Dry type refining method and dry type refining apparatus of metal resources

Abstract

To provide a dry type refining method in which a desired metal is efficiently recovered from metal resources and a small environmental load is generated, and a dry type refining apparatus using the method.SOLUTION: A dry type refining method of metal resources includes: a first step of storing metal resources containing metal compounds into a furnace having a gas inflow port and a gas outflow port; a second step of exhausting the combustion gas from the gas outflow port while allowing combustion gas to flow into the gas inflow port to hold the inside of the furnace in a reduction atmosphere; a third step of intermittently irradiating the metal resources with pulse discharge under the reduction atmosphere; and a fourth step of recovering the metal compound decomposed by the third step as a purified product, where the pulse discharge is performed along a flow-through direction of the combustion gas in the third step.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for dry refining of metal resources, and particularly to a method for dry refining of metal resources containing a metal compound having a metal selected from the group consisting of gold, platinum group, silver, zinc, magnesium, aluminum, silicon, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, lead, tin, bismuth, gallium, indium, germanium, molybdenum, tellurium, cesium and tungsten as a constituent element.

Background Art

[0002] In recent years, the demand for recycling rare metals and precious metals such as gallium and indium from urban ores such as waste electronic devices has been increasing. For example, electronic components such as GaN semiconductors, Ga 2 O 3 semiconductors, LED elements, IGZO liquid crystal displays, and ITO transparent electrodes contain valuable metals such as gallium, indium, gold, and silver. In addition, printed circuit boards contain metals such as copper, and lead-free solder contains metals such as tin and bismuth. As a method for separating and recovering gallium and indium from such waste electronic components, for example, a dry refining method using a fluidized bed has been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since such metal resources as urban minerals exist in various forms, there is still room for improvement in the dry refining method. In particular, LED (Light Emitting Diode) lighting has high luminous efficiency and a long lifespan, so it has spread widely from the perspective of energy conservation. On the other hand, regarding the recycling of gallium used in the light-emitting part of LED elements, the technology has not yet been established. In addition, for other Ga 2 O 3 It is also necessary to refine and recycle metal resources such as gallium from power semiconductors and GaN power semiconductors.

[0005] Also, from the perspective of environmental impact, in the conventional dry refining technology, a huge amount of energy such as combustion reaction is input in the reduction process, and a large amount of CO 2 is emitted simultaneously with reduction. For example, when reducing and sintering iron ore, coke is used, so a large amount of CO 2 is emitted. From the perspective of carbon neutrality, it is desired to realize a process with less input energy and less CO 2 emission. In recent years, not only the exemplified gallium and iron ore, but also the improvement of recycling methods for metal resources targeting various metal elements has been demanded. Therefore, an object of the present invention is to provide a dry refining method for efficiently recovering a desired metal from a metal resource and having a small environmental impact, and a dry refining apparatus using the method.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventor came up with the idea of intermittently irradiating a metal resource with pulsed discharge in a reducing atmosphere and found that a desired metal can be efficiently recovered from the metal resource. That is, the gist configuration of the present invention is as follows.

[0007] <1> A first step of storing a metal resource containing a metal compound in a furnace having a gas inlet and a gas outlet; A second step of introducing combustion gas into the gas inlet and exhausting the combustion gas from the gas outlet to maintain a reducing atmosphere inside the furnace; A third step of intermittently irradiating the metal resource with pulsed discharge in the reducing atmosphere; A fourth step of recovering the metal compound decomposed in the third step as a refined product, and includes: In the third step, a dry refining method of the metal resource, in which the pulsed discharge is performed along the flow direction of the combustion gas.

[0008] <2> The dry refining method according to <1>, wherein the combustion gas is generated by combustion of a hydrocarbon gas and / or a gas containing hydrogen.

[0009] <3> In the fourth step, the refined product is obtained with different element mixing ratios on the upstream side and the downstream side in the flow direction of the combustion gas. The dry refining method according to <1> or <2>.

[0010] <4> In the third step, the temperature on the gas inlet side in the furnace is 100 °C or more lower than the melting point of the refined product. The dry refining method according to any one of <1> to <3>.

[0011] <5> The frequency of the pulsed discharge is 50 Hz or more. The dry refining method according to any one of <1> to <4>.

[0012] <6> The furnace is a vertical tubular furnace. The dry refining method according to any one of <1> to <5>.

[0013] <7> The metal resource is urban ore. The dry refining method of the metal resource according to any one of <1> to <6>.

[0014] <8> The metal resource is powdered ore. The dry refining method according to any one of <1> to <7>.

