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Beneficiation of fluorite by flotation in a new chemical scheme
Minerals Engineering 16 (2003) 597–600 This article is also available online at: www.elsevier.com/locate/mineng
Beneficiation of fluorite by flotation in a new chemical scheme Y. Zhang a, S. Song
a,b,*
a
b
Department of Resources Engineering, Wuhan University of Science and Technology, Jianshe Road 1, 430081 Wuhan, China Instituto de Metalurgia, Universidad Aut onoma de San Luis Potosı, Av. Sierra Leona 550, San Luis Potosı, C.P. 78210, S.L.P., Mexico Received 18 December 2002; accepted 1 April 2003
Abstract In this work, the froth flotation of fluorite from an ore in China has been studied using an enhanced sodium naphthenate as collector and a salted copper sulfate as the depressant of phosphate minerals. The experimental results show that the enhanced sodium naphthenate is an effective collector in fluorite flotation at a low slurry temperature. The substitution of the enhanced sodium naphthenate for a commonly used fatty acid as collector in fluorite flotation not only greatly lowered slurry temperature in the system, but also increased the separation efficiency and reduced the reagent cost, resulting in significant economic benefits for fluorite flotation plants in northern areas. Also, it was found that the elimination of phosphate minerals from the fluorite concentrate could be successfully achieved using the salted copper sulfate as a depressant. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Froth flotation; Non-metallic ores; Flotation collectors; Flotation depressants
1. Introduction Fluorite (CaF2 ) is an important fluorine mineral, which is mostly used for the production of hydrofluoric acid and as a flux in steel making. Other uses are the manufacture of glass, fiberglass, pottery and enamel, etc. Most fluorite ores have to be upgraded before entering the fluorite market. The most commonly used beneficiation process is froth flotation, producing fluorite concentrates of up to 99% purity. Typically, fatty acid is used as collector in fluorite flotation, and water glass as a depressant of silicate gangues; the ore pulps are heated to 35–85 °C in the system (Crozier, 1992). If the content of calcite, phosphates and iron oxides in the fluorite ores are high, other depressants, such as tannin and starch, are also needed (Raju and Prabhakar, 2000). Recently, there have been numerous reports on the modification of the chemical scheme in fluorite flotation, in order to increase the separation efficiency and lower the operation costs. De Leeuw et al. (1998) reported that methanoic acid could selectively adsorb onto fluorite surfaces in preference to calcite surfaces at ambient temperature. This means that fluorite flotation to re-
*
Corresponding author. Tel./fax: +52-444-8254326. E-mail address: [email protected] (S. Song).
move calcite might be achieved at a much lower temperature if methanoic acid is used as collector, resulting in a large reduction in energy consumption. Helbig et al. (1998, 1999) found that sodium N -dodecanoyl sarcosine (anionic collector) in combination with dodecylammonium chloride (cationic collector) as co-collectors could greatly enhance the flotability of fluorite, compared with the use of the anionic collector alone. Also, fluorite flotation could be improved by using effective depressants when fatty acid is used as collector. For example, acidized sodium silicate was reported to depress calcite strongly in preference of fluorite at ambient temperature, leading the fluorite flotation to be achieved at a lower temperature (Zhou and Lu, 1992). China is the biggest exporter of fluorite concentrate in the world. There are many fluorite flotation plants, some of which are located in northern China, which has a long cold winter. In these plants, energy consumption from heating ore slurry in the flotation circuits plays an important part in the operation costs. Therefore, there is a great need to lower the slurry temperature in fluorite flotation by using a new collector to replace fatty acid. In this work, an enhanced sodium naphthenate was studied as collector to substitute for fatty acid in fluorite flotation, in order to carry out the flotation at ambient temperature. The study was performed on a fluorite ore from the Fenglin fluorite mine, located in the Hebei
0892-6875/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0892-6875(03)00136-5
598
Y. Zhang, S. Song / Minerals Engineering 16 (2003) 597–600
province of China (northern China). The objective of this work was to find a more effective collector for fluorite flotation, and thus reduce the operation costs of the flotation circuit. Also, a new depressant for phosphate minerals, namely salted copper sulfate, was tested on the fluorite ore in order to reduce the P2 O5 content of the fluorite concentrate.
