Comprehensive recovery of copper and cobalt by acid burning slag

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Dur'ngoi copper mine is a large copper and cobalt deposits in the 1960s and 1970s found that 20, has now completed daily processing raw ore 8kt, a joint system of processing mining 2.4 million t of each year will be more than 100 million t of tailings into the tail Mine warehouse. Dur'ngoi tailings containing 40.7% iron, 38.5% sulfur, 0.35% copper, 0.81% zinc, gold 0.44g / t, silver 7.6g / t, cobalt 11.3g / t. High iron and sulfur content, rich in valuable metals, and extremely valuable development and utilization value. After the pyrite sulphuric acid slag is processed, the qualified iron powder can be obtained for sale, and the slag contains valuable metal elements such as Cu, Co, Au, Ag, etc., so the sulphur iron slag is used as a secondary resource. It is a good comprehensive utilization of raw materials.

First, the experimental materials

 Sulfur concentrate is mainly used for boiling roasting to produce acid, while waste heat power generation, roasting temperature is generally controlled at 800 ~ 900 °C. In order to simulate the actual production situation, the boiling roasting experiment temperature was controlled at 850 ° C, and the produced slag was provided for the subsequent experiments. 

Sulfur concentrate contains Au0.32g/t, Ag6.47g/t, and other multi-element chemical analysis results (%): Cu0.31, Co0.073, Zn0.29, TFe44.9, TS47.9, MgO 0.25, CaO1 .11, SiO 2 1.22. The fine concentrate of sulfur concentrate is very fine, of which -0.074mm accounts for 90.67%, and -0.038mm accounts for 55.37, which has an adverse effect on filtration and roasting dust removal. The sulfur concentrate has a bulk density of 2.35 g/cm 3 .

After the sulfur concentrate is boiled at 850 °C, the slag contains Au 0.22g/t and Ag 6.22 g/t. The remaining multi-element chemical analysis results (%): Cu0.45, Co0.11, TFe63.4, TS1.42 . It can be seen that the elements of Fe, S and Cu in the slag do not meet the requirements of qualified iron fine powder; Cu and Co elements are all enriched. The slag bulk density was 1.30 g/cm 3 .

Second, the experimental process and experimental results and discussion

(1) Acid leaching experiment

1. Effect of leaching time on leaching rate

Acid leaching conditions: 850 ° C boiling furnace slag, initial acid concentration of 100 g / t, liquid-solid ratio of 2: 1, acid immersion temperature of 80 ° C, acid leaching slag washed 4 times, the experimental results are shown in Table 1.

Table 1 Effect of leaching time on leaching rate

Acid immersion time

Slag meter leaching rate /%

Cu

Co

Fe

1

70. 17

62. 00

1. 97

2

74. 44

64. 72

1. 42

3

74. 44

65. 62

1. 44

4

78. 70

62. 00

0. 98

6

76. 49

63. 70

1. 35

It can be seen from Table 1 that the leaching rate of copper and cobalt increases with the acid leaching time. When the leaching time exceeds 4 h, the leaching rate of copper and cobalt no longer increases; considering the actual production situation, the acid leaching time is selected for 2 h.

2. Effect of initial acid concentration on leaching rate

Acid leaching conditions: boiling furnace slag at 850 ° C, liquid-solid ratio 2:1, acid leaching time 2 h, acid immersion temperature 80 ° C, acid leaching residue water washing 4 times, the experimental results are shown in Table 2.

Table 2 Effect of initial acid concentration on leaching rate

Acid immersion time

Slag meter leaching rate /%

Cu

Co

Fe

20

57.26

47.37

1. 54

40

61.53

50.09

0. 44

60

70.08

58.26

1. 69

80

76.49

63.70

1. 75

100

70.08

57.35

1. 71

120

67.94

57.35

1. 90

160

76.49

65.52

1. 75

200

74.36

62.79

1. 46

It can be seen from Table 2 that when the acid concentration is between 20 and 80 g/L, the leaching rate of copper and cobalt increases with the increase of acid concentration, and the leaching rate is the highest when the acid concentration is 80 g/L. The leaching rate of copper and cobalt has little effect. Considering the factors of production cost, equipment requirements and subsequent processes, the initial acid leaching concentration is 40 g/L.

3. Effect of reducing agent on leaching rate

Sodium sulfite and sulfur dioxide gas were used as reducing agents, respectively. Acid leaching conditions: boiling furnace slag at 850 ° C, initial acid concentration 100 g /, liquid-solid ratio 2:1, acid immersion temperature 80 ° C, acid leaching residue 4 times, acid leaching time 2h. Experimental results: the leaching rates of copper and cobalt were 74.36% and 64.61%, respectively, when sodium sulfite was used as reducing agent, and the leaching rates of copper and cobalt were 80.77% and 71.87%, respectively, when sulfur dioxide gas was used as reducing agent.

Comparing with the results of Table 2, the addition of reducing agent increased the leaching rate of copper and cobalt, and the leaching rate of copper and cobalt as the reducing agent of sulfur dioxide gas increased more obviously. Considering the actual situation in the industry, it is recommended to use sulfur dioxide as a reducing agent.

4, the impact of the number of washing on desulfurization

After acid leaching and filtration, fresh water was added and stirred, and the filtration time was 10 min each time, and the liquid-solid ratio was 1.5:1. The sulfur element in the acid leaching residue was analyzed. The experimental results are shown in Table 3.

