I. Introduction
Southeastern Guizhou is one of the concentrated distribution areas of China's fine-grained disseminated gold deposits. The micro-disseminated gold ore is complex in nature and has a special type of technology. Over the years, many scientific research and design units have conducted research on smelting and smelting, and some research results have been obtained, but there are still some technical problems that need to be solved.
This experiment takes the sang gold mine in Yunnan Province as the research object, conducts leaching test research, and provides reference for the company's production.
Second, the ore characteristics
The ore type is an oxidized ore, and the mineral rock is an altered silt mudstone or siltstone and a small amount of basic vein rock. The ore structure is a gel structure and an imaginary structure. The main metallic minerals limonite ore, pyrite, copper ore, arsenopyrite, pyrrhotite, maghemite, tetrahedrite. Analysis of the chemical composition of the ore indicates that gold is the main recycled useful component with a gold grade of 0.70 g/t. 0.28% arsenic content in the ore, clay minerals such as sericite about 47%. Gold is mainly encapsulated in oxidized minerals such as limonite, and there are a large number of iron-dyed clay minerals in the ore (mainly sericite, whose crystals are layered), which also adsorbs a certain amount of ultramicroscopic gold.
Screening analysis of ore samples broken to less than 40 mm mainly investigated the yield and gold distribution of seven fractions. The gold grade of the coarser grade is higher, and it can be seen that the grain size of the gold is not fine, and the fine ore is not required to be seen when the ore is leached.
Table 1 - 40mm ore screening analysis results
Particle size / mm | Yield/% | Gold grade /g·t -1 | Gold distribution rate /% | ||
individual | Grand total | individual | Grand total | ||
+10.0 | 33.25 | 33.25 | 0.56 | 28.18 | 28.18 |
-10.0+5.0 | 16.29 | 49.55 | 0.84 | 20.59 | 48.72 |
-5.0+1.0 | 14.01 | 63.56 | 0.94 | 19.94 | 68.71 |
-1.0+0.28 | 10.45 | 74.01 | 0.80 | 12.68 | 81.38 |
-0.28+0.154 | 2.53 | 76.54 | 0.55 | 2.10 | 83.48 |
-0.154+0.076 | 2.81 | 79.35 | 0.36 | 1.52 | 85.00 |
-0.076 | 20.65 | 100.00 | 0.48 | 15.00 | 100.00 |
total | - | - | 0.66 | - | - |
Third, cyanide leaching test study
(1) Comprehensive sample preparation. 32 bags of single sample drying, crushed to -40mm, shrinking out 1 / 8 to make a test sample, analyze the gold grade of each bag sample. According to the gold grade and test requirements, the 240kg comprehensive sample is restricted. It is required that the calculated grade of the ore blending coincides with the average grade of 0.70 g/t of the multiple samples of the comprehensive sample.
(2) Leachability test. In order to understand the leachability of gold in the ore, and to provide process parameters for the column leaching test, the ore was subjected to cyanidation leaching test. The indicators such as NaCN and alkali consumption and gold leaching rate were mainly investigated.
Cyanide leaching fixed conditions: 100 g / time of ore, particle size -1 mm, slurry concentration of 40%, initial concentration of NaCN of 0.4%. , Industrial lime adjusts the pH value of 10 to 11, and shakes the bottle for 18 hours. The test results show that the leaching rate of the gold residue in the ore is 87.14%, the NaCN consumption is 261.2g/t, and the industrial lime dosage is 5kg/t. The ore is easier to leach. (3) Column immersion test. The ore crushed to a certain particle size is charged into the column, and the pH of the ore is adjusted by a solution prepared by using NaOH. When the pH value of the exudate is adjusted to 10 to 11, a NaCN solution having a pH of ≥ 2 and a concentration of about 0.4 , is prepared. Adjust the spray speed of the solution, test the spray intensity of about 8 ~ 12L / m 2 · h1, spray the leaching solution for a period of time, sample the NaCN concentration and analyze the gold grade. After the leaching is completed, the column leaching residue is washed with a certain amount of water, the washing water is metered, the NaCN concentration is sampled and the gold grade is analyzed. Finally, the leaching residue is taken out, dried, shrunk, and sampled, and the gold grade in the leaching residue is analyzed. The column immersion test conditions and results are shown in Table 2, respectively.
