EP0597522B1 - Process for the selective flotation of a sulphide ore containing copper, lead and zinc - Google Patents

Description

The present invention relates to a process for the selective flotation of a sulfidic copper-lead-zinc ore, wherein the raw ore is ground and slurried with water, the suspension formed is aerated to set a certain redox potential, then successively with SO₂, with Ca (OH) ₂ and is conditioned with collectors and foamers and then the Cu flotation takes place.

The influence of the oxygen concentration, the redox potential and the pH of the flotation medium for the amount of discharge and for the quality of the selectivity of individual metals obtained from ores by flotation has been described several times as prior art.

In "The role of oxygen in sulfide ore flotation", Panaiotov, V .: Semkov, N .; Arnaudov, R .: Mirchev, V. (Bulg.) Obogashch. Rud (Leningrad) 1986, (4), 16-18 (Russ) describes that increasing the oxygen concentration has different effects on the discharge of different metals. Furthermore, it is concluded that the control of the redox potential can be used to optimize the selective application of minerals from complex ores by flotation.

In "Algorithms of the conditioning of a slurry of uniform copper-nickel sulfide ores", K.G. Bakinov, Yu. V. Shtabov (USSR) Teor. Osn. Kontrol Protsessov of Flotatsii 1980, 198 to 204 (Russ) describes the improvement of the flotation of sulfidic polymetallic ores by optimizing the redox potential.

In "Evaluation of processes occuring the flotation of pulp", SB Leonov, ON Bel'kova, Veshchestv. Sostav Obogatimost Miner. Syr'ya 1978, 74-8 (Russ) become effects described, which result inter alia from the redox potentials in the aqueous phase and in sulfidic minerals in the flotation slurry and the hydrophobization of the sulfidic ores. The selective flotation of lead sulfide, zinc sulfide and copper sulfide is also described.

From the published Soviet patent application SU-A-1 066 657 a method emerges in which the redox potential is achieved by changing the degree of aeration, namely by changing the amount of aeration in the slurry. The aeration time and the time of the change rates of the redox potentials over the entire measured aeration time are measured in minutes.

From XVI International Mineral Processing Congress, edited by E. Forssberg, Elsevier Science Publishers BV, Amsterdam 1988 "Selective Flotation of a sulfidic complex ores with special reference to the interaction of specific surface, redox potential and oxygen content", AN Beysavi, LP Kitschen , Pages 565 - 578, the selective Cu flotation results from copper-lead-zinc ores, which are particularly rich in pyrite. It was shown that an optimal setting of the redox potential before the first flotation stage, hence the copper flotation stage, brings about a remarkable improvement in the selectivity. The publication also shows that the redox potential itself depends on the grain size of the ground ore, the pH and the regulators. The ore was finely ground, then slurried in water, then the suspension was filtered and the filter cake was washed intensively with fresh water to remove the so-called toxic "constituents", e.g. B. S²⁻, S₂O₃²⁻, S₄O₆²⁻, SO₃²⁻ and SO₄²⁻ to remove. The solids were reslurried and the slurry was first aerated to set a certain redox potential, then conditioned with SO₂, then conditioned with CaO and finally with collectors and foamers. The redox potential and the Oxygen content and the pH values measured. The redox potential selected for the Cu flotation was adjusted by the amount of oxygen supplied in the aeration before conditioning with SO₂. The investigations have shown the great dependence of Cu flotation on the redox potential. The tests were carried out in the redox potential range from -260 mV to +183 mV. It has been shown that, for. B. at -260 mV the foam consists almost exclusively of pyrite and only 1.3% of the solid in the foam is copper. With redox potentials of 171 mV to 183 mV, it could be shown that galena begins to change into the foam and therefore 34 to 41% of the lead in the ore was already present in the foam. It could also be shown that there is an optimal range for the redox potential for the ores investigated, in which both the yield for the copper reaches a high percentage and a good selectivity of the copper in the Cu flotation is obtained. This publication teaches that the values for the output of the copper and for the selectivity of the copper separation can no longer be optimized. The other publications discussed above also contain no indication of how the output and selectivity can be further optimized.

The invention has for its object to provide an economical method for flotation of a sulfidic copper-lead-zinc ore, wherein the maximum yield of copper with the highest selectivity for the copper and with minimal losses of lead and zinc is obtained in the copper flotation.

The object is achieved by the method steps (a), (b) and (c) mentioned in the characterizing part of patent claim 1.