sodium cyclopentene carboxylate ((CH2 )4 CHCOONa) and sodium cyclohexane carboxylate ((CH2 )5 CHCOONa). These naphthenates were then mixed separately with the fatty acid aqueous emulsion in the same ratio and using the same methods, producing naphthenate and fatty acid mixtures. Each of the mixtures was used as collector for fluorite flotation tests in this work.
2. Experimental
2.2.2. Salted copper sulfate In this experiment, a salted copper sulfate was used as the depressant of phosphate minerals in fluorite flotation. It was prepared as follows: First, 1% copper sulfate (CuSO4 ) solution and 2% sodium chloride (NaCl) solution were prepared, separately, in the same volume. Then, at a solution temperature of 55 °C, the CuSO4 solution was slowly poured into the NaCl solution, while a mild mechanical agitation was used to obtain the salted copper sulfate solution.
2.1. Ore sample The fluorite ore sample used in this work was collected from the Fenglin fluorite mine. It was crushed to )2 mm for the flotation tests feed using a jaw crusher. The ore sample consisted of fluorite, quartz, feldspar, kaolin, barite, apatite, mica and calcite, etc. The chemical analysis results are given in Table 1. 2.2. Reagents 2.2.1. GY-2 An enhanced sodium naphthenate with the commercial name of GY-2 was used as collector for fluorite flotation in this work. This was provided by the Wuhan Petrochemical Incorporation, and was made by mixing an oil refinery byproduct with a fatty acid aqueous emulsion. The main components of the byproduct were sodium naphthenates with various hydrocarbon numbers (C3 –C6 ). The fatty acid aqueous emulsion was prepared by pouring fatty acid into a sodium hydroxide aqueous solution under strong mechanical agitation. The main compositions of the reagent GY-2 are given in Table 2. The oil refinery byproduct was distilled to obtain sodium cyclopropane carboxylic ((CH2 )2 CHCOONa), sodium cyclobutane carboxylate ((CH2 )3 CHCOONa),
Table 1 Result of chemical analysis of the Fenglin fluorite ore sample Species
CaF2
SiO2
S
P2 O5
CaCO3
Fe2 O3
Al2 O3
Content (%)
60.23
32.11
0.025
0.084
0.44
1.48
3.01
Table 2 Main composition of the reagent GY-2 Component
Sodium naphthenate
Fatty acid
Water
Inorganic salt
Free alkali
Content (%)
33.13
6.63
51
<5
<3
2.2.3. Other reagents In this experiment, industrial pure water glass from Wuhan Chemical was used as the depressant of silicate minerals in fluorite flotation. The module (ratio of SiO2 and Na2 O) was determined to be 2.6. Industrial pure fatty acid from Wuhan Petrochemical Incorporation was used as collector in fluorite flotation, for comparison with GY-2. The sodium hydroxide, sodium carbonate, copper sulfate and sodium chloride used in this work were from Wuhan Chemical, and were chemical pure. Tap water was used throughout the tests. 2.3. Flotation flowsheet The fluorite flotation tests were carried according to the flowsheet shown in Fig. 1. The fluorite ore sample was first wet-ground to be 90% minus 200 meshes. Then, the slurry was conditioned, while 1000 g/ton water glass and a given amount of collector were added. Also, enough sodium carbonate was added to adjust the slurry to a pH of 9.5, and the slurry temperature was adjusted to a given value. The result was rougher flotation, the tailings from which were further treated by scavenger flotation, and the concentrate from which was cleaned by six-step cleaner flotation. Cleaner flotation I was carried out without reagent, the tailing from which was recirculated to the scavenger flotation. In cleaner flotation II, 200 g/ton water glass was added to greatly depress the silicate minerals. The tailings from cleaner flotation III were recirculated to the rougher flotation, instead of to cleaner flotation II. In cleaner flotation V and VI, a given amount of the salted copper sulfate was added to depress the phosphate minerals, in order to reduce the P2 O5 content of the final fluorite concentrate to less than 0.02%.
