The tailings accumulated in many mines over the years contain a certain amount of copper with recovery value. Moreover, the copper in the flotation tailings is mostly in oxidized minerals. Many mines are already using these resources. Below are the tailings dip of the two companies. Take the actual situation.
I. Miami Copper Company
Miami, Arizona, has accumulated approximately 34.5 million tons of tailings since its mining in 1911. Early tailings contained up to 0.723% copper and 0.114% in the late stage. Approximately 50% is less than 28 μm (560 mesh), but there are also many large ore inclusions in it. The tailings are actually slurried, containing about 80% solids, and the liquid has a pH of 4.5 and already contains a certain amount of copper. They drilled 147 holes in the tailings accumulation area, sampled and analyzed, and used the data to establish a mathematical model that included particle size, total copper content, copper oxide content and bulk density of the entire tailings dam. It can be used to estimate the total tonnage, grade and particle size distribution of copper. On this basis, a small pilot plant was established. After years of testing, it was finally decided to establish a production plant in 1987.
They used two hydraulic jet pumps with a pressure of 15.8 MPa to mine 453 tons per hour. The slurry contained 32.4% solids and sieved the nuggets larger than 1.6 mm through a sieve. The slurry enters a stirred tank, is acid adjusted to pH = 1.5, stays for only a few minutes, and then enters a thickener with a diameter of 100 m to continue the leaching. The overflow enters a clarifier at a rate of 190 L/s. After the flocculant is clarified, the supernatant contains 0.6-1 g/L of copper and is sent to the extraction. The bottom stream plus the raffinate was repulped, and then entered into a second small thickener with a diameter of 50 m for two-stage leaching. The secondary leaching leachate is used in conjunction with other solutions for hydraulic mining. The total leaching rate was 54% and the acid consumption was about 5 t/t (Cu). After the bottom stream is slurryed, it is sent to an open pit of 7.3 km through a polyethylene pipe at a speed of 2 m/s. After settling, the water is returned to use. The surrounding rock of this pit is very dense and below the groundwater level, and it is planned to stop at the groundwater level.
Second, Enchangjia United Copper Company
The most famous use of tailings is the Zambian Enchangjia United Copper Company (NMCC), which used the tailings to build a leaching-extraction plant with an annual output of 70,000 tons of copper (now 82,000 t/a). ). 45000t tailings treatment every day, half of the new tailings beneficiation plant, half of the accumulation of old tailings. The tailings contain an average of 0.86% soluble copper, and the particle size is 55% less than 75 μm, mainly malachite. The leaching equipment is 15 (formerly 6) air agitation tanks with a diameter of 10.6 m and a height of 18 m and seven thickeners of ф 76 m × 3 m. The leaching solution has a flow rate of 50 m 3 /min and a solid content of 35% to 50%. The residence time in the leaching tank was 2 h and 8 h in the thickener. The leach solution contains about 5 g/L of copper and <0.5 g/L of sulfuric acid. The raffinate copper is 1g/L, and the acid is added to 12-14g/L, which can be used as a leach solution. The total copper recovery is 63% and the acid consumption is about 3t/t (Cu). The Anamax Twin Butts of the American Alamars Company uses a mechanical agitation tank with a 50% slurry concentration when leaching.
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