If the optimal redox potential is set during aeration before SO₂ conditioning, this value increases further during flotation. As a result, redox potentials are achieved in the Cu flotation, in which other metal sulfides, such as PbS (galena) and ZnS (zinc blende) are activated and discharged with the foam of the Cu flotation, which reduces the selectivity of the copper in the Cu flotation. Cu flotation is to be understood as the flotation stage in which the copper is applied. In addition to the deterioration in the quality of the Cu concentrate, the non-selectivity also results in losses of Pb or / and Zn. If 70 to 90% of the optimal redox potential is reached before the Cu flotation, therefore before the SO₂ conditioning, 90% of the copper gravel is (CuFeS₂) activated before the Cu flotation, whereby PbS and ZnS are not yet activated. The redox potential only reaches its optimal value during the Cu flotation. At this point, the transition of the copper from the cloudy to the foam has ended and copper has already been discharged with the foam. The copper can thus be removed selectively with the foam. The redox potential during the aeration before the SO₂ conditioning is adjusted by introducing the corresponding percentage of oxygen that is necessary to achieve the optimal value for the redox potential. If the redox potential is to be 70 to 90% of the redox potential required for selective copper flotation, 70 to 90% of the amount of oxygen required to achieve the optimal redox potential is introduced during the aeration. In the subsequent addition of SO₂, it has proven to be very advantageous to add 1000 g of SO₂ per ton of solid to the slurry.

A preferred embodiment of the invention is that the optimum redox potential desired for Cu flotation is 60 to 75 mV. It has advantageously been found that for copper-lead-zinc ores, the 0.6 to 1.4% by weight of Cu, 0.6 to 1.4% by weight of Pb and 2.0 to 3.0% by weight Contain Zn, with which the highest yield of copper and the highest selectivity for copper in the Cu flotation were achieved with the Cu flotation.

A preferred embodiment of the invention is that the optimum redox potential desired for Cu flotation is from 155 to 170 mV. It has been found to be advantageous for copper-lead-zinc ores containing 4 to 6% by weight of Cu, 0.1 to 0.5% by weight of Pb and 11.0 to 12.5% by weight of Zn of copper flotation under these conditions, the highest copper yield and the highest selectivity for copper were achieved in the copper flotation.

A preferred embodiment of the invention is that the optimum redox potential desired for Cu flotation is from 325 to 340 mV. It has advantageously been found that copper-lead-zinc ores containing 0.4 to 1.5% by weight of Cu, 0.01 to 0.1% by weight of Pb and 0.02 to 0.15% by weight of Zn contain, with the copper flotation under these conditions the highest yield of copper and the highest selectivity for copper in the copper flotation were achieved.

A preferred embodiment of the invention is that when the suspension is aerated before the Cu flotation, a redox potential of 75 to 85% of the optimum redox potential desired for the Cu flotation is set.

A preferred embodiment of the invention is that the Cu flotation takes place at a pH of 9.0 to 9.7.

A particularly preferred embodiment of the invention is that the Cu flotation takes place at a pH of 9.3 to 9.5.

A preferred embodiment of the invention is that the suspension resulting from the Cu flotation is adjusted to a pH of 9.3 to 12 with Ca (OH) ₂, is used in a Pb flotation with collectors and foamers and Pb with the foam is removed. It has advantageously been found that the application of Pb is particularly high in this pH range and the selectivity of Pb over Zn is very favorable.

A particularly preferred embodiment of the invention is that the optimum redox potential of 80 to 360 mV desired for the Pb flotation is set by the ventilation in the Pb flotation. It has advantageously been found that in the Pb flotation, a very particularly high yield of Pb and a very particularly favorable selectivity towards Zn are achieved in this area for the redox potential.

A preferred embodiment of the invention is that the resulting as the Pb flotation suspension is conditioned with CuSO₄ and then adjusted to a pH of 11.5 to 12.5 with Ca (OH) ₂, with collectors and foamers in Zn flotation is used and Zn is removed with the foam. It has proven to be advantageous to set the course of the Pb flotation in this pH range, in which a particularly large amount of Zn present could be observed.

A particularly preferred embodiment of the invention is that the optimum redox potential of 110 to 450 mV desired for the Zn flotation is set by the ventilation during the Zn flotation. It has advantageously been found that the application of Zn in this area is particularly high for the redox potential.

The invention is illustrated by means of examples.

