Our annual consumption of large amounts of metallic copper, copper concentrate rely heavily on imports, and therefore increasingly important copper recovery from copper smelting slag. Copper and copper smelting slag is the product of a high temperature fire, the main component of copper sulfide, a magnetic iron ore, vitreous silicate minerals and the like. After the reform of the copper fire smelting process, the sulfides are reduced and the oxides are slightly increased, resulting in a more complicated slag. Practice has proved that the treatment of copper slag by the beneficiation method has the advantages of low cost, high copper recovery rate, low grade of waste slag and low power consumption compared with the conventional fire method, and it occupies in the field of comprehensive recovery of valuable elements of copper slag. Important position. There are many factors affecting the slag flotation, such as the smelting process, the slag cooling method and the slag composition. The cooling method of the slag plays a decisive role in the slag mineral processing index. The high temperature slag will cause the slag to form an amorphous structure during the water quenching process, and the copper mineral crystal grain size is fine and dispersed, and is embedded in other minerals which are dendritic or needle-like, which will prevent grain precipitation and migration and aggregation. Thereby, the growth of the precipitated copper phase particles is prevented, and even if it is finely ground, it is difficult to dissociate most of the monomer copper particles from the gangue, and it is difficult to recover copper in the slag. At present, there are few reports on the refining furnace water quenching slag, the main reason is that the flotation recovery rate is low, only about 40%-50%. In this paper, through the analysis of the properties of slag and the discussion of flotation process parameters, the optimal conditions for improving the copper recovery rate in slag are sought.
First, the nature of the sample
The sample is the water quenching slag of the reverberatory furnace workshop of a copper smelter in Hubei. The appearance is black, brittle and hard, and the structure is dense. The multi-element analysis results of the slag sample and the copper phase analysis results are shown in Table 1 and Table 2, respectively.
Table 1 Multi-element analysis results of slag (mass fraction) /%
Cu
Ni
Pb
Zn
Sn
Sb
Mo
Fe
S
SiO 2
Al 2 O 3
1.060
0.008
0.867
1.711
0.188
0.145
0.080
36.41
1.821
25.431
3.756
Table 2 Results of slag copper phase analysis
Different
content/%
Occupancy rate /%
Copper sulphide
0.896
84.53
Copper oxide
0.137
12.9
Metal copper
0.027
2.57
Total copper
1.06
100

The analysis results of Table 1 and Table 2 show that the content of copper in the slag is 1.06%, mainly in the form of copper sulfide, followed by copper oxide, and the content of metallic copper is relatively small. The most elements in the slag are iron and silicon. Further analysis by Mossbauer method shows that 53.3% of the iron in the slag exists in the fayalite phase, 14% in the presence of calcium olivine, and the remaining 32.5% in the presence of Fe 3 O 4 ; In addition to forming iron olivine with iron oxide, silicon is mostly wollastonite and amorphous glass. Moreover, the copper, iron, silicon and other minerals in the slag are closely symbiotic and intertwined, and the fine particles are unevenly embedded, so that the copper in the slag is difficult to dissociate from the gangue monomer, which seriously affects the selection index.

Second, the experimental method

(1) Sample preparation

The copper smelting water slag from the site was crushed and sieved to obtain a sample size of -1 mm for flotation experiments.

(2) Experimental equipment and pharmaceuticals

XMQ-240X90 cone ball mill , XFD-0.75L single tank flotation machine, 101 type electric blast drying oven.

Butyl xanthate (for industrial use), black butylammonium drugs (for industrial use), pine oil (for industrial use), sodium sulfide (analytically pure), sodium hexametaphosphate phosphate (AR).

(3) Experimental methods

Weigh a certain amount of slag, grind to a certain particle size with a concentration of 60%, put it into the flotation tank to adjust the slurry, adjust the medicine, float for 6 minutes, dry, weigh, analyze and calculate the copper recovery rate of the flotation product. .

The flotation process is shown in Figure 1.

