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Copper oxide bacteria leaching production practice
First, the old copper mining district official mountain bacterial leaching test mining industry
(1) Overview of the leaching area
The leaching area is the old mining area of ​​the 5 m section of Songshan Mountain. The surface has fallen, and the ore body belongs to the high-middle temperature hot liquid metasomatic deposit in the contact zone, and the ore belongs to the middle and late oxidation stage of the sulfide ore. The sulfation is strong and the phase composition is complex, including the surface covering and the residual ore. The surface coverings include iron cap, red clay layer and yellow clay layer. The iron cap has a copper grade of 0.2~0.5%, and the clay layer contains a copper grade of 0.2~0.25%, all of which are low grade ore. Due to the low-grade, metal complex storage conditions, it can not yet be used by the current mining industry. In the residual ore, the primary sulfide ore is mainly pyrite and copper-bearing pyrrhotite, accounting for 34.2%, and oxidized ore (including secondary sulfide ore and copper oxide) accounts for 35.1%. Iron caps account for about 30.7% of copper.
Songshu Mountain has been exploited since the Tang Dynasty. There are a lot of hollows in the ore body. The mining method has been carried out by the caving method for more than 5 meters, so the top plate and the surface cover have fallen. The looseness of the cover facilitates water seepage, which is an advantageous condition for leaching. The unfavorable conditions are: the surface is not flat, the cloth liquid is not uniform, the residual ore is covered and the bacteria liquid is difficult to enter.
(two) process
The ferrous sulfate is oxidized into a high-iron sulphate leaching solution by the catalytic action of the living body. The spraying liquid method is used to sprinkle the bacterial liquid into the surface percolation field, and the leaching solution is leached through the surface covering and the residual ore. The leaching liquid is collected from the original mining tunnel in the water tank and pumped to the surface with acid resistance. The copper-rich liquid enters the iron replacement column for iron replacement to produce powdery precipitated copper; the tail liquid is mixed with acid and injected into the bacterial regeneration tank, and the aerated bacteria oxidize Fe 2+ to Fe 3+ to prepare the bacterial liquid. The bacterial liquid and the excess tail liquid are mixed and acidified, and then raised to the surface to spray the leaching. Lean ore liquefaction is added to the replenishing water (Fig. 1).
Figure 1 Bacterial leaching process in the old mining area
(3) Percolation technical parameters
Total iron, Fe 2+ , Fe 3+ concentration and ratio in leaching solution:
Separation was carried out with leaching solutions of total iron concentrations of 2, 4, 6, 8, 10 g/l and different ratios (Fe 2+ and Fe 3+ ), wherein pH = 2.0 ± 0.05.
By comparison, the leaching solution has a better leaching effect when the pH of the leaching solution is 2.0±0.05, Fe=6 g/L, Fe 2+ = 3 g/L, and Fe 3+ = 3 g/L. Exceeding this indicator is not significant. However, in the field test, the total iron concentration can only reach 1.5~3g/L. Only the ratio of Fe 2+ and Fe 3+ can be controlled, and it is necessary to further explore ways to increase the concentration of total iron.
Percolation strength and rotation system
The amount of water sprayed per unit area (diafiltration intensity) directly affects the leaching scale and the copper ion concentration of the leachate. When the mine uses a water spray of 1 m 3 per hour at 100 m 2 , the final average grade of the leachate will increase by about 15%, and the acid consumption will also decrease accordingly. Therefore, the percolation strength is recommended to be 1 m 3 per 100 m 2 per hour.
Due to the ongoing experiment, the cycle of rotation is still to be explored.
(4) Main indicators of industrial testing
The percolation field irrigation area is about 4000 m 2
The average output of leaching solution is 368 m 3 / day
Average Cu concentration 0.41 g / liter
Monthly leaching of copper 4610 kg
The highest amount of copper leaching 323 kg / day
Leachate loss rate 40~50%
The average grade of tail water is 0.067 g / liter
Copper recovery rate 93%
Sponge copper grade about 60%
2. Sulphur leaching treatment of copper tailings in the Shanbaifang copper mine of Shuikou
The Baifang Copper Mine of Shuikoushan Mining Bureau has a large number of poor ore and tailings containing copper and rare metals. In recent years, with the help and guidance of the Institute of Microbiology of the Chinese Academy of Sciences, research work on the recovery of copper and rare metals from tailings by sulfuric acid-bacterial leaching has been developed and officially put into production in 1972.
The production practice in the past few years proves that the process of leaching out the ore by sulfuric acid-bacteria can comprehensively leaching copper and rare metals in the ore. The recovery rate is high, the operation is simple, the equipment is small, and the cost is low. An effective way to benefit and comprehensively utilize mineral resources.