Y. Zhang, S. Song / Minerals Engineering 16 (2003) 597–600
Feed
90% −200 mesh
Grinding
Rougher flotation
Tailings
Scavenger flotation
Cleaner flotation I
Cleaner flotation II
Cleaner flotation III
Cleaner flotation IV
Cleaner flotation V
Cleaner flotation VI
Concentrate Fig. 1. Flowsheet of the fluorite flotation of the Fenglin fluorite ore.
3. Results and discussions Fig. 2 illustrates the effect of slurry temperature on fluorite recovery from the flotation of the Fenglin fluorite ore, using the reagent GY-2 as collector at various dosages. The grades of all the concentrates ranged between 98% and 98.5% CaF2 . It can be seen that at a low GY-2 addition, e.g. 0.2 kg/ton, the slurry temperature strongly influenced the fluorite recovery. At 6.5 °C, the
FLUORITE RECOVERY, %
100
90
80 0.2 kg/ton GY-2 0.4 kg/ton GY-2 0.6 kg/ton GY-2
70
60
50 6
8
10
12
14
16
o
SLURRY TEMPERATURE, C
Fig. 2. Fluorite recovery from the flotation of the Fenglin fluorite ore as a function of slurry temperature by using the reagent GY-2 as collector.
599
recovery was about 52%, compared with that of 61% at 15 °C. With an increase in the addition of GY-2, the slurry temperature effect declined. At 0.4 kg/ton GY-2 addition, the difference in fluorite recovery was about 4% between the two temperatures; at 0.6 kg/ton GY-2 addition, the fluorite recovery was almost constant in the temperature range, being about 85%. These results suggest that the reagent GY-2 can be effectively used as the collector in fluorite flotation at a low slurry temperature, if the addition is over a critical value. Table 3 shows the beneficiation results of fluorite flotation using GY-2 as collector at a low slurry temperature (10 °C), in comparison with the results of using fatty acid as collector at a higher slurry temperature (35 °C). The addition of the collectors in the two flotation tests was 600 and 850 g/ton, respectively. It is evident that although the addition was smaller and the slurry temperature was lower, GY-2 achieved a beneficiation result slightly superior to fatty acid in the fluorite flotation. The grades of CaF2 and impurities in the two concentrates were very similar, and the fluorite recovery obtained using GY-2 was about 1% higher than that obtained using fatty acid. This comparison indicates that the reagent GY-2 is an effective collector for fluorite flotation at a low temperature. Clearly, the substitution of GY-2 for fatty acid in fluorite flotation can not only greatly lower the slurry temperature, but also increase the separation efficiency. Considering that GY-2 is much cheaper than fatty acid, this substitution may also allow a saving on reagent cost in fluorite flotation. The effect of the hydrocarbon number of the sodium naphthenates (C3 –C6 ) in the reagent GY-2 on the fluorite flotation was experimentally studied. The results are illustrated in Fig. 3, in the form of fluorite recovery as a function of collector addition at a slurry temperature of 20 °C. The ratio of sodium naphthenate and fatty acid was 5:1 for all the collectors. The grades of all the concentrates ranged between 98% and 98.5% CaF2 . It can be seen that sodium cyclopropane carboxylic ((CH2 )2 CHCOONa) exhibited the weakest collecting property in the fluorite flotation, whereas sodium cyclohexane carboxylate ((CH2 )5 CHCOONa) was the strongest. At the same amount of addition, the larger the hydrocarbon number of naphthenates, the higher was the fluorite recovery achieved, which is not unfamiliar to flotation scientists and engineers. At 0.6 kg/ton addition, the enhanced sodium cyclopentene carboxylate ((CH2 )4 CHCOONa) and sodium cyclohexane carboxylate achieved much higher fluorite recovery than GY-2. It indicates that C5 and C6 naphthenates in GY-2 might play a very important role in the fluorite flotation as shown in Fig. 2, although there could be a combined effect of the various naphthenates on collecting property in the flotation system. The phosphor removal from fluorite concentrate as a function of the salted copper sulfate addition is shown in
