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Rougher flotation of copper minerals in columns
Minerals Engineering 18 (2005) 731–733
Technical note
This article is also available online at: www.elsevier.com/locate/mineng
Rougher flotation of copper minerals in columns C.H. Sampaio a
a,*
, W. Aliaga a, M. Villanueva
b
Mineral Processing Laboratory, Center of Technology, Federal University of Rio Grande do Sul, P.O. Box 15021, ZIP 91501-970 Porto Alegre, Brazil b Catholic University of the North, Antofagasta, Chile Received 24 July 2004; accepted 8 December 2004
Abstract In this work, rougher flotation of low grade copper minerals (0.6–0.7% Cu) was tested in column cells at laboratory scale. A negative bias regime was used in order to create a levitating effect on particle–bubble aggregates to promote gross particle flotation. Over 80% recovery was obtained on the flotation of coarse mineral (100%—84 lm) with concentrate grades around 2.7%. The process was not optimized, hence, it may be possible to reach even better results. 2005 Elsevier Ltd. All rights reserved. Keywords: Non-ferrous metallic ores; Sulphide ores; Column flotation
1. Introduction
2. Materials and methods
Almost every copper plant in the world presents flotation circuits incorporating columns (Rubinstein, 1995; Finch and Dobby, 1990). However, their main use is for fine mineral flotation at cleaning stages where columns show clear advantages over conventional cells. The application of columns only to flotation of fines is not due to a limitation on the technique. Columns has been successfully tested on gross industrial minerals; namely, KCl and Apatite (Soto and Barbery, 1991; Soto and Aliaga, 1993), Fluorite (Brum, 2004). In addition, Soto (1989) showed that columns could be used as a kind of flash flotation device provided that some modifications of the conventional technique are made. In this work, column flotation for copper minerals was tested on a rougher stage at laboratory scale.
The column was built on 4 in. diameter PVC tubes. The total height was around 4 m. The negative bias was established by injecting water upward, 68 cm above the lower end. The air was blown through a fritted steel cylinder installed 10 cm above the bottom. The air hold-up was measured by hydrostatic difference using two vertical glass tubes 154 cm apart. The pulp was fed by a Masterflex peristaltic pump. The mineral sample, as received from the third region of Chile, was 100%— 14 in. size. From the total sulfide content, 60% was pyrite, and the rest was mainly chalcopyrite. The samples, after homogenization, was divided into two fractions: (a) Sample a, 100%—1.7 mm size, was sieved first and the oversize ground on a roller crusher. (b) Sample b, 100%—840 lm, was all ground at once in the roller crusher.
* Corresponding author. Tel.: +55 51 33167067; fax: +55 51 33167116. E-mail address: [email protected] (C.H. Sampaio). URL: http://dali.ct.ufrgs.br/laptom/ (C.H. Sampaio).
0892-6875/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2004.12.006
For each test, a total volume of 36 l of pulp (30% w/w solid) was prepared. It was conditioned during 8 min at a pH around 11 with SF-114 as collector and MIBC
732
C.H. Sampaio et al. / Minerals Engineering 18 (2005) 731–733 100
5
Conc. Rec.
Concentrate (%Cu)
4
80
3
60
2
40
1
20
Recovery (%Cu)
as frother (40 g/ton each for sample a and 30 g/ton for sample b). The pH, was kept constant in the alkaline region adding lime. To run the tests, the column was run first with water and air until a steady state was reached. Then, the pulp was pumped in and bias water was injected. The system was left running for around three residence time before sampling. Extreme care was taken with tailings due to the coarse size of samples. 3. Results and discussions
0
0
0.0
The d50 for sample a was near 600 lm while for sample b was around 200 lm. The relative fraction of coarse particles appeared abnormally high for sample a due to the sieving stage prior grinding which avoided overgrinding. On the other hand, sample a had 12.3%— 44 lm while sample b had 31.9%. Both samples were coarser than standard granulometric size used in conventional rougher flotation. A series of eight tests, in duplicate, were carried out with sample a. The conditions and metallurgical results are shown in Table 1. If tests 1 and 2 are compared, it can be seen that air flow improves Cu recovery. As noted in Table 1, an increase of 0.5 cm/s raises about 8% the recovery of copper. Nevertheless, the grade of the concentrate is reduced. On the other hand, comparing tests 1 through 4, it can be seen that an increase in both, bias water and air, the recovery of Cu increase further. On the contrary, increasing feed rates from 0.6 cm/s to 1.0 cm/s, copper recovery deteriorates. Observing the last four tests, it can be concluded that increase in feed rate deteriorates both the grade and the recovery. Neither the variation of the bias nor the gas rate seem to change the behaviour of the cell at that feed rate. Recovery deterioration is not observed with sample b for feed rates up to 1.5 cm/s. For that fact, the tests with that sample were all carried out using 1.5 cm/s of feed.
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Gas Velocity (cm/s)
Fig. 1. Recovery of copper as a function of gas rate (Jg). Jf = 1.5 cm/s; Jw = 0.4 cm/s; hold-up = 23 ± 2%.
