Experimental study on grinding and floating process of rich silver ore

Suichang gold mine is a mine of mining for over 20 years, is the rare high-silver quartz vein gold deposit. Now using a flotation stage grinding stage a zinc cyanide gold concentrate powder recovered acidified water a replacement technology for production. The ore is an easy-to-select metallurgical ore. Due to continuous improvement in the selection and smelting technology over the years, the recovery rate of gold and silver has remained at a high level. However, in recent years, with the depth of mining and changes in mining bodies, the ore properties have changed significantly, resulting in a decrease in the recovery rate of gold and silver flotation. Nature of the ore changes visual performance: â‘ , the dark mineral content of the ore is increased substantially by the appearance; magnetic mineral content â‘¡ ore increases, crushed iron removal device are the nuggets aspirated; â‘¢ ore difficult to grind than before ; 4 The mud content in the pulp increases and the viscosity increases.

To this end, by asking a number of research units to conduct experiments and research, there is a certain understanding of the reasons for the reduction of ore properties and flotation recovery rate.

The change of ore properties is mainly manifested by the fineness of gold inlay size, the occurrence state and the change of mineral composition, and the content of dark minerals in pyrite graphite , magnetite, pyrrhotite, chlorite and epidote in ore. increase. More than 0.14 particles in gold minerals were reduced from 70% to 23%. The carrier minerals of gold change and are transferred from pyrite to gangue. About 5% of the gold is ultrafine particles dispersed in the gangue.

Due to the finer grain size of the gold in the ore, fine grinding can improve the flotation recovery rate to a certain extent, but the quality of the gold concentrate will decrease. Observing the products in the on-site production process under the microscope also found that in a flotation of gold concentrate, due to the fine grain size of some pyrite, there is no monomer dissociation from quartz, a large amount of pyrite and quartz. The continuum, even some of the pyrites are mixed with the poor, while the second-stage flotation of the gold concentrate has a large number of flocculent slime and pyrite. This is because 90% of the useful minerals are recovered in a section of flotation. After the second stage of grinding, the condition of flotation deteriorates. The remaining 10% of useful minerals are too small, and it is difficult to recover by large enrichment ratio. After the selection of the agent, the second gold concentrate was mixed with the pyrite, resulting in an increase in the impurity content of the final gold concentrate.

In this regard, there is a view that grinding fineness and grinding and floating process setting methods are important factors affecting the flotation recovery rate and gold concentrate grade. Under the existing equipment conditions, the original stage grinding stage flotation process It is changed to the secondary flotation process of the second-stage grinding. The grinding fineness is maintained at -0.074mm, which accounts for more than 85%, which can improve the recovery rate of flotation. At the same time, it can also reduce the yield of gold concentrate, reduce the amount of cyanide treatment and reduce cyanide. Cost, improve the overall economic efficiency of the enterprise

Well, in practice. Can changing the existing grinding and floating process setting method can improve the gold concentrate grade and ensure the flotation recovery rate, reduce the cyanidation cost, and improve the economic benefits of the enterprise? In order to verify the technical and economic indicators of the two process settings, Changjin Mine used the existing two grinding and floating production systems of the plant to carry out industrial tests using the stage grinding stage flotation and the second stage grinding one flotation process.

First, the nature of the ore

The Suichang Gold Mine is a medium-temperature hydrothermal, superficial, sulphide-rich, gold-silver-bearing quartz vein type deposit, and the useful component is gold and silver. Mineral composition of the ore is relatively simple, in addition to silver trace minerals, metallic minerals are mainly pyrite, pyrrhotite lesser extent, yellow copper ore, marcasite, sphalerite and galena, brightness trace Copper ore, copper ore and silver ore. The main non-metallic minerals are quartz and feldspar, followed by chlorite, epidote, calcite and dolomite, as well as a small amount of sericite, illite and kaolinite.

The gold in the ore is mainly present in the form of chlorinated gold and gangue, while the microscopic gold is the main form of production of gold minerals. The microscopic gold minerals are in the form of gold, intergranular gold and fissure gold. Natural gold accounts for 70% of the sulfides, about 30% of the gangue, and about 5% of the towels are dispersed in the gangue.

The main symbiotic minerals of gold minerals are pyrite and quartz, and the secondary gold minerals also have a close embedded relationship with the attapulgite. The main continuous mineral of pyrite is quartz, and other associated minerals include almost all non-metallic minerals such as sulfides, gold minerals and epidote in the ore.

