JP4885119B2 - Selective reduction of copper-containing calcined products. - Google Patents

Description

Field of Invention

  The present disclosure relates to a method for recovering copper from a sulfide material comprising a metal intimately mixed with copper. The method is particularly useful for treating copper-containing mats or fractions of such mats.

Background of the Invention

  Copper and nickel are close melt thermodynamic relatives, and it is difficult to efficiently separate nickel from copper when processing ores and mats. U.S. Pat. No. 4,168,217 (the "217 patent") describes copper as a sulfide-based material containing at least one of the metals iron, nickel and cobalt, such as a copper-containing mat or mat fraction (e.g. Bessemer). Mat)), wherein the material is completely roasted at a temperature of at least about 750 ° C. to form a calcined material substantially free of sulfur, and after cooling the calcined material, Leaching at a temperature of at least about 50 ° C. to remove the concentrated leachate in which most of the copper initially present in the material is dissolved, all the iron, nickel and cobalt originally present in the material Describes a method for separating from leach residue containing most of In the method of the '217 patent, the resulting calcined product contains a large amount of CuO in a solid solution with NiO that does not easily leach out.

  U.S. Pat.No. 4,135,918 is a method for recovering copper from a particulate sulfide-containing material containing at least one other metal from the group of iron, nickel and cobalt in addition to copper, Roasting the material at a temperature of at least about 750 ° C. for a time sufficient to form a substantially sulfur-free calcined product, the sulfuric acid formed with the calcined product and water, or in situ. Supplementing and forming a slurry with at least a sufficient amount of sulfuric acid to satisfy the stoichiometric amount for forming the sulfate of the other metal, said slurry under reducing gas under pressure Heating to at least 110 ° C. in the presence of sulphates, sulphates other metals, reduces copper to elemental form, and pressurizes the product of solid heat containing other metals and elemental copper Those who do it by separating into liquids containing substances It describes. As mentioned above, the calcined material contains a large amount of CuO in a solid solution with NiO or ferrite that does not easily leach out.

  A method for recovering copper from a sulfide-based material is also described in U.S. Pat. No. 4,120,697, where the sulfide-based material is roasted to form a calcined product and the calcined product is particulated. Carbonaceous reducing agent and a small amount of at least one halogen for halogenating precious copper contained in the calcined product, which can be thermally converted to gaseous halogen or hydrogen halide at segregation roasting temperature Mixed with a chloride salt, and the mixture is heated to a segregation roasting temperature of about 650 ° C. to about 700 ° C., at which temperature the precious copper in the calcined material is reacted to form a copper halide, Copper halide is conveyed to the particulate carbonaceous reducing agent, where metallic copper is deposited on the carbonaceous reducing agent from the copper halide, and the deposited metallic copper is recovered. This process involves the formation of a salt to reduce copper to the metal form after calcination, but this salt needs to be further processed and separated by flotation or other physical separation.

  Thus, to a desired degree between copper present in the mixture and other metals such as nickel, cobalt and iron, without various additional processing steps that increase the time and cost of manufacture. It has been difficult to achieve selectivity. There remains a need to provide more efficient methods for purifying copper and other metals from mixtures.

Summary of the Invention

A method for recovering copper from a sulfide-containing material containing at least one other metal selected from the group consisting of iron, nickel and cobalt in addition to copper, wherein the sulfide-containing material is substantially free of sulfur. Roasting for a time sufficient to form a calcined material that is not contained in the calcined material, sufficient to selectively reduce the CuO in the calcined material to Cu ₂ O and to form a reduced calcined material. A method is provided that includes subjecting the reduced calcined product to oxidative leaching and recovering the copper. The reduction step separates copper from the nickel oxide matrix because Cu ₂ O is insoluble in NiO.

A method for selectively reducing CuO in a calcined product containing at least one other metal selected from the group consisting of iron, nickel and cobalt in addition to copper to Cu ₂ O, wherein the material is sulfur Roasting for a time sufficient to form a calcined material substantially free of calcination, the calcined product selectively reducing CuO in the calcined product to Cu ₂ O to form a reduced calcined product A method comprising exposing to a sufficient heat and reducing atmosphere.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the present invention, prior to leaching, CuO (tenorite) is selectively reduced to Cu ₂ O (cuprite) in a calcined product in a suitable reducing atmosphere and sufficiently high temperature to provide nickel, iron, cobalt and It surprisingly effectively separates copper from mixtures of other metals that may be present. In addition to making copper oxide available for leaching, the reduction process also makes NiO refractory. For example, in one representative experiment, by subjecting an overall roasted Bessemer mat with a Cu / Ni ratio of 1.0 to the technique described herein, about 97.8% copper was extracted. Nickel extraction was only about 0.3%.

  The methods disclosed herein can be applied to a wide range of copper-containing materials and are also useful for processing materials with relatively low amounts of metals other than copper. For example, the method is suitable for materials where the copper content far exceeds the total content of other metals. This is usually not the case for ores or concentrates that can also be processed by the techniques described herein, but for mats and various metallurgical residues obtained from, for example, acid leaching or nickel carbonylation processes. Would also be true.

  In one embodiment, any calcined material that contains copper and at least one other metal and is substantially free of sulfur can be used in the present invention. Various techniques for obtaining such calcined products are well known to those skilled in the art. In fact, any technique can be used to treat sulfide containing materials and remove most of the sulfur. For example, the temperature at which roasting takes place is usually considered important to achieve the desired good leaching properties of the resulting calcined product. Well known techniques (see, eg, US Pat. No. 4,168,217) recommend a minimum temperature of about 750 ° C., preferably about 800 ° C., and should not exceed about 950 ° C. In the present invention, the roasting temperature may be higher than previously used. However, if the roasting temperature is too high, deleterious melting of the calcined product will occur, so the temperature should normally not exceed about 1050 ° C. Thus, the present invention allows roasting to proceed at a higher rate when the temperature is high but below the melting point of the calcined product. When the temperature is maximized, the reaction rate increases. In a preferred embodiment, the sulfide material is roasted in an atmosphere containing excess oxygen to ensure removal of almost 100% of the sulfur. At such temperatures, a holding time of about 0.5 hours to about 3 hours has been found to be sufficient to reduce the sulfur content of the feed to about 0.5% or less. Unless otherwise indicated, all percentages stated herein are weight percentages. As used herein, “substantially” means almost or exactly.

  In the case of mats or mat fractions, in contrast to the prior art, the composition of the mat or mat fraction to be treated has little to do with copper extraction and the selectivity that can be achieved. In fact, the relative concentration of each component is not critical because the method is effective over almost all ranges of copper, iron and nickel ratios.

  Roasting can take place in any of a variety of known forms of equipment and can proceed autogenously. It is preferable to use a fluidized bed roasting apparatus, because such a roasting apparatus allows a high throughput and the sulfur dioxide concentration in the exhaust gas is relatively high. For the purpose of fluidized bed roasting, the feed is preferably in the form of particles, preferably from about 100 to about 600 microns in diameter. If the initial raw material is a fine powder, pelletization may be necessary. However, when the raw material is derived from a previously melted mat, desired particles can be produced by water granulation of a high temperature mat. The latter method is preferable because it generates less dust during the fluidized bed roasting operation.

For example, a copper-containing calcined product manufactured by complete roasting can contain a large amount of CuO in a solid solution with Ni. The calcined product is then subjected to selective reduction using a relatively high temperature and a moderately mild reducing atmosphere, thereby forming Cu ₂ O out of NiO, effectively removing CuO from the nickel oxide matrix. It is considered to be removed. In a preferred embodiment, the reducing gas mixture is selected so that there is not too much reductant to ensure selective reduction and to avoid the formation of nickel metal. The range of pO ₂ (oxygen partial pressure) and temperature required to achieve effective reduction is illustrated in the phase diagram and can be determined using well known techniques. FIG. 1 is a graph of the superiority of copper and nickel, in which the gray region performs a reduction from CuO to Cu ₂ O without forming nickel metal that can impair downstream leaching efficiency. It shows the area where can be. The minimum pO ₂ is shown in the region where the nickel metal is stable (dashed line). Arrow increases the temperature, by operating at low pO _2, it shows that it is possible achieve maximum rate and recovery. Black diamonds indicate potential reduction target conditions. The maximum pO ₂ is where CuO is reduced to Cu ₂ O. Preferably, the conversion to Cu ₂ O is performed at as high a temperature as possible with as low pO ₂ as possible without forming nickel metal. Even if copper metal is formed, it is effectively leached by oxidative leaching.

