KR20060122942A - Selective reduction of cupriferous calcine - Google Patents

Abstract

A process for selectively reducing calcine from a copper/nickel containing sulfidic material includes subjecting the calcine to a mildly reducing atmosphere at relative high temperatures. CuO is selectively converted to Cu2O which can easily be separated by leaching from other metals which may be present in the material.

Description

Selective Reduction of Copper-Containing Lime {SELECTIVE REDUCTION OF CUPRIFEROUS CALCINE}

Field of invention

The disclosure herein relates to the recovery of copper from sulfide materials containing metals that are intimately mixed with copper. The present invention is particularly useful for the treatment of copper-containing mats or portions of such mats.

Background of the Invention

Copper and nickel are closely related to dissolution thermodynamics and it has been difficult to efficiently separate nickel from copper during ore and mat processing. U.S. Patent 4,168,217 ("'217 patent") discloses a step of dead-roasting the material at a temperature above about 750 ° C. to provide substantially sulfur free lime, cooling the lime and then at least about 50 ° C. Leaching in an aqueous sulfuric acid solution at a temperature, and leaching residue containing most of the iron, nickel and cobalt initially present in the material with a leach liquor in which most of the copper initially present in the material is dissolved. A method for recovering copper from sulfide materials containing at least one of metal iron, nickel and cobalt, such as copper-containing mats and portions of mats (such as besomer mats), by separating from leach residues It starts. In the method of the '217 patent, the resulting lime contains a large amount of CuO in a solid solution with NiO that is not readily leached.

U.S. Patent No. 4,135,918, roasts the material at a temperature above about 750 ° C. for a sufficient time to provide substantially sulfur-free lime, to supplement the sulfuric acid formed immediately and to satisfy the stoichiometry of sulfate formation of other metals. Forming a slurry of lime with water or an aqueous solution containing at least a sufficient amount of sulfuric acid, heating the slurry to at least 110 ° C. under pressure and in the presence of a reducing gas to sulfate other metals and to form copper in elemental form Reducing, and separating the article of pressure-heating treatment into a solution containing other metals and a solid residue containing elemental copper, in addition to copper, at least one of iron, nickel and cobalt Reduction of copper from particulate sulfide-containing materials containing other metals It discloses a. As mentioned above, lime contains a large amount of CuO in solid solution with ferrite or NiO which is not easily leached.

A method for recovering copper from sulfide materials is also disclosed in US Pat. No. 4,120,697, which includes the following steps; Roasting the sulfide material to produce lime, mixing lime with the particulate carbon-containing reducing agent and one or more halogen salts, wherein the halogen salts are separated and roasted in small amounts to halogenate the copper value contained in the lime Thermally deformable with hydrogen halide or gaseous halogen at a temperature, and heating the mixture to a separation roast temperature of about 650 ° C. to about 700 ° C., at which temperature the copper values in the lime react with the particulate carbon-containing reducing agent. It forms a transported copper halide, where metallic copper is precipitated from the copper halide onto the carbon-containing reducing agent, and the precipitated metallic copper is recovered. Such methods include the formation of salts after lime to reduce copper to metallic form, which must be further processed and separated by floatation and other physical separations.

Therefore, it was difficult to achieve the desired degree of selectivity between copper and other metals such as nickel, cobalt and iron present in the mixture without various additional steps that increase manufacturing time and cost. There is a continuing need to provide an efficient method of purifying copper and other metals from the mixture.

Summary of the Invention

In addition to copper, a method is provided for recovering copper from a sulfide-containing material containing one or more other metals selected from the group consisting of iron, nickel and cobalt, which method is sufficient for a time sufficient to provide substantially sulfur free lime. Roasting the sulfide-containing material, selectively reducing CuO in lime to Cu ₂ O to place lime in a sufficient heating and reducing environment to form reduced lime, and oxidizing and leaching the reduced lime to recover copper It includes a step. The reduction step separates copper from the nickel oxide matrix by insolubility of Cu ₂ O in NiO.

In addition to copper, there is provided a method for selectively reducing CuO to Cu ₂ O in lime containing one or more other metals selected from the group consisting of iron, nickel and cobalt, which provides a substantially sulfur free lime. Roasting the material for a sufficient time, and selectively reducing CuO in the lime to Cu ₂ O to place the lime in a sufficient heating and reducing environment to form reduced lime.