The results are plotted as a function of gas rate in Fig. 1. It can be seen, from Fig. 1, that recovery of copper increases as the gas flow rate is increased, showing a maximum at around 84% Cu for 1.5 cm/s gas rate. The concentrate grade shows a steady decrease as recovery increases, as was expected. The decreases observed in the recovery above 2.5 cm/s of air gas was due to gas saturation because some burping was observed. No other configuration has been tested yet to find out the better conditions. The only aim here was to establish the feasibility of columns to work as rougher flotation cells.
4. Conclusions • Column cells can work as rougher flotation machines. • They must be operated at negative bias. • A considerable saving in grinding energy may result from diminishing mass regrinding.
Table 1 Column flotation parameters and metallurgical results Test #
1 2 3 4 5 6 7 8
Surface velocity Jf,w,g (cm/s) Feed
H2O
Gas
0.6 0.6 0.6 0.6 1.0 1.0 1.0 1.0
0.2 0.2 0.4 0.4 0.2 0.2 0.4 0.4
2.0 2.5 2.0 2.5 2.0 2.5 2.0 2.5
Hold-up (%)
Grade (% Cu)
Rec. (% Cu)
Conc.
Tail
22 25 23 24 26 27 0.27 0.28
2.56 2.32 1.52 1.64 1.80 1.88 2.08 1.72
0.32 0.27 0.25 0.23 0.34 0.34 0.36 0.37
57.2 65.3 72.6 74.0 57.8 57.3 53.2 53.8
C.H. Sampaio et al. / Minerals Engineering 18 (2005) 731–733
Acknowledgement The authors would like to acknowledge the collaborative work between UFRGS and Metallurgical Department, Catholic University of the North, Chile. References Brum, I.A.S., 2004. Flotation of fluorite. Doctoral Research Work, Personal communications, Rio Grande do Sul Federal University.
733
Finch, J., Dobby, G.S., 1990. Column Flotation. Pergamon Press. Rubinstein, J.B., 1995. Column Flotation, Process, Design and Practices. Gordon and Breach Science Publishers. Soto, H., 1989. Column flotation with negative bias. In: Dobby, G., Rao, S. (Eds.), Processing of Complex Ores. Pergamon Press, pp. 379–385. Soto, H., Barbery, G., 1991. Minerals and Metallurgical Processes 8 (1), 16–21. Soto, H., Aliaga, W., 1993. Trans. Inst. Mines Metall., Sect C No. 103.
Technical note
This article is also available online at: www.elsevier.com/locate/mineng
Rougher flotation of copper minerals in columns C.H. Sampaio a
a,*
, W. Aliaga a, M. Villanueva
b
Mineral Processing Laboratory, Center of Technology, Federal University of Rio Grande do Sul, P.O. Box 15021, ZIP 91501-970 Porto Alegre, Brazil b Catholic University of the North, Antofagasta, Chile Received 24 July 2004; accepted 8 December 2004
Abstract In this work, rougher flotation of low grade copper minerals (0.6–0.7% Cu) was tested in column cells at laboratory scale. A negative bias regime was used in order to create a levitating effect on particle–bubble aggregates to promote gross particle flotation. Over 80% recovery was obtained on the flotation of coarse mineral (100%—84 lm) with concentrate grades around 2.7%. The process was not optimized, hence, it may be possible to reach even better results. 2005 Elsevier Ltd. All rights reserved. Keywords: Non-ferrous metallic ores; Sulphide ores; Column flotation
1. Introduction
2. Materials and methods
Almost every copper plant in the world presents flotation circuits incorporating columns (Rubinstein, 1995; Finch and Dobby, 1990). However, their main use is for fine mineral flotation at cleaning stages where columns show clear advantages over conventional cells. The application of columns only to flotation of fines is not due to a limitation on the technique. Columns has been successfully tested on gross industrial minerals; namely, KCl and Apatite (Soto and Barbery, 1991; Soto and Aliaga, 1993), Fluorite (Brum, 2004). In addition, Soto (1989) showed that columns could be used as a kind of flash flotation device provided that some modifications of the conventional technique are made. In this work, column flotation for copper minerals was tested on a rougher stage at laboratory scale.
The column was built on 4 in. diameter PVC tubes. The total height was around 4 m. The negative bias was established by injecting water upward, 68 cm above the lower end. The air was blown through a fritted steel cylinder installed 10 cm above the bottom. The air hold-up was measured by hydrostatic difference using two vertical glass tubes 154 cm apart. The pulp was fed by a Masterflex peristaltic pump. The mineral sample, as received from the third region of Chile, was 100%— 14 in. size. From the total sulfide content, 60% was pyrite, and the rest was mainly chalcopyrite. The samples, after homogenization, was divided into two fractions: (a) Sample a, 100%—1.7 mm size, was sieved first and the oversize ground on a roller crusher. (b) Sample b, 100%—840 lm, was all ground at once in the roller crusher.
