CA2728519C - Method for leaching nickel matte in the presence of added copper - Google Patents
Method for leaching nickel matte in the presence of added copper Download PDFInfo
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- CA2728519C CA2728519C CA2728519A CA2728519A CA2728519C CA 2728519 C CA2728519 C CA 2728519C CA 2728519 A CA2728519 A CA 2728519A CA 2728519 A CA2728519 A CA 2728519A CA 2728519 C CA2728519 C CA 2728519C
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/02—Obtaining nickel or cobalt by dry processes
- C22B23/025—Obtaining nickel or cobalt by dry processes with formation of a matte or by matte refining or converting into nickel or cobalt, e.g. by the Oxford process
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B15/00—Obtaining copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B15/00—Obtaining copper
- C22B15/0063—Hydrometallurgy
- C22B15/0065—Leaching or slurrying
- C22B15/0067—Leaching or slurrying with acids or salts thereof
- C22B15/0071—Leaching or slurrying with acids or salts thereof containing sulfur
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0407—Leaching processes
- C22B23/0415—Leaching processes with acids or salt solutions except ammonium salts solutions
- C22B23/043—Sulfurated acids or salts thereof
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0453—Treatment or purification of solutions, e.g. obtained by leaching
- C22B23/0461—Treatment or purification of solutions, e.g. obtained by leaching by chemical methods
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
- C22B3/08—Sulfuric acid, other sulfurated acids or salts thereof
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention relates to a method for leaching pyrometallurgically produced, copper-containing sulfidic nickel matte. The nickel matte is first fed to an atmospheric leach step from which is obtained a nickel-bearing solution and a copper- and nickel-bearing leach residue, wherein the weight ratio of copper to nickel is not more than about 1. This is followed by adding a copper--containing solid matter into the leach residue and conducting the leach residue to pressure leaching. After the pressure leaching, there can be obtained a leach residue, which consists of copper sulfide precipitate relatively pure as regards iron and which also contains the precious metals of nickel matte.
Description
METHOD FOR LEACHING NICKEL MATTE IN THE PRESENCE OF ADDED COPPER
Field of the invention The present invention relates to a method for leaching pyrometallurgically pro-duced nickel mattes in a multistep hydrometallurgical process.
Prior art A large portion of the world's nickel is produced hydrometallurgically from pyrome-tallurgically produced nickel mattes. Generally, such a production process involves the leaching of nickel contained in the matte by a multistep process, followed by purifying the nickel-bearing aqueous solution and reclaiming the nickel. The leach-ing process is determined according to the composition and properties of em-ployed nickel matte. These, on the other hand, are influenced by the grade of con-centrate used as a raw nickel material and by its metallurgical smelting process.
There is a prior known method described in US patent publication 6,039,790 for recovering nickel in one and the same process from two pyrometallurgically pro-duced nickel mattes, one of which contains a remarkable percentage of iron. In the method, leaching of the nickel matte that contains iron is carried out in one step by conducting solution from the leaching cycle of the less iron containing matte into the leaching of the iron containing matte at a stage where the iron of the less iron containing matte is in soluble form. The iron contained in the mattes is advanta-geously precipitated as jarosite and the solution created in the leaching of the iron containing matte is conducted back into the leaching cycle of the less iron contain-ing matte.
A similar method has been described in US patent publication 6,206,951, wherein copper-rich sulfidic and metallic nickel mattes are leached in a multi-stage process. Nickel is leached from sulfidic nickel matte by means of copper sulfate in a pressure leach process. The required copper sulfate is obtained from the leach-ing of metallic nickel matte, as well as by leaching the copper-rich material in a separate copper leaching process.
GB patent publication 2,108,480 describes a process developed for sulfidic nickel mattes rich in copper, wherein nickel is first treated by a pressure leach under oxi-dizing conditions with an anolyte obtained from copper electrolysis. Once at least
Field of the invention The present invention relates to a method for leaching pyrometallurgically pro-duced nickel mattes in a multistep hydrometallurgical process.
Prior art A large portion of the world's nickel is produced hydrometallurgically from pyrome-tallurgically produced nickel mattes. Generally, such a production process involves the leaching of nickel contained in the matte by a multistep process, followed by purifying the nickel-bearing aqueous solution and reclaiming the nickel. The leach-ing process is determined according to the composition and properties of em-ployed nickel matte. These, on the other hand, are influenced by the grade of con-centrate used as a raw nickel material and by its metallurgical smelting process.
There is a prior known method described in US patent publication 6,039,790 for recovering nickel in one and the same process from two pyrometallurgically pro-duced nickel mattes, one of which contains a remarkable percentage of iron. In the method, leaching of the nickel matte that contains iron is carried out in one step by conducting solution from the leaching cycle of the less iron containing matte into the leaching of the iron containing matte at a stage where the iron of the less iron containing matte is in soluble form. The iron contained in the mattes is advanta-geously precipitated as jarosite and the solution created in the leaching of the iron containing matte is conducted back into the leaching cycle of the less iron contain-ing matte.
A similar method has been described in US patent publication 6,206,951, wherein copper-rich sulfidic and metallic nickel mattes are leached in a multi-stage process. Nickel is leached from sulfidic nickel matte by means of copper sulfate in a pressure leach process. The required copper sulfate is obtained from the leach-ing of metallic nickel matte, as well as by leaching the copper-rich material in a separate copper leaching process.