Description of the Drawings

1 is a representative view.

FIG. 2 is a graphical depiction curve showing the CO ₂ / CO ratio at oxygen pressure (atm) and total pressure 1 atm over temperature action. The shaded portion below the cross curve indicates metastable.

Description of Preferred Embodiments

The present invention provides for the separation of CuO (black copper ore) in lime under a suitable reducing environment and sufficiently high temperature prior to leaching to provide highly effective separation of copper from a mixture of nickel, iron, cobalt and / or other metals that may be present. Selective reduction to Cu ₂ O is initiated. In addition to making copper oxides usable for leaching, the reduction step also makes NiO difficult to dissolve. For example, in a representative experiment, treating a bulk roasted besmer mat with a Cu / Ni ratio of 1.0 with the techniques disclosed herein yields about 97.8% copper extraction while extracting only about 0.3% nickel.

The method disclosed herein is applicable to a wide range of copper-containing materials and is even useful for processing materials with relatively low amounts of metals other than copper. For example, this method is also suitable for much more materials, since the content of copper exceeds the total content of another metal. This would not be the case in the case of ores and concentrates which can also be treated according to the techniques disclosed herein, but also various metallurgical residues obtained from the mat as well as, for example, acid leaching processes or nickel carbonylation processes. In the case of water it is generally appropriate.

In either aspect, it is contemplated that any substantially sulfur free lime material containing copper and one or more other metals may be used herein. The skilled person is well aware of various techniques for obtaining such lime. In fact, any technique can be used to treat sulfide containing materials to remove most of the sulfur. For example, the temperature at which roasting is performed is considered important to achieve the desired good leaching properties of the resulting lime. In known techniques (see, eg, US Pat. No. 4,168,217), a minimum temperature of about 750 ° C. is recommended, preferably about 800 ° C. and should not exceed about 950 ° C. According to the invention, the roasting temperature may be higher than in the prior art. However, too high roasting temperatures can lead to disadvantageous dissolution of lime, so the temperature should generally not exceed about 1050 ° C. Thus, according to the present invention, roasting can proceed at a high rate at high temperatures but below the melting point of lime. Maximizing the temperature increases the reaction rate. In a preferred embodiment, roasting of the sulfide material is carried out in an environment containing excess oxygen to ensure that nearly 100% of sulfur is removed. It has been found that a hold time of about 0.5 to 3 hours at such a temperature is sufficient to reduce the content of the raw material to about 0.5% or less. Unless specifically stated otherwise, all percentages mentioned herein are weight percentages. As used herein, "substantially" means almost or exactly.

In the case of a mat or part of a mat, in contrast to the prior art, the composition of the mat or part of the mat being treated is less concerned with copper extraction and the selectivity achieved. Indeed, the relative concentrations of each component are not critical because the methods herein are effective in almost all ranges of copper, iron and nickel ratios.

The roasting step can be effected in various known types of apparatus and can proceed spontaneously. Fluid-bed roasters are preferably used because of the relatively high concentration of sulfur dioxide in the off-gas as well as the higher throughput in the roaster. For fluid bed roasting the raw material should preferably be in the form of particles of about 100 to about 600 microns in diameter. If the initial raw material is a fine powder, pelletization may be required. However, if the initial raw material is from a previously melted mat, the desired particles can be produced by water granulation of the hot mat. The latter approach is preferred in that it causes less dust during fluid bed roasting operations.

For example, copper-containing lime produced by complete roasting may contain large amounts of CuO in solid solution with Ni. Lime effectively removes CuO from the nickel oxide matrix through an appropriate mild reduction environment, which is believed to form Cu ₂ O outside NiO, and selective reduction using relatively high temperatures. In a preferred embodiment, a reducing gas mixture is selected which does not form too much and does not form nickel metal in the reducing agent to ensure that the reduction is selective. The range of temperature and pO ₂ (partial pressure of oxygen) required to achieve successful selective reduction is shown in the phase diagram and can be determined using known techniques. FIG. 1 is a representative view of copper and nickel where the gray sections show where in the region reduction of CuO to Cu ₂ can be affected without the formation of nickel metal which may damage downstream leaching efficiency. The minimum pO ₂ is shown in the region where the nickel metal is stable (hatched line). The arrows indicate that the process at increasing temperatures and low pO ₂ achieves maximum speed and recovery. Black diamonds represent potential target conditions for reduction. The maximum pO ₂ is a region where CuO is reduced to Cu ₂ O. Preferably, the conversion to Cu ₂ O is effected at the lowest possible pO ₂ and at the highest possible temperature without the formation of nickel metal. If copper metal is formed, it can be successfully leached by oxidative leaching.

