Determination of the expansion plan of a gold mine smelting plant

Great Lakes gold ore dressing plant in the original 200t / d all slime cyanidation - expansion, expansion project mainly deal with CIP series and 100t / a flotation series based on the 644m middle primary ore less deep ore bodies. How to choose a reliable, economical and rational process is the key to the expansion project. At that time, there were two opinions: one opinion was that the whole mud cyanidation process should be adopted. The main reason was that the whole mud cyanidation series index of the original smelting plant was significantly higher than the flotation, and the flotation operation was unstable, and the recovery rate was high. Low, the use of whole mud cyanide is relatively safe, another opinion that the flotation-concentrate cyanide process is to be used, the main reason is the flotation-concentrate cyanide process investment province, test indicators and the whole mud cyanidation process Close, and low operating costs, comprehensive benefits.

First, the nature of the ore

The Dahu Gold Mine is a medium- and low-temperature hydrothermal filling gold deposit. According to the characteristics of oxidation and oxidation zone, the deposit is divided into oxidation zone and primary zone. The oxidation zone is mainly distributed above the 644m elevation, and its metal only accounts for 18.57% of the total metal content. The primary zone is distributed at 644m, but the local zone is dominated by mixed ore. Mining industry can be divided into Type: Medium sulphide - sulfide gold ores and gold-bearing quartz veins oxide lean and semi-oxidized ores.

(1) Properties of primary ore

1. Mineral composition and ore structure and structure The ore metal minerals account for 8.46% of the total minerals. Mainly pyrite (accounting for 87.35% of the relative content of metallic minerals), times as native gold, brass ore, galena, etc., but the content is very low, a single gold minerals native gold. Gangue minerals accounted for 91.54% of the total of mineral, quartz, followed by the emblem feldspar, plagioclase feldspar, and calcite. The ore structure has a self-shaped-semi-automorphic grain structure, a grain structure, a fragmentation structure, a containment structure, an etched structure, a metamorphic perforated structure, and the like. The ore structure is dominated by disseminated structures, followed by fine veins, strips, and block structures.

2. The occurrence state and granularity of gold

Gold and submicroscopics accounted for half of the ore, free gold accounted for 47.66% of the total gold, gold accounted for 50.98% of the pyrite, and gold accounted for 1.36% of the gangue. The enriched mineral of the submicroscopic gold is pyrite, in which gold is unevenly distributed. Natural gold and pyrite are closely symbiotic, followed by quartz and chalcopyrite. Gold exists mainly in the form of gold in pyrite and quartz, and exists in the form of gold and cracked gold in chalcopyrite.

Natural gold is embedded in the ore in the form of gold, fissure gold and intergranular gold, mainly wrapped in gold. According to the results of microscopic analysis, the packaged gold accounted for 61.01%, the fracture gold accounted for 27.43%, the intergranular gold accounted for 11.55%, and the gold particle size ranged from 0.2 to 0.005 mm, of which coarse grain gold (O.295-0.074 mm) accounted for 14.76%. Medium grain gold (0.074 ~ 0.037mm) accounted for 27.20%, fine grain gold (0.037 ~ 0.O1mm) and fine gold (<0.01mm) accounted for 58.04%.

3. Characteristics and particle size of major gold-bearing minerals

Pyrite is a metal sulfide with high content and distribution in the ore. The general particle size is >0.1mm. Pyrite has a multi-stage mineralization stage. The early pyrite crystals are mostly produced by self-shaped-semi-self-shaped cubes, and the particles are coarser, generally >0.5 mm. The metamorphism of the medium or late pyrite is mainly semi-self-shaped cube or pentagonal dodecahedron, and the particle size is generally >0.1 mm. Pyrite is closely related to gold minerals, and 70% to 75% of gold minerals are related to pyrite. It can be seen that pyrite is the main gold-bearing mineral in primary ore.

Because of the high content of metal sulfides in the ore, large particle size, and close relationship with gold, it is beneficial to recover gold by flotation.

(2) Oxidized ore properties

The main metal minerals in oxidized ore are hematite, limonite, pyrite, secondary chalcopyrite, and arsenopyrite. The gangue minerals are mainly quartz. Gold is mainly composed of natural gold, and its inlaid cloth is finer in size, both <O.074mm. The form of the inlay is mainly horny, wheat grain, and needle-like, and the round shape and the long-horn shape are secondary, and the small amount is sharp-angled granular and plate-like.

2. Brief description of the production status before the expansion of the plant

(1) The Taihu Gold Mine was completed in 1988 with a 100t/d mining project to treat the oxidized ore in the Luoshan mining area, using a full mud cyanide-carbon slurry gold extraction process. Subsequently, the 100t/d flotation series was expanded to treat the mixed ore, and the flotation concentrate was sent to the whole mud cyanidation series. The two series of production indicators for July and August 1993 are listed in Table 1. The recovery rate of flotation is sometimes only 70%.

Table 1 Raw smelting plant production indicators

Note: The raw ore grade of the carbon slurry series is 25.66% and 30.8% of the flotation concentrate added.