GB patent publication 2,108,480 describes a process developed for sulfidic nickel mattes rich in copper, wherein nickel is first treated by a pressure leach under oxi-dizing conditions with an anolyte obtained from copper electrolysis. Once at least
2 70% of nickel values in the matte are extracted, the leaching is continued under non-oxidizing conditions. The solution from this stage is conducted to an atmospheric purification leach, in which the solution is stripped of copper by means of finely powdered matte. Precipitate from the purification leach is conducted to a nickel pressure leach, and the precipitate remaining after that is conducted to an oxidizing pressure-leaching process of copper. The residual precipitate mainly comprises iron previously contained in the matte.
US patent publication 5,628,817 discloses still another multi-stage leaching process developed for nickel matte, wherein the leaching of nickel takes place in at least two stages in conditions where free sulfuric acid is essentially absent. The method is of the same type as the one used in US publication 6,039,790 in the leaching of matte with a low iron content. The finely ground matte is first subjected to a two-step oxidizing atmospheric leach and thereafter to a two-step pressure leach, wherein the first step is carried out in non-oxidizing or mildly oxidizing conditions and the second step in oxidizing conditions. As opposed to the previously described method, the entire copper content is leached in the latter atmospheric leaching and the removal of iron takes places by precipitation from the solution downstream of the first pressure leaching step.
The most severe limitation of prior known leaching processes, such as those described above, is the applicability thereof to certain types of nickel matte only. For example, the method disclosed in GB patent publication 2,108,480 is only applicable to sulfidic nickel mattes with a remarkably high copper content (the weight ratio of nickel/copper less than 2,5, i.e. the weight ratio of copper/nickel more than 0,4). On the other hand, the processes described in US patent publications 6,039,790 and 6,206,951 are not suitable for metallic nickel mattes containing precious metals as the precious metals therein end up in the iron precipitate.
2a Accordingly, there is still demand for a method with a versatility of adapting to a variety of nickel mattes, whose contents of copper, nickel, iron, sulfur, as well as precious metals may fluctuate without a major effect on the recovery of various metals and on the quality of products recovered from the leaching process.
Summary of the invention According to one embodiment, a method for leaching pyrometallurgically produced, copper-containing sulfidic nickel matte, wherein a sulfidic nickel matte is fed to an atmospheric leach step from which is obtained a nickel-bearing solution and a copper- and nickel-bearing leach residue, whereby a copper-bearing solid matter is added into the nickel matte before the leaching or to the copper- and nickel-bearing leach residue after the leaching in such an amount that the weight ratio of copper to nickel in the copper- and nickel-bearing leach residue is more than about 1, wherein the solid matter has its source in a latter stage of the method or the solid matter consists of synthetically produced copper sulfide, and the copper- and nickel-bearing leach residue is conducted to pressure leaching.
US patent publication 5,628,817 discloses still another multi-stage leaching process developed for nickel matte, wherein the leaching of nickel takes place in at least two stages in conditions where free sulfuric acid is essentially absent. The method is of the same type as the one used in US publication 6,039,790 in the leaching of matte with a low iron content. The finely ground matte is first subjected to a two-step oxidizing atmospheric leach and thereafter to a two-step pressure leach, wherein the first step is carried out in non-oxidizing or mildly oxidizing conditions and the second step in oxidizing conditions. As opposed to the previously described method, the entire copper content is leached in the latter atmospheric leaching and the removal of iron takes places by precipitation from the solution downstream of the first pressure leaching step.
The most severe limitation of prior known leaching processes, such as those described above, is the applicability thereof to certain types of nickel matte only. For example, the method disclosed in GB patent publication 2,108,480 is only applicable to sulfidic nickel mattes with a remarkably high copper content (the weight ratio of nickel/copper less than 2,5, i.e. the weight ratio of copper/nickel more than 0,4). On the other hand, the processes described in US patent publications 6,039,790 and 6,206,951 are not suitable for metallic nickel mattes containing precious metals as the precious metals therein end up in the iron precipitate.
2a Accordingly, there is still demand for a method with a versatility of adapting to a variety of nickel mattes, whose contents of copper, nickel, iron, sulfur, as well as precious metals may fluctuate without a major effect on the recovery of various metals and on the quality of products recovered from the leaching process.
Summary of the invention According to one embodiment, a method for leaching pyrometallurgically produced, copper-containing sulfidic nickel matte, wherein a sulfidic nickel matte is fed to an atmospheric leach step from which is obtained a nickel-bearing solution and a copper- and nickel-bearing leach residue, whereby a copper-bearing solid matter is added into the nickel matte before the leaching or to the copper- and nickel-bearing leach residue after the leaching in such an amount that the weight ratio of copper to nickel in the copper- and nickel-bearing leach residue is more than about 1, wherein the solid matter has its source in a latter stage of the method or the solid matter consists of synthetically produced copper sulfide, and the copper- and nickel-bearing leach residue is conducted to pressure leaching.
3 A feature of some embodiments is that the copper-nickel weight ratio of the de-livered solid matter may be raised, to higher than about 1, by the addition of a copper-bearing solid substance. The copper-bearing solid substance may be added downstream of the atmospheric leaching step into leach residue.
Solid matter may be obtained by circulating the leach residue from a latter stage of the method. Another possibility is, for example, the use of synthetically pro-duced copper sulfide, precipitated especially with hydrogen sulfide.