The characteristics of the mine containing copper tailings are: rare metals accompanying copper, the ore is acidic, but the gangue carbonate content is high, the grain size is fine (1 mm), it is sticky, and the percolation performance is poor. The grade of tailings and the composition of the copper mineral phase are listed in Table 32.1.60.
The process of bacteria participating in the high-iron soluble tailings of sulfuric acid is shown in Figure 2.
Figure 2 Process of bacterial leaching treatment of tailings
The copper-containing tailings have three parts: flotation tailings, re-selected tailings and slime, which are currently treated.
The flotation tailings have a particle size of 99%-20 mesh, good percolation, and can be directly leached separately.
Re-selected tailings, with a particle size of -2 mm, accounting for 95%, better percolation, and can be directly treated separately.
The slime is formed by the fine particles of the flotation tailings and the re-selected tailings. It is fine-grained and cannot be diafiltered separately. Therefore, it is mixed with heavy sand (1:1).
(1) Bacterial culture
The strain is a strain of Thiobacillus ferrooxidans No. 9 which is separated and screened by Tongguanshan copper ore. The bacterial culture is carried out using a renji-free medium. The culture conditions are shown in Table 1.
Table 1 ferrous oxidation rate under different culture conditions
Inoculum
%
Amount of culture fluid
%
Fe 2+
g/L
pH
Temperature °C
Nutrient addition
Fe2+ ​​is completely oxidized
Time required for Fe3+, d
(NH 4 ) 2 SO 4
K 2 HPO 4
KC1
0.004
0.006
0.006
0.50
20.0
About 25
About 30
About 25
About 25
About 30
12.84
4.24
6.03
7.70
4.49
2.0
1.8
1.9
2.0
2.0
24~28
28~32
28~31
24~30
24~30
2
1.5
2
2
-
0.5
1.0
0.5
0.5
-
0.5
1.0
-
-
-
7
4.5
About 3
Near 2
1.5
Note: The culture process is ventilated 4 times a day (about 6 hours in total), and the rest are given an appropriate amount of compressed air.
It can be seen from Table 1 that when the conditions of Fe 2+ concentration, temperature and pH are almost the same, the speed of bacterial ferrous oxide is greatly related to the inoculum amount, in order to rapidly culture the bacterial high-iron leaching agent and reduce the pressure wind power. Consumption should be expanded or continuously cultured.
(2) Percolation leaching
The flotation tailings contain 0.11~0.2% copper, and the re-selected tailings contain 1.25~1.5% copper. Both tailings contain rare metals.
Because the tailings are fine in size and difficult to percolate, the leaching tank is used for production. The alkaline gangue in the acidified water and ore is first added. When the pH of the solution reaches about 2.0, the immersion of high-iron (Fe 2+ ) is added. Mineral or leaching of lean liquid (referred to as copper and rare metal reduced, higher Fe 2+ leachate) is circulated until the copper and rare metals in the leaching solution are lower. Then, the copper high-iron liquid with extremely low metal content is added, and when the concentration of the leaching solution is lower, it is washed with water for two or three days. The tailings leaching time was 20 days, and the leaching results are shown in Table 2.
Table 2 Leaching results
Leaching pool
Numbering
Feeding amount
t
Sulfuric acid consumption
Kg/t
Humidity °C
Leaching cycle
d
copper,%
Rare metal leaching rate, %
Raw ore
Infusion
Leach rate
1
2
3
100
100
100
34
32
30
25~35
25~35
25~35
27
18
twenty three
0.81
1.25
1.51
0.17
0.48
0.44
79.02
61.60
70.86
86.40
51.85
80.37
(3) Recovery of copper
The tail liquid after adsorption of rare metals contains about 2 to 1.5 (g/L) of copper, and the copper is recovered by sponge replacement by iron filings or scrap iron. The operating conditions of the replacement process are:
1. The higher the copper content of the replacement liquid, the better. The iron content should be reduced as much as possible, pH=1.8~2.0.
2. When the pH of the solution is about 1.5 and the concentration of copper is 2~4 (g/L), the iron consumption ratio is 2~2.5 times that of copper. When the pH is about 2 and the copper concentration is high, the iron consumption ratio is 1.5 times that of copper.
3, replacement time and temperature, scrap iron quality and quantity, solution acidity and displacement mode, generally in the case of temperature > 20 ° C ventilation, 6 hours can be replaced.
4. Immediately after the replacement, the tail liquid is discharged, and the Fe 2+ concentration and acidity in the tail liquid are adjusted to be used as a bacterial culture solution.
(4) Main technical and economic indicators
The total recovery of rare metals is 75~80%, and the total recovery of copper is 70~75% (the leaching rate is 75~80%, and the precipitation rate is 90~95%). Sponge copper contains 60~65% of copper, 40~45 kg of sulfuric acid per ton of minerals, and 2.5 tons of copper per ton of copper is 2,000 yuan per ton of copper.
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Phosphate ore sorting technology