Experimental study and production practice of cyanide gold extraction and cyanide copper floatation of copper-bearing gold concentrate

Guangdong Gaoyao Hetai gold mine Department of altered mylonite type deposits have high mining village, west cloud two mines. Prior to 1998, a single flotation process contains copper production amounted to 3% to 6% of the gold concentrate, after the completion of cyanide can be directly smelter production GB finished gold, it has been listed on the Shanghai Gold Exchange.

The gold-bearing ore is composed of a series of gold-containing silicified martensite, silicified mylonite, and silicified mylonized schist. The metal content in the ore is low. Mainly pyrite, pyrrhotite, chalcopyrite, native gold and silver deposit, containing a small amount followed sphalerite, galena and arsenopyrite (the content only 2.27%), further quartz, sericite Non-metallic minerals such as calcite . The results of multi-element analysis of ore are shown in Table 1. The gold minerals in the ore are finer in size, mainly produced by fine grain gold, of which -37+lO Accounted for 56.32%, -lO 36.80%; medium-grain content is low, of which -74+37 Only 2.35%, +74 Accounted for 4.53%. The form of natural gold is mainly sharp-angled, followed by round and granular, plate-like, and needle-like, and a few are horns and long horns.

Table 1 Results of multi-element analysis of ore /%

Natural gold is mainly embedded in various minerals. The pyrrhotite and gangue particles account for 61.53%, followed by the package gold. The gangue, pyrrhotite and chalcopyrite account for 23.84%. Stone fracture gold only accounts for 14.63%.

I. Experimental study on cyanidation of copper-bearing gold concentrate

(1) Conditional test

The cyanidation test material is a gold concentrate in the production process. The gold grade is above 90g/t, and the copper grade is about 3.00%. The condition test is carried out. According to the process parameters of cyanide gold extraction, the relationship between the amount of calcium oxide or pH, pretreatment time, sodium cyanide dosage, slurry concentration, grinding fineness and cyanide leaching time on the leaching rate of gold cyanide Research. The results show that the optimum process conditions for gold extraction by cyanide are: calcium oxide dosage 10~15kg/t or pHl~12, sodium cyanide dosage 15kg/t, pulp concentration 33%, cyanidation leaching time 24h, fine grinding Degree-41 More than 90%, cyanide leaching rate of more than 96%.

(2) Comprehensive condition test

According to the selected optimal experimental conditions, the relationship between the optimal optimum process conditions for cyanide gold extraction and the effect on cyanide gold extraction was studied. The results show that the optimal process conditions for cyanidation are suitable for the cyanide of the final gold concentrate produced in Hetai Gold Mine. The obtained cyanidation index is also very good, and it can realize the real estate gold. The gold grade of cyanide slag is 3.00g/t, the gold leaching rate can reach over 97%, but the dosage of sodium cyanide still reaches 15/t; meanwhile, the copper grade in cyanide slag still reaches 3.28%, which has high economic value.

The above research can be concluded that a major obstacle to the gold extraction of copper-containing gold concentrates is the cyanide-soluble copper minerals and other sulfides in the concentrate, so the consumption of sodium cyanide is high, even if alkali treatment is used. Cyanide consumption still reaches 15/t. However, gold concentrate has good cyanide gold extraction index, and the gold leaching rate is over 97%. At the same time, it also indicates that the finer the cyanidation leaching index of the grinding grain is, the better. According to the above test conditions, how to further reduce the consumption of sodium cyanide, reduce the adverse effects of copper in cyanide leaching, reduce the grade of cyanide slag, and recover copper in cyanide residue, is the key to realizing the real estate gold.

Second, reduce the consumption of sodium cyanide, improve the leaching rate of gold cyanide test

Entrusted by the Changchun Gold Research Institute to carry out the gold concentrate cyanide gold extraction test, the results show that because the gold content in the gold concentrate is more than 3.00%, the consumption of a large amount of sodium cyanide, while the cyanide slag grade is still high. To this end, the Hetai Gold Mine established a gold concentrate cyanidation leaching research team in 1996. After more than a month of research, the special additive A, which is cheaper, was used to reduce the impact of copper on cyanide leaching. A breakthrough was made and success was achieved, reducing the consumption of sodium cyanide to 4-6 kg/t. The gold cyanide leaching rate is above 97.57%, and the cyanide residue grade is below 2.40g/t. The best comprehensive test conditions: pretreatment time 5h, pH 11 ~ 12, grinding fineness 90% ~ 41 The slurry concentration is 33%, the leaching time is 24h, the sodium cyanide dosage is 6kg/t, and the additive is about 6kg/t. The test results are shown in Table 2.

Table 2 Using additive A to reduce the test results of sodium cyanide

From the test results in Table 2, it is known that the use of additive A to reduce the influence of copper and other minerals on cyanide leaching is successful. Not only reduces the consumption of sodium cyanide, but also the gold leaching rate reaches 97.59%, the index is ideal, and it can fully realize the real estate gold.

Third, production practice

The Hetai Gold Mine Cyanide Workshop began construction in 1997 and was officially put into operation in 1998. At the initial stage of production, the designed production capacity is 50t for daily processing of gold concentrate, and then expanded to a 100t cyanide workshop. The cyanidation process is: pretreatment + gold concentrate dehydration + poor liquid slurry adjustment + two leaching two washings + zinc powder replacement + gold mud smelting + cyanide slag float copper. Our mine is the first qualified refining enterprise of Shanghai Gold Exchange. The registered “Jinding” brand gold has a quality of over 99.995% and passed the ISO9000-2000 quality system certification. It was listed on the Shanghai Gold Exchange on October 30, 2002. . Since the cyanide workshop was put into production in 1998, the gold leaching rate has reached over 98%, the consumption of sodium cyanide is 4~5kg/t, and the consumption of additive A is 5~6kg/t, which has achieved good economic and social benefits. . The cyanide leaching indicators in the past five years are shown in Table 3. The results in Table 3 show that in the first year of production, the leaching rate of gold reached 97.78%, and the grade of cyanide slag was 1.55 g/t.