Some embodiments of the method comprise processing nickel mattes in such a way that the nickel and iron contained in the mattes are converted into soluble form and the copper and precious metals end up in leach residue.
Sulfidic nickel matte may be leached first in an atmospheric step by means of sulfuric acid and air, such that soluble copper precipitates but iron remains in the solution. Following a solid-liquid separation, the solid matter is conducted to a pressure leach. The pressure leach may be a two-step process and of the type in which the first step comprises leaching mostly copper and the second step leaches nickel and iron as copper is precipitating. After the pressure leach, the leach residue may consist of copper sulfide precipitate quite pure in terms of iron and contains the precious metals (such as Au, Pt and Pd) of nickel mattes.
Metallic nickel matte may be processed in a separate atmospheric step by means of sulfuric acid and oxygen for leaching metallic components of the matte, i.e. most of the nickel and iron. The solution, as well as sulfidic components and precious metals remaining in the matte, may be conducted to the atmospheric leaching step of sulfidic nickel matte.
The method according to some embodiments may be applicable for a wide vane-ty of nickel mattes, which may contain for example varying amounts of copper, iron, and precious metals, as well as may be sulfidic and/or metallic in terms of their composition. According to some embodiments of the method the leach resi-dues of mattes may end up in the same precipitate, which contains copper and precious metals coming along with nickel mattes. In addition, the discussed cop-per sulfide precipitate may be relatively pure and contain just a little iron.
The res-idence time for the first pressure leach step may be kept remarkably short, less
Solid matter may be obtained by circulating the leach residue from a latter stage of the method. Another possibility is, for example, the use of synthetically pro-duced copper sulfide, precipitated especially with hydrogen sulfide.
Some embodiments of the method comprise processing nickel mattes in such a way that the nickel and iron contained in the mattes are converted into soluble form and the copper and precious metals end up in leach residue.
Sulfidic nickel matte may be leached first in an atmospheric step by means of sulfuric acid and air, such that soluble copper precipitates but iron remains in the solution. Following a solid-liquid separation, the solid matter is conducted to a pressure leach. The pressure leach may be a two-step process and of the type in which the first step comprises leaching mostly copper and the second step leaches nickel and iron as copper is precipitating. After the pressure leach, the leach residue may consist of copper sulfide precipitate quite pure in terms of iron and contains the precious metals (such as Au, Pt and Pd) of nickel mattes.
Metallic nickel matte may be processed in a separate atmospheric step by means of sulfuric acid and oxygen for leaching metallic components of the matte, i.e. most of the nickel and iron. The solution, as well as sulfidic components and precious metals remaining in the matte, may be conducted to the atmospheric leaching step of sulfidic nickel matte.
The method according to some embodiments may be applicable for a wide vane-ty of nickel mattes, which may contain for example varying amounts of copper, iron, and precious metals, as well as may be sulfidic and/or metallic in terms of their composition. According to some embodiments of the method the leach resi-dues of mattes may end up in the same precipitate, which contains copper and precious metals coming along with nickel mattes. In addition, the discussed cop-per sulfide precipitate may be relatively pure and contain just a little iron.
The res-idence time for the first pressure leach step may be kept remarkably short, less
4 than 45 minutes, thus providing a high leaching capacity considering the size of process equipment.
Some embodiments of the invention will now be described in more detail with reference to the flowchart depicted as a figure.
Description of the drawing Fig. 1 shows in a flowchart the leaching of pyrometallurgically produced nickel mattes by a multistep hydrometallurgical process. In the figure, reference numer-als designate unit processes as follows:
1 Atmospheric removal of copper In 2 Atmospheric leach A Sulfidic Ni-matte 3 I pressure leach B Metallic Ni-matte 4 ll pressure leach C Air (oxygen)
Some embodiments of the invention will now be described in more detail with reference to the flowchart depicted as a figure.
Description of the drawing Fig. 1 shows in a flowchart the leaching of pyrometallurgically produced nickel mattes by a multistep hydrometallurgical process. In the figure, reference numer-als designate unit processes as follows:
1 Atmospheric removal of copper In 2 Atmospheric leach A Sulfidic Ni-matte 3 I pressure leach B Metallic Ni-matte 4 ll pressure leach C Air (oxygen)
5 Removal of iron Out
6 Solution purification D Fe-precipitate
7 Nickel electrolysis E Cu-precipitate F Ni-cathode Detailed description of a few embodiments of the invention As shown in the flowchart, finely ground sulfidic nickel matte is fed to an atmos-pheric copper removal step 1. The term sulfidic nickel matte refers to pyrometal-lurgically produced smelter matte, in which most of the metal content is present in the form of sulfidic components, such as for example nickel sulfide Ni3S2, cop-per sulfide Cu2S, and nickel-iron sulfide (Ni,Fe)9S8. The sulfur concentration of sulfidic nickel matte is typically 15-25%, nor is it strongly magnetic. The concen-trations of various metal and impurities may fluctuate even quite extensively, but the total weight percentage of nickel, copper and iron is nevertheless typically more than 60%.