600
Y. Zhang, S. Song / Minerals Engineering 16 (2003) 597–600
Table 3 Comparison of GY-2 with fatty acid as collector for the flotation of Fenglin fluorite ore Collector used
Collector addition (g/ton)
Slurry temperature (°C)
Concentrate assaying (%) CaF2
SiO2
S
P2 O 5
CaF2
SiO2
S
P2 O5
GY-2 Fatty acid
600 850
10 35
98.34 98.28
0.57 0.51
0.023 0.019
0.015 0.014
85.61 84.50
1.50 1.31
25.60 21.28
19.16 15.76
phor removal sharply increased. At the 0.6 kg/ton addition, about 96% phosphate minerals was eliminated from the fluorite concentrate. With 0.5 kg/ton salted copper sulfate, the P2 O5 content in the fluorite concentrate was 0.014%, which is much less than the minimum P2 O5 content required by superfine fluorite concentrate. Obviously, the salted copper sulfate is an effective depressant for phosphate minerals in fluorite flotation.
FLUORITE RECOVERY, %
100
80
60 (C)3 mixture (C)4 mixture
40
(C)5 mixture (C)6 mixture
4. Summary and conclusions
20
60
From the experimental studies in this work, a new chemical scheme for fluorite flotation, namely enhanced sodium naphthenate as collector and salted copper sulfate as the depressant of phosphate minerals, has been presented. This chemical scheme could allow fluorite flotation to be effectively achieved at ambient temperature and phosphate minerals to be deeply eliminated from fluorite concentrate. Enhanced sodium naphthenate, with the commercial name of GY-2, was found to be an effective collector in fluorite flotation at a low slurry temperature. There could be significant economic benefits if the reagent GY2 is substituted for fatty acid as the collector in fluorite flotation, due to large savings in energy consumption due to the absence of slurry heating, a reduction in reagent costs and the increase in flotation efficiency. This economic benefit would be especially great for fluorite flotation plants in cold areas.
40
References
0 0.2
0.4
0.6
0.8
ADDITION OF COLLECTOR, kg/ton Fig. 3. Effect of hydrocarbon number of naphthenate in the reagent GY-2 on the fluorite recovery from the flotation of the Fenglin fluorite ore.
100
PHOSPHOR REMOVAL, %
Recovery (%)
80
20 0.3
0.4
0.5
0.6
0.7
ADDITION OF SALTED COPPER SULFATE, kg/ton
Fig. 4. Phosphor removal from fluorite concentrate as a function of the salted copper sulfate addition in the flotation of the Fenglin fluorite ore.
Fig. 4. The salted copper sulfate addition appeared in the graph was the sum of the addition in the cleaner flotation V and VI. It can be observed that as the increase of the salted copper sulfate addition, the phos-
Crozier, R.D., 1992. Flotation, Theory, Reagents and Ore Testing. Pergamon, Oxford. De Leeuw, N.H., Parker, S.C., Rao, K.H., 1998. Modeling the competitive adsorption of water and methanoic acid on calcite and fluorite surfaces. Langmuir 14, 5900–5906. Helbig, C., Baldauf, H., Mahnke, J., Stochelhuber, K.W., Schulze, H.J., 1998. Investigation of Langmuir monofilms and flotation experiments with anionic/cationic collector mixtures. International Journal of Mineral Processing 53, 135–144. Helbig, C., Baldauf, H., Lange, T., Newmann, R., Pollex, R., Weber, E., 1999. New binary collectors with increased flotation efficiency. Tenside Surfactants Detergents 36, 58–62. Raju, G.B., Prabhakar, S., 2000. Beneficiation of fluorspar by column flotation. Minerals & Metallurgical Processing 17, 167–172. Zhou, Q., Lu, S., 1992. Acidized sodium silicate––an effective modifier in fluorite flotation. Minerals Engineering 5, 435–444.