pO ₂ can be adjusted by mixing the appropriate gas in the appropriate amount according to the known art. For example, the CO, CO _2, H ₂ and H ₂ O mixture is is known to create a reducing environment. 2 shows that pO ₂ is CO and CO ₂ It can be controlled by mixing the gas at the proper ratio. In particular, FIG. 2 shows a curve representing the CO ₂ / CO ratio at oxygen pressure (atm) and the total pressure of 1 atm over temperature. The shaded portion under the hatch indicates metastable. Similar tables exist for H ₂ / H ₂ O mixtures. H ₂ And CO ₂ is CO, CO ₂ , H ₂ And H ₂ O mixtures to form. Less than 10 ⁻⁶ , preferably about 10 ⁻¹⁰ pO ₂ may be used. One example of a mixture is about 3-5% H ₂ to act as a pO ₂ of ˜10 ⁻¹⁰ −10 ⁻¹² at about 1000 ° C. H ₂ containing (% by volume) and the balance CO ₂ And gas mixing of CO ₂ . Other mixtures may comprise CO ₂ / CO of ˜1000 (˜10 ⁻¹¹ pO ₂ ) at about 1000 ° C. In one aspect, pO ₂ may be controlled by partial combustion of the fuel conventionally performed by those skilled in the art. By measuring the concentrations of CO and CO _{2 in} the gas, the oxygen concentration (pO ₂ ) can be measured indirectly, and the fuel / air ratio changes to maintain the appropriate CO ₂ / CO ratio, ie pO ₂ . CO ₂ / CO gas evolution can be obtained from solid carbon via a Boudouard reaction.

The relatively high temperatures available herein are suitable for enhancing the reducing environment. One skilled in the art can readily determine the appropriate temperature at which the rate of reaction can be maximized. See, for example, FIGS. 1 and 2. As a practical matter, copper oxide starts to melt at about 1050 ° C, which temperature effectively limits the upper range. Therefore, the preferred temperature range is about 750 ° C to about 1050 ° C, more preferably about 1000 ° C. Although any suitable oven or furnace can be used as the vessel for the reduction disclosed herein, high mixing reactors, such as dynamic fluidized bed apparatus, are preferred to achieve high reaction rates.

The reduced lime produced by the reductions disclosed herein may be suspended in an aqueous sulfuric acid solution, which may readily comprise a spent electrolyte from a copper electrowinning process, after cooling and, if necessary, grinding, optionally to dissolve Cu ₂ O, Oxidation can be leached. The solvent may contain some dissolved copper in addition to the free sulfuric acid. Leaching temperatures of at least about 50 ° C. are typically required to achieve a practical leaching rate, while temperatures of about 80 ° C. or higher can have an undesirable effect on increasing nickel and iron dissolution. In a preferred embodiment, leaching temperatures of about 60-70 ° C. with retention times of about 2-3 hours have been found to produce good results. After solid-liquid separation, the solution can be used to electrowin high purity copper products, while the residue is treated to recover all nickel and cobalt as well as all precious metals that may be present in the raw materials.

The following examples are disclosed to illustrate aspects of the present invention. Therefore, the examples should not be considered as limiting aspects of the invention. Some embodiments of the present invention will be described with reference to the accompanying drawings.

Example  One

Bessemer mats (Cu (40.7%), Ni (39.7%), Co (0.54%), Fe (0.91%) and S (18%) were roasted in a 12 inch (30.4 cm) fluidized bed. Lime was used as raw material for the reduction experiment.

A 500 gram sample of lime was loaded into a 2 inch (5.1 cm) diameter mini plant fluidized bed and heated to 1000 ° C. The CO ₂ / CO ratio was adjusted to 1000 to act as a pO ₂ of about 10 ⁻⁸ (see FIG. 2). Fluidizing gas flow rates were 10 L / min N 2, 25 L / min CO ₂ and 0.025 L / min CO. The conditions were maintained for 1 hour and the heaters of the furnace were turned off. The material cooled rapidly by injecting gas. A second reduction experiment was conducted to determine the effect of longer hold times during reduction. The experiment was carried out under the same conditions but 2 hours.