In addition to sulfidic nickel matte, the atmospheric copper removal step 1 is also supplied with a copper- and iron-bearing solution from an atmospheric leach step 2 and from a second pressure leach step 4. In addition to these, the discussed step is supplied with air. The removal of copper is performed in atmospheric con-ditions and at a temperature of 80-100 C. The elemental nickel and nickel sulfide present in the matte precipitate copper existing in the solution as copper sulfate upon being themselves oxidized into nickel sulfate according to the following re-5 action equations:
Ni + CuSO4 N1SO4 + Cu (1) Ni3S2 + 2 CuSO4 ¨0 Cu2S + NiS +2 NiSO4 (2) Ni3S2 + 2 CuSO4 +1/2 02 2 MS + NiSO4 + Cu20 (3) In a continuously running operation, the reactors present a rising pH-profile in which the precipitation of copper occurs, in response to the above reactions, in acidic conditions at the start of the process step as the solution has a pH of less than 4. The leaching of metals consumes oxygen and, as pH rises, copper pre-cipitates also as alkaline copper sulfate CuS0412Cu(OH)2. From the standpoint of the effective extraction of copper and iron, however, this zone may be kept as brief as possible in terms of its residence time in order to minimize the concurrent precipitation of iron. The precipitate, i.e. the leach residue from this step, is deliv-ered after the liquid-solid separation to a first pressure leach step 3 and the solu-tion is conducted to an iron removal 5.
The finely ground metallic nickel matte is conducted to the atmospheric leach step 2. The term metallic nickel matte refers to pyrometallurgically produced smelter matte, in which most of the metal content is present in the form of metal-lic components, such as for example elemental nickel Ni , copper Cu , and iron Fe and/or in compositions (alloy) of these metals. The sulfur concentration of metallic nickel matte is typically less than 15% and it is highly magnetic.
The concentrations of various metals and impurities may fluctuate even quite exten-sively, but the total weight percentage of nickel, copper and iron is nevertheless typically more than 80%.
The leaching of metallic nickel matte is performed in atmospheric conditions and at a temperature of 80-100 C. In addition to nickel matte, the atmospheric solu-tion is supplied with oxygen and sulfuric acid. Some of the sulfuric acid can be replaced by an acid-containing anolyte obtained from a nickel electrolysis 7.
The principal leaching reactions are:
Ni + H2SO4 +1/202 N1SO4 + H20 (4) Cu + H2SO4 + % 02 CuSO4 + H20 (5) Fe + H2SO4 + 1/2 02 FeSO4 + H20 (6) The formation of hydrogen during leaching may be prevented by an abundant in-troduction of oxygen and the precipitation of iron by maintaining the solution at a low pH, lower than 2,0. The leach residue and the solution from this step are conducted to the atmospheric copper removal 1.
The first pressure leach step 3 is supplied with oxygen as well as with an acid-containing anolyte from the nickel electrolysis 7. The copper concentration of a solid matter delivered to the pressure leach step is increased by circulating some copper-bearing solid substance from a liquid-solid separation downstream of the second pressure leach step 4 into the precipitate coming from the atmospheric copper removal 1. The input solid substance has a preferred copper/nickel weight ratio of 1-2,5. The temperature in the first pressure leach step is higher than 100 C, and may be within the range of 110-120 C and the partial oxygen pressure may be higher than 200 kPa. The principal leaching reactions of the first pressure leach step are:
5 Cu1.8S +4 H2SO4 + 12 02 ¨> 9 CuSO4 +4 H20 (7) Ni3S2 + H2SO4 + 02 NiSO4 +2 NiS + H20 (8) The step is mainly intended for leaching a sufficient amount of copper for the leaching of nickel effected in the second pressure leach step. This is enabled by recycling, if necessary, a copper-bearing solid matter into an autoclave, which solid matter in this case consists of precipitate containing copper-sulfide from a liquid-solid separation downstream of the second pressure leach step 4. By virtue of recycling the precipitate, the method according to some embodyments may enable leaching also nickel mattes of low copper contents. Besides, by virtue of a high copper/nickel weight ratio of the solid matter, the first pressure leach step can be managed in a remarkably brief residence time, less than about 1 hour, even less than about 45 minutes, thus preventing nickel sulfide from reacting too far according to a reaction (9) presented below. This is of importance as regards the proper functioning of the second pressure leach step.
4 NiS + H2SO4 + % 02 Ni3S4 + NiSO4. + H20 (9) Leaching is manageable also in highly acidic conditions, but it may be carried out in such a way that some of the leached copper precipitates in the form of alkaline copper sulfate, the solution having a pH of not lower than about 3 at the end of the step.
Alternatively, the copper/nickel weight ratio of a solid matter to be fed into the first pressure leach step 3 can be increased by supplementing the precipitate coming from the atmospheric copper removal 1 for example with synthetic copper sulfide precipitated with hydrogen sulfide or with some other copper-containing solid of the type that dissolves rapidly in the conditions of the first pressure leach step 3.
