I. Introduction

Wulaga gold mine is mining, dressing and smelting joint production enterprises, east and west open pit mining plant two, there are two beneficiation plants, a flotation beneficiation process - gold concentrate cyanidation - Zinc powder replacement, and the other is carbon Pulp mill.

The total gold recovery rate of the existing process of the flotation plant is only about 75%. In the past ten years, a large number of experimental studies have been carried out on the ore by domestic and foreign research institutes. The results show that the main reason for the low recovery rate of the ore dressing is that the gold has a fine grain size and it is difficult to make the package under mechanical grinding conditions. Solutions of gangue or gold in the pyrite or from exposure. The flotation plant produces about 100 tons of gold concentrate per day, and the gold grade of cyanide tailings is about 7g/t, and the amount of metal lost every year is as high as 200kg. In the past, this part of cyanide tailings was combined with flotation tailings and discharged into the tailings dam. In order to further recover the gold lost in the cyanide tailings, after extensive experimentation and demonstration, it is the most economical and effective method to treat the tailings by pre-concentration, roasting acid and cinder cyanide process. To this end, in February 2003, the relevant technical transformation of the flotation plant was carried out.

Second, the flotation plant process and mineral processing indicators

According to the nature of the ore, in order to achieve better index of flotation, the crushing and grinding operations are strengthened. The three-stage and one-closed process is used for crushing, and the second-stage closed-circuit process is used for grinding. The flotation operation adopts one rough selection, second selection and secondary sweeping. The flotation concentrate is re-grinded and then enters the cyanidation operation. The mineral processing process is shown in Figure 1. The production indicators of the factory are shown in Table 1.

Table 1 Main technical indicators of flotation plant

Third, experimental research

Aiming at the ore nature of the Wulatun gold mine, a large number of experimental research work has been carried out by many research institutes at home and abroad. A comparative test of various sorting methods, a comparative test of a variety of new collectors , and a systematic investigation and small-scale experiment of the whole process of mineral processing were carried out in 2001. The test results show that the ore adopts the conventional beneficiation process, and the technical indicators of mineral processing are not significantly improved. Summarizing the past research results and production practices, we will transfer the research focus to the cyanide tailings for further recovery of gold and comprehensive utilization.

The flotation plant cyanide tailings is about 100t per day, its particle size -325 mesh accounts for more than 90%, the gold grade is about 7g/t, and the sulfur grade is about 20%. The main metal mineral in tailings is pyrite. The content of metal minerals such as copper , lead and zinc is low. Other minerals mainly include mica , quartz and some muddy minerals. In order to further recover gold from the cyanide tailings, a large chute and a suede chute were laid at the end of the tail. Although the grade of the chute concentrate was improved, the recovery rate was very low, the operation recovery rate was <10%, and the economic benefit was not good. Due to the fine size of the tailings, the use of jig sorting is not ideal.

In order to improve the sulfur grade of the cyanide tailings and to reach the acid grade, the hydrocyclone is used for degreasing and enrichment.

The test procedure is shown in Figure 2, and the test results are shown in Table 2.

Table 2 Test results of cyclone desalination

4. Technical renovation project for comprehensive utilization of cyanide tailings

Nearly 30,000 tons of cyanide tailings per year, gold grade 7g / t, sulfur grade 20%, all discharged to the tailings pond for many years, not only economic losses, but also wasted mineral resources. Through various tests and arguments, it is considered that the use of cyclone desulfurization and enrichment, filter press filter press, dry ore to produce acid, and slag return to grinding cyanide system can comprehensively recover gold and sulfur from cyanide tailings. After calcination of the cyanide tailings, the fine gold coated by pyrite is exposed in the formed hematite voids, which is favorable for cyanide leaching. The test results show that the gold leaching rate of cinder cyanide operation can reach about 65%, which can achieve the purpose of comprehensive recovery of gold and sulfur from cyanide tailings. This technical transformation project is carried out on the basis of not destroying the original process. Using the original plant of the flotation plant, some idle equipment is removed, a cyclone sorting and pressure filtration system is added, and the filter cake is sent to the sulfuric acid plant for acid production. The technical upgrading project was completed in May 2003. The new equipment specifications for technical transformation are shown in Table 3.

Table 3 New main equipment for technical transformation

V. Analysis of economic benefits

After the transformation of this process. It can produce 120,000 tons of cyclone filter cake per year, gold grade 8.5g/t, sulfur content 25%, and gold recovery rate of cinder cyanide system up to 60%.

(1) Annual output of gold: 18 × 8.5 × 60% = 91.8kg

(2) Gold production value: 91800×85=78.03 million yuan/a

(3) Annual production of sulfuric acid: 18000t

(4) Sulfuric acid production value: 18000 × 370 = 6.66 million yuan / a

(5) Annual gross output value: 780.3+666=l446.3 million

(6) Annual operating cost of the cyclone filter press system:

25.66+41.03=666,900 yuan (spare parts consumption and power costs)

(7) Acid production cost: 150 × 18000 = 2.7 million yuan / a

(8) Production cost of burning cyanide system:

L10×18000=1.98 million yuan/a

(9) Transportation cost: transportation distance 230km, freight rate 0.35 yuan / t · km

Annual freight: 18000 × 230 × 0.35 = 1.45 million

(10) Other production costs: 200,000 yuan / a

(11) Total annual production cost: 66.69+270+198+145+20=6.33 million yuan

(12) Annual profitable: 1446.3-699.69=746.61 million yuan/a

Conclusion

Most of the gold in the flotation gold concentrate cyanide tailings of the Wulatun gold mine is embedded in pyrite or other metal minerals by fine-grained gold, which cannot be recovered by conventional cyanidation process. Through experiments and production practices, it has been proved that the cyanidation tailings have achieved good results by pressure filtration, roasting, {melting acid, slag re-grinding and cyanidation process, which has increased the total gold recovery rate by 5.3% and increased the gold output by 91.8 per year. Kg, at the same time can produce 18,000 tons of sulfuric acid, can increase profits of 7.6661 million yuan per year, bringing considerable economic benefits to the enterprise.

At present, the desulfurization and enrichment process of the cyclone is adopted, and the loss of gold and sulfur in the cyclone overflow is still relatively large. In the future, further research is needed to find a more reasonable and effective method for the best effect.

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