pO ₂ can be adjusted by mixing an appropriate amount of a suitable gas by a well-known technique. For example, mixtures of CO, CO ₂ , H ₂ and H ₂ O are well known for creating a reducing atmosphere. FIG. 2 shows that pO ₂ can be adjusted by mixing CO and CO ₂ gas in the proper ratio. In particular, FIG. 2 is a graph showing a curve representing the relationship between the oxygen partial pressure (atmospheric pressure), the temperature and the CO ₂ / CO ratio at a total pressure of 1 atm. The shaded area under the curve indicated by the dashed line indicates a metastable state. Similar tables exist for H ₂ / H ₂ O mixtures. H ₂ and CO ₂ can be mixed to form a mixture of CO, CO ₂ , H ₂ and H ₂ O. Less than 10 ⁻⁶ pO ₂ can be used, with about 10 ⁻¹⁰ being preferred. An example of a mixture is a gas mixture of H ₂ and CO ₂ that contains about 3-5% (vol%) H ₂ with the remainder being CO ₂ , and is about 10 ⁻¹⁰ to 10 ⁻¹² at about 1000 ° C. cause of pO _2. Another mixture can include a _CO 2 / CO of about 1000 to about 1000 ° C. (pO ₂ of about ^{10 -11).} In one aspect, pO ₂ can be controlled by partial combustion of the fuel, as is commonly done by those skilled in the art. By measuring the CO and CO ₂ concentration in the gas, the oxygen concentration (pO ₂ ) can be measured indirectly, changing the fuel / air ratio and the appropriate CO ₂ / CO ratio, ie pO ₂ , maintain. CO ₂ / CO gas generation can also be obtained from solid carbon by the Boudouard reaction.

  The relatively high temperature that can be used here is a suitable temperature to enhance the reduction conditions. One skilled in the art can readily determine the appropriate temperature to maximize the rate of reduction. See, for example, FIGS. As a practical matter, copper oxide begins to melt at about 1050 ° C., which effectively limits the upper range. Accordingly, a preferred temperature range is from about 750 ° C to about 1050 ° C, with about 1000 ° C being more preferred. Any suitable oven or furnace can be used as the reduction vessel described herein, but highly mixed reactors, such as dynamic fluidized bed equipment, are preferred to achieve high rates. .

The reduced calcined product produced by the reduction described herein is cooled and, if necessary, ground and subjected to oxidative leaching, eg, used electrolyte obtained from copper electrowinning operations. It can be slurried with an aqueous sulfuric acid solution that can conveniently be included to selectively dissolve Cu ₂ O. The leaching agent can contain some dissolved copper in addition to free sulfuric acid. Achieving practical leaching rates typically requires a leaching temperature of at least about 50 ° C., but temperatures above about 80 ° C. have an undesirable effect of increasing nickel and iron dissolution. There is. In a preferred embodiment, a retention time of about 2-3 hours with a leaching temperature of about 60-70 ° C. has been found to give good results. After separating the solid-liquid, the liquid can be used for the electrowinning of high purity copper products, while treating the residue, all nickel and cobalt, and any precious metals that may be present in the feedstock. It can be recovered.

  The following examples are intended to illustrate certain embodiments of the invention. Accordingly, these examples do not limit any aspect of the invention. Several examples of the method of the present invention will be described with reference to the accompanying drawings.

Example 1
Bessemer mat (Cu (40.7%), Ni (39.7%), Co (0.54%), Fe (0.91%) and S (18%)) flowing 12 inches (30.4 cm) Roasted in the floor. The calcined product was used as a raw material for the reduction test.