From the first pressure leach step, the slurry is passed in its existing state as the only feed to the second pressure leach step 4. The passage of slurry can be im-plemented by pushing the flurry first to a normal air pressure and by pumping therefrom, by direct pumping, or without pumping by maintaining the first pres-sure leach step at a pressure higher than the second pressure leach step. Tem-perature in the second pressure leach step may be higher than 140 C, and may be within the range of 140-160 , and nickel sulfides dissolve as nickel sulfate functions as the oxidizer:
In addition to sulfidic nickel matte, the atmospheric copper removal step 1 is also supplied with a copper- and iron-bearing solution from an atmospheric leach step 2 and from a second pressure leach step 4. In addition to these, the discussed step is supplied with air. The removal of copper is performed in atmospheric con-ditions and at a temperature of 80-100 C. The elemental nickel and nickel sulfide present in the matte precipitate copper existing in the solution as copper sulfate upon being themselves oxidized into nickel sulfate according to the following re-5 action equations:
Ni + CuSO4 N1SO4 + Cu (1) Ni3S2 + 2 CuSO4 ¨0 Cu2S + NiS +2 NiSO4 (2) Ni3S2 + 2 CuSO4 +1/2 02 2 MS + NiSO4 + Cu20 (3) In a continuously running operation, the reactors present a rising pH-profile in which the precipitation of copper occurs, in response to the above reactions, in acidic conditions at the start of the process step as the solution has a pH of less than 4. The leaching of metals consumes oxygen and, as pH rises, copper pre-cipitates also as alkaline copper sulfate CuS0412Cu(OH)2. From the standpoint of the effective extraction of copper and iron, however, this zone may be kept as brief as possible in terms of its residence time in order to minimize the concurrent precipitation of iron. The precipitate, i.e. the leach residue from this step, is deliv-ered after the liquid-solid separation to a first pressure leach step 3 and the solu-tion is conducted to an iron removal 5.
The finely ground metallic nickel matte is conducted to the atmospheric leach step 2. The term metallic nickel matte refers to pyrometallurgically produced smelter matte, in which most of the metal content is present in the form of metal-lic components, such as for example elemental nickel Ni , copper Cu , and iron Fe and/or in compositions (alloy) of these metals. The sulfur concentration of metallic nickel matte is typically less than 15% and it is highly magnetic.
The concentrations of various metals and impurities may fluctuate even quite exten-sively, but the total weight percentage of nickel, copper and iron is nevertheless typically more than 80%.
The leaching of metallic nickel matte is performed in atmospheric conditions and at a temperature of 80-100 C. In addition to nickel matte, the atmospheric solu-tion is supplied with oxygen and sulfuric acid. Some of the sulfuric acid can be replaced by an acid-containing anolyte obtained from a nickel electrolysis 7.
The principal leaching reactions are:
Ni + H2SO4 +1/202 N1SO4 + H20 (4) Cu + H2SO4 + % 02 CuSO4 + H20 (5) Fe + H2SO4 + 1/2 02 FeSO4 + H20 (6) The formation of hydrogen during leaching may be prevented by an abundant in-troduction of oxygen and the precipitation of iron by maintaining the solution at a low pH, lower than 2,0. The leach residue and the solution from this step are conducted to the atmospheric copper removal 1.
The first pressure leach step 3 is supplied with oxygen as well as with an acid-containing anolyte from the nickel electrolysis 7. The copper concentration of a solid matter delivered to the pressure leach step is increased by circulating some copper-bearing solid substance from a liquid-solid separation downstream of the second pressure leach step 4 into the precipitate coming from the atmospheric copper removal 1. The input solid substance has a preferred copper/nickel weight ratio of 1-2,5. The temperature in the first pressure leach step is higher than 100 C, and may be within the range of 110-120 C and the partial oxygen pressure may be higher than 200 kPa. The principal leaching reactions of the first pressure leach step are:
5 Cu1.8S +4 H2SO4 + 12 02 ¨> 9 CuSO4 +4 H20 (7) Ni3S2 + H2SO4 + 02 NiSO4 +2 NiS + H20 (8) The step is mainly intended for leaching a sufficient amount of copper for the leaching of nickel effected in the second pressure leach step. This is enabled by recycling, if necessary, a copper-bearing solid matter into an autoclave, which solid matter in this case consists of precipitate containing copper-sulfide from a liquid-solid separation downstream of the second pressure leach step 4. By virtue of recycling the precipitate, the method according to some embodyments may enable leaching also nickel mattes of low copper contents. Besides, by virtue of a high copper/nickel weight ratio of the solid matter, the first pressure leach step can be managed in a remarkably brief residence time, less than about 1 hour, even less than about 45 minutes, thus preventing nickel sulfide from reacting too far according to a reaction (9) presented below. This is of importance as regards the proper functioning of the second pressure leach step.
4 NiS + H2SO4 + % 02 Ni3S4 + NiSO4. + H20 (9) Leaching is manageable also in highly acidic conditions, but it may be carried out in such a way that some of the leached copper precipitates in the form of alkaline copper sulfate, the solution having a pH of not lower than about 3 at the end of the step.
Alternatively, the copper/nickel weight ratio of a solid matter to be fed into the first pressure leach step 3 can be increased by supplementing the precipitate coming from the atmospheric copper removal 1 for example with synthetic copper sulfide precipitated with hydrogen sulfide or with some other copper-containing solid of the type that dissolves rapidly in the conditions of the first pressure leach step 3.
