to the ground. The ore can be piled up to 6 m high, with a lateral slope of 4% from the center to the edge and a longitudinal slope of 5%. The heap leaching site is large enough to complete the cycle leaching, washing and ingress and egress. The immersed ore is washed and returned to the packing for underground mining. The leaching operation consumes 3.5~4 kg/kg of copper and the iron consumption is 1.5 kg/kg of copper. In order to prevent the corrosion of sulfuric acid, the relevant equipment is lined with epoxy asphalt coating or rubber and stainless steel.

Figure 2 Mangula heap leaching process

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