* Corresponding author. Tel.: +55 51 33167067; fax: +55 51 33167116. E-mail address: [email protected] (C.H. Sampaio). URL: http://dali.ct.ufrgs.br/laptom/ (C.H. Sampaio).
0892-6875/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2004.12.006
For each test, a total volume of 36 l of pulp (30% w/w solid) was prepared. It was conditioned during 8 min at a pH around 11 with SF-114 as collector and MIBC
732
C.H. Sampaio et al. / Minerals Engineering 18 (2005) 731–733 100
5
Conc. Rec.
Concentrate (%Cu)
4
80
3
60
2
40
1
20
Recovery (%Cu)
as frother (40 g/ton each for sample a and 30 g/ton for sample b). The pH, was kept constant in the alkaline region adding lime. To run the tests, the column was run first with water and air until a steady state was reached. Then, the pulp was pumped in and bias water was injected. The system was left running for around three residence time before sampling. Extreme care was taken with tailings due to the coarse size of samples. 3. Results and discussions
0
0
0.0
The d50 for sample a was near 600 lm while for sample b was around 200 lm. The relative fraction of coarse particles appeared abnormally high for sample a due to the sieving stage prior grinding which avoided overgrinding. On the other hand, sample a had 12.3%— 44 lm while sample b had 31.9%. Both samples were coarser than standard granulometric size used in conventional rougher flotation. A series of eight tests, in duplicate, were carried out with sample a. The conditions and metallurgical results are shown in Table 1. If tests 1 and 2 are compared, it can be seen that air flow improves Cu recovery. As noted in Table 1, an increase of 0.5 cm/s raises about 8% the recovery of copper. Nevertheless, the grade of the concentrate is reduced. On the other hand, comparing tests 1 through 4, it can be seen that an increase in both, bias water and air, the recovery of Cu increase further. On the contrary, increasing feed rates from 0.6 cm/s to 1.0 cm/s, copper recovery deteriorates. Observing the last four tests, it can be concluded that increase in feed rate deteriorates both the grade and the recovery. Neither the variation of the bias nor the gas rate seem to change the behaviour of the cell at that feed rate. Recovery deterioration is not observed with sample b for feed rates up to 1.5 cm/s. For that fact, the tests with that sample were all carried out using 1.5 cm/s of feed.
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Gas Velocity (cm/s)
Fig. 1. Recovery of copper as a function of gas rate (Jg). Jf = 1.5 cm/s; Jw = 0.4 cm/s; hold-up = 23 ± 2%.
The results are plotted as a function of gas rate in Fig. 1. It can be seen, from Fig. 1, that recovery of copper increases as the gas flow rate is increased, showing a maximum at around 84% Cu for 1.5 cm/s gas rate. The concentrate grade shows a steady decrease as recovery increases, as was expected. The decreases observed in the recovery above 2.5 cm/s of air gas was due to gas saturation because some burping was observed. No other configuration has been tested yet to find out the better conditions. The only aim here was to establish the feasibility of columns to work as rougher flotation cells.
4. Conclusions • Column cells can work as rougher flotation machines. • They must be operated at negative bias. • A considerable saving in grinding energy may result from diminishing mass regrinding.
Table 1 Column flotation parameters and metallurgical results Test #
1 2 3 4 5 6 7 8
Surface velocity Jf,w,g (cm/s) Feed
H2O
Gas
0.6 0.6 0.6 0.6 1.0 1.0 1.0 1.0
0.2 0.2 0.4 0.4 0.2 0.2 0.4 0.4
2.0 2.5 2.0 2.5 2.0 2.5 2.0 2.5
Hold-up (%)
Grade (% Cu)
Rec. (% Cu)
Conc.
Tail
22 25 23 24 26 27 0.27 0.28
2.56 2.32 1.52 1.64 1.80 1.88 2.08 1.72
0.32 0.27 0.25 0.23 0.34 0.34 0.36 0.37
57.2 65.3 72.6 74.0 57.8 57.3 53.2 53.8
C.H. Sampaio et al. / Minerals Engineering 18 (2005) 731–733
Acknowledgement The authors would like to acknowledge the collaborative work between UFRGS and Metallurgical Department, Catholic University of the North, Chile. References Brum, I.A.S., 2004. Flotation of fluorite. Doctoral Research Work, Personal communications, Rio Grande do Sul Federal University.
733
Finch, J., Dobby, G.S., 1990. Column Flotation. Pergamon Press. Rubinstein, J.B., 1995. Column Flotation, Process, Design and Practices. Gordon and Breach Science Publishers. Soto, H., 1989. Column flotation with negative bias. In: Dobby, G., Rao, S. (Eds.), Processing of Complex Ores. Pergamon Press, pp. 379–385. Soto, H., Barbery, G., 1991. Minerals and Metallurgical Processes 8 (1), 16–21. Soto, H., Aliaga, W., 1993. Trans. Inst. Mines Metall., Sect C No. 103.