Study on mineral processing technology and benefit analysis of primary ore deposit in a gold deposit

I. Overview of deposit characteristics

Gansu Zaozigou gold mine located northwest of Hezuo about 10km, after years of geological survey geological exploration units, determined that the deposit is - in large epithermal structural alteration type gold deposit.

The deposit is located in the cooperation between the Xinbao-Lishishan complex anticline south wing of the south Qinling Mountains--the Jixian large fault zone, and is located in the Tongren-Xiahe-Yixian gold metallogenic belt. The ore-bearing structure is the oil-bearing beam-Zaazigou fault fracture zone, and the regional tectonic line is generally NWW-SEE. The NW and near-SN secondary faults are developed in the mining area, and the strata in the area are strongly fold, fault structure and intrusion. The rock is also quite developed.

The ore-bearing rocks in the mining area are mainly composed of fragmented altered slate and diorite and diorite , and widely distributed veins, irregularly produced diorite and diorite dykes. different levels of mineralization, and a width of more than ten meters hornfels weak mineralization and pyrite alteration zones.

The gold ore body is mainly produced in the contact zone between the altered diorite and the surrounding rock. The distribution of the ore body is mainly limited to the “diamond block” cut by the main fault. The distribution pattern of the ore body is strictly controlled by NE, NW and near. The SN is controlled by three groups of fracture structures, and the ore body shape is plate-like, strip-like, and vein-like. The main ore body has an average thickness of 1.16 to 4.85 m. The length is 480~1040m, the extension depth is more than 400m, the average grade of ore body is 1.07~54.87×10 ^-6 , and the average grade of the deposit is 4.43×10 ^-6 . It is estimated that the reserves of 333+334 grade gold resources have reached a large scale.

Second, the status of mineral deposit development

Since the end of the 1990s, the economic benefits of mines in the continuous development process have become increasingly significant. However, since 2002, with the increase of mining depth, the output and economic benefits of enterprises have shown a downward trend year by year. The main reason is that the surface oxide ore has been basically recovered, and the surface below 50m is a primary ore (about the total resources). 80%), the deep primary mine has become the main miners now.

However, mining enterprises are still using the original production process to produce. For the limited mineral resources mixed with a large amount of mixed ore and even primary ore, on the one hand, the mineral resources are seriously wasted, on the other hand, the economic benefits of the enterprise are bound to suffer. Unnecessary loss. Therefore, it is urgent to study the mineral processing process of the original ore for this situation.

Third, ore processing technical performance

(1) Ore characteristics

Jujuzigou gold ore can be divided into oxidized ore and primary ore according to natural types. The characteristics of primary ore are described as follows:

1. Ore structure. Self-formed-semi-self-shaped granular, granular structure, its granular structure, vein structure, scattered scattered structure, fine vein disseminated structure.

2. Mineral composition. Metallic minerals include pyrite, arsenopyrite, stibnite, and secondary mineral magnetite, pyrrhotite, hematite and limonite, gangue minerals are sericite - water mica, kaolin, Quartz and calcite . No gold is seen in the ore.

3. Ore chemical composition. Au 9.8×10 ^-6 , Cu 0.007%, Pb 0.004%, Zn 0.01%, Tfe 6.32, Hg 0.32%, Sh 0.24%, inorganic C 1.56%, organic C O.30%, As 2.29%.

4. The state of occurrence of gold. The gold in the ore mainly exists in the form of inclusions in metal sulfides such as pyrite, arsenopyrite, stibnite, and pyrrhotite. A small amount is present in silicate minerals, and no gold or gold is found. Independent minerals.

It can be seen from the ore characteristics of the primary ore that the useful component is gold, and the harmful components are arsenic , antimony, carbon and the like. Gold is evenly distributed in the primary ore, and there is no gold or gold-containing independent mineral. The uniform distribution of gold in the base metal sulfide is very unfavorable to the flotation process.

(II) Comparison of mineral processing tests of primary mines

The ore dressing comparison test samples were collected from the primary ore bodies of the Au ₁ ore body, in which the ore body sample position was 18.9×10 ^-6 , the surrounding rock sample position was 0.33×10 ^-6 , and the surrounding rock sample position was 1.49×lO ^-6 . The mining sample and the surrounding rock are distributed in a certain proportion, so that the test sample grade is 9.1l×10 ^-6 .