A 500 gram sample of the calcined product was placed in a 2 inch (5.1 cm) diameter miniplant fluidized bed and heated to 1000 ° C. The CO ₂ / CO ratio was adjusted to 1000 and pO ₂ was about 10 ⁻⁸ (see FIG. 2). The fluidizing gas flow rates were 10 L / min N2, 25 L / min CO ₂ and 0.025 L / min CO. These conditions were maintained for 1 hour and the furnace heater was turned off. A gas flow was used to rapidly cool the material. A second reduction test was performed to confirm the effect of increasing the residence time during the reduction. This test was carried out under the same conditions but for 2 hours.

Several bench scale leaching tests were performed on two reduced samples. A 25 gram sample of the calcined product was used in a 250 mL solution containing 180 g / L sulfuric acid. In the first test, copper was oxidized to CuO and leached by adding 30% concentration of H ₂ O ₂ . The test results are shown in Table 1 below. Additional tests used oxygen and air sparges to oxidize copper. See Table 2 below. The solution was leached at 80 ° C. for 2 hours. These samples were filtered and the solution and residue were sent for analysis.

  In another leaching test, the calcined product was ground in a Blueler mill for 15 seconds and sprinkled with air to oxidize. Tests were also conducted using a spent copper electrolyte stream obtained from a copper electrowinning facility instead of a pure sulfuric acid solution. Most tests used a 500 mL beaker and a magnetic stirrer. The last test used a wet smelting leaching device to improve partial agitation and increase gas dispersion. The results of Phase # microprobe analysis for Test # 1 are shown in Table 3 below.

The reduced calcined product had a porous structure when observed under an optical microscope. Under reduction, it appears that CuO in the solid solution with NiO in the roasted Bessemer mat was released as Cu ₂ O and formed the observed porous structure. By removing CuO from the NiO matrix during the reduction, copper is utilized for leaching. Moreover, NiO becomes more refractory after CuO is removed from the solid solution. A baseline test was performed on the roasted Bessemer mat and it was found that the nickel in solution was 9.4% and the copper dissolved only 73%, so NiO is refractory when in solid solution with CuO. It is proved that it is not sex. SEM / EDX (semi-quantitative) analysis from the 1 hour reduction-leaching test (Table 3) shows that CuO is reduced from about 30% to 6.6% (± 4.2) in solid solution with NiO. It shows that. This corresponds to a residue assay of 4.4% CuO. The improved leaching results observed with the 2-hour reduction indicate that more CuO was released (CuO 2.3% in the residue).

In experiments conducted using H ₂ O ₂ for oxidation, the coarse or calcined material was not ground prior to leaching. The resulting leach residue is very fine, indicating that removal of copper oxide releases residual NiO particles.

  In a leaching test using air and without pulverization, copper recovery was only 65% (Table 2). By grinding the reduced calcination prior to leaching, results comparable to those performed using peroxides were obtained. The 95% copper recovery in test # 7 (Table 2, crushed calcined, air sparge) is equivalent to tests # 1 and # 2 (Table 1, not pulverized, peroxide) with 95% copper recovery is there. Ni, Fe and Co losses to the solution increased slightly due to sample grinding.

  The leaching test # 12 was conducted with enhanced stirring. The sample was not crushed and 90% copper recovery was achieved, compared to 65% copper recovery when using air sparge and magnetic rotating rod (test # 6). This test demonstrates that enhanced stirring improves copper dissolution.

  Thus, by using oxygen for milling optimization, enhanced agitation, and / or copper recovery, results equivalent to the use of hydrogen peroxide can be achieved.

Table 1 Analysis of selected tests using hydrogen peroxide for oxidation

Sample was not crushed Test distribution
Ni Cu Co Fe Ni Cu Co Fe
Test # 1 residue% 74.2 3.5 1.1 2.0 99.8 4.7 99.8 99.3
(1 hour liquid gpL 0.11 42.89 0.001 0.017 0.2 95.3 0.2 0.7
reduction)
Test # 2 residue% 74.1 3.5 1.0 2.0 99.8 4.5 99.8 98.6
(1 hour liquid gpL 0.092 38.1 0.001 0.008 0.2 95.5 0.2 1.4
reduction)
Test # 5 residue% 75.7 1.8 1.1 2.0 99.7 2.2 99.6 99.0
(2 hours liquid gpL 0.177 49.91 0.003 0.015 0.3 97.8 0.4 1.0
reduction)

