JP5423046B2 - Method for leaching copper raw materials containing copper sulfide minerals - Google Patents

Description

  The present invention relates to a method for leaching a copper raw material containing a copper sulfide mineral, and more specifically, from a copper raw material containing a copper sulfide mineral, in particular, from a low-grade copper raw material containing a large amount of pyrite and containing a small amount of copper sulfide mineral, The present invention relates to a method of leaching copper while feeding oxygen gas in a pressurized container, and leaching copper in a high yield while suppressing the oxidation of sulfur in the copper raw material to a minimum.

In general, copper ores containing copper sulfide minerals include chalcopyrite (charcopyrite: CuFeS ₂ ), chalcocite (charcosite: Cu ₂ S), chalcopyrite (bonite: Cu ₅ FeS ₄ ), copper indigo ( Pyrite and other gangue components coexist with copper sulfide minerals such as kobelite (CuS). In order to separate and recover copper from copper ores containing these copper sulfide minerals, first, copper concentrate obtained by beneficiation of copper ore is charged into a smelting furnace and melted at a high temperature to produce impurity elements. In general, a dry smelting method in which the obtained crude copper is electrolytically purified to recover product copper is combined with electrolytic purification.
On the other hand, as a hydrometallurgical method, copper is leached from a copper raw material enriched with copper sulfide minerals such as copper concentrate using chlorine gas, chloride ions, or sulfuric acid, and solvent extraction from the leachate, neutralization treatment, etc. A method of separating impurity elements by a method and then performing electrowinning has also been developed.

For example, it contains 10 to 40 g / L of iron ions and 10 to 60 g / L of sulfuric acid, and the content ratio of trivalent iron ions to divalent iron ions is 2 or more in the [Fe ³⁺ / Fe ²⁺ ] ratio. A method of leaching a copper sulfide mineral by adjusting the oxygen partial pressure to 0.2 to 0.7 MPa and the temperature to 50 to 105 ° C. using a leaching start solution (see, for example, Patent Document 1). Proposed. This method is characterized in that it is leached under atmospheric pressure at a relatively low temperature and with a low oxygen partial pressure, so that oxidation of sulfur in the copper sulfide mineral is suppressed. Here, since the unoxidized sulfur can be separated and recovered as a single sulfur, it is advantageous in that it is easy to handle and that the time and cost of neutralizing sulfuric acid produced by sulfur oxidation are reduced. However, since the leaching temperature is low and the oxidation rate of the copper sulfide mineral is slow, there is a problem in industrial production that it takes a long time to obtain a high leaching rate of copper. In particular, when the leaching temperature is less than 80 ° C., the leaching rate is significantly reduced even if the iron concentration in the leaching solution is sufficient.

As another method, for example, in a pressure vessel, an aqueous solution containing copper sulfide mineral and iron sulfate or an aqueous sulfuric acid solution is used as a slurry, and oxygen is maintained at a temperature of 220 to 275 ° C., preferably 235 ° C. or higher. A method of leaching a copper sulfide mineral by introducing gas or air (see, for example, Patent Document 2) has been proposed. In this method, since the whole ore is strongly oxidized at a high temperature, the reaction rate is fast, so that copper can be leached in a high yield. Here, all of the copper sulfide mineral is dissolved, and all the sulfur becomes sulfate ions. In addition, the iron component contained in the copper sulfide mineral reacts with sulfuric acid and elutes into the solution as iron sulfate. Further, it is hydrolyzed in a high-temperature oxidizing atmosphere to separate the sulfuric acid component, and iron oxide called hematite. (III) (Fe ₂ O ₃ ).

  Therefore, since sulfuric acid can be generated from sulfur contained in the ore itself, there is an advantage that sulfuric acid does not need to be present in the leaching start liquid at the start of leaching, but the sulfuric acid content of iron sulfate is reduced by hydrolysis. Because it is regenerated into sulfuric acid, a process such as adding a neutralizing agent to neutralize excess sulfuric acid is required before the process of recovering copper from the leachate. There was a problem that. Moreover, in order to operate at a high temperature and high pressure exceeding 200 ° C., a pressure vessel and a pump having a material that can withstand pressure, temperature, and further corrosion are required, so that capital investment and repair costs are high. There was also a problem.

