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Comprehensive recovery of gold and valuable metals from tailings
Recently our gold mines, tailings gold grade manufacturers in 0. 5g / t more than the number of them, especially those old mines in the early development of gold, due to technical immaturity, backward production technology, tailings gold grade more High, some even as high as 4g / t or more, while the tailings also contain a certain amount of other valuable metals. For these tailings, a suitable process can be used to recover gold and comprehensively recover a part of valuable metals. This not only makes full use of mineral resources, but also obtains good economic benefits.
A gold mine in southern China, since 1955, has more than stockpiling tailings 350,000 t, where the average grade of gold, antimony, tungsten were 4.2g / t, 0.8%, 0.18 %, metal reserves were 1.473t, 2517t 569t. According to the nature of the old tailings, a series of experimental studies by the Changchun Gold Research Institute have shown that flotation and recovery of some of the gold in the old tailings should be carried out by flotation, and the flotation tailings should be cyanated and leached to recover gold. Since most of the plutonium in the old tailings has been oxidized, the recovery rate is not high when the flotation is recovered, and the remaining plutonium still affects the cyanidation leaching. The institute uses a kind of MNP oxidant to oxidize and pre-cyanide the flotation tailings, and then obtain good results. Finally, the cyanide tailings are reused for flotation to recover tungsten. The recovery rates of gold, antimony and tungsten reached 81.18%, 20.17% and 61.00%, respectively. According to the production scale of 100t/d, only the calculation of gold can generate an annual output value of 11.46 million yuan. After deducting the cost, at least a profit of 5.88 million yuan can be obtained every year. If you add the output value of tantalum and tungsten, the profit will increase.
Lingbao County is the second largest gold production county in China. According to the data, many mines use amalgamation -flotation process. The average grade of tailings discharged per year is about 1.2g/t. The ore in this area is mainly composed of yellow iron. For the type of mine, gold is unevenly embedded in medium and fine grains, and natural gold accounts for 60.11% of the total gold. After Guangzhou Nonferrous Metal Research Institute of the three kinds of research process tailings area has been the recovery of gold were found in the residual gold tailings mainly pyrite with students, and some finely ground mineral processing plant because of the thick, golden load Iron ore does not dissociate from the monomer, thus affecting the recovery of gold.
A tailings (average grade 0.74g/t) which has been dissociated from most of the gold-bearing iron ore, using hydraulic classification, +74μm product is treated by spiral-shaker re-election process, -74μm product is flotation Processed, 49.05% gold can be recovered.
The B tailings and C tailings, which are not sufficiently dissociated by the gold-bearing iron ore, are treated by regrind and re-election. Among them, the B tailings (average grade 0.99g/t) were first hydrodynamically graded, and the +74μm part was re-milled, and the same -74μm part was combined, and the gold was recovered by flotation. The gold concentrate grade was 30.47g/t, and the recovery rate was 43.51%. The C tailings (average grade 1.40g/t) are firstly selected by flotation, then the coarse concentrate is reground, and after grinding, the concentrate is obtained with a grade of 35.90g/t. The recovery rate was 46.27%. If the crude concentrate was re-milled and then recovered by cyanide leaching, the gold leaching rate was 50.82%.
Shandong Sanshandao Gold Mine is currently the largest gold mine manufacturer in China. The tailings of the plant is sold as a by-product sulfur concentrate to the acid plant, with an annual output of 28,300 tons of tailings (sulfur concentrate), which was included in the tailings. Lead 7% to 10%, so that the acid plant has a burning phenomenon, resulting in poor sales and backlog of tailings. Experimental studies have found that cyanide contained in tailings inhibits sulphide of various non-ferrous metals, but it does not effectively inhibit galena. Therefore, the cyanide form contained in the tailings is fully utilized, and the necessary inhibitors (such as ZnSO 4 ) are added to enhance the inhibition, and the lead is separated from the tailings by a flotation process. According to the production practice, due to the implementation of the flotation process, more than 2,100 tons of lead can be produced each year, and the output value is more than 3 million yuan. It also solves the problem of sales of sulfur concentrate, and also recovers some gold and silver .
There are dozens of mercury-mixed mills recovering gold along the Dadu River in Kangding, Sichuan. The gold in the tailings after amalgamation is generally 3~5g/t, and some are as high as l0g/t. In the past, most of these tailings were discharged into the Dadu River, which caused waste of resources on the one hand and mercury in the tailings on the other hand. Since 1993, 60% to 90% of gold in tailings can be recovered by cyanidation, which is very effective. The cyanide tailings are treated and then stored in a concentrated manner to reduce environmental pollution.
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