Experimental Study on Mineral Processing Technology of Gold Deposits in Yunnan Province

I. Introduction

Northwest Yunnan original gold ore is used in all slime cyanidation heap leaching process for extracting gold and, since the mine contains iron, lead, zinc, arsenic, and sulfur and other elements, and other mineral fine refractory gold complex ^[1], resulting in the leaching The effect is poor. And cyanide is a highly toxic chemical, and the leaching process has a bad impact on the local environment. In order to solve the environmental pollution problem caused by the gold extraction method in the region, gold is used in the region to enrich the gold with the Canadian Falcon centrifugal concentrator . The original ore contains 7.7g/t of gold and the gold concentrate contains up to 514.03g/ t, tailings containing gold 0.36g / t, gold recovery rate of 95.4%, obtained satisfactory test indicators, for the next industrial application of non-cyanide selection process to deal with gold mines in the region.

Second, the nature of the ore

The test ore samples were taken to various mining sites within the mine area and then mixed into test ore samples. The overall sample gold grade was 7.7 g/t.

(1) Main mineral characteristics

The metal minerals in the ore include brown (erythr) iron ore, magnetite, siderite, lead iron ore, smithsonite, hydrozinc ore, willemite, heteropolar ore, a small amount of leucite, galena, yellow Iron ore, natural gold, silver and gold, and natural silver. The gangue minerals are mainly calcite , dolomite, quartz and clay minerals.

(II) Multi-element analysis of raw ore

The results of multi-element analysis of raw ore are shown in Table 1.

Table 1 Multi-element analysis results of raw ore

(3) Mineral characteristics and occurrence status of gold

1. Form and embedding characteristics of gold

The gold phase analysis results in the ore are shown in Table 2. The gold in the ore is mainly in the form of natural gold.

Table 2 Results of phase analysis of ore gold

Natural gold is golden yellow or yellow with white hue, the reflection color is bright yellow, the surface has pitting (iron oxide film), homogeneity, ductility, various forms, mainly irregular granular or nuclear crystal Second, there are filaments, rods, branches, etc. ^[2] . The particle size analysis of gold in the ore indicates that the natural gold particle size of the ore is fine, the maximum particle size is 0.15mm, generally 0.01-0.06mm, mainly medium-fine grain gold, and there is still <0.01mm particle gold.

2. The embedding characteristics of natural gold

The embedding characteristics of gold were obtained by heavy sand separation and microscopic observation (see Table 3). It can be seen from the table that the natural gold is mainly medium-fine grain visible gold, embedded in the mineral particles and fissures such as limonite, maghemite, lead iron ore, pyrite (artifact), quartz, etc. Intergranular gold and fissure gold, followed by particulate gold, are mainly embedded in micro-particles or wrapped in limonite and magnetite aggregates with a particle size of <0.01 mm.

Table 3 Embedding characteristics of ore gold

3. The state of occurrence of gold

The occurrence status of gold is shown in Table 4. Gold is mainly produced in limonite, magnetite and pyrite, accounting for 79,169% of the total. This indicates that gold is closely related to the above minerals. These minerals are the main carrier minerals of gold. The gold content in lead and zinc minerals accounts for 20.32%, which is the secondary carrier of gold, and the content of Au in gangue minerals is less.

Table 4 Distribution of gold content and gold in various minerals in ore

Third, the beneficiation test

(1) Re-election test

The gold in the ore is mainly in the form of natural gold, and the natural gold density is large and can be recovered by re-election. However, the ore identification results show that natural gold exists in the state of fine particles, and the conventional re-election effect is not good. The re-election process of fine-grained minerals can be strengthened by the centrifugal force field. We used the Canadian Falcon centrifugal concentrator to re-elect the ore. The Falcon centrifugal concentrator is simple in design and can generate centrifugal acceleration with a gravity acceleration of 150-300 times. The price is low, the operation is simple, the maintenance and maintenance cost is low, there is no environmental pollution, the production cost is low, and the application is wide. It can handle Au, Ag, Sn. , W, Ta, Pt, Pd, Nb and other precious metals. The fineness of the equipment sorting material is determined by the gravity of up to 150-300G, which can effectively recover -011mm grade useful minerals. After the ore sample was ground to 80%-0.074mm, a rough selection and a selection were performed using a Falcon centrifugal concentrator. The test procedure is shown in Figure 1. The test results are shown in Table 5. It can be seen from the data in the table that the Falcon centrifugal concentrator selects the gold mine to have a large enrichment ratio and the gold recovery rate is high.

Figure 1 re-election test process

Table 5 Re-election test results

The second re-election test ore grinding fineness is still 80%. The second re-election test ore grinding fineness is still 80%-0.074mm, the beneficiation process is two rough selection, one selection, selected tailings Returns rough selection 1. The flow chart is shown in Figure 2, and the test results are shown in Table 6.

Figure 2 Re-election closed-circuit test flow chart

Table 6 Re-election closed-circuit test results

(2) Cyanide stirring leaching test

In the laboratory, the ore is ground to 75% to 90% to 0.074 mm, and then subjected to cyanide leaching by a stirring leaching method. The leaching time was 48 h, and the leaching results are shown in Table 7.

Table 7 Stirring cyanide leaching test results

It can be seen from Table 7 that the cyanide leaching effect is poor. When the grinding fineness is 80%-90%-0.074mm, the leaching rate of gold is basically the same. The main reason is the ore itself. On the one hand, natural gold is difficult. Cyanide leaching, on the other hand, most of the gold is wrapped by other minerals ^[3] , which is not conducive to leaching.

Fourth, the conclusion

The comparison of the Falcon centrifugal concentrator re-election test and the cyanide agitation leaching test results show that the re-election process shows a greater advantage regardless of the recovery rate of gold or the environmental impact of production. The selection process is relatively simple, and the production control is convenient. The centrifugal concentrator produced in Canada is expensive and has a large investment, but the production cost is low. The most important thing is to provide production conditions for the realization of non-cyanide sorting in the region, which is beneficial to reduce environmental pollution.

references

[1] Zhang Yijun. The third volume of the ore dressing manual, Volume III [M]. Beijing: Metallurgical Industry Press, 1990, 204.

[2] Zhang Shoufan. Mineralogy [M]. Beijing: The Commercial Press, the first edition of March 1956, Xu Tianyun, Xu Zhengchun. Gold cyanidation and smelting [M]. Shenyang: Shenyang Gold College, 1985 11 month.

Author unit

China University of Geosciences (Zhang Aiping)

Yunnan Vocational College of Land and Resources (Fang Zeming)

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