From the first pressure leach step, the slurry is passed in its existing state as the only feed to the second pressure leach step 4. The passage of slurry can be im-plemented by pushing the flurry first to a normal air pressure and by pumping therefrom, by direct pumping, or without pumping by maintaining the first pres-sure leach step at a pressure higher than the second pressure leach step. Tem-perature in the second pressure leach step may be higher than 140 C, and may be within the range of 140-160 , and nickel sulfides dissolve as nickel sulfate functions as the oxidizer:
8 Ni3S2 + 27 CuSO4 + 4 H20 24 NiSO4 + 15 Cui.BS + 4 H2SO4 (10) 6 NiS + 9 CuSO4 + 4 H20 6 NiSO4 + 5 Cul BS + 4 H2SO4 (11) As the acid concentration rises in non-oxidizing conditions, the slurry leaches al-so iron and arsenic during the second pressure leach step. The liquid-solid sepa-ration downstream of the step is a source of relatively pure copper sulfide precipi-tate, having just a low iron concentration and containing the precious metals (such as Au, Pt and Pd) received along with nickel mattes and practically non-leached in the above-defined conditions. A desired portion of the precipitate is re-turned the feed of the first pressure leach step 3. The copper sulfide precipitate separated from the process can be fed for example to a copper smelting facility or subjected to metallurgical further processing by some prior known method.
The solution from liquid-solid separation is conducted to the atmospheric copper removal 1.
A leaching process product solution (PLS), subsequent to the atmospheric cop-per removal 1, is conducted, downstream of the liquid-solid separation, to the iron removal 5. The iron removal is effected with some prior known method, such as by precipitating the iron with oxygen 02 and by neutralizing the acid evolved in the precipitation process for example with lye NaOH. Following the iron removal, the precipitate is separated and the solution is conducted to a solution purifica-tion 6, wherein the solution is stripped of cobalt and other impurities detrimental to nickel production by some prior known method, for example by liquid-liquid ex-traction. The pure nickel sulfate solution is used for producing nickel products by known methods, such as for example cathode by means of the nickel electrolysis 7. Nickel electrolysis provides a source of an acid-containing nickel solution or anolyte, the sulfuric acid contained therein being useful in the presently de-scribed leaching process.
Some embodiments ofthe invention will be described further by way of the ac-companying non-limiting examples:
Example 1 Atmospheric copper removal step Ground sulfidic nickel matte with a composition of 67% Ni, 3,0% Cu, 2,0% Fe and 23% S was leached in laboratory into a copper-containing nickel sulfate solu-tion. Leaching was conducted in a heated cover-equipped steel reactor provided with agitation and aeration. The solution volume was two liters, air feed 50 L/h, temperature 85 C and leaching time one hour. Other conditions and results are shown in table 1. The results reveal that there is achieved a practically complete precipitation of the parent solution copper while leaching nickel and iron.
This in-8a dicates a separation of copper and iron.
Table 1 Solution Solid V (L) pH Ni (pIL) Cu (a(L) Fe m (a) Ni % Cu %
Fe %
Feed 2.0 1.2 109 2.1 2.6 164 67.3 3.0 2.0 End 2.0 4.3 119 0.004 3.2 156 60.8 5.5 1.8 Example 2 Two-step pressure leach The leach residue of nickel matte, treated as in example 1 and with a composi-tion of 63% Ni, 6,2% Cu, 2,2% Fe and 23% S, was leached with a laboratory au-toclave in a two-step fashion. Prior to leaching, the solid matter had its cop-per/nickel weight ratio changed by having copper sulfide precipitate containing 66% Cu and 28% S admixed within the leach residue. In the series of tests, the solution volume was 1 liter and the pressure in autoclave was 8 bar. During the first pressure leach step, the temperature was 112 C and the autoclave was supplied with oxygen under the agitator. Leaching time was 45 minutes. After this, the supply of oxygen was shut off and the autoclave was heated for the sec-ond pressure leach step to the temperature of 147 C. Leaching time in the sec-ond pressure leach step was two hours and during this period the autoclave was not supplied with oxygen. Other conditions and the results of pressure leach tests are shown in table 2.
The results reveal that the leaching of nickel is also managed in highly acidic conditions, but may be carried out in such a way that the solution pH at the end of the first pressure leach step is not lower than 3. Between tests 1 and 2 is also visible the effect of a copper/nickel weight ratio in the solid matter. At a higher copper/nickel weight ratio, substantially more copper becomes leached during the first pressure leach step and thereby an improved recovery of nickel is achieved in the second pressure leach step. The results further reveal that the leaching of iron takes place at the latest during the second pressure leach step, such that the ob-
The solution from liquid-solid separation is conducted to the atmospheric copper removal 1.
A leaching process product solution (PLS), subsequent to the atmospheric cop-per removal 1, is conducted, downstream of the liquid-solid separation, to the iron removal 5. The iron removal is effected with some prior known method, such as by precipitating the iron with oxygen 02 and by neutralizing the acid evolved in the precipitation process for example with lye NaOH. Following the iron removal, the precipitate is separated and the solution is conducted to a solution purifica-tion 6, wherein the solution is stripped of cobalt and other impurities detrimental to nickel production by some prior known method, for example by liquid-liquid ex-traction. The pure nickel sulfate solution is used for producing nickel products by known methods, such as for example cathode by means of the nickel electrolysis 7. Nickel electrolysis provides a source of an acid-containing nickel solution or anolyte, the sulfuric acid contained therein being useful in the presently de-scribed leaching process.