Beneficiation of fluorite by flotation in a new chemical scheme Y. Zhang a, S. Song
a,b,*
a
b
Department of Resources Engineering, Wuhan University of Science and Technology, Jianshe Road 1, 430081 Wuhan, China Instituto de Metalurgia, Universidad Aut onoma de San Luis Potosı, Av. Sierra Leona 550, San Luis Potosı, C.P. 78210, S.L.P., Mexico Received 18 December 2002; accepted 1 April 2003
Abstract In this work, the froth flotation of fluorite from an ore in China has been studied using an enhanced sodium naphthenate as collector and a salted copper sulfate as the depressant of phosphate minerals. The experimental results show that the enhanced sodium naphthenate is an effective collector in fluorite flotation at a low slurry temperature. The substitution of the enhanced sodium naphthenate for a commonly used fatty acid as collector in fluorite flotation not only greatly lowered slurry temperature in the system, but also increased the separation efficiency and reduced the reagent cost, resulting in significant economic benefits for fluorite flotation plants in northern areas. Also, it was found that the elimination of phosphate minerals from the fluorite concentrate could be successfully achieved using the salted copper sulfate as a depressant. Ó 2003 Elsevier Science Ltd. All rights reserved. Keywords: Froth flotation; Non-metallic ores; Flotation collectors; Flotation depressants
1. Introduction Fluorite (CaF2 ) is an important fluorine mineral, which is mostly used for the production of hydrofluoric acid and as a flux in steel making. Other uses are the manufacture of glass, fiberglass, pottery and enamel, etc. Most fluorite ores have to be upgraded before entering the fluorite market. The most commonly used beneficiation process is froth flotation, producing fluorite concentrates of up to 99% purity. Typically, fatty acid is used as collector in fluorite flotation, and water glass as a depressant of silicate gangues; the ore pulps are heated to 35–85 °C in the system (Crozier, 1992). If the content of calcite, phosphates and iron oxides in the fluorite ores are high, other depressants, such as tannin and starch, are also needed (Raju and Prabhakar, 2000). Recently, there have been numerous reports on the modification of the chemical scheme in fluorite flotation, in order to increase the separation efficiency and lower the operation costs. De Leeuw et al. (1998) reported that methanoic acid could selectively adsorb onto fluorite surfaces in preference to calcite surfaces at ambient temperature. This means that fluorite flotation to re-
*
Corresponding author. Tel./fax: +52-444-8254326. E-mail address: [email protected] (S. Song).