It can be seen from Table 3 that the acid leaching residue obtained by the acid leaching without S0 2 can be reduced to 0.1% or less by stirring with water for 5 times; the acid leaching slag obtained by the S0 2 acid leaching is washed 6 times with stirring. The sulfur content is still around 0.4%; taking into account the actual situation of industrial production, it can be washed in a thick wash - filtered and washed - 1 or 2 times with stirring.

Table 3 Effect of washing times on desulfurization

Initial acid concentration

/(g·L -1 )

Acid leaching residue S

content/%

Washing times

20

0. 26

4 times (not connected to S02)

20

0.071

5 times (not connected to S02)

40

0.21

4 times (not connected to S02)

40

0.062

5 times (not connected to S02)

100

0.26

4 times (not connected to S02)

1 00

0. 10

5 times (not connected to S02)

40

0.56

5 times (access to S02)

40

0.38

6 times (passing people S02)

5. Effect of cyclic acid leaching on leaching rate

Acid leaching conditions: 850 ° C boiling furnace slag, initial acid concentration of 40g / L, liquid-solid ratio of 1.5:1, acid immersion temperature of 80 ° C, acid immersion time of 2h, no S0 2 , 40% acid leaching after filtration The amount is returned to the leaching, and sulfuric acid and water are added at the same time, and the acid leaching conditions are the same as above. The acid leaching residue was washed twice, and the experimental results are shown in Table 4.

It can be seen from Table 4 that from the analysis of the acid leaching slag element, the cyclic acid leaching does not substantially affect the leaching rate of copper, cobalt and iron; from the analysis of the acid immersion liquid, the cyclic acid leaching can increase the concentration of copper and cobalt in the solution.

(2) Comprehensive acid leaching

According to the best process parameters obtained by acid leaching experiment, the comprehensive acid leaching conditions: initial acid concentration 40 g / L, liquid-solid ratio 1.5:1, acid immersion temperature 80 ° C, acid immersion time 2 h, access to S0 2 The acid leaching residue was washed 7 times. The results showed that the leaching rates of copper and cobalt in the slag meter reached 70.08% and 60.07%, respectively, while the leaching rates of copper and cobalt in the liquid meter were only 50.67% and 49.65%. The reason is that there is a cumulative error in the experimental and chemical analysis, and the slag meter is the standard here.

Table 4 Effect of cyclic acid leaching on leaching

sample

Acid leaching residue /%

Slag meter leaching rate /%

Acid leaching solution / (g·L -1 )

Acid consumption per ton of burnt residue / t

Cu

Co

Fe

S

Cu

Co

Fe

Cu

Co

Fe

H 2 So 4

1

0.17

0.051

65.69

1.07

63.67

53.72

2.99

1.26

0.3

5.41

26.5

18.9

2

0.18

0.054

64.63

0.89

61.53

51

4.56

2.04

0.5

7.93

30.4

28.4

(three) adjust the PH

The concentration of sulfuric acid in the acid leaching solution is 20-30 g/L. Considering the cost and the characteristics of the reagent, the pH is adjusted to 1.5 to 2.0 with limestone , then filtered, and filtered for human extraction. Experiments have shown that the amount of limestone is approximately 18 kg per cubic acid leaching solution.

(4) Copper extraction experiment

Qi using extraction using Lix984N, the diluent is kerosene. Using a section of extraction, compared to 1:1, the extractant concentration is 5%, stirring for 3 to 5 minutes. The results show that the copper extraction rate reaches 93.6%, and cobalt and iron are hardly extracted.

The load has a camera phase using 180 g/LH 2 S0 4 back extraction, compared to 1:1, stirring for 3 to 5 minutes. The results show that the copper stripping rate reaches 93.8%.

(5) Cyanide gold extraction experiment

Take the composite acid leaching residue, the liquid-solid ratio is 1.5:1, adjust the PH=10.5~11 with Ca(OH) 2 , the amount of activated carbon is 20~30g/L, the amount of NaCN is 3~10kg per ton of acid leaching residue, leaching time 24, 48h.

The results show that the leaching rates of Au and Ag are only 37.5% and 26.7%, respectively. Since the content of gold and silver in the slag is too low, it is economically impossible to recover the gold and silver in the slag by using the whole mud cyanide-carbon slurry method.

(6) Experiments on removing iron and sinking cobalt

Iron removal conditions: 80 ° C, limestone adjustment PH5 or so, adding H 2 O 2 oxidant (or air), time 2.5h. The results show that the iron removal rate is >99.9%, and the limestone consumption is 22 kg per cubic raffinate.

Cobalt with Na 2 CO 3 , pH = 8 to 8.5, 80 ° C. The results show that the precipitation rate is >98.5%, and the consumption of Na 2 C0 3 is 3 kg per cubic raffinate.

Third, the conclusion

(1) The use of boiling roasting - acid leaching - extraction - in addition to the iron sinking process can obtain qualified iron fine powder (Fe > 65%, S < 0.4%), while copper, cobalt can be comprehensively recovered;

(2) Acid leaching process parameters: one-stage acid leaching, initial acid concentration 40g/L, acid immersion temperature 80°C, leaching time 2h, S0 2 as a reducing agent, and acid leaching residue to be washed 7 times. The leaching rates of copper and cobalt slag gauges were 70.08% and 60.07%, respectively.

(3) The copper extraction rate is 93.6%, the stripping rate is 93.8%, the raffinate removal rate is >99.9%, and the sedimentation rate is >9 8.5%;

(4) It is economically unfeasible to recover gold and silver in the slag by using whole mud cyanide-carbon slurry method. The leaching rates of Au and Ag cyanide are 37.5% and 26.7%, respectively.

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