Some embodiments ofthe invention will be described further by way of the ac-companying non-limiting examples:
Example 1 Atmospheric copper removal step Ground sulfidic nickel matte with a composition of 67% Ni, 3,0% Cu, 2,0% Fe and 23% S was leached in laboratory into a copper-containing nickel sulfate solu-tion. Leaching was conducted in a heated cover-equipped steel reactor provided with agitation and aeration. The solution volume was two liters, air feed 50 L/h, temperature 85 C and leaching time one hour. Other conditions and results are shown in table 1. The results reveal that there is achieved a practically complete precipitation of the parent solution copper while leaching nickel and iron.
This in-8a dicates a separation of copper and iron.
Table 1 Solution Solid V (L) pH Ni (pIL) Cu (a(L) Fe m (a) Ni % Cu %
Fe %
Feed 2.0 1.2 109 2.1 2.6 164 67.3 3.0 2.0 End 2.0 4.3 119 0.004 3.2 156 60.8 5.5 1.8 Example 2 Two-step pressure leach The leach residue of nickel matte, treated as in example 1 and with a composi-tion of 63% Ni, 6,2% Cu, 2,2% Fe and 23% S, was leached with a laboratory au-toclave in a two-step fashion. Prior to leaching, the solid matter had its cop-per/nickel weight ratio changed by having copper sulfide precipitate containing 66% Cu and 28% S admixed within the leach residue. In the series of tests, the solution volume was 1 liter and the pressure in autoclave was 8 bar. During the first pressure leach step, the temperature was 112 C and the autoclave was supplied with oxygen under the agitator. Leaching time was 45 minutes. After this, the supply of oxygen was shut off and the autoclave was heated for the sec-ond pressure leach step to the temperature of 147 C. Leaching time in the sec-ond pressure leach step was two hours and during this period the autoclave was not supplied with oxygen. Other conditions and the results of pressure leach tests are shown in table 2.
The results reveal that the leaching of nickel is also managed in highly acidic conditions, but may be carried out in such a way that the solution pH at the end of the first pressure leach step is not lower than 3. Between tests 1 and 2 is also visible the effect of a copper/nickel weight ratio in the solid matter. At a higher copper/nickel weight ratio, substantially more copper becomes leached during the first pressure leach step and thereby an improved recovery of nickel is achieved in the second pressure leach step. The results further reveal that the leaching of iron takes place at the latest during the second pressure leach step, such that the ob-
9 PCT/F12009/050540 tamed leach residue comprises relatively pure copper sulfide precipitate which can be recycled into the feed of a two-step pressure leaching process.
Table 2 Solution Solid nzs 04 (g/L pH Ni (WO Cu WO Fe (g/t m Ni %
Cu % Fe % C tieNi ratio Test Feed 52.0 73 1.0 1.0 140 26.0 40.5 1.0 1,5 End of step I 1.1 83 20.2 1.6 10.3 45.4 0.2 End of step II 0.0 112 0.3 1.0 85.6 2.4 67.1 0.06 Test 2 Feed 62.0 73 1.0 1.0 180 20.0 40.2 0.7 22 End of step I 1.2 GO 20.3 1.6 10.7 54.8 0.1 End of step II 0.6 111 7.8 1.7 103 0.8 70.4 0.04 Test 3 Feed 17.0 73 1.0 1.0 170 22.1 45.0 0.8 2D
End of step I 3.0 83 24.3 0.06 10.1 40.8 1.6 End of step II 0.0 105 8.1 1.6 83.5 0.05 74.8 0.07 Example 3 Atmospheric leaching Ground metallic nickel matte with a composition of 48% Ni, 7,4% Cu, 30% Fe and 5,7% S was leached in laboratory into an acidified nickel sulfate solution.
Leaching was conducted in a heated cover-equipped steel reactor provided with agitation and aeration. The solution volume was two liters, oxygen feed 50 L/h, temperature 85 C and leaching time three hours. Other conditions and the results are shown in table 3. The results indicate that metallic nickel matte can be leached in atmos-pheric conditions in such a way that practically all that remains in the leach residue are sulfidic components. The test also demonstrates that iron remains in a dis-solved state as long as the solution is maintained at a low pH.
Table 3 Solution Solid H2SO4. (gI-) pH Ni (W Cu (04 Fe WO m (g) Ni % Cu % Fe % S %
Feed 72.0 80 0.1 124 48.1 7.4 30.3 5.7 End 1.8 85 0.002 16 27.5 27.1 29.8 9.8 26.8
Table 2 Solution Solid nzs 04 (g/L pH Ni (WO Cu WO Fe (g/t m Ni %
Cu % Fe % C tieNi ratio Test Feed 52.0 73 1.0 1.0 140 26.0 40.5 1.0 1,5 End of step I 1.1 83 20.2 1.6 10.3 45.4 0.2 End of step II 0.0 112 0.3 1.0 85.6 2.4 67.1 0.06 Test 2 Feed 62.0 73 1.0 1.0 180 20.0 40.2 0.7 22 End of step I 1.2 GO 20.3 1.6 10.7 54.8 0.1 End of step II 0.6 111 7.8 1.7 103 0.8 70.4 0.04 Test 3 Feed 17.0 73 1.0 1.0 170 22.1 45.0 0.8 2D
End of step I 3.0 83 24.3 0.06 10.1 40.8 1.6 End of step II 0.0 105 8.1 1.6 83.5 0.05 74.8 0.07 Example 3 Atmospheric leaching Ground metallic nickel matte with a composition of 48% Ni, 7,4% Cu, 30% Fe and 5,7% S was leached in laboratory into an acidified nickel sulfate solution.
