Tangdan low grade copper oxide ore, the mineral composition of complex embedded fine particle size, the oxidation rate and a high rate, a high gangue content of calcium, magnesium, copper is a typical refractory oxide. Since copper oxide ore Tangdan characterized as a "high oxidation rate, high associativity, high calcium and magnesium, low-grade" and "pickling - Extraction - Motor" and other bio-metallurgical methods are not applicable. Therefore, the ammonia leaching method becomes the only choice for Tangdan refractory copper oxide hydrometallurgy. In recent years, based on years of research, the author has successfully developed a joint process of “normal temperature and atmospheric pressure ammonia leaching-extraction-electrowinning-slag flotationâ€, which has been successfully applied to production and achieved good economic and environmental benefits. This paper mainly introduces the test and production results of the normal temperature and atmospheric pressure ammonia leaching part.
First, the test method condition flow
(1) Test method
The ore sample is dry-ground by ø200×250 cylindrical rod mill to the required particle size for use. The leaching agent is prepared according to different concentration requirements and is calibrated for use. Small leaching test Each test was weighed 700 g of raw ore sample, and the leaching agent was added according to the liquid-solid ratio of the test design, and stirred and leached with a JJ-1 booster electric mixer in a 1500-3000 mL beaker. After the leaching is completed, the slurry is immediately filtered, the slag is leached for washing, filtered and dried, and the sample is sampled, and the sample bag is sealed and sent to the analysis center for analysis and analysis; the leaching solution is metered, the sample is mixed, and the sample is sent to the analysis center for analysis.
(2) Test chemicals and equipment
The test reagents ammonia, ammonia hydrogencarbonate and ammonium fluoride ammonium were all analytically pure. The test equipment includes: ø200×250 cylindrical rod mill; JJ-1 booster electric mixer; beaker; measuring cylinder; multi-purpose vacuum filter: XTLZ ø260/200ø; electric blast drying oven.
(3) Analysis of sample phase
The raw mineral phase composition of the small test of Tangdan copper oxide ore is shown in Table 1.
Table 1 Results of raw mineral phase analysis of Tangdan copper oxide small test
project | content% | Distribution rate% |
Free CuO | 0.480 | 44.65 |
Combined with CuO | 0.180 | 16.74 |
Active CuS | 0.370 | 34.42 |
Inert CuS | 0.045 | 4.19 |
Total Cu | 1.075 | 100 |
Note: The oxidation rate is 61.39%.
(4) Test procedure
The combined process of "normal temperature and atmospheric pressure ammonia leaching - extraction - electrowinning - slag flotation" is shown in Figure 1.
Figure 1 Normal temperature and atmospheric pressure ammonia leaching-extraction-electrowinning-slag flotation principle process
Second, the ammonia leaching mechanism
The ammonia leaching process mainly uses the reaction of copper to form a complex with ammonia, so that copper enters the solution from the ore, thereby achieving separation from the gangue. Under normal pressure, ammonia reacts with malachite and chrysocolla as follows:
malachite:
(1)
Chrysocolla:
(2)
In the presence of oxygen, ammonia reacts with Cu 3 FeS 3 as follows:
(3)
3. Research on the influencing factors of copper leaching rate
(1) Effect of ammonia concentration on leaching rate
The curve of copper leaching rate as a function of ammonia concentration is shown in Fig. 2. The leaching rate of copper increases with the increase of ammonia concentration. When the concentration of ammonia is in the range of 0~2 mol/L, the leaching rate is greatly affected by the concentration of ammonia. When the ammonia concentration is greater than 2 mol/L, the leaching rate is less affected by the ammonia concentration.
Figure 2 Effect of ammonia concentration on copper leaching rate
The ore particle size is -0.074mm, the grain size is 80%, the leaching time is 1h, the liquid-solid ratio is 2:1, room temperature.
n(NH 3 ):n(NH 4 HCO 3 )=2:1.
(2) Effect of leaching time on leaching rate
The curve of copper leaching rate as a function of time is shown in Figure 3. When the leaching time is in the range of 0 to 2 h, the leaching rate is greatly affected by the time. When the leaching time exceeds 2 h, the leaching rate is less affected by time.
Figure 3 Effect of leaching time on leaching rate
The ore particle size is -0.074 mm, 80%, ammonia water concentration is 2 mol/L, liquid-solid ratio = 2:1, room temperature, n(NH 3 ):n(NH 4 HCO 3 ) = 2:1.
(III) Effect of ore particle size on leaching rate
The curve of copper leaching rate as a function of grinding grain size is shown in Fig. 4. The leaching rate increases with the increase of the -0.074 mm fraction in the ore. However, if the particle size is too fine, the viscosity of the slurry will increase, but the leaching speed will be reduced, and the grinding cost will be increased, which will cause difficulty in solid-liquid separation operation.