1. Direct cyanidation leaching test

The main leaching test is carried out. The specific scheme is to first grind the raw ore to lO ~ -0.074 mm, and then leaching by direct cyanide leaching or alkali leaching - cyanidation. The leaching rate of gold is only 16.6% and 17.2%.

It can be seen from the test results that although the direct cyanidation leaching method is simple in process, low in investment and low in cost, the recovery rate of gold is too low, resulting in waste of resources. Therefore, the primary ore deposit of the Zaozigou gold deposit cannot be directly cyanide leached. Process.

2, flotation test

The grinding concentration is 62.5%, the grinding fineness is 81.6% -200 mesh, and the flotation concentration is 25%. After one rough selection, one selection, one sweeping, the flotation openness indicator is the concentrate yield 13.56%. The Au grade in the concentrate is 36.Ol×10 ^-6 , the recovery rate is 53.59%, the medium ore yield is 19.14%, the medium grade Au grade is 10.76×10 ^-6 , and the recovery rate is 22.62%.

The amount of crude drug selected: water glass 400×10 ^-6 , Ding xanthate 400×10 ^-6 , black medicine 200×10 ^-6 , No. 2 oil 32×10 ^-6 .

Sweep the dosage: Dinghuang medicine 200×10 ^-6 , black medicine 100×1O ^-6 , No. 2 oil 16×10 ^-6 .

From this test, we can see that there are several problems in flotation:

(1) The main reason is that no gold is found in the ore, and the gold is wrapped in metal sulfide in a microscopic or other form (not identified), and some of the sulfide particles are fine and encapsulated by silicate. Therefore, the flotation recovery rate is not ideal.

(2) The ore mud is more serious. When the concentration of flotation pulp is reduced to 25%, the flotation effect is better, which affects the efficiency of beneficiation.

(3) The total recovery rate of concentrate + medium gold is 76.21%, and the yield is 32.70%; the grade of medium ore is lower, and the yield is 19.14%, and the processing volume of subsequent processes is still very large. If the mine continues to be disposed of or discarded, further experimental research is required.

(4) During the flotation process, the amount of chemicals is large, which increases the cost of mineral processing.

3. Roasting cyanidation test

The purpose of roasting is to make the ore produce pores and cracks, which is beneficial to fine-grained gold. The disperse gold is dissociated from it, which is beneficial to the coating gold exposure, so that the gold mineral can contact and react with the sodium cyanide solution, thereby increasing the gold leaching rate; Remove harmful cyanide elements such as arsenic and carbon from the ore.

(1) Laboratory roasting cyanidation leaching test. The ore is ground to a fineness of -lmm; calcined in a horse boiling furnace, the calcination temperature is 650 ° C, time 3 h, after cooling, water is added to make the concentration reach 40%, the pH is adjusted to lO ~ ll, sodium cyanide is added, and mechanical stirring After immersing for 40 hours under conditions, the precious liquid and the leaching residue were filtered, and the recovery rate of gold was 75.0%.

(2) Roasting cyanide leaching production test. The production process is shown in Figure 1.

1 rotary kiln bake × L = l100 mm × 14000 mm.

2 The ore capacity is about 15t/d.

3 roasting 1t ore cost 60 yuan, plus subsequent cyanide, the total cost per ton of ore is 190 yuan.

4 The total recovery rate is 75%, and the tailings contain gold 0.4×10 ^-6 .

5 plus lime roasting oxidation effect is good, can also make the arsenic and sulfur in the ore converted into arsenate and sulfate form fixed in the calcine, reduce environmental pollution; also make the loose sand porous and easy to be cyanidated; Reduce the residence time of the calcine in the kiln, thereby improving the efficiency of sand production and reducing energy consumption.

According to the above test analysis and comparison, it is considered that the roasting-cyanide leaching effect of the ore technology processing process is better, and the harmful components such as sulfur and arsenic are fixed in the calcine.

Fourth, the economic significance of mineral deposit development

(1) Analysis of exploration and development conditions of gold deposits

The census work has calculated the resources of gold deposits to reach the scale of large deposits, the technical conditions for the development of deposits are good, the hydrogeological conditions are simple, and the engineering geological conditions are not complicated.