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

Second, the test process

We maintain the original stage grinding stage flotation process in the two systems of the two grinding systems, and transform the B system into a two-stage grinding primary flotation process and simultaneously produce. The process flow is shown in Figure 1.

The grinding systems of the two systems are the same and the throughput is 150t/d. The grinding fineness of a section is -0.074mm, 60%, the fineness of the second section is maintained at -0.074mm, which accounts for more than 85%. The collector is made of black medicine and Y89 yellow medicine, and the foaming agent is No. 2 oil. The difference is that the system uses lime as a modifier, while the system B uses sodium carbonate as a regulator and water glass as a dispersant.

Third, test data and statistical processing

Industrial trials continued for 82 days, a total of 241 shifts, and a large amount of data was obtained. We use the VFP program to perform statistical calculations on indicators, and use the statistical analysis software package SPSS to process and analyze all data and secondary data.

(1) Description of test results

The production data of the two systems were processed, and the scatter plots of gold grade and recovery, silver grade and recovery, and sulfur grade and enrichment ratio were obtained, and their fitting curves are shown in Figure 2-4.

It can be seen from the above three figures that compared with the flotation process in the stage grinding stage, the secondary flotation process is used in the second stage grinding. Although the enrichment ratio is improved, the recovery rates of gold and silver are significantly reduced. The difference can also be seen from the cumulative average of the indicators of the two system industry tests (see Table 2).

Table 2 Comparison of the average values ​​of the indicators of the two system industrial tests

(2) Technical and economic comparison

1. Comparison of indicators using different processes

From the curves of Fig. 2, Fig. 3 and Fig. 4, it can be calculated that the minimum value of the gold ore of the two systems is 10.24g/t, and the secondary flotation process of the second stage grinding is compared with the flotation process of the stage grinding stage. The recovery rates of gold and silver decreased by 1.14 and 1.74 percentage points respectively, but the enrichment ratio increased by 1.09 and the gold concentrate yield decreased by 1.1 percentage points.

2. Comparison of economic benefits using different processes

As far as the B system is concerned, the second-stage grinding primary flotation process is adopted, and the increase in the cost of the medicament is 0.1 million yuan/month. The electricity and other expenses saved by the reduction of the flotation machine are 22,000 yuan/month. The recovery rate of gold and silver cyanide is 95% and 90% respectively. The economic loss caused by the decrease of flotation recovery rate is:

Gold: 4404t / month × 10.24g / t × 1.14% × 95% × 70 yuan / 9 = 34188 yuan / month

Silver: 4404t / month × 156.79g / t × 1.74% × 90% × 0.98 yuan / g = 10597 yuan / month

According to the metal cost of the cyanide unit of the Suichang Gold Mine, the cost is 2.3 yuan/g.

The cost of cyanidation saved by reducing the amount of gold concentrate metal is:

4404t / month × 10.248 / t × 1.14% × 2.3 yuan / g = 1182 yuan / month

It can be seen that compared with the flotation process in the stage grinding stage, if the two systems use the two-stage grinding primary flotation process, the economic benefit of the monthly plant selection will be reduced by 45,000 yuan.

4. Discussion on the setting method of grinding and floating process and the factors affecting cyanidation cost

(1) Grinding and floating process setting method

The grain size of natural gold in the ore is. About 45% of 0.074-0.14mm, about 23% more than 0.14mm, that is, about 69% more than 0.074mm, about 23% less than 0.074mm, and the natural gold particle size and distribution produced in sulfide. The rate is greater than the natural gold in the gangue.

The second-stage grinding primary flotation process can better control the process conditions such as the second-stage grinding concentration, improve the grinding efficiency, and avoid the large amount of minerals, pyrite and quartz in the gold concentrate, and improve the fineness. Mineral grade. However, 23% of the natural gold in the ore is greater than 0.14mm. This part of the gold cannot be recovered in time when it is ground to -0.074mm, which accounts for 85% of the fineness. The slime will also contaminate the surface of the gold particles and reduce the floatability of the gold, which inevitably affects the recovery of gold.

The natural gold particle size range of the ore is relatively large. The stage grinding stage flotation process can be used to reduce over-grinding. After a period of grinding, the coarse-grained gold can be recovered in time. In the second-stage flotation, the fine-grained gold is fully singled. The body dissociates, and there is enough time to recover a part of the gold that cannot be completely dissociated from the gangue, so that although a large number of continuous organisms are put into the concentrate, the recovery rate can be appropriately increased. However, the concentration of the slurry after the second stage flotation decreased, which reduced the grinding efficiency of the secondary grinding, and increased the flotation tank used for the two flotation. Increase the cost of flotation.