As another method, for example, in a pressure vessel, while coexisting copper concentrate and coal as a catalyst, while maintaining the temperature in the vessel at 120 to 180 ° C, preferably 135 to 175 ° C, There has been proposed a method in which oxygen gas is fed and leached so as to maintain the pressure at a value corresponding to 0.1 to 3 MPa (see, for example, Patent Document 3). This method is a method of leaching in a temperature range that is intermediate between the above two leaching methods, and can solve the problems of both of them, namely, the improvement of copper leaching rate and the suppression of sulfur oxidation rate to some extent. It has the advantage of being able to.
That is, in copper sulfide minerals with a high proportion of copper, the reaction with sulfuric acid and oxygen gas is fast in sphalerite (Cu ₅ FeS ₄ ), chalcocite (Cu ₂ S) or copper indigo (CuS). It is possible to achieve both oxidation inhibition and high copper leaching rate at the same time. However, the most common chalcopyrite (CuFeS ₂ ) produced abundantly as a copper sulfide mineral has a property that it reacts slowly with sulfuric acid and oxygen gas and is difficult to be leached, so that it is leached by strengthening the leaching conditions. At the same time, there was a problem that sulfur oxidation also increased.

  As another method, for example, copper concentrate obtained by flotation of high-grade copper ore mainly composed of chalcopyrite is leached under high temperature and high pressure, and contains ferric ion and sulfuric acid. There has been proposed a method for recovering copper from a copper ore by obtaining a copper leachate and using the copper leachate for heap leaching or butt leaching of low-grade copper ore (see, for example, Patent Document 4). Here, in leaching under high temperature and high pressure, the temperature is preferably 150 to 220 ° C., the pressure is set higher than atmospheric pressure, and the oxygen partial pressure is preferably 0.1 to 2.0 MPa. Under conditions, it is disclosed to oxidize sulfur to sulfate ions. Therefore, in this method, although sulfuric acid produced by leaching under high temperature and high pressure is used as a leaching agent for the subsequent low-grade copper ore, the equipment and equipment associated with leaching under high temperature and high pressure as in the conventional method are used. Cost problem is not solved.

As described above, in the conventional method, in the leaching of the most common chalcopyrite (CuFeS ₂ ) abundantly produced as a copper sulfide mineral, it is possible to simultaneously achieve sulfur oxidation inhibition and a high copper leaching rate. There was a problem that I could not.

Furthermore, another problem is related to pyrite coexisting with copper sulfide minerals. That is, it is normal that iron sulfide minerals such as pyrite (pyrite: FeS ₂ ) coexist in copper sulfide minerals, particularly copper ores containing chalcopyrite as a main component as copper sulfide minerals. Here, the standard oxidation-reduction potential (standard hydrogen electrode) between chalcopyrite and sulfate is 380 mV, while the standard oxidation-reduction potential (standard hydrogen electrode) between pyrite and sulfate is 424 mV. Comparing only the reduction potential, in theory, pyrite is less likely to be oxidized, but in fact, it is known that pyrite is preferentially oxidized in the temperature range above the melting point of sulfur. . This reason will be described later.
For this reason, when a low-grade copper raw material containing a large amount of pyrite and containing a small amount of copper sulfide mineral is leached using sulfuric acid, it is contained in the obtained leachate, compared to the case of treating a copper raw material with a low pyrite content. There is a problem that the concentration of sulfuric acid is greatly increased, which increases the cost and labor of the neutralization treatment in the subsequent process.

  From the above situation, in the method of leaching copper from a copper raw material containing a copper sulfide mineral, particularly a low grade copper raw material containing a large amount of pyrite and containing a small amount of copper sulfide mineral, oxidation of sulfur in the copper raw material is carried out. There has been a need for a method of leaching copper in high yield while minimizing it.

US Pat. No. 6,537,440 US Pat. No. 6,497,745 US Pat. No. 5,730,776 JP 2003-328050 A (first page, second page, paragraph 0034)

  In view of the above-mentioned problems of the prior art, the object of the present invention is to produce a copper raw material containing a copper sulfide mineral, particularly a low-grade copper raw material containing a large amount of pyrite and containing a small amount of copper sulfide mineral, in a pressurized container. An object of the present invention is to provide a method for leaching copper in a high yield while suppressing oxidation of sulfur in the copper raw material to a minimum in a method for leaching copper while feeding oxygen gas.

  In order to achieve the above object, the present inventors have conducted extensive research on a method of leaching copper from a copper raw material containing a copper sulfide mineral while feeding oxygen gas in a pressurized container. Oxygen to be fed so as to form a slurry composed of a copper raw material and a sulfuric acid aqueous solution in a container and maintain the temperature in the container at a predetermined value so that the pressure increase by the oxygen gas in the container becomes a predetermined value. When the gas was leached out, high yields of copper were achieved even with low grade copper raw materials that contained a large amount of pyrite and low copper sulfide minerals while minimizing the oxidation of sulfur in the copper raw materials. The present invention was completed by finding that it can be leached at a high rate.

That is, according to the first invention of the present invention, a method of leaching copper from a copper raw material containing chalcopyrite while feeding oxygen gas in a pressurized container,
In the pressure vessel, a slurry composed of a copper raw material and an aqueous sulfuric acid solution is formed, and while maintaining the temperature in the vessel at 102 to 112 ° C., the pressure in the vessel is the equilibrium gas phase partial pressure at that temperature. A method for leaching a copper raw material containing chalcopyrite is provided in which the oxygen gas fed is adjusted so that the pressure is increased to 0.6 to 2 MPa.

According to the second invention of the present invention, in the first invention, the amount of sulfuric acid contained in the slurry is a chemical equivalent required for converting copper contained in the chalcopyrite into copper sulfate. The method of leaching a copper raw material containing chalcopyrite characterized by being 1 to 2 times the above is provided.

According to a third invention of the present invention, in the first invention, the slurry concentration at the start of leaching of the slurry is 10 to 300 g / L, and the method for leaching copper raw material containing chalcopyrite Is provided.

  The method for leaching a copper raw material containing a copper sulfide mineral according to the present invention includes a copper raw material containing a copper sulfide mineral, particularly a low-grade copper raw material containing a large amount of pyrite and a small amount of copper sulfide mineral, in a pressurized container. In the method of leaching copper while feeding gas, copper can be leached in a high yield while suppressing the oxidation of sulfur in the copper raw material to a minimum, and its industrial value is extremely large. That is, sulfur in the copper raw material can be separated into the leaching residue as simple sulfur or pyrite that can be easily treated, and the amount of neutralizing agent used can be reduced when treating the leachate. Processing costs can be reduced.

Hereinafter, the leaching method of the copper raw material containing the copper sulfide mineral of the present invention will be described in detail.
The method for leaching a copper raw material containing a copper sulfide mineral of the present invention is a method of leaching copper from a copper raw material containing a copper sulfide mineral while feeding oxygen gas in a pressurized vessel, While forming a slurry comprising a copper raw material and a sulfuric acid aqueous solution and maintaining the temperature in the container at 102 to 112 ° C., the pressure in the container is 0.5 to 2 MPa to the equilibrium gas phase partial pressure at that temperature. The oxygen gas to be fed is adjusted so as to be a value obtained by boosting the pressure.

  In the present invention, the temperature in the pressurized container is maintained at 102 to 112 ° C., and the pressure in the container is set to a value obtained by increasing the equilibrium gas phase partial pressure at that temperature by 0.5 to 2 MPa. It is important to adjust the oxygen gas to be fed. Thereby, copper can be leached in a high yield while suppressing oxidation of sulfur in the copper raw material to a minimum.

That is, in the conventional method, regarding the phenomenon that pyrite is oxidized preferentially, a slurry composed of a copper raw material containing chalcopyrite and pyrite and an aqueous sulfuric acid solution is formed, and at a temperature of 120 ° C. or higher, oxygen gas The behavior of leaching of chalcopyrite and pyrite with feeding was observed with a microscope. As a result, first, sulfur generated on the surface by the oxidation is melted, and then, in the melted sulfur, chalcopyrite is preferentially included in the sulfur droplets, while pyrite is almost entirely contained in the sulfur droplets. It was found that it was not taken in and dispersed in the aqueous solution as single particles.
Here, since the chalcopyrite taken in this sulfur melt is covered with hydrophobic sulfur, the contact with the sulfuric acid aqueous solution is interrupted and the oxidation is suppressed. On the other hand, pyrite exists alone in an aqueous solution, and there is no other material that is easily oxidized. That is, in the conventional method, pyrite is preferentially oxidized to chalcopyrite.

  On the other hand, in the method of the present invention, by maintaining the temperature in the pressure vessel at 102 to 112 ° C., oxidation of pyrite in the copper raw material can be suppressed and priority can be given to oxidation of chalcopyrite. That is, it is known that the melting point of sulfur is generally around 113 ° C. Therefore, by maintaining the temperature below the melting point at which sulfur does not form a melt, for example, 112 ° C. or less, it is possible to prevent chalcopyrite from being included in sulfur. As a result, only the chalcopyrite can be selectively leached according to the value of the oxidation-reduction potential described above, and the leaching rate of copper can be improved. On the other hand, the lower the temperature, the lower the reaction rate. At a leaching temperature lower than 102 ° C., a practical reaction rate cannot be obtained, so the copper leaching rate decreases.

  In the method of the present invention, the sulfur gas is adjusted by adjusting the oxygen gas to be fed so that the pressure in the pressurized container becomes a value obtained by increasing the equilibrium gas phase partial pressure at that temperature by 0.5 to 2 MPa. The copper leaching rate can be increased while minimizing the oxidation of the copper. That is, when the pressure increase by oxygen gas is less than 0.5 MPa, the oxygen partial pressure becomes low and the oxidation reaction is insufficient, so that the copper leaching rate is low. On the other hand, when the pressure increase by oxygen gas exceeds 2 MPa, the oxygen partial pressure increases and the oxidation of sulfur is promoted.

  Here, the leaching reaction of chalcopyrite with sulfuric acid is performed according to the following formula (1). Thereafter, the obtained iron (II) sulfate is hydrolyzed in the presence of oxygen and fixed in the form of hematite. That is, hematite is stable to acid and is the most suitable fixed form.

Formula (1): CuFeS ₂ + O ₂ + 2H ₂ SO ₄ → CuSO ₄ + FeSO ₄ + 2S ⁰ + 2H ₂ O

  In the above method, the amount of sulfuric acid contained in the slurry is not particularly limited, but the chemical equivalent required to convert copper contained in the copper sulfide mineral contained in the slurry to copper sulfate. It is preferable that it is 1-2 times. That is, at the initial stage of leaching, when the amount of sulfuric acid is not more than 2 times the mol of copper, the reaction proceeds as in the above formula (1), so that sulfur oxidation can be suppressed. On the other hand, if the amount of sulfuric acid is less than 1 times that of copper, the progress of the leaching reaction is insufficient.

  In the above method, the slurry concentration at the start of leaching is not particularly limited, but is preferably 10 to 300 g / L. That is, if the slurry concentration is less than 10 g / L, the amount of leaching of copper per unit volume of the leaching equipment is small, the equipment becomes huge, and the productivity also decreases. On the other hand, when the slurry concentration exceeds 300 g / L, copper sulfate and iron sulfate exceed the solubility, coat the ore particles, and the reactivity decreases.

The copper material used in the above method, is not particularly limited, chalcopyrite (Cal Kopai Light: CuFeS _2), chalcocite (Cal co Site: _Cu 2 S), bornite _(Bonaito: Cu 5 FeS ₄ ), Copper ore in which pyrite, other gangue components coexist with copper sulfide minerals such as copper indigo (Cobelite: CuS), copper concentrate obtained by subjecting the copper ore to flotation, or What is at least 1 sort (s) chosen from the copper smelting intermediate containing the copper of the sulfide form obtained by a dry smelting method or a wet smelting method is used. In particular, a copper raw material containing chalcopyrite and pyrite is preferably used.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The metal used in the examples and comparative examples was analyzed by ICP emission analysis.

Example 1
The composition was Cu: 20.6% by mass, Fe: 25.7% by mass, and S: 24.6% by mass, and copper concentrate containing chalcopyrite and pyrite as main minerals was used by microscopic observation.
First, the copper concentrate was pulverized using a wet bead mill so that particles having a size of 10 μm or less accounted for 80% by mass or more.
Next, 200 g of the pulverized copper concentrate was mixed with a sulfuric acid aqueous solution having a composition of Cu: 1.3 g / L, Fe: 45.3 g / L, S: 64.2 g / L, and free sulfuric acid concentration: 95 g / L. A slurry was obtained by mixing with 1 liter of a leaching starting solution consisting of and stirred lightly. The molar ratio of copper in the copper concentrate and sulfuric acid in the leaching start solution is about 1.6. The slurry concentration is 95 g / L. Furthermore, 0.5 g / L of sodium lignin sulfonate was mixed with this slurry as a surfactant that improves the peelability of sulfur and copper ore.
Subsequently, the slurry was charged into a pressure vessel and heated to 105 ° C. while stirring. The pressure at 105 ° C. was about 0.1 MPa. Here, while maintaining this temperature, oxygen gas was blown in, the pressure was increased to 1.5 MPa, and this state was maintained for 2 hours.
Thereafter, the slurry after the reaction was taken out and filtered to separate into a filtrate and a residue. Each analysis was performed, and the copper leaching rate was determined from the ratio of copper distributed to the filtrate. Analyze the sulfur concentration change in the filtrate and the elemental sulfur, sulfide sulfur, and sulfuric acid sulfur grade in the residue, and calculate the ratio of sulfur contained in the copper sulfide mineral to sulfate ion. The sulfur oxidation rate was determined. The results are shown in Table 1.

(Example 2)
The temperature in the pressure vessel was 110 ° C., and the pressure at that time was about 0.15 MPa. While maintaining this temperature, oxygen gas was blown in, the pressure was increased to 0.75 MPa, and the total pressure was increased. In order to make the same, except that nitrogen gas was blown up to about 1.5 MPa, it was carried out in the same manner as in Example 1, and the copper leaching rate and the sulfur oxidation rate were determined. The results are shown in Table 1.

(Comparative Example 1)
The temperature inside the pressure vessel was 160 ° C., and the pressure at that time was about 0.6 MPa. While maintaining this temperature, oxygen gas was blown in and the pressure was increased to 2.0 MPa. It carried out similarly to Example 1 and calculated | required the copper leaching rate and the sulfur oxidation rate. The results are shown in Table 1.

(Comparative Example 2)
The temperature in the pressure vessel was 120 ° C., and the pressure at that time was about 0.2 MPa. While maintaining this temperature, oxygen gas was blown in and the pressure was increased to 2.0 MPa. It carried out similarly to Example 1 and calculated | required the copper leaching rate and the sulfur oxidation rate. The results are shown in Table 1.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that the temperature in the pressure vessel was 95 ° C. and oxygen gas was blown into the pressure vessel and the pressure was increased to 1.5 MPa. The oxidation rate was determined. The results are shown in Table 1.

(Comparative Example 4)
Except that the pressure after the oxygen gas was blown into the pressure vessel was 0.3 MPa, the same procedure as in Example 1 was performed to determine the copper leaching rate and the sulfur oxidation rate. The results are shown in Table 1.

(Comparative Example 5)
The copper leaching rate and the sulfur oxidation rate were determined in the same manner as in Example 1 except that the pressure after the oxygen gas was blown into the pressure vessel was 2.5 MPa. The results are shown in Table 1.

  From Table 1, in Example 1 or 2, in the slurry which consists of a copper raw material and sulfuric acid aqueous solution, and maintaining the temperature in a pressure vessel at 102-112 degreeC, the pressure in this container is the temperature in that temperature. Since the oxygen gas to be fed was adjusted so that the equilibrium gas phase partial pressure was increased to 0.5 to 2 MPa and the method according to the present invention was performed, oxidation of sulfur in the copper raw material was suppressed. However, it can be seen that copper can be leached in high yield. On the other hand, in Comparative Examples 1-5, since the temperature in a pressure vessel or the pressure | voltage rise by oxygen gas does not meet these conditions, it turns out that a satisfactory result is not obtained in a copper leaching rate or a sulfur oxidation rate. .

  As is clear from the above, the leaching method of the copper raw material containing the copper sulfide mineral of the present invention leaches copper in a high yield while minimizing the oxidation of sulfur in the copper raw material. It is suitable as a leaching method for copper raw materials containing chalcopyrite and pyrite.

Claims (3)

A method of leaching copper from a copper raw material containing chalcopyrite while feeding oxygen gas in a pressurized container,
In the pressure vessel, a slurry composed of a copper raw material and an aqueous sulfuric acid solution is formed, and while maintaining the temperature in the vessel at 102 to 112 ° C., the pressure in the vessel is the equilibrium gas phase partial pressure at that temperature. A method for leaching a copper raw material containing chalcopyrite , wherein oxygen gas to be fed is adjusted so that the pressure is increased to 0.6 to 2 MPa. Amount of sulfuric acid contained in the slurry is yellow of claim 1, characterized in that the copper contained in the chalcopyrite is 1-2 times the stoichiometric amount required to convert the copper sulfate A method for leaching copper raw materials containing copper ore . The method for leaching a copper raw material containing chalcopyrite according to claim 1, wherein the slurry concentration at the start of leaching of the slurry is 10 to 300 g / L.