(II) Analysis of the reasons for the high and low production rate of flotation recovery in the original smelting plant.

a. The original flotation series treatment ore mainly consists of 644m middle or higher oxidized zone ore, and a small amount is deep ore prospective primary ore, which has different degrees of oxidation. In addition, the transportation and mineralization facilities in production are not perfect, and the mixed oxidized ore of carbon slurry and the primary ore of flotation series are serious, so that the flotation series treatment ore contains a considerable part of oxidized ore. Difficult choice of oxidized ore has an adverse effect on flotation recovery.

b. The original flotation series equipment is simple, the pharmaceutical system is not reasonable, and the flotation recovery rate is low.

c. In the original production, the raw ore is mixed into the flotation after mixing with mercury , so that the concentration of the slurry is low and the flotation time is short, which is not conducive to the improvement of the flotation recovery rate.

(III) Completed the technical transformation in 1994, the capacity of the whole mud cyanidation series increased from 100t/d to 200t/d, and the flotation recovery rate also increased to 93%.

Third, the results of the test

The Luoyang Branch of the Changchun Gold Research Institute conducted a smelting test on 30 primary ore samples taken from the middle of 610-640m. A total of “amalgamation-flotation”, “flotation-concentrate cyanide” and “all mud” were made. The comparison test of various schemes such as cyanide has the following results.

(1) Mercury-flotation

Raw ore grade 4.59g/t

Grinding fineness 65%≤0.O7mm

Mercury recovery rate 28.76%

Flotation recovery rate 63.82%

Total gold recovery rate 92.58%

(2) Flotation - concentrate cyanidation

Raw ore grade 4.59g/t

Grinding fineness 65%≤0.O7mm

Flotation recovery rate 94.39

Gold concentrate grade 30.5g/t

Leaching grinding fineness 95% ≤ O.O7mm

Leaching concentration 4O%

Leaching time 30h

Dip grade 1.0g/t

Gold leaching rate 96.72

Total gold recovery rate 90.74% ~ 9O.97%

(3) Total mud cyanidation

Raw ore grade 4.59g/t

Grinding fineness 95%≤0.07mm

Leaching concentration 33%~40%

When leaching, 24h

Dip grade 0.4g/t

Gold leaching rate 91.28%

Total gold recovery rate 90.52%~90.65%

The test is finally recommended to use the "flotation - concentrate cyanidation" process.

Fourth, the comparison of the design process flow plan

It can be seen from the comparison test results that the three test procedures can obtain better sorting results. However, according to the national environmental protection policy, the new amalgamation process is not allowed, so the design does not adopt the “amalgamation-flotation” process. The “flotation-concentrate cyanidation” and “full mud cyanidation” two process selection indicators are basically similar, each with its own characteristics, expanding the production capacity of 200t/d. The production capacity of the whole plant will reach 500t/a, and the technical and economic indicators of its design are shown in Tables 2 and 3.

Table 2 Comparison of flotation-gold concentrate cyanide and whole mud cyanidation process (1)

Table 3 Comparison of flotation-gold concentrate cyanide and whole mud cyanidation process (2)

As can be seen from Table 2, the total recovery rate of the whole mud cyanidation process gold is 3.8% higher than that of the flotation-concentrate cyanidation process. This is mainly due to the fact that the coarse gold (>0.074mm) in the ore is more, accounting for 14.7%. Coarse gold has a certain adverse effect on flotation. When the gold particles are >0.2 mm, the flotation method is difficult to recover; the other flotation operation is relatively strict. The design considers the on-site production status to ensure that the production indicators after production are up to the design specifications. The economic effects of the design are expected to be achieved, and the design indicators of the flotation-concentrate cyanidation process are adjusted to a large extent for comparison. The whole mud cyanide annual production of finished gold l9.22 ~ 20.62kg, increased output value of 185.3 ~ 19.88 million. However, its direct investment in the smelting plant has a total investment of 2,190,800 yuan. Production and operation costs are 1.846 million yuan per year. The main reason is that the total mud cyanide grinding cost is high, the cost of chemicals is large, the investment cost of sewage treatment is large, and the investment in auxiliary projects and operating expenses increase.

V. Flotation - Adaptability of concentrate cyanidation process to post-production in mines

The gold ore in the deep ore body of the Dahu Gold Mine is a low-grade gold-bearing ore in the gold-bearing deposits of the Xiaoqinling area. According to geological data, the gold grade of the deep ore body from top to bottom will gradually decrease. According to the mining plan in which the mining order is rich first and then poor, it is expected that the original ore grade of the expansion and smelting plant will be 5-6g/t, and the original ore grade will be only 3~4g/t. When dealing with the decline in the grade of raw ore gold, the shortcomings of high production and operating costs of the whole mud cyanidation process will be more prominent, and the flotation-fines cyanide process will further increase the production and operation costs due to the reduction of the amount of influent flotation concentrate. reduce. Therefore, the flotation-concentrate cyanidation process is more adaptable to the later production of the mine.

Conclusion

Based on the above analysis and comparison results, the flotation-concentrate cyanidation process has the advantages of low investment, low operating cost, stable operation and strong adaptability to deep primary minerals in the whole mud cyanidation process. Therefore, the expansion project of Dahu Gold Mine The design ultimately adopted this process with better overall benefits.

The project was completed and put into operation at the end of 1996. The recovery rate of flotation was 92%-95%, and the total recovery rate of gold reached 90%, exceeding the design index. Production certification design using flotation - concentrate cyanidation process is correct.

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