The Zaozigou water source in the mining area is rich. At present, there is a 10kV transmission line, which is close to the networked line. It is relatively easy to rebuild and expand. The mining area is within 10km from the cooperative urban area. The transportation and materials supply are convenient; In ethnic areas, economic and technological development is underdeveloped, and the development of projects plays a leading role in revitalizing the local economy. Therefore, the external conditions of project development are better.

The scale of mine production, the planned processing capacity is 500t/d, the annual working day is 300d, the annual mining stone volume is 150,000t, and the service life is 10 years, which meets the requirements of the average medium-sized enterprise service period of 10~2O years.

The main ore body generally has a small thickness of about 1 to 5 m. The production is steep, the extension is large, and the strike is long, which is not suitable for open pit mining. According to the topographical conditions, the ore body above the diving surface is developed with flat rafts, and the subdivision caving method is used for mining. However, because the ore is easy to agglomerate, the segment height and the size of the collapse zone should be limited to reduce the backlog of ore in the pit.

(2) Selection of technical and economic indicators

According to the actual production situation of similar mining enterprises and Zaozigou gold mines, combined with market research, the following technical and economic indicators are selected:

1. The mining recovery rate is 80%; 2. The mining depletion rate is 10%; 3. The ore grade gold is 4.0×10 ^-6 ; 4. The total mining cost is 90 yuan/t; 5. The full cost of flotation is 170 yuan/t; 6. The total cost of roasting and subsequent processes is 190 yuan/t; 7. The price of gold is 160 yuan/g.

(3) Technical indicators and economic benefits

The test technical indicators and economic benefits of three kinds of beneficiation methods such as conventional cyanidation, flotation cyanidation and roasting cyanide leaching are shown in Table 1.

Table l Technical indicators and economic benefits of different mineral processing methods

The main parameters indicate: the selected ore grade gold is 4.0×10 ^-6 , the estimated cost is based on the conventional cyanidation method, the flotation process is increased by 60 yuan/t, the roasting process is increased by 80 yuan/t; the cost estimation and profit estimation are per ton of ore. Calculation, no additional management fees, etc.

(4) Sensitivity analysis

According to the selected technical and economic indicators, the economic benefits of the deposit, the conventional cyanidation method has no profit at all, so this method can not be used, only the flotation cyanidation or roasting cyanide can be used. The comparative analysis of the economic benefits of these two beneficiation methods is shown in Table 2.

Table 2 Comparison of economic benefits of different mineral processing methods

As we all know, the economic benefits of mining enterprises mainly depend on the processing cost and gold price. In order to understand the ability of enterprises to offset the market, we have made two options of flotation cyanidation and roasting cyanide in price increase (processing cost increase) and gold price decline. The economic benefits of the enterprises (sensitivity analysis), the comparative analysis results are shown in Table 3.

Table 3 Analysis of the sensitivity of economic benefits

It can be seen from the comparison of the above two schemes: First, roasting cyanidation is obviously superior to flotation cyanidation, especially economic benefits; second, both schemes have certain ability to withstand market risks; third, enterprises cannot Left and right, enterprises must improve their economic efficiency, mainly relying on reducing production costs, and working hard to improve the process to improve the recovery rate.

V. Conclusion

The Zaozigou gold deposit is a medium-low temperature hydrothermal tectonic altered rock type large gold deposit. For its primary ore, through the experimental comparison of various mineral processing techniques, the roasting cyanide leaching method should be selected for the beneficiation process. Processing ore with this method has several advantages:

(1) The ore is leached by roasting cyanidation, which can make the leaching rate reach 75%, greatly improve the comprehensive recovery rate of gold, and at the same time achieve the purpose of making full use of limited mineral resources.

(2) By roasting the ore, the ore can be cracked, which is beneficial to the dissociation of gold, and the harmful components such as sulfur and arsenic can be fixed in the calcine.

(3) Using this method to process ore, the economic benefit of 290 yuan per ton of ore can be recovered, the investment cost can be recovered in a short time, and the capital flow of the enterprise can be accelerated.

Through the analysis of recent international and domestic market analysis and mine investment environment, the development of the original ore of the Zaozigou gold deposit is very good, and it has a very good economic significance of mine development, which can enable the enterprise to obtain considerable economic benefits.

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