[0015] <9> The refined product recovered in the fourth step is in particulate form. The furnace is a vertical tubular furnace, and the refined product is deposited at the lower part of the furnace. The dry refining method according to any one of <1> to <8>.

[0016] <10> A furnace having a gas inlet and a gas outlet, and storing a metal resource containing a metal compound; A combustion device located upstream of the gas inlet and allowing combustion gas to flow into the furnace from the gas inlet; An electrode inserted into the gas inlet and an electrode installed on the side of the gas outlet, and a pulse discharge unit in which the path between the downstream side of the electrode inserted into the gas inlet and the upstream side of the electrode installed on the side of the gas outlet is along the central axis direction of the furnace; A dry refining apparatus having the above.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a dry refining method for efficiently recovering a desired metal from a metal resource and having a small environmental load, and a dry refining apparatus using the method.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0019] First, prior to the description of the embodiments of the dry refining method of metal resources according to the present invention, the terms used in this specification will be described.

[0020] <Metal resources> In this specification, metal resources broadly refer to those containing metal compounds, which may be derived from industrial waste called urban ores, or may be ores before smelting such as powdered ores.

[0021] <<Metal compound>> In this specification, a metal compound may be anything that contains a metal, or may be a mixture containing a metal. Also, the type of metal element is not particularly limited, but the metal compound preferably contains a metal selected from the group consisting of gold, platinum group, silver, zinc, magnesium, aluminum, silicon, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, lead, tin, bismuth, gallium, indium, germanium, molybdenum, tellurium, cesium, and tungsten, which are treated as valuable metals in its constituent elements.

[0022] <<Urban ore>> In this specification, urban ore refers to useful resources (such as rare metals) present in household appliances and the like discarded in cities. Examples of these include, for those containing gallium, waste of LEDs used in household fluorescent lamps, etc., GaN power semiconductors, Ga 2 O 3 power semiconductors, IGZO liquid crystal displays, CIGS solar cells, etc. Also, for those containing indium, ITO transparent electrodes, for those containing gold, electric circuits such as CPUs, for those containing platinum group elements (such as platinum and palladium), exhaust gas purification filters, etc. In addition, anode slime generated during electrolytic refining and electroplating, which contains precious metals (gold and platinum group), can be mentioned.

[0023] <<Powdered ore>> In this specification, powdered ore refers to ore in powder form. Generally, powdered ore refers to iron ore with a particle size of about 10 μm to 5 mm, but is not limited thereto. Powdered ore is used in metal smelting, such as cassiterite (SnO 2 ), hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), goethite (FeO(OH)), chalcopyrite (CuFeS 2 ), galena (PbS), sphalerite (ZnS), bismuthinite (Bi 2 S 3 ), molybdenite (MoS 2 ), scheelite (CaWO 4 ), ferberite ((Fe,Mn)WO 4 ), chromite (FeCr 2 O 4 ), magnesiochromite (MgCr 2 O 4 ), pentlandite ((Fe,Ni) 9 S 8 ), linnaeite (Co 3 S 4 ) and other common ores may be used.

[0024] <Purified product> The purified product refers to all compounds containing the desired metal obtained by purifying metal resources. Not only when the desired metal alone is isolated from metal resources, but also if the purity of the desired metal after treatment is higher than that at the stage when metal resources are input as raw materials, it can be called a purified product. Taking Ga as an example, not only the single Ga separated from an element containing Ga, etc. is of course a purified product, but also the one recovered as Ga oxide is a purified product.

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0026] (Dry refining apparatus) The dry refining apparatus according to the present invention has a gas inlet and a gas outlet, a furnace for storing a metal resource containing a metal compound, a combustion device located upstream of the gas inlet for flowing combustion gas into the furnace from the gas inlet, and electrodes inserted into the gas inlet and an electrode installed on the side of the gas outlet. A path between the downstream side of the electrode inserted into the gas inlet and the upstream side of the electrode installed on the side of the gas outlet follows the central axis direction of the furnace, and has a pulse discharge unit. Referring to FIG. 1, a schematic diagram of a specific example of the dry refining apparatus will be described. The dry refining apparatus 100 in FIG. 1 includes at least a furnace 30 for storing a metal resource 40 containing a metal compound, a gas inlet 10 for flowing gas into the furnace 30, and a gas outlet 20 provided in a part of the lid 35 of the furnace 30, and a combustion device 50 located upstream of the gas inlet 10 for flowing combustion gas into the furnace 30 from the gas inlet 10, and a pulse discharge unit 80 including a lower electrode 82 inserted into the gas inlet 10 and an upper electrode 81 installed on the side of the gas outlet 20. In the example of FIG. 1, the path between the upper end of the lower electrode 82 and the lower end of the upper electrode 81 of the pulse discharge unit 80 follows the central axis direction of the vertical tubular furnace 30. For example, the dry refining method according to the present embodiment can be implemented using this dry refining apparatus 100.