move calcite might be achieved at a much lower temperature if methanoic acid is used as collector, resulting in a large reduction in energy consumption. Helbig et al. (1998, 1999) found that sodium N -dodecanoyl sarcosine (anionic collector) in combination with dodecylammonium chloride (cationic collector) as co-collectors could greatly enhance the flotability of fluorite, compared with the use of the anionic collector alone. Also, fluorite flotation could be improved by using effective depressants when fatty acid is used as collector. For example, acidized sodium silicate was reported to depress calcite strongly in preference of fluorite at ambient temperature, leading the fluorite flotation to be achieved at a lower temperature (Zhou and Lu, 1992). China is the biggest exporter of fluorite concentrate in the world. There are many fluorite flotation plants, some of which are located in northern China, which has a long cold winter. In these plants, energy consumption from heating ore slurry in the flotation circuits plays an important part in the operation costs. Therefore, there is a great need to lower the slurry temperature in fluorite flotation by using a new collector to replace fatty acid. In this work, an enhanced sodium naphthenate was studied as collector to substitute for fatty acid in fluorite flotation, in order to carry out the flotation at ambient temperature. The study was performed on a fluorite ore from the Fenglin fluorite mine, located in the Hebei
0892-6875/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0892-6875(03)00136-5
598
Y. Zhang, S. Song / Minerals Engineering 16 (2003) 597–600
province of China (northern China). The objective of this work was to find a more effective collector for fluorite flotation, and thus reduce the operation costs of the flotation circuit. Also, a new depressant for phosphate minerals, namely salted copper sulfate, was tested on the fluorite ore in order to reduce the P2 O5 content of the fluorite concentrate.
sodium cyclopentene carboxylate ((CH2 )4 CHCOONa) and sodium cyclohexane carboxylate ((CH2 )5 CHCOONa). These naphthenates were then mixed separately with the fatty acid aqueous emulsion in the same ratio and using the same methods, producing naphthenate and fatty acid mixtures. Each of the mixtures was used as collector for fluorite flotation tests in this work.
2. Experimental
2.2.2. Salted copper sulfate In this experiment, a salted copper sulfate was used as the depressant of phosphate minerals in fluorite flotation. It was prepared as follows: First, 1% copper sulfate (CuSO4 ) solution and 2% sodium chloride (NaCl) solution were prepared, separately, in the same volume. Then, at a solution temperature of 55 °C, the CuSO4 solution was slowly poured into the NaCl solution, while a mild mechanical agitation was used to obtain the salted copper sulfate solution.
2.1. Ore sample The fluorite ore sample used in this work was collected from the Fenglin fluorite mine. It was crushed to )2 mm for the flotation tests feed using a jaw crusher. The ore sample consisted of fluorite, quartz, feldspar, kaolin, barite, apatite, mica and calcite, etc. The chemical analysis results are given in Table 1. 2.2. Reagents 2.2.1. GY-2 An enhanced sodium naphthenate with the commercial name of GY-2 was used as collector for fluorite flotation in this work. This was provided by the Wuhan Petrochemical Incorporation, and was made by mixing an oil refinery byproduct with a fatty acid aqueous emulsion. The main components of the byproduct were sodium naphthenates with various hydrocarbon numbers (C3 –C6 ). The fatty acid aqueous emulsion was prepared by pouring fatty acid into a sodium hydroxide aqueous solution under strong mechanical agitation. The main compositions of the reagent GY-2 are given in Table 2. The oil refinery byproduct was distilled to obtain sodium cyclopropane carboxylic ((CH2 )2 CHCOONa), sodium cyclobutane carboxylate ((CH2 )3 CHCOONa),
Table 1 Result of chemical analysis of the Fenglin fluorite ore sample Species
CaF2
SiO2
S
P2 O5
CaCO3
Fe2 O3
Al2 O3
Content (%)
60.23
32.11
0.025
0.084
0.44
1.48
3.01
Table 2 Main composition of the reagent GY-2 Component
Sodium naphthenate
Fatty acid
Water
Inorganic salt
Free alkali
Content (%)
33.13
6.63
51
<5
<3
2.2.3. Other reagents In this experiment, industrial pure water glass from Wuhan Chemical was used as the depressant of silicate minerals in fluorite flotation. The module (ratio of SiO2 and Na2 O) was determined to be 2.6. Industrial pure fatty acid from Wuhan Petrochemical Incorporation was used as collector in fluorite flotation, for comparison with GY-2. The sodium hydroxide, sodium carbonate, copper sulfate and sodium chloride used in this work were from Wuhan Chemical, and were chemical pure. Tap water was used throughout the tests. 2.3. Flotation flowsheet The fluorite flotation tests were carried according to the flowsheet shown in Fig. 1. The fluorite ore sample was first wet-ground to be 90% minus 200 meshes. Then, the slurry was conditioned, while 1000 g/ton water glass and a given amount of collector were added. Also, enough sodium carbonate was added to adjust the slurry to a pH of 9.5, and the slurry temperature was adjusted to a given value. The result was rougher flotation, the tailings from which were further treated by scavenger flotation, and the concentrate from which was cleaned by six-step cleaner flotation. Cleaner flotation I was carried out without reagent, the tailing from which was recirculated to the scavenger flotation. In cleaner flotation II, 200 g/ton water glass was added to greatly depress the silicate minerals. The tailings from cleaner flotation III were recirculated to the rougher flotation, instead of to cleaner flotation II. In cleaner flotation V and VI, a given amount of the salted copper sulfate was added to depress the phosphate minerals, in order to reduce the P2 O5 content of the final fluorite concentrate to less than 0.02%.
