Experimental Study on Beneficiation of a Low Grade Primary Gold Ore

A primary gold mine ore grade of 2.86g / t, ore industry type quartz vein type gold ore. The main valuable element that can be recycled is gold. System identified by the rock, heavy sand identification, physical image of chemical analysis, X-diffraction analysis, spectral analysis and other means, a metal sulfide ores found mainly pyrite, followed by a small amount of yellow copper ore, galena, sphalerite ore, chalcocite, blue chalcocite, covellite and a small amount of molybdenite and the like; a metal oxide mainly hematite, limonite, magnetite, goethite, iron titanium; gangue minerals There are quartz, feldspar , mica , hornblende, kaolin and so on. The embedding of natural gold in the ore is mainly intergranular gold, inclusion gold and fracture gold. Most of the natural gold in the ore is continually or occasionally associated with galena and pyrite, and is embedded in fine or fine veins between galena and gangue, pyrite and gangue and gangue mineral particles. A considerable part is small and granular, grainy, wrapped in pyrite and gangue minerals; some gold is embedded in the cracks or micro-cracks of minerals, and the form of fissure gold is controlled by fissures and is irregularly granular. A small amount is encapsulated in gangue (mainly quartz, feldspar, mica), which is difficult to dissociate and recover in the process of grinding and beneficiation . This primary gold mine should not be used in a direct leaching process and requires flotation to obtain a higher grade gold concentrate and optimum recovery.

First, the nature of the ore

The results of multi-element chemical analysis of raw ore are shown in Table 1. According to the results of microscopy, thin film identification and electron probe and XRD test, the gangue minerals are mainly composed of quartz, feldspar and mica minerals, followed by a small amount of chlorite, amphibole and tremolite. , a very small amount of epidote, zoisite, carbon, zircon . Gold is mainly produced in the form of natural gold. The main carrier mineral of gold is pyrite, followed by galena. The natural gold in the ore is produced by intergranular gold and fissure gold, and secondly by sulfide-coated gold.

Table 1 Results of multi-element chemical analysis of ore

*Au is in g/t.

Second, the test plan

The study on the composition of the ore dressing sample shows that the main metal sulfides in the sample are pyrite, galena, sphalerite and chalcopyrite. The size of the gold inlay is not uniform, but mainly fine-grained gold. Gold is closely related to metal sulfides. For this type of ore, it is suitable to use a flotation process to concentrate the gold in the gold concentrate and then further process it. In this paper, the main factors affecting gold flotation are studied: grinding fineness, flotation concentration, pulp pH value, collector type and dosage, and laboratory closed-circuit process test.

Third, the beneficiation test

(1) Grinding fineness test

The study of ore properties shows that the symbiotic relationship between gold-bearing minerals and gangue minerals is relatively close, so the grinding must reach a certain level in order to dissociate the useful mineral monomers. Grinding fineness test and conditions (grinding fineness is a variable) are shown in Figure 1, and the test results are shown in Figure 2.

Figure 1 Grinding fineness test procedure

Figure 2 Grinding fineness test results

It can be seen from the results of the grinding fineness test that the fineness and too fineness of the ore grinding are not ideal for the flotation index. According to the observation of flotation phenomenon and the change of crude concentrate grade and recovery rate, when the grinding fineness is -200 mesh content of 65%, the gold concentrate grade and recovery rate are both high, so the grinding fineness is adopted. More reasonable.

(2) Pulp pH test

The pH of the pulp is one of the main factors affecting the flotation effect. In this experiment, sodium carbonate was used to adjust the pH value of the slurry, and the effect of pH values ​​of different pulps on flotation was investigated. The test procedure and some conditions are shown in Figure 1 (the amount of sodium carbonate is a variable), and the test results are shown in Figure 3.

Figure 3 slurry pH test results

The results in Figure 3 show that the crude concentrate has a grade of 22.87 g/t and a recovery of 93.25% at a pulp pH of 8.5 (the amount of sodium carbonate is 1500 g/t). The pH value of the slurry, from the surface phenomenon, affects the collector's capture of useful minerals, but essentially affects the electrode potential of the mineral surface, thereby regulating the effective effect of the collector. Considering comprehensively, it is best to add 1500g/t sodium carbonate and adjust the pH value of the slurry to 8.5.

(3) Flotation concentration test

Flotation concentration is one of the important factors affecting the flotation index. Too large or too small is not good for flotation. The test procedure and selection conditions are shown in Figure 1 (concentration is a variable), and the test results are shown in Figure 4.

Figure 4 Results of rough selection flotation concentration test

The yield of gold concentrate is 22. 7g / t, and the recovery rate of gold is 92.58% when the concentration of the flotation is 31%. Therefore, the appropriate rough selection concentration for this test was determined to be 31%.

(4) Test of type and dosage of collector

The flotation effect of butyl xanthate, Y89, amyl xanthate, butyl xanthate + butylamine black drug was investigated under the condition of 60g/t of collector. The experimental procedure and some conditions are shown in Figure 1. (Collector type variable), the test results are shown in Table 2.

Table 2 Test results of collector types

The test results show that the single use of the conventional sulfide ore collector butyl xanthate, after the rough selection, the gold grade can reach 22.2g / t, the gold recovery rate of 88.21%. Therefore, in order to simplify the pharmaceutical system and save costs, this study selected a single butyl xanthate as a collector, and at the same time, under different dosages, according to the flow and conditions shown in Figure 1 (the collector is a variable), The test results are shown in Figure 5.

Figure 5 Collector dosage test results

Under the optimal pharmaceutical system conditions, a rough selection, three selections, and two sweeping laboratory closed-circuit tests were conducted. The test procedure is shown in Figure 6. The test results are shown in Table 3.

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