[0027] The furnace 30 used in the dry refining apparatus 100 is a furnace for accommodating raw materials. In order for gas to flow through and make the internal atmosphere a reducing atmosphere, gas can flow from the gas inlet 10 through the gas outlet 20, and it is preferably made of a material with low gas permeability. The material of the furnace 30 is preferably a material that does not cause chemical changes such as melting and reaction through a series of refining steps, and examples include stainless steel, nickel alloy, alumina, and quartz.

[0028] Further, the structure of the dry refining apparatus 100 is not particularly limited and may be horizontal, but it is preferably a vertical tubular furnace illustrated in FIG. 1 in that gravity acts in a direction opposite to the gas flow direction and it can take the form of a jet fluidized bed.

[0029] The pulse discharge unit 80 in FIG. 1 is a discharge unit that emits arbitrary arc discharges. From the viewpoints of the electrode itself not melting even at high temperatures and having high conductivity, it is preferable that the pulse discharge unit 80 employs platinum, molybdenum, tungsten, or a carbon rod for the upper electrode 81 installed on the side of the gas outlet 20, and it is preferable that the pulse discharge unit 80 employs platinum, molybdenum, tungsten, or carbon for the lower electrode 82 inserted into the gas inlet 10. The combustion device 50 may be any device that can ignite a combustible gas and sequentially supply the combustion gas to the metal resource storage part, such as a gas burner.

[0030] In the dry refining apparatus 100 of FIG. 1, the reducing gas flows in from the gas inlet 10 at the lower part of the furnace 30, passes through the metal resource 40, and is discharged from the gas outlet 20 at the upper part of the furnace 30. At this time, the metal resource 40 is exposed to both the heat caused by the pulse discharge emitted from the pulse discharge unit 80 and the heat caused by the combustion emitted by the gas combustion device 50. In the present invention, for example, the dry refining of a metal resource containing a metal compound can be performed using this dry refining apparatus 100.

[0031] (Dry refining method) The dry refining method according to the present embodiment includes a first step of storing a metal resource 40 containing a metal compound in a furnace 30 having a gas inlet 10 and a gas outlet 20, a second step of maintaining the inside of the furnace 30 in a reducing atmosphere by flowing a combustion gas into the gas inlet 10 and exhausting the combustion gas from the gas outlet 20, a third step of intermittently crushing the metal resource 40 by pulse discharge under the reducing atmosphere, and a fourth step of recovering a refined product obtained by oxidizing and cooling the metal compound vaporized in the third step to be reduced. Further, in the third step, pulse discharge is performed along the flowing direction of the combustion gas. Hereinafter, each step will be described in detail with reference to the dry refining apparatus 100 described above with reference to FIG. 1.

[0032] <The first step> In the first step, a metal resource 40 containing a metal compound is stored in a furnace 30 having a gas inlet 10 and a gas outlet 20. At this time, the metal resource 40 containing the metal compound may be introduced, for example, from the gas inlet 10 or the gas outlet 20. When it is a vertical tubular furnace, it is also possible to introduce the metal resource 40 into the furnace 30 with the lid 35 open. Moreover, it is not limited to this, and a resource inlet may be separately provided in the furnace 30 and used. The size of each fragment of the metal resource 40 is not particularly limited as long as it is large enough to be introduced from the gas outlet 20, and it is preferably large enough not to flow out from the gas inlet 10, but a fall prevention valve may be provided in the furnace 30. Incidentally, prior to storing in the furnace 30, it is preferable to crush or the like by any method in order to optimize the size of the metal resource 40. Further, in order to remove organic components and the like that become impurities when obtaining a purified product, wet treatment such as calcination treatment or acid dissolution may be performed in advance at the stage of the raw material of the metal resource 40.

[0033] <Second step> In the second step, while introducing combustion gas into the gas inlet 10, the combustion gas is exhausted from the gas outlet 20 to maintain a reducing atmosphere inside the furnace 30. The combustion gas is a post-combustion gas in which a combustible gas has been combusted and the combustion reaction has been completed. Carbon compounds, hydrogen compounds, nitrogen compounds contained in the gas, as well as oxygen monoxide and hydrogen generated by incomplete combustion serