Low-grade copper oxide ore and leaching test of residual ore

The copper industry used leaching and mining earlier, first applied to the off-surface ore stripped from open pit mines, and gradually developed to the residual ore and pillars lost in the underground stope, and leached copper in situ. Leaching copper by leaching method accounts for about 15% to 20% of total copper production in the United States, which fully indicates the vitality of leaching mining. In the middle section of the 0m middle section and the middle section of the -40m section of the Wushan copper mine in Jiangxi Province, the caving method is mainly used for mining. Due to the complex geological conditions of the ore body, the ore is loose and spontaneously ignited, and the atmospheric rainfall seeps into the stope, deteriorating the mining conditions and causing the mine. During the mining process, there are 160,000 tons of residual ore in the caving area; about 3.93 million tons of unmined oxidized ore in the south ore belt, totaling about 4 million tons, with an average grade of 1.3% to 3.5%. . If this part of the residual ore grade is reduced from 1.5% to 0.4% to 0.5%, the mine can recover 1.5 million tons of copper ore per year, which is equivalent to the establishment of a small copper mine. To this end, the ore is tested for leachability. The purpose is to determine the leachability of the ore and its influencing factors through small tests, and to provide reasonable process parameters for on-site semi-industrial tests.
1 Mechanism of leaching process
Leaching of ore is a chemical thermodynamic process and a heterogeneous reaction kinetic process. The process actually includes the following steps:
(1) The leaching agent in the leaching solution migrates and diffuses to the surface of the solid ore particles by means of convection diffusion and molecular diffusion;
(2) the leaching agent in the leaching solution diffuses inward from the outer surface of the ore particles through the pores and fissures in the ore through the pores and cracks in the ore to the inner surface of the ore;
(3) the leaching agent chemically reacts with the useful mineral component on the inner surface of the ore to form a soluble compound dissolved in the solution;
(4) the soluble compound formed by the reaction diffuses from the inner surface of the solid ore particle to the outer surface;
(5) The soluble compound formed by the reaction diffuses outward from the outer surface of the solid ore particle into the bulk solution.
It can be seen from the whole process that (1) and (5) above are a diffusion process, and (2), (3) and (4) are a chemical reaction process. The leaching of copper oxide minerals involves the chemical reaction of the leaching agent with the copper compound and the diffusion process of the leaching agent and the product, so the leaching process depends on the reaction kinetics and diffusion kinetics, and the total mass transfer rate is a major Controlling factor.
2 leachability test
2.1 Mineral properties Wushan Copper Mine belongs to the medium-temperature hydrothermal skarn type copper-sulfur deposit, which is divided into two ore belts. Northern Industrial Minerals type copper pyrite type copper carbonate rock, kaolin followed by copper, copper-containing topical igneous. The ore is mostly loose, with a copper grade of 1.5% to 2.0% and a copper oxidation rate of more than 30%. The southern ore belt is a skarn type, which is present in the contact zone between carbonate and granodiorite porphyry. . The type of ore is copper-bearing skarn type, followed by copper-bearing marble and copper-bearing granodiorite porphyry. The ore mainly has grain structure and fracture structure. The copper grade is about 2.0%, and the oxidation rate of copper is greater than 30%.
2.2 Leachability test
In order to seek ways to recover copper from residual oxidized minerals in the goaf and low-grade oxidized minerals in order to make full use of mineral resources and improve the economic benefits of the mine, the indoor leachability test of the copper ore is carried out to find out The relationship between suitable leaching agent and concentration of leaching solution, pH value, reaction time and leaching rate provides design basis for underground leaching test. The chemical composition and phase composition of the ore are shown in Table 1 and Table 2, respectively.
Table 1 Multi-element analysis of raw ore
Cu S Pb Zn Fe Mo Al ₂ O ₃ SiO ₂ CaO MgO C
1.03 2.30 0.006 0.074 10.80 0.0033 4.35 52.70 8.66 1.10 2.36