With the strengthening of management work and the improvement of workers' operational skills, process optimization and technical improvement, the index of cyanide leaching is getting better and better. From January to September 2002, the grade of cyanide slag dropped to 1.00g/t, and the gold leaching rate increased. By 98.98%, the gold leaching rate increased by 1.2% compared with the first year of production. The copper cyanide gold extraction process technology has reached the domestic leading level and passed the technical appraisal organized by the China Gold Association.

Table 3 Statistics of cyanide leaching indicators in recent years

Fourth, cyanide tailings recovery copper

Most of the copper contained in the flotation concentrate of Hetai Gold Mine exists in the state of chalcopyrite and is floatable, so it is recovered by flotation. The multi-element analysis of cyanide tailings and the phase analysis results of the main recovery of the target mineral copper minerals are shown in Tables 4 and 5. At the initial stage of the cyanide plant, due to various reasons, the cyanide contained in the cyanide dipping slag has the effect of inhibiting flotation of copper. The float copper process is immature and has insufficient experience, resulting in abnormal copper floatation process, resulting in a large amount of Copper or silver cyanide slag is discharged into the tailings pond, causing large economic losses. Therefore, it is very important to restore the normal production of the floating copper process as soon as possible and create value. Through the analysis of ore properties and small-scale experimental research on cyanide tailings, it was decided to use the flotation process to recover copper minerals and residual gold and silver minerals in cyanide residue. Since the fineness of grinding required for cyanidation of flotation concentrate is -37grn, 90%, the monomer dissociation of copper mineral under this condition is shown in Table 6.

Table 4 Results of multi-element analysis of cyanide tailings /%

Table 5 Results of copper mineral phase analysis of cyanide tailings /%

Table 6 Copper mineral monomer dissociation measurement results /%

It can be seen from Table 6 that the monomer dissociation degree of copper mineral in cyanide residue is not high, only 48.6%, which will affect the grade of flotation copper concentrate. To this end, in order to achieve the goal of maximizing the recovery rate under the premise of satisfying the copper concentrate grade, it is required to strengthen the management of grinding operations in production. Reduce the concentration of the cyclone feed, stabilize its ore supply and ore concentration, increase the working pressure of the cyclone, improve the classification efficiency of the cyclone, and make the grinding fineness reach -37 More than 95%. The flotation operation conditions are strictly controlled to achieve a higher recovery rate while ensuring the copper concentrate grade.

Due to the high content of cyanide in the cyanide residue, it can reach 2~4g/L, and the moisture content of the filter cake is 16%-22%. Such high cyanide concentration will have a strong influence on copper minerals, which is not conducive to Floating copper operation. To this end, the additive B is added during the slurry adjustment to eliminate the influence of the residual cyanide on the copper floating operation. On the other hand, the copper-selecting agent C 90g/t is added, and the copper agent D 40g/t is selected to obtain a better copper selection index. When the copper grade of cyanide slag is more than 3.00%, the grade of copper concentrate is over 18%, which has achieved good economic benefits. At the same time, due to the addition of additive B, most of the cyanide is eliminated, which is also beneficial to environmental protection.

The production process of float copper is a rough selection, two selections, and two sweeps. The operating conditions are 50t/d of processing and grinding fineness-38. 88.5% or more, filter cake moisture 17% ~ 22%, pulp concentration 27%, slurry flow 120L / min, crude selection plus drugs: floating copper agent B 60g / t, pharmaceutical C 25g / t, pine oil 30g / t; Sweep the addition of B 30g / t, the agent C 15g / t. The production index of floating copper over the years is shown in Table 7.

It can be seen from the production practice that with the continuous improvement of the process flow, the improvement of the worker's operation level, the floating copper index is getting better and better; on the other hand, due to the strengthening of the on-site technical management work of the float copper process, the float copper process It is also becoming more and more stable, which is conducive to the stability and improvement of the floating copper index.

Table 7 Floating copper production index/% in recent years

Conclusion

(1) The gold-altered ridge-type deposits in the Hetai Gold Mine, the fine grain size of gold is fine, and most of them are fine-grained gold and fissure gold. The content of copper in gold ore is over 0.28%, and the gold concentrate contains copper. More than 3%, it is difficult to choose smelting ore, but the use of special agent A to reduce the impact of copper on cyanide gold, can achieve good cyanide indicators.

(2) It is the key to stabilizing the process and improving the technical indicators by strengthening technical management and staff training, improving workers' operational skills, implementing various rules and regulations, and strengthening the daily on-site management of engineers and technicians to solve problems in production in a timely manner.

(3) Due to the use of copper-selecting chemicals B, C, and D, copper in the cyanide residue and residual gold and silver are further recovered, which improves the economic benefits of the enterprise. The copper-containing gold concentrate is directly cyanidated and gold-added, the cyanide residue recovers copper and the residual gold and silver new technology, which has great promotion and application value to the same type of gold mine. The continuous production process of copper-containing gold concentrate cyanide gold extraction and cyanide slag float copper, which is recognized by the China Gold Association in 2002, is the only one of its kind in China.

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