(2) The composition and influencing factors of the cost of capture

We analyzed the cyanide production cost data of the Suichang Gold Mine in recent years. From the analysis results, the proportion of the direct cost of cyanide is large as shown in Table 3.

Table 3 Main items of direct cost of cyanidation

For the above six direct cyanide production cost data, after removing the abnormal data, SPSS is used for partial correlation analysis (3), and the partial correlation between cyanide treatment amount, cyanogen grade and cyanide direct cost main component is obtained. 4 is shown.

Table 4 Partial Correlation Coefficients of Major Cyanide Treatment, Cyanide Grade and Cyanide Cost Main Items

It can be seen from Table 4 that the uncorrelated probability of the cost of electricity, sodium cyanide and zinc powder and cyanide treatment is less than 0.5%, the partial correlation coefficient is greater than 0.5, linear correlation; 2 the original cyanide grade and the above several costs are not The correlation probabilities are all 10% larger and have no correlation. It shows that the direct cost of cyanide is mainly affected by the amount of cyanide treatment.

However, the correlation analysis of the main material consumption of cyanide main materials in the Suichang Gold Mine in the past five years, the correlation between the cyanide treatment amount, the cyanide gold and silver grade and the cyanide main material consumption is shown in Table 5 (to make the table Data that is concise and unrelated is not listed, the same below).

As can be seen from Table 4, the cost of electricity is affected by the amount of cyanide treatment. The electricity consumption and sodium cyanide consumption are affected by the original grade of gold cyanide. The original gold and silver cyanide grade will affect the sodium consumption.

Table 5 Correlation coefficient of cyanide treatment amount, unit cost of cyanide gold and silver and cyanide main material

Further analysis shows the partial correlation between the cyanide treatment amount, the cyanogen grade and the cyanide main material unit consumption as shown in Table 6.

Table 6 Partial Correlation Coefficients of Cyanide Treatment, Cyanide Grade and Cyanide Main Material Unit Consumption

Based on the above aspects, it can be seen that the amount of electricity and sulfuric acid varies within a certain range, and the unit consumption decreases with the increase of cyanide treatment, so it has a negative correlation with the amount of cyanide treatment; The unit consumption of sodium cyanide increases with the increase of the original grade of gold cyanide; while the unit consumption of sodium hydroxide and sulfuric acid used in sewage treatment increases with the increase of the original grade of gold and silver cyanide.

We believe that because of the cyanide production of rich silver ore, the replacement process requires high-cyanide and high alkali concentration. When the amount of cyanidation is constant, the original cyanide grade is high and the amount of metal in the cyanogen is high. . The amount of sodium cyanide required to maintain high cyanide concentration increases, and the unit consumption of sodium cyanide increases. With the increase in the grade of cyanide gold and silver, the consumption of sulfuric acid and other materials used in sewage treatment increases.

Therefore, for silver-rich gold ore, the unit cost is related to the amount of cyanide treatment and the grade of cyanogen, which is related to the amount of metal of cyanogen gold and silver. When the unit cost of cyanide is constant, reducing the amount of flotation gold concentrate has a certain impact on reducing the total cost of cyanide, but reducing the amount of flotation gold concentrate will increase the original cyanide grade, which in turn will increase the cost per unit of cyanide. Therefore, reducing the gold concentrate yield and increasing the gold concentrate grade will not reduce the total cost of cyanide. In terms of recovery rate loss, the use of a two-stage grinding primary flotation process has no positive significance for improving the economic benefits of enterprises.

V. Conclusion

(1) R-inch silver-rich quartz vein gold ore with fine grain size in the Suichang gold deposit. In practice, the flotation process in the stage grinding stage is compared with the second stage grinding flotation process. The rate is better.

(2) The rich silver ore is different from the gold ore containing less silver or less silver. The production cost of gold concentrate cyanide is affected by the treatment volume and the original grade of cyanide. Therefore, the use of the second-stage grinding primary flotation process can improve the concentrate grade of the silver-rich gold ore in the Suichang gold mine and reduce the cyanide treatment capacity, but has no effect on reducing the production cost of gold concentrate cyanidation. The process should be set up primarily to increase recovery.

(3) As far as the flotation gold concentrate cyanidation process is concerned, the silver-rich quartz vein gold ore currently processed in the Suichang Gold Mine is suitable for production in the stage grinding stage flotation process.

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