Table 2 Analysis of selected tests using air as leached oxidant

Test is a one hour reduction test distribution
went
Ni Cu Co Fe Ni Cu Co Fe
Test # 6 residue% 57.4 22.5 0.8 1.7 99.3 34.8 99.3 97.6
(1 grinding liquid gpL 0.448 41.4 0.007 0.046 0.7 65.2 0.7 2.4
None)
Test # 7 Residue% 70.9 4.08 0.981 1.8 99.1 5.0 99.1 96.9
(Crushing) Liquid gpL 0.512 52.3 0.007 0.051 0.9 95.0 0.9 3.1

Test # 12 residue% 70.2 7.3 1.0 1.9 99.7 9.6 99.4 98.4
(Non-pulverized liquid gpL 0.132 33.5 0.03 0.017 0.3 90.4 0.6 1.6
Stirring)

Table 3 SEM / EDX microprobe analysis of leach residue

Phase average 2S. D. Maximum minimum
FeO 2.34 1.65 4.39 6.47
CeO 1.77 1.17 3.7 0.71
NiO 89.34 4.8 94.91 85.15
CuO 6.55 4.16 10.82 3.91

Example 2
The influence of iron in the Cu—Ni—Fe system was evaluated. Three types of samples: 1) Flash furnace mat (Cu-23%, Ni-22.6%, Co-0.664%, Fe-25.2%, S-26.7%), 2) Synthetic mat (Cu-14.9%, Ni-16%, Co-0.435%, Fe-39.2%, S-29.4%), and 3) Bulk Cu-Ni concentrate (Cu-12. 1) %, Ni-9.25%, Co-0.278%, Fe-37.5%, S-32.3%). Good copper separation was achieved in each case. The test results are shown in Table 4. The following procedure was used for each sample.

The sample was melted and granulated with water. About 2 kg of the granulated sample was placed in a refractory pan and heated to about 900 ° C. for about 24 hours in an ambient air atmosphere to roast the material. Fluidized bed reduction was performed by placing 1 kg of roasted material into a 2 inch (5.1 cm) diameter fluidized bed, using air for flow at approximately 45 slpm, and heating to 1000 ° C. (external electrical element). . This material was “re-roasted” at 1000 ° C. for 10 minutes, then the air atmosphere was replaced with a gas mixture (20 slpmN ₂ , 25 slpmCO ₂ , 0.025 slpmCO). The material was then reduced at 100 ° C. for 2 hours, at which point the furnace was turned off (leaving the gas mixture) and allowed to cool for about 30 minutes. To perform the oxidative leaching, 25 grams of sulfuric acid was mixed with 250 mL of distilled water in a 500 mL beaker, heated and maintained at 80 ° with stirring using a hot plate and stirring mechanism. 25 grams of material to be leached was added to the beaker. Hydrogen peroxide (30 mL) was gradually added at time = 0, and was gradually added again at time = 1 hour. The test was stopped at 2 hours and the sample was filtered. Each weight and volume was recorded.

Table 4 Results of roasting-selective reduction-leaching of high iron mats

Sample did not grind Test distribution

Ni Cu Co Fe Ni Cu Co Fe
Flash residue% 40.7 3.1 1.0 32.5 96.4 13.3 89.8 70.8
Furnace mat liquid gpL 0.891 21.77 0.069 8.22 3.6 93.3 10.2 29.2

Synthetic high iron residue% 25.3 3.0 0.6 44.8 95.2 13.3 93.6 78.0
Mat ¹ liquid gpL 0.836 12.41 0.031 9.35 4.8 86.7 6.4 22.0

Bulk residue% 18.3 5.5 0.5 50.3 92.4 21.7 90.2 71.7
Cu-Ni liquid gpL 0.925 10.863 0.036 13.108 7.6 78.3 9.8 28.3
Concentrate
^One synthetic high iron mat was made by mixing a flash furnace mat with iron sulfide. This mixture was melted and granulated with water.

  This example shows that for the roasting-reduction-leaching process, copper extraction increases as the iron level in the raw material decreases. Copper ferrite can be converted to cuprite. Free cuprites are easily leached. Another important observation is that nickel extraction into solution increases as iron in the feed increases. Nickel extractions of 3.6-7.6% were observed, whereas low iron (1% Fe) Bessemer mat calcined extracted only 0.3% nickel.