EXAMPLES

The tests were carried out with the ores listed below with the levels of Cu, Pb and Zn listed in the table. Ore type Cu Pb Zn E _opt ¹⁾ % By weight % By weight % By weight mV Portuguese Ore I 0.85 0.85 2.37 68 Turkish Ore (Cayeli) II 5.00 0.21 11.7 164 Turkish Ore (Küre) III 0.97 0.05 0.07 327 ¹⁾ optimal redox potential

Comparative Example ²⁾ Ore type E 1 ⁶⁾ Staging ³⁾ Salary ⁴⁾ Spread ⁵⁾ mV % Cu Pb Zn Cu Pb Zn I. 68 5.7 12.1 0.80 1.50 80.2 5.4 3.6 ²⁾ the comparative example is taken from the prior art publication by AN Beysavi and LP Kitschen. ^{3) In} the comparative example, discharge means the percentage of the ore used that was discharged with the flotation foam. In Examples 1 to 3, discharge means the balanced amount of solids discharged. ^{4) In} the comparative example, content means the percentage distribution in the discharge. In Examples 1 to 3, content means the proportions of Cu, Pb and Zn in% by weight in the discharge. ⁵⁾ The comparative example shows what percentage of the amounts of Cu, Pb and Zn originally present in the ore were discharged. In Examples 1 to 3, yield reflects the weight percentages of Cu, Pb and Zn, based on the amounts of Cu, Pb and Zn originally present in the ore. ⁶⁾ Redox potential, set in the ventilation before the SO₂ introduction (in the comparative example = optimal redox potential)

example 1

One kg of ore (ore type I) was ground in a wet mill to a grain size of d₈₀ = 18 µm and placed in a flotation cell (2 liters). Sufficient water was added until a solids content of 500 g / l was reached in the suspension. Then air (2 l / min) was introduced into the flotation cell until the redox potential of 55 mV was set. After the redox potential of 55 mV had been set, the introduction of air was switched off. Then 20 ml of a 5 wt .-% SO₂ containing aqueous solution were added to the flotation cell. The SO₂-containing aqueous solution lasted for 5 minutes. The appropriate amount of lime milk (suspension of 10 g CaO and 90 ml H₂O) was then added to adjust the desired pH to 9.5. Lime milk lasted 2 minutes. A mixture of 40 mg Na isopropyl xanthate and 40 mg Hostaflot ^(R) was then added to the flotation cell as a collector in 1923. The action time of the collectors was 5 minutes.

Then 20 mg of Flotol ^(R) B was added to the flotation cell as a foamer. The action time of the foamer was 1 min. Then air (2 l / min) was led into the flotation cell. The flotation foam was continuously monitored by regularly taking samples of the newly formed foam and examining it microscopically. The flotation was continued until the discharge of copper in the newly formed foam became very low according to the microscopic examination. The flotation was then ended. When the flotation was ended, the optimum value for the redox potential of 68 mV desired for the Cu flotation was measured. The amount of solid discharged in the flotation foam was 50 g. The test results are shown in the table below. Ore type E 1 ⁶⁾ E 2 ⁷⁾ Staging ³⁾ Salary ⁴⁾ Spread ⁵⁾ mV mV G Cu Pb Zn Cu Pb Zn I. 55 68 50 13.9 0.75 1.35 81.3 4.4 2.9 ^{3) In} the comparative example, discharge means the percentage of the ore used that was discharged with the flotation foam. In Examples 1 to 3, discharge means the balanced amount of solids discharged. ^{4) In} the comparative example, content means the percentage distribution in the discharge. In Examples 1 to 3, content means the proportions of Cu, Pb and Zn in% by weight in the discharge. ⁵⁾ The comparative example shows what percentage of the amounts of Cu, Pb and Zn originally present in the ore were discharged. In Examples 1 to 3, yield reflects the weight percentages of Cu, Pb and Zn, based on the amounts of Cu, Pb and Zn originally present in the ore. ⁶⁾ Redox potential, set in the ventilation before the SO₂ introduction (in the comparative example = optimal redox potential) ⁷⁾ Redox potential, measured in Cu flotation (in examples 1 to 3 = optimal redox potential)

Example 2

carried out as Example 1, with the difference that before the SO₂ addition as much air was introduced into the flotation cell until a redox potential of 142 mV was set and the optimal redox potential of 164 mV was measured at the end of the flotation. Ore type E 1 ⁶⁾ E 2 ⁷⁾ Staging ³⁾ Salary ⁴⁾ Spread ⁵⁾ mV mV G Cu Pb Zn Cu Pb Zn II 142 164 52 23 0.3 3.8 88.0 30.0 6.9 ^{3) In} the comparative example, discharge means the percentage of the ore used that was discharged with the flotation foam. In Examples 1 to 3, discharge means the balanced amount of solids discharged. ^{4) In} the comparative example, content means the percentage distribution in the discharge. In Examples 1 to 3, content means the proportions of Cu, Pb and Zn in% by weight in the discharge. ⁵⁾ The comparative example shows what percentage of the amounts of Cu, Pb and Zn originally present in the ore were discharged. In Examples 1 to 3, yield reflects the weight percentages of Cu, Pb and Zn, based on the amounts of Cu, Pb and Zn originally present in the ore. ⁶⁾ Redox potential, set in the ventilation before the SO₂ introduction (in the comparative example = optimal redox potential) ⁷⁾ Redox potential, measured in Cu flotation (in examples 1 to 3 = optimal redox potential)