Table 2 Copper phase analysis %
Name Copper sulfide Combined copper oxide Soluble copper + free copper oxide Total copper South ore belt 1.14 0.19 0.59 1.92
North Belt 1.05 0.17 0.56 1.78
The leaching test is first done by soaking in a beaker. The leaching conditions include: ore particle size, leaching agent concentration, strengthening agent dosage, oxidant dosage, solid-liquid ratio, leaching period, leaching system, etc. The main factors affecting the leaching rate are the first five factors. The test was carried out using an orthogonal design method. The design factors are leaching agent concentration A, oxidizing agent dosage B, strengthening agent dosage C, ore particle size D, leaching time E. The interaction between the various factors is not considered at present, and only the orthogonal design of the above factors is adopted. According to the influencing factors, five orthogonal experiments were carried out using L ₂₄ (6×4×23), L9 (3 ⁴ ) and L12 (6×2 ² ) orthogonal schemes. The test scheme and test results are shown in Table 3~ 7.
It can be seen from Table 3 that the effect of time on the leaching rate is generally as long as possible, but with the extension of time, the leaching rate increases more slowly, and the initial leaching rate rises rapidly; The main influencing factors in the sub-test were the leaching time E, followed by the leaching agent concentration A; the highest point of each factor, namely A5B1C1E1, was the best process condition for this test, which combined the effects of various factors on the leaching rate; The primary and secondary relationship of each factor is: E→A→C→B.

Table 3 L ₂₄ (6 × 4 × 2 ³ ) test plan and test results

Table 4 L9 (34) test plan and test results

It can be seen from Table 4 that the initial leaching rate rises rapidly, and the leaching rate rises more slowly with time; the most important influencing factor of this test is B, followed by E; the highest point of each factor, namely A ₂ B ₂ C ₁ E _{3 is} the best process condition for this test; the primary and secondary relationship of each factor is: B→E→A→C.

Table 5 L ₁₂ (6 × 2 ² ) test plan and test results

It can be seen from Table 5 that the initial leaching rate rises faster, and the leaching rate rises more slowly with time; the most important influencing factor of this test is A, followed by C; the highest point of each factor, namely A ₅ B ₅ C _{5 is} the best process condition for this test; the primary and secondary relationship of each factor is: A→C→B; when the concentration of leaching agent A is increased, the two reagents B and C have no obvious effect on the leaching rate.

Table 6 L ₂₂ (6 × 2 ² ) test plan and test results

Note: The leaching time is 2 days. It can be seen from Table 6 that the initial leaching rate rises faster, and the leaching rate rises more slowly with the extension of time; the most important influencing factor of this test is A, followed by D; The highest point, A ₁ B ₁ D ₁ , is the best process condition for this test; the primary and secondary relationship of each factor is: A→D→B.
According to the above four test results of the North Ore Belt, the ore leaching parameters should be: A (3%), B (0.25%), C (2.5%), E (1). At this time, the leaching rate can reach 60% to 75%. Therefore, it is recommended to use the above leaching process parameters in the downhole semi-industrial test.

table 7 L ₉ (3 ⁴ ) Test plan and test results

It can be seen from Table 7 that the initial leaching rate rises faster, and the leaching rate rises more slowly with time. The main factor affecting the leaching rate in this test is A, followed by C; the highest point of each factor, namely A3B1C2E3 The optimum process conditions for this test; the primary and secondary relationships of each factor are: A→C→B→E; the optimal leaching parameters are: A (3%), B (0.25%), C (2.5%), E (1).
3 Conclusion
(1) When the ore is in A (3%), B (0.25%), C (2.5%), E (1) conditions, the leaching rate can reach 60% to 75%;
(2) The leaching of ore is more complicated, and the influencing factors are also multi-faceted. In addition, the oxidation rate of ore is not too high, only about 30%. With a single acid leaching, the leaching rate is difficult to increase and must be strengthened. The means of leaching, namely adding oxidant B and strengthening agent C;
(3) By means of the orthogonal design method, not only the test workload can be reduced, but also the influence of various accidental errors on the result inference can be effectively avoided, and the research results are more accurate and reliable. At the same time, using the orthogonal design to test, the primary and secondary effects of each factor in the test and the effect of each factor on the index can be distinguished by fewer test times, so as to find out better production process conditions.

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