Y. Zhang, S. Song / Minerals Engineering 16 (2003) 597–600
Feed
90% −200 mesh
Grinding
Rougher flotation
Tailings
Scavenger flotation
Cleaner flotation I
Cleaner flotation II
Cleaner flotation III
Cleaner flotation IV
Cleaner flotation V
Cleaner flotation VI
Concentrate Fig. 1. Flowsheet of the fluorite flotation of the Fenglin fluorite ore.
3. Results and discussions Fig. 2 illustrates the effect of slurry temperature on fluorite recovery from the flotation of the Fenglin fluorite ore, using the reagent GY-2 as collector at various dosages. The grades of all the concentrates ranged between 98% and 98.5% CaF2 . It can be seen that at a low GY-2 addition, e.g. 0.2 kg/ton, the slurry temperature strongly influenced the fluorite recovery. At 6.5 °C, the
FLUORITE RECOVERY, %
100
90
80 0.2 kg/ton GY-2 0.4 kg/ton GY-2 0.6 kg/ton GY-2
70
60
50 6
8
10
12
14
16
o
SLURRY TEMPERATURE, C
Fig. 2. Fluorite recovery from the flotation of the Fenglin fluorite ore as a function of slurry temperature by using the reagent GY-2 as collector.
599
recovery was about 52%, compared with that of 61% at 15 °C. With an increase in the addition of GY-2, the slurry temperature effect declined. At 0.4 kg/ton GY-2 addition, the difference in fluorite recovery was about 4% between the two temperatures; at 0.6 kg/ton GY-2 addition, the fluorite recovery was almost constant in the temperature range, being about 85%. These results suggest that the reagent GY-2 can be effectively used as the collector in fluorite flotation at a low slurry temperature, if the addition is over a critical value. Table 3 shows the beneficiation results of fluorite flotation using GY-2 as collector at a low slurry temperature (10 °C), in comparison with the results of using fatty acid as collector at a higher slurry temperature (35 °C). The addition of the collectors in the two flotation tests was 600 and 850 g/ton, respectively. It is evident that although the addition was smaller and the slurry temperature was lower, GY-2 achieved a beneficiation result slightly superior to fatty acid in the fluorite flotation. The grades of CaF2 and impurities in the two concentrates were very similar, and the fluorite recovery obtained using GY-2 was about 1% higher than that obtained using fatty acid. This comparison indicates that the reagent GY-2 is an effective collector for fluorite flotation at a low temperature. Clearly, the substitution of GY-2 for fatty acid in fluorite flotation can not only greatly lower the slurry temperature, but also increase the separation efficiency. Considering that GY-2 is much cheaper than fatty acid, this substitution may also allow a saving on reagent cost in fluorite flotation. The effect of the hydrocarbon number of the sodium naphthenates (C3 –C6 ) in the reagent GY-2 on the fluorite flotation was experimentally studied. The results are illustrated in Fig. 3, in the form of fluorite recovery as a function of collector addition at a slurry temperature of 20 °C. The ratio of sodium naphthenate and fatty acid was 5:1 for all the collectors. The grades of all the concentrates ranged between 98% and 98.5% CaF2 . It can be seen that sodium cyclopropane carboxylic ((CH2 )2 CHCOONa) exhibited the weakest collecting property in the fluorite flotation, whereas sodium cyclohexane carboxylate ((CH2 )5 CHCOONa) was the strongest. At