Example 3

carried out as Example 1, with the difference that before the SO₂ addition as much air was introduced into the flotation cell until a redox potential of 262 mV was set and the optimal redox potential of 327 mV was measured at the end of the flotation. Ore type E 1 ⁶⁾ E 2 ⁷⁾ Staging ³⁾ Salary ⁴⁾ Spread ⁵⁾ mV mV G Cu Pb Zn Cu Pb Zn III 262 327 54 9.5 0.05 0.22 81.0 8.3 26.0 ^{3) In} the comparative example, discharge means the percentage of the ore used that was discharged with the flotation foam. In Examples 1 to 3, discharge means the balanced amount of solids discharged. ^{4) In} the comparative example, content means the percentage distribution in the discharge. In Examples 1 to 3, content means the proportions of Cu, Pb and Zn in% by weight in the discharge. ⁵⁾ The comparative example shows what percentage of the amounts of Cu, Pb and Zn originally present in the ore were discharged. In Examples 1 to 3, yield reflects the weight percentages of Cu, Pb and Zn, based on the amounts of Cu, Pb and Zn originally present in the ore. ⁶⁾ Redox potential, set in the ventilation before the SO₂ introduction (in the comparative example = optimal redox potential) ⁷⁾ Redox potential, measured in Cu flotation (in examples 1 to 3 = optimal redox potential)

Claims (11)

1. A method for the selective flotation of a sulphidic copper/lead/zinc ore, wherein the crude ore is ground and is formed into a slurry with water, the resulting suspension is aerated in order to set a given redox potential, then conditioning is effected successively with SO₂, with Ca(OH)₂ and with collecting agents and frothing agents, and then the Cu flotation is effected, characterised by the process steps

   a) aeration of the suspension before the Cu flotation, wherein a redox potential of 70 to 90% of the optimum redox potential desired for the Cu flotation is set by introducing a corresponding quantity of oxygen,

   b) conditioning of the suspension from (a) with SO₂, Ca(OH)₂ and with at least one collecting agent and frothing agent, and

   c) aeration of the conditioned suspension for Cu flotation, wherein the desired optimum redox potential of 60 to 340 mV is set, the Cu flotation is effected at a pH value of 8.5 to 10.5 and Cu is removed from the flotation with the froth.
2. A method according to Claim 1, characterised in that the optimum redox potential desired for the Cu flotation is 60 to 75 mV.
3. A method according to Claim 1, characterised in that the optimum redox potential desired for the Cu flotation is 155 to 170 mV.
4. A method according to Claim 1, characterised in that the optimum redox potential desired for the Cu flotation is 325 to 340 mV.
5. A method according to one of Claims 1 to 4, characterised in that upon the aeration of the suspension before the Cu flotation a redox potential of 75 to 85% of the optimum redox potential desired for the Cu flotation is set.
6. A method according to one of Claims 1 to 5, characterised in that the Cu flotation is effected at a pH value of 9.0 to 9.7.
7. A method according to one of Claims 1 to 6, characterised in that the Cu flotation is effected at a pH value of 9.3 to 9.5.
8. A method according to one of Claims 1 to 4, characterised in that the suspension produced as a discharge of the Cu flotation is set with Ca(OH)₂ to a pH value of 9.3 to 12, is introduced with collecting agents and frothing agents into a Pb flotation and Pb is removed with the froth.
9. A method according to Claim 8, characterised in that the redox potential of 80 to 360 mV desired for the Pb flotation is set by the aeration during the Pb flotation.
10. A method according to one of Claims 1 to 4, characterised in that the suspension produced as a discharge of the Pb flotation is conditioned with CuSO₄ and then is set with Ca(OH)₂ to a pH value of 11.5 to 12.5, is introduced with collecting agents and frothing agents into a Zn flotation and Zn is removed with the froth.
11. A method according to Claim 10, characterised in that the redox potential of 110 to 450 mV desired for the Zn flotation is set by the aeration during the Zn flotation.