A new way to increase the production capacity and recovery rate of a silver mine cyanide plant

I. Introduction

Turkey Etibank - Gumuskoy silver minerals are five different types of ore, its chemical composition and mineral composition vary. The fine granulation process of the mine has been to completely grind the mixed ore into a slime. The mixed ore clay mineral content is nearly 15%, and the recovery rate of the ore is about 60%. The ore contains clay minerals that affect efficient crushing and sieving, thus causing the crusher to not feed. Further, it is known not only clays liquid-solid separation process to bring some troubles, increased drug consumption, but also reduces the dissolution of noble metal in cyanide solution. It has been reported that the clay minerals are separated from the multi-metal silver ore to purify the mineral components and the cyanidation efficiency will be improved.

We conducted a preliminary feasibility study on the entire fine granulation process that has been applied to the cyanide plant to compare it with the cyanidation of the demineralized ore.

Second, materials and methods

(1) Materials

Experimental research on the mixed ore that is representative of the plant. For the cyanidation test, the mixing of various ores is as follows:

Siliceous tuff 50%

Altered tuff l5%

Limonite ore containing 15% manganese

Dolomitic ore 10%

Original process tailings 10%

The results of partial chemical analysis of mixed ore samples are listed in Table 1.

Table 1 Chemical analysis of mixed ore

Mineral analysis showed that most of the silver is present in the magenta silver, argentite, silver tetrahedrite ore and natural copper and silver form. The particle size of the mineral silver is generally less than 50 μm. Barite, galena, white lead, stibnite, quartz, dolomite, sphalerite, hard manganese, iron hydroxide, and a clay mineral composed of gangue minerals.

(two) method

The material was soaked for 24 hours. Wet screening test is carried out with a particle size of 30mm to 0.038μm to ensure that the proposed technical and economic indicators are superior to the current operating results of the plant. Based on this, the amount of slime with the least amount of silver loss is determined.

Next, the unde-sludge sample was cyanated and the de-sludge sample was tested to obtain the optimum leaching parameters.

The cyanidation test was carried out in an open beaker with a beaker volume of 2 L and a stirring device of a mechanical stirrer with a rotational speed of 400 rpm. The cyanidation solid material was 200 g, and the agent was sodium cyanide and pure sodium hydroxide having a purity of 98.5%. Periodic analysis leachate Ag, CaO and CN ^-, so that the drug concentration is kept constant, and the PH value of O ₂ is also detected. At the end of each test, the noble liquid and the leaching residue were measured by atomic absorption spectrometry, and the free cyanide concentration of the leaching solution was measured by titration with silver nitrate.

Cost analysis based on data obtained from denitrification of raw ore shows that the benefits of pretreatment are numerous.

Third, the results

(1) first soaking and desliming, then wet screening

After 24 h immersion, the wet sieving analysis results are shown in Table 2.

Table 2 Screening analysis results of mud removal samples

Soaking makes the clay completely dispersed. Accumulated 14.8% of the material (the amount of silver lost is 5%), the particle size is less than 0.038mm. Thus, the silver content of the delimed sample increased from 273 g/t to 305 g/t.

(2) Cyanide

At the Gurouskoy Silver Separation Plant, the cyanidation test was carried out on the unde-sludged mixed ore under similar conditions. The results are as follows:

Plant selection conditions

Feeding particle size - 0.150mm

Solid particle weight percentage 30%

Slurry temperature room temperature

Solution pH 11.0～11.5

Sodium cyanide concentration 15g/L

Lead nitrate dosage 350g/t

Leaching time 48h

Leaching result

Silver leaching rate 56%

Sodium cyanide consumption 2.5kg/t

Calcium oxide consumption 8.6kg/t

Subsequently, the demineralized ore (soaked ore) was cyanated according to the optimal test parameters to compare the silver leaching rate and the chemical consumption. The results obtained by this research are as follows:

Test conditions

Feeding particle size -0.106mm

Solid particle weight percentage 30%

Slurry temperature room temperature

Sodium cyanide concentration 1.5g/L

Leaching time 48h

Leaching result

Silver leaching rate 63.8%

Sodium cyanide consumption 1.5kg/t

Calcium oxide consumption 9.0kg/t

The leaching rate of the demineralized ore is about 60.6%, and under certain test conditions, the leaching rate can reach 63.8%. According to this test data, compared with the plant selection conditions, the silver leaching rate increased by 8.2%, and the sodium cyanide unit consumption was reduced by 40%. However, in the latter experiment, the lime unit consumption increased by about 12.5% ​​due to the pH in the solution. The value is slightly higher.

Fourth, cost analysis

According to the results obtained in this experiment, the cost basis analysis was carried out on the two methods in terms of production capacity, total silver recovery rate and drug consumption consumption. All calculations were based on the full load operation of the plant. .

(1) Current operational economic evaluation

The current operating cost data of the silver cyanide plant is as follows:

Annual production capacity of the plant is 1 million t/a

The factory silver leaching rate is 56.0%

Total silver recovery (including liquid-solid separation, de-sludge and refining processes) 50.4%

Annual production of silver l0.08 million t / a

Annual sodium cyanide dosage 2500t/a

Annual calcium cyanide dosage 8600t/a

Annual flocculant dosage 70t/a (0.07kg per ton of ore flocculant)

(II) New method economic evaluation

The cost of desilting cyanidation of raw ore is as follows:

Annual production capacity of the plant is 1.17 million t/a

The annual cyanidation amount of the plant is 1 million t/a (the silver grade is 224 g/t)

Select factory silver leaching rate 63.8%

Total silver recovery (including liquid-solid separation, de-sludge and refining processes) 57.4%

Annual production of silver l29 million t / a

Annual sodium cyanide dosage 1500t/a

Annual calcium oxide dosage 9000t/a

Annual sales of lead acid consumption 350t/a

Annual flocculant dosage 40t/a (0.04kg per ton of ore flocculant)

(III) Analysis of two process costs

The cost analysis of the two processes (process a and process b) is summarized as follows:

Table 3 Total income

Table 4 Total cost

If the silver selection plant adopts the new method introduced in this research, the annual net income can be increased to 5.277 million US dollars. The annual cost can be reduced by 1.239 million US dollars.

V. Conclusion

Desliming the ore prior to cyanidation can provide technical and economic benefits. The addition of a de-sludge unit at the Etihank Centennial Silver Concentrator will generate an additional $660 million in additional revenue and, in addition, all the problems associated with crushing and sieving .

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