Figure 4 Effect of grinding fineness on leaching rate
Ammonia water concentration 2mol / L, liquid-solid ratio = 2:1, room temperature, leaching time 2h,
n(NH 3 ):n(NH 4 HCO 3 )=2:1.
(4) Effect of liquid-solid ratio on leaching rate
The curve of copper leaching rate as a function of slurry solid ratio is shown in Fig. 5. The leaching rate of copper increases with the increase of the slurry solid ratio. The liquid-solid ratio increases, and the viscosity of the slurry decreases, which is advantageous for the diffusion of reactants and products.
Figure 5 Effect of liquid-solid ratio on leaching rate
The ore particle size is -0.074mm, the grain size is 80%, the ammonia concentration is 2mol/L, room temperature.
n(NH 3 ):n(NH 4 HCO 3 )=2:1.
(5) Effect of temperature on leaching rate
The curve of copper leaching rate as a function of slurry temperature is shown in Fig. 6. The leaching temperature has a significant effect on the leaching rate of copper, and the leaching rate of copper increases with increasing temperature.
Figure 6 Effect of reaction temperature on leaching rate
The ore particle size is -0.074 mm, the particle size is 80%, the reaction time is 2 h, the ammonia concentration is 2 mol/L, the liquid-solid ratio is 2:1, and n(NH 3 ):n(NH 4 HCO 3 )=2:1.
(6) Effect of activator ammonium hydrogen fluoride on leachate
In order to obtain a higher leaching rate, the use of the activator ammonium hydrogen fluoride is considered. It is leached by the activator NH 3 -NH 4 HF 2 system, which mainly uses the ionic radius of fluoride ion to be small, and has strong penetrating ability in ore ions, and the internal diffusion rate block; at the same time, the fluorine is easy to be combined with copper at normal temperature and pressure. The mineral acts to form a fluorosilicate, which destroys the original structure of the copper in the ore, frees the copper, and is converted into a solution by the complexation of ammonia to form a copper ammonia complex. At normal temperature, the activation effect of the activator on the ore is not obvious. When the reaction temperature is higher than 30 °C, the activation effect is more obvious. The comparison between atmospheric ammonia leaching and activated ammonia leaching is shown in Fig. 7.
Figure 7 Comparison of atmospheric ammonia leaching and activated ammonia leaching
The ore particle size is -0.074mm, the grain size is 80%, and the leaching time is 2h.
Liquid-solid ratio = 2:1, room temperature, n(NH 3 ):n(NH 4 HCO 3 )=2:1,
n(NH 3 ):n(NH 4 HF 2 )=3.5:0.6 during activated leaching
Fourth, the statistical results of production applications
The production of low-grade copper oxide ore in Tangdan at room temperature and atmospheric pressure ammonia leaching shows that the ammonia concentration is 1.45 mol/L, the leaching particle size is -0.074mm, the grain size is 80%-85%, the liquid-solid ratio is 2:1, and the leaching time is 2h. Under the conditions, the ideal index of total copper leaching rate of 46.86% was obtained, which is consistent with the small test index. From March 2006 to October 2007, Kunming Ruiyuan Giant Metallurgical Co., Ltd. processed 800,000 tons of raw ore. The statistical results of industrial production cumulative indicators are listed in Tables 2 and 3.
Table 2 Statistical results of raw mineral phase analysis in industrial production
project | content% | Distribution rate% |
Free CuO | 0.48 | 42.86 |
Combined with CuO | 0.20 | 17.86 |
Active CuS | 0.39 | 34.82 |
Inert CuS | 0.05 | 4.46 |
Total Cu | 1.12 | 100.00 |
Note: The oxidation rate is 60.72%.
Table 3 Statistical results of industrial production indicators
Ï(NH 3 )/(mol·L - 1 ) | Ï(CO 3 )/(mol·L - 1 ) | Pulp concentration% | Leaching time h | Leaching temperature °C | Leach rate% |
1.45 | 0.48 | 33.65 | 2 | 30 | 46.86 |
V. Conclusion
(1) The leaching process is a key process for recovering metals in the ammonia-wet metallurgical process. The leaching process is controlled by factors such as leaching agent concentration, leaching particle size, liquid to solid ratio, leaching time, leaching temperature, and activator.
(2) Tangdan low-grade copper oxide ore is suitable for industrial production under normal temperature and atmospheric pressure ammonia leaching: ammonia concentration 1~2 mol·L, ore particle size -0.074mm grain size 80%-85%, liquid solid Ratio 2:1, leaching time 2h.
(3) The industrial production index is basically consistent with the small test index, indicating that the technical conditions proposed by the small test are reliable.
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