Several bench scale leaching experiments were performed on two reduced samples. A 25 gram sample of lime in 250 mL of solution containing 180 g / L sulfuric acid was used. In the first experiment, 30% strength H ₂ O ₂ was added to oxidize copper to CuO to allow leaching. The experimental results are shown in Table 1 below. Further experiments used oxygen and air spray to oxidize copper. See Table 2 below. The solution was leached at 80 ° C. for 2 hours. The sample was filtered and the solution and residue analyzed.

Other leaching experiments were performed by grinding lime for 15-s in a Blueler grinder with air injection for oxidation. Experiments were performed using a spent copper electrolyte stream from a copper electrowinning plant instead of pure sulfuric acid solution. The final experiment used a wet smelting leaching apparatus for improved particle agitation and increased gas dispersion. The results of phase identification microprobe analysis of Experiment # 1 are shown in Table 3 below.

The reduced lime had a porous structure when observed under an optical microscope. Under reduction, CuO in solid solution with NiO in the roasted besomer mat was released to Cu ₂ O, thus forming the observed porous structure. Removal of CuO from the NiO matrix during the reduction made it possible to leach copper. Moreover, NiO became more difficult to dissolve after CuO was removed from the solid solution. Baseline experiments were performed on roasted besomer mats, resulting in copper dissolution of 9.4% nickel and only 73% of the solution, indicating that NiO was not difficult to dissolve in solid solution with CuO. SEM / EDX (quasi-quantitative) analysis (Table 3) from the 1-hour reduction-leak experiment showed that CuO was reduced to ˜30% to 6.6% (± 4.2) in solid solution with NiO. This relates to the residue evaluation of 4.4% CuO. The improved leaching results observed in the 2-hour reduction indicate that even CuO was released (2.3% CuO in the residue).

Coarse lime was not ground prior to leaching in the experiments performed using H ₂ O ₂ for oxidation. The resulting leach residue was very fine, indicating that removal of copper oxides resulted in liberation of residual NiO particles.

Leaching experiments performed with air and without grinding showed only 65% copper recovery (Table 2). Grinding prior to leaching of the reduced lime gave results comparable to the experiments performed with peroxides. 95% copper recovery (Table 2, ground lime, air blast) in Experiment # 7 is commensurate with Experiments # 1 and # 2 (Table 1, no grinding, peroxide), which also had 95% copper recovery . The loss of Ni, Fe, and Co into the solution slightly increased in sample milling.

Leaching experiment # 12 was performed using increased agitation. The sample was not crushed and air spray and magnetic spin bars (Experiment # 6) were used to achieve 65% copper recovery and 90% copper recovery. This experiment shows that increased agitation increases the dissolution of copper.

Therefore, by optimizing grinding, increasing agitation and / or using oxygen to recover copper, equivalent results to using hydrogen peroxide have been achieved.

Example  2

The effect of iron in the Cu-Ni-Fe system was evaluated. Three samples were tested: 1) Flash Furnace Matte (Cu-23%, Ni-22.6%, Co-0.664%, Fe-25.2%, S-26.7%), 2) Synthetic Mats Matte] (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%) Excellent separation of copper was achieved in each experiment. Table 4 is a summary of the experimental results. The following method was used for each sample.

The sample was dissolved and water granulated. About 2 kg of the granulated sample was placed in a refractory pan and heated to ˜900 ° C. for ˜24 hours under ambient air environment to provide roasted material. Fluid bed reduction was first done by placing 1 kg of roasted material into a 2 inch (5.1 cm) diameter fluidized bed and heating to 1000 ° C. with air for fluidization of ˜45 slpm (external electrical element). The material was “re-baked” at 1000 ° C. for 10 minutes and then the air environment was replaced with a gas mixture (20 slpm N ₂ , 25 slpm CO ₂ , 0.025 slpm CO). The material was then reduced at 1000 ° C. for 2 hours at which point the furnace was switched off (with the gas mixture left) and cooled for ˜30 minutes. To provide oxidation leaching, 25 grams of sulfuric acid was mixed with 250 mL distilled water in a 500 mL beaker, heated and maintained at 80 ° C. with stirring using a hotplate and stirring system. 25 grams of material to be leached was added to the beaker. 30 mL of hydrogen peroxide was added slowly at time = 0 hours and again slowly at time = 1 hour. The experiment was stopped at 2 hours and the sample was filtered. Each weight and volume was recorded.