the same amount of addition, the larger the hydrocarbon number of naphthenates, the higher was the fluorite recovery achieved, which is not unfamiliar to flotation scientists and engineers. At 0.6 kg/ton addition, the enhanced sodium cyclopentene carboxylate ((CH2 )4 CHCOONa) and sodium cyclohexane carboxylate achieved much higher fluorite recovery than GY-2. It indicates that C5 and C6 naphthenates in GY-2 might play a very important role in the fluorite flotation as shown in Fig. 2, although there could be a combined effect of the various naphthenates on collecting property in the flotation system. The phosphor removal from fluorite concentrate as a function of the salted copper sulfate addition is shown in
600
Y. Zhang, S. Song / Minerals Engineering 16 (2003) 597–600
Table 3 Comparison of GY-2 with fatty acid as collector for the flotation of Fenglin fluorite ore Collector used
Collector addition (g/ton)
Slurry temperature (°C)
Concentrate assaying (%) CaF2
SiO2
S
P2 O 5
CaF2
SiO2
S
P2 O5
GY-2 Fatty acid
600 850
10 35
98.34 98.28
0.57 0.51
0.023 0.019
0.015 0.014
85.61 84.50
1.50 1.31
25.60 21.28
19.16 15.76
phor removal sharply increased. At the 0.6 kg/ton addition, about 96% phosphate minerals was eliminated from the fluorite concentrate. With 0.5 kg/ton salted copper sulfate, the P2 O5 content in the fluorite concentrate was 0.014%, which is much less than the minimum P2 O5 content required by superfine fluorite concentrate. Obviously, the salted copper sulfate is an effective depressant for phosphate minerals in fluorite flotation.
FLUORITE RECOVERY, %
100
80
60 (C)3 mixture (C)4 mixture
40
(C)5 mixture (C)6 mixture
4. Summary and conclusions
20
60
From the experimental studies in this work, a new chemical scheme for fluorite flotation, namely enhanced sodium naphthenate as collector and salted copper sulfate as the depressant of phosphate minerals, has been presented. This chemical scheme could allow fluorite flotation to be effectively achieved at ambient temperature and phosphate minerals to be deeply eliminated from fluorite concentrate. Enhanced sodium naphthenate, with the commercial name of GY-2, was found to be an effective collector in fluorite flotation at a low slurry temperature. There could be significant economic benefits if the reagent GY2 is substituted for fatty acid as the collector in fluorite flotation, due to large savings in energy consumption due to the absence of slurry heating, a reduction in reagent costs and the increase in flotation efficiency. This economic benefit would be especially great for fluorite flotation plants in cold areas.
40
References
0 0.2
0.4
0.6
0.8
ADDITION OF COLLECTOR, kg/ton Fig. 3. Effect of hydrocarbon number of naphthenate in the reagent GY-2 on the fluorite recovery from the flotation of the Fenglin fluorite ore.
100
PHOSPHOR REMOVAL, %
Recovery (%)
80
20 0.3
0.4
0.5
0.6
0.7
ADDITION OF SALTED COPPER SULFATE, kg/ton
Fig. 4. Phosphor removal from fluorite concentrate as a function of the salted copper sulfate addition in the flotation of the Fenglin fluorite ore.
Fig. 4. The salted copper sulfate addition appeared in the graph was the sum of the addition in the cleaner flotation V and VI. It can be observed that as the increase of the salted copper sulfate addition, the phos-
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