Leaching was conducted in a heated cover-equipped steel reactor provided with agitation and aeration. The solution volume was two liters, oxygen feed 50 L/h, temperature 85 C and leaching time three hours. Other conditions and the results are shown in table 3. The results indicate that metallic nickel matte can be leached in atmos-pheric conditions in such a way that practically all that remains in the leach residue are sulfidic components. The test also demonstrates that iron remains in a dis-solved state as long as the solution is maintained at a low pH.
Table 3 Solution Solid H2SO4. (gI-) pH Ni (W Cu (04 Fe WO m (g) Ni % Cu % Fe % S %
Feed 72.0 80 0.1 124 48.1 7.4 30.3 5.7 End 1.8 85 0.002 16 27.5 27.1 29.8 9.8 26.8
Claims (9)
1. A method for leaching pyrometallurgically produced, copper-containing sulfidic nickel matte, wherein - a sulfidic nickel matte is fed to an atmospheric leach step from which is obtained a nickel-bearing solution and a copper- and nickel-bearing leach residue, whereby a copper-bearing solid matter is added into the nickel matte before the leaching or to the copper- and nickel-bearing leach residue after the leaching in such an amount that the weight ratio of copper to nickel in the copper- and nickel-bearing leach residue is more than about 1, wherein the solid matter has its source in a latter stage of the method or the solid matter consists of synthetically produced copper sulfide, and - the copper- and nickel-bearing leach residue is conducted to pressure leaching.
2. A method as set forth in claim 1, wherein copper, but not iron, is precipitated from the solution in an atmospheric copper removal.
3. A method as set forth in any one of claims 1-2, wherein the pressure leaching is a two-step process and that temperature in the first pressure leach step is within the range of 100-120°C.
4. A method as set forth in claim 3, wherein the residence time in the first pressure leach step is less than about 1 hour.
5. A method as set forth in claim 3 or 4, wherein temperature in the second pressure leach step is higher than about 140°C.
6. A method as set forth in any one of claims 1-5, wherein the atmospheric leaching step of sulfidic nickel matte is also supplied with a solution and a leach residue obtained from an atmospheric leaching of metallic nickel matte.
7. A method as set forth in claim 6, wherein the atmospheric leaching of metallic nickel matte is conducted by means of sulfuric acid and oxygen at a pH sufficiently low for a dissolved iron not to precipitate.
8. A method as set forth in any one of claims 1-7, wherein separated leach residues of nickel mattes end up in the same precipitate, which also contains the copper and precious metals that were present in the nickel mattes.
9. The method of claim 8, wherein the leach residues contain also precious metals that were present in the nickel mattes.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20085627A FI121380B (en) | 2008-06-19 | 2008-06-19 | Method for dissolving pyrometallurgical nickel stones |
| FI20085627 | 2008-06-19 | ||
| PCT/FI2009/050540 WO2009153409A1 (en) | 2008-06-19 | 2009-06-18 | Method for leaching nickel matte in the presence of added copper |
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| CA2728519A1 CA2728519A1 (en) | 2009-12-23 |
| CA2728519C true CA2728519C (en) | 2016-09-13 |
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| AU (1) | AU2009259277B2 (en) |
| CA (1) | CA2728519C (en) |
| FI (1) | FI121380B (en) |
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| CA2983350A1 (en) | 2015-04-21 | 2016-10-27 | University Of Saskatchewan | Methods for simultaneous leaching and extraction of precious metals |
| CN113526576B (en) * | 2021-05-31 | 2022-06-03 | 金川集团股份有限公司 | Preparation method of high-nickel low-acid low-sodium nickel sulfate solution |
| CN113957243B (en) * | 2021-10-22 | 2023-10-17 | 金川镍钴研究设计院有限责任公司 | Method for realizing open circuit of nickel, copper and iron in high-nickel matte and enriching noble metals |
| CN115323189A (en) * | 2022-08-24 | 2022-11-11 | 中国恩菲工程技术有限公司 | Treatment method of nickel and sulfur with high copper content |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US3962051A (en) * | 1974-12-26 | 1976-06-08 | Amax Inc. | Atmospheric leaching of matte containing iron |
| CA1173655A (en) * | 1981-10-30 | 1984-09-04 | Derek G.E. Kerfoot | Acid leach process for treating magnetic and non- magnetic nickel-copper mattes |
| CA1234289A (en) * | 1984-10-24 | 1988-03-22 | Derik G.E. Kerfoot | Recovery of platinum group metals from nickel-copper- iron matte |
| US5344479A (en) * | 1992-03-13 | 1994-09-06 | Sherritt Gordon Limited | Upgrading copper sulphide residues containing nickel and arsenic |
| US5993514A (en) * | 1997-10-24 | 1999-11-30 | Dynatec Corporation | Process for upgrading copper sulphide residues containing nickel and iron |
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| FI20085627A0 (en) | 2008-06-19 |
| FI20085627A (en) | 2009-12-20 |
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| WO2009153409A1 (en) | 2009-12-23 |
| AU2009259277B2 (en) | 2015-02-12 |
| CA2728519A1 (en) | 2009-12-23 |
| AU2009259277A1 (en) | 2009-12-23 |
| ZA201100473B (en) | 2011-10-26 |
| WO2009153409A4 (en) | 2010-02-18 |
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