Figure 1 Flotation experiment process
Third, the experimental results and discussion
(1) Experiment of pulp pH value
In the grinding particle size of -0.074mm grain content of 90%, flotation concentration of 30%, butyl yellow medicinal amount of 80g / t, pine oil consumption of 60g / t and other conditions under the conditions of the pulp pH value of the flotation index Impact, the results are shown in Figure 2.

Figure 2 Effect of pH on flotation index
As can be seen from Fig. 2, the recovery of copper in the range of pH 5.0-8.0 is substantially unchanged, so that flotation is selected under natural water conditions (i.e., pH is about 7.0) without adding a pH adjuster.
(2) Grinding particle size experiment
The concentration of flotation pulp is 30%, the pH value is 7.0, the dosage of butyl yellow is 80g/t, the amount of pine oil is 60g/t, and the effect of grinding particle size on flotation index is shown in Fig. 3.

Figure 3 Effect of grinding particle size on flotation index
It can be seen from Fig. 3 that when the content of -0.074mm is increased from 75% to 95%, the recovery rate of copper is significantly increased from 18.6% to 39.02%, and the content of -0.074mm is increased from 95% to 95%. At 98%, the recovery rate of copper was not obvious, only increased from 39.02% to 39.45%, but the grade of copper concentrate decreased from 4.6% to 4.3%. This is because after the grinding particle size reaches a certain level, the monomer dissociation of the mineral is greatly improved, but at the same time the muddy phenomenon of the ore is serious, resulting in a sharp drop in the grade of the copper concentrate. Since the slag itself is hard and difficult to grind, considering the production cost, it is preferable to determine the grinding particle size to be -0.074 mm and the grain content is 95%.
(3) Slurry concentration experiment
The butyl yellow dosage is 200g/t, the pine alcohol oil is 60g/t, the grinding particle size is 0.074mm, and the grain size is 95%. Under the condition of pH 7.0, the effect of the pulp concentration on the flotation index is shown in Fig. 4.

Figure 4 Effect of slurry concentration on flotation index
It can be seen from Fig. 4 that as the concentration of pulp increases, the grade of copper concentrate gradually increases, and the copper recovery rate first increases and then decreases. Considering the recovery rate and grade of copper, the optimum slurry concentration is determined to be 30%.
(4) Activator dosage experiment
From the copper phase analysis, it is known that there is a part of copper oxide in the slag. The flotation method of copper oxide mineral mainly adopts sulfide flotation, and sodium sulfide is the main activator of copper oxide mineral. The slurry concentration is 30%, the grinding particle size is 0.074mm, the grain content is 95%, the pH value is 7.0, the butyl yellow dosage is 200g/t, and the pine alcohol oil is 60g/t. The amount of sodium sulfide is used to evaluate the flotation index. The effect is shown in Figure 5.

Figure 5 Effect of sodium sulfide dosage on flotation index
It can be seen from Fig. 5 that when the amount of sodium sulfide is increased from 200g/t to 800g/t, the copper grade and recovery rate are gradually increased. When the amount of sodium sulfide is 800g/t, the copper concentrate grade reaches the maximum value, and the amount of sodium sulfide is used. When it is increased to 1000g/t, the copper recovery rate remains basically the same and the copper grade drops sharply. This is because when the amount of sodium sulfide is less than 800g/t, sodium sulfide mainly activates copper oxide. When the amount of sodium sulfide exceeds 800g/t, the proportion of other minerals and gangue floating in the slag increases, resulting in flotation concentrate. The grade of copper has dropped. Therefore, the optimum amount of sodium sulfide was determined to be 800 g/t.
(5) Dispersant dosage experiment
Sodium hexametaphosphate is used as dispersing agent, the concentration of pulp is 30%, the grinding grain size is -0.074mm, the grain content is 95%, the pH value is 7.0, the butyl yellow dosage is 200g/t, the pine alcohol oil is 60g/t, six. The effect of the amount of sodium metaphosphate on the flotation effect is shown in Figure 6.

Figure 6 Effect of sodium hexametaphosphate dosage on flotation index
It can be seen from Figure 6 that when the amount of sodium hexametaphosphate is increased from 200g/t to 800g/t, the recovery of copper increases from 44.06% to 54.69%, and the amount of sodium hexametaphosphate continues to increase to 1000g/t. The increase in recovery was not significant, while the copper concentrate grade fell from 4.3% to 3.9%. This is because the water quenching slag has a muddy phenomenon during the fine grinding process. Sodium hexametaphosphate can weaken the electrical properties between the particles, disperse the ore particles, improve the flotation conditions, and improve the recovery rate of copper. Therefore, the optimum amount of sodium hexametaphosphate was determined to be 800 g/t.
(6) Experiments on the types and dosages of collectors
It has been found through experiments that the use of single butyl xanthate as a collector has a poor recovery effect on copper in water quenching slag. Therefore, this experiment uses a mixture of butyl xanthate and butyl ammonium black drug. Experiments were carried out under the experimental conditions of grinding particle size of -0.074mm, grain content of 95%, pH value of 7.0, slurry concentration of 30%, sodium sulfide dosage of 800g/t, sodium hexametaphosphate dosage of 800g/t, etc. The effect of the dosage on the flotation index is shown in Figure 7.

Figure 7 Effect of collector on flotation index
Concentrate grade of 1-yellow drug + black drug (1:1) when mixed: 2- concentrate grade when using xanthate;
3- concentrate grade when using black medicine; copper recovery rate when mixed with 4-yellow medicine + black medicine (1:1);
5-Recovery of copper when using black medicine; 6-Recovery of copper when using xanthate
It can be seen from Fig. 7 that under the same dosage conditions, the flotation effect of the mixture of butyl xanthate and butylamine black medicine is better than that of butyl xanthate and butylamine black medicine alone. When the dosage of the mixed agent was increased from 80g/t to 240g/t, the recovery rate increased from 48.17% to 64.65%, and the copper concentrate grade reached 4.54%. When the amount exceeds 240 g/t, the copper recovery rate does not increase much, and the grade gradually decreases. This is because the butyl xanthate has a better effect on the recovery of copper sulfide ore, but the effect on the recovery of copper oxide ore is poor, while the butyl ammonium black drug has a good collection effect on the copper oxide ore. There is a slight activation, and the combination of the two makes up for the deficiency of a single collector. The ratio of black medicine to xanthate is based on the exploratory test. Under the condition of a certain amount of collector, if the amount of xanthate is increased to reduce the amount of black medicine, the copper recovery rate will increase but the grade will decrease. On the contrary, increase the black medicine. The dosage, due to the good selectivity of the black drug but the poor harvesting ability, will reduce the recovery rate of the copper. The comprehensive consideration is to determine the ratio of xanthate to black drug is 1:1, and the optimum dosage is 240g/t.
(7) Comprehensive experiment
According to the flow shown in Figure 1, the original ore copper grade is 1.06%, the grinding particle size is -0.074mm, the grain size is 95%, the pulp concentration is 30%, pH=7.0, and the collector (butylammonium black and butyl xanthate) When the amount of 1:1 (prepared), activator (sodium sulfide) and dispersant (sodium hexametaphosphate) is 240, 800, 800 g/t, copper crude grade of 4.54% and copper recovery of 64.65% can be obtained. mine.
Fourth, the conclusion
(1) The refining furnace water quenching slag is complicated in nature, and the minerals such as copper, iron and silicon are closely symbiotic and intertwined, and the fine particles are unevenly distributed, which makes it difficult to recover copper in the slag.
(2) Experiments have shown that the use of fine grinding and mixing collectors can effectively improve the recovery rate of copper. When grinding grain size -0.074mm grain content is 95%, pulp concentration is 30%, pH value is 7.0, collector (butylammonium black drug and butyl xanthate are prepared in 1:1), activator (sodium sulfide) When the amount of dispersant (sodium hexametaphosphate) is 240, 800, 800 g/t, the recovery rate of a rough copper is 64.65%, and the grade of crude concentrate copper is 4.54%.

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