¹ was produced in a high iron content of the mat (Synthetic High Iron Matte) Synthesis of glare by mixing with the mat (Flash Furnace matte) and iron sulfide cargo. The mixture was dissolved and granulated with water.

This sample shows that for roasting-reduction-leaching processes, the extraction of copper increases as the iron levels in the raw materials decrease. Copper ferrites can be converted to cuprite. Free cuprite can be easily leached. Another important observation is that the extraction of nickel into solution increases with increasing iron in the raw material. A 3.6-7.6% nickel extraction was observed compared to low iron (1% Fe) Bessemer mat lime with only 0.3% nickel extracted.

In accordance with the rules, specific embodiments of the present invention are described and disclosed. Various modifications may be made to the examples and embodiments presented herein without departing from the scope and spirit of the invention as defined by the appended claims. Those skilled in the art will appreciate that there may be variations in the invention protected by the claims and that the features of the invention may be advantageously used irrespective of other features.

Claims (20)

Roasting the material for a sufficient time to provide substantially sulfur-free lime, selectively reducing CuO in the lime to Cu ₂ O and placing the lime in a sufficient heating and reducing environment to form a reduced lime Oxidizing the reduced lime to recover copper. A method for recovering copper from sulfide-containing materials, in addition to copper, containing one or more other metals selected from iron, nickel and cobalt groups. The method of claim 1, wherein the reducing environment is low enough to reduce CuO to Cu ₂ O but not so low as to reduce NiO to Ni metal. The method of claim 1, wherein the reducing environment is pO ₂ To 10 ^-10 . The method of claim 1, wherein said sufficient heating range is between 750 ° C and 1050 ° C. The method of claim 1 wherein the sulfide containing material is a beseme mat. The method of claim 1 wherein the oxidative leaching is in sulfuric acid. The method of claim 1 wherein the reducing environment contains a mixture selected from the group consisting of CO / CO ₂ , H ₂ / H ₂ O and combinations thereof. The method of claim 1 wherein the lime is reduced in a controlled environment using a fluid bed apparatus. 7. The aqueous solution of sulfuric acid according to claim 6, wherein the leaching solution is electrowinned to recover copper from the leaching solution from the oxidative leaching, and the spent electrolyte is recovered from the electrowinning process to leach another feed of reduced lime material. Method of construction. 6. The method of claim 5, wherein the Bessamer mat is completely roasted to remove all sulfur. The method of claim 4, wherein the temperature is 1000 ° C. 6. Roasting the material for a sufficient time to provide substantially sulfur free lime, selectively reducing CuO in the lime to Cu ₂ O and placing the lime in a sufficient heating and reducing environment to form reduced lime Method of selectively reducing the CuO into Cu ₂ O in the lime containing at least one other metal selected from copper or other In addition, iron, nickel and cobalt group. The method of claim 12, wherein the reducing environment is optional, the CuO in the lime characterized in that a is sufficiently low, but NiO fit a the partial pressure of oxygen reducing the CuO into Cu ₂ O No low enough to be reduced to Ni metal by Cu ₂ O Reduction method. The method of claim 13, wherein the reducing environment is pO ₂ Selectively reducing CuO to Cu ₂ O in lime characterized by ˜10 ⁻¹⁰ . The method of claim 12, wherein the sufficient heat ranges method of selectively reducing the CuO in the lime, characterized in that 750 to 1050 ℃ ℃ as Cu ₂ O. The method of claim 12, wherein the temperature is 1000 ° C., wherein CuO is selectively reduced to Cu ₂ O in lime. The method of claim 12, wherein the sulfide containing material is a method of selectively reducing the CuO in the lime, characterized in that the Bessemer matte with Cu ₂ O. 18. The method of claim 17 wherein the Bessemer matte is a method of selectively reducing the CuO into Cu ₂ O in the lime, characterized in that the fully roasted to remove all the sulfur. The method of claim 12, wherein the lime is a method of selectively reducing the CuO into Cu ₂ O in the lime, characterized in that the reduction in a controlled environment using a fluid bed apparatus. 13. The method of claim 12, further comprising oxidizing the reduced lime to recover copper, wherein CuO is selectively reduced to Cu ₂ O in the lime.

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