  Based on the provisions of the law, specific embodiments of the present invention have been illustrated and described. Various accumulations can be made to the examples and embodiments described herein without departing from the scope and spirit of the invention as defined in the claims. It will be apparent to those skilled in the art that modifications may be made within the form of the invention encompassed by the claims and that certain features of the invention may be advantageously used without correspondingly using other features. You may be able to use it.

It is an advantage graph of copper and nickel. And oxygen pressure (atmospheric pressure) is a graph showing a curve representing the relationship between the CO 2 _/ CO ratio in the temperature and total pressure 1 atm. The shaded area under the curve crossed by the dashed line indicates a metastable state.

Claims (18)

A method for recovering copper from sulfide-containing materials including iron, nickel and cobalt in addition to copper,
By roasting the material, and Turkey sulfur content to form 0.5% or less of the calcine,
Exposing the calcine temperature and reducing atmosphere 750 ° C. to 1050 ° C., the CuO in the calcine selectively reduced to Cu 2 _O, to form a reduced calcine, this time, the reducing The atmospheric oxygen partial pressure is low enough to reduce CuO to Cu ₂ O, but not low enough to reduce NiO to metallic Ni,
Subjecting the reduced calcined product to oxidative leaching, and recovering the copper. The method of claim 1, wherein the sulfur-containing material is roasted in a fluidized bed roasting apparatus in an atmosphere containing excess oxygen at a temperature of 750 ° C. to 1050 ° C. for 0.5 to 3 hours. It said oxygen partial pressure of the reducing atmosphere is 1 0 ^-10 atm method of claim 1.   The method of claim 1, wherein the sulfide-containing material is a Bessemer mat.   The method of claim 1, wherein the oxidative leaching is performed in sulfuric acid. The method of claim 1, wherein the reducing atmosphere comprises a mixture selected from the group consisting of CO / CO ₂ , H ₂ / H ₂ O, and combinations thereof. The calcine is reduced in a fluidized YukaSo 置中 The method of claim 1.   For subjecting the leachate exiting the oxidative leaching to electrowinning, recovering copper from the leachate, recycling the spent electrolyte exiting the electrowinning operation, and leaching a further supply of reduced calcined material 6. The method of claim 5, comprising an aqueous sulfuric acid solution.   The method of claim 4, wherein the Bessemer mat is completely roasted to remove all sulfur. The temperature is 1 000 ° C., The method of claim 1. A method of selectively reducing CuO in a calcined product containing iron, nickel and cobalt in addition to copper to Cu ₂ O,
By roasting the material, and Turkey sulfur content to form 0.5% or less of the calcine, and exposing the calcine temperature and reducing atmosphere 750 ° C. to 1050 ° C., the calcined product CuO contained therein is selectively reduced to Cu ₂ O to form a reduced calcined material. At this time, the oxygen partial pressure of the reducing atmosphere is sufficiently low to reduce CuO to Cu ₂ O. A method comprising: not being low enough to reduce NiO to metallic Ni. The method of claim 11, wherein the sulfur-containing material is roasted in a fluidized bed roasting apparatus in an atmosphere containing excess oxygen at a temperature of 750 ° C. to 1050 ° C. for 0.5 to 3 hours. It said oxygen partial pressure of the reducing atmosphere is 1 0 ^-10 atm, a method for selectively reducing CuO the calcine in claim 11 Cu ₂ O. The temperature is 1 000 ° C., a method for selectively reducing CuO the calcine in claim 11 Cu ₂ O. The method for selectively reducing CuO in a calcined product to Cu ₂ O according to claim 11, wherein the sulfide-containing material is a Bessemer mat. The method for selectively reducing CuO in a calcined product to Cu ₂ O according to claim 15, wherein the Bessemer mat is completely roasted to remove all sulfur. Wherein said calcine is reduced in a fluidized YukaSo 置中, selectively reduces CuO of calcine in claim 11 Cu 2 _O. It is subjected to oxidative leaching the reduced calcine, and copper, further comprising a recovering method for selectively reducing CuO the calcine in according to Cu 2 _O in claim 11.

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