Table 2 Column immersion test conditions
Ore size / mm | Ore weight / kg | Granulated cement consumption / kg · -1 | Column height / cm |
-40 | 81.7 | - | ~175 |
Pile specific gravity / g · cm -3 | Saturated water content / L · t -1 | Spray strength / L · m -2 · h -1 | Initial spray NaCN concentration / ‰ |
1.65 | 202.38 | 8.5~10.5 | ~0.4 |
It can be seen from the test results that after 25 days of leaching, the leaching rate of the slag meter is 80.0%, and the gold grade of the tail slag is reduced to 0.14 g/t.
(4) Other leaching methods to explore the test. In order to further increase the leaching rate, an infusion leaching, an acid thiourea leaching and a tail slag re-leaching test were carried out.
1. Add an immersion test for the infusion. Leaching and fixing conditions: 100g/time of ore, particle size-1mm, slurry concentration 40%, initial concentration of NaCN is 1.0‰, lime adjustment value pH value is 10～11, shake flask cyanidation for 18h. The cyanide leaching test results showed that the leaching rate of the gold slag meter was not significantly improved by adding an auxiliary agent such as H 2 O 2 , CaO 2 or NH 4 Cl.
2. Thiourea leaching. Leaching conditions: 100g/time of ore, ore size-1mm, slurry concentration 40%, thiourea dosage 10kg/t, Fe 2 (SO 4 ) 39kg/t, sulfuric acid to adjust pH value 1-2. The test results show that the leaching rate of gold thiourea is not as high as the direct cyanidation leaching rate.
3. The tail slag is re-dipped. Since the column leaching liquid gold concentration and the tail slag gold grade are still relatively high, the tail slag leaching is again leached to investigate the possibility that the leaching rate is increased if the column immersion time is extended.
A part of the column dipping tailings was crushed to -5 mm, and a certain amount of column dipping tailings which were not broken and crushed to -5 mm were taken, placed in an organic tank, and allowed to stand for immersion for two days with a 0.4 N NaCN solution. Leaching test The results show that the column dipping tailings are immersed in the tank for two days, and the leaching rates of the -40mm and -50mm tailings relative to the ore are 6.57% and 5.03%, respectively. It can be seen that if the column immersion time is extended, the gold leaching rate is improved, but the leaching period is prolonged, the amount of leaching liquid is increased, and the gold concentration of the solution is lowered.
Fourth, the conclusion
1. The impregnation test is carried out on the composite sample broken to -1mm, the concentration of slurry is 40%, the initial concentration of NaCN is 0.4‰, the consumption of NaCN is 261.2g/t, the pH of lime is adjusted to 10~11, and the amount of industrial lime is 5kg/t. After the shake flask was cyanated for 18 hours, the gold leaching rate of the slag was 87.17%, and the gold grade was reduced to 0.09 g/t.
2. The sample was crushed to -40mm and immersed in a column for 25 days. The NaCN consumption was 171.7g/t, the leaching rate of gold residue was 80.0%, and the gold grade of tailings was reduced to 0.14g/t.
3. Other leaching methods such as leaching of leaching agent, sulfur leaching and extension of column immersion time have no obvious effect on gold leaching.
4. The above test results show that the composite sample is easier to leaching under the conventional cyanide leaching conditions. This test provides a technical basis for the leaching of the Sangjin Mine.
references:
1. Ma Jing, Ma Jiwu, 2001. Experimental study on Jianchaling Gold Mine and its smelting [J]. Gold Science and Technology. 10(2): 35-39.
2, Cai Shijun, Zhao Zhixin, Zhao Anlong. 2003. Research and practice of liquefaction and leaching of arsenic-rich and copper-gold ore in Laojiaoshan gold mine[J].金.24(5):38-40.
3. Zhou Zhongding. 2003. Experimental study on gold selection of micro-drawing type gold ore [J]. Gold. 24(6): 43-45.
4. Tan Haiming.Experimental study on ore leaching of a gold ore body in southern China[J].ä¸å›½çŸ¿ä¸š.14(2):38-42.
(Author's introduction Li Hua, Zijin Mining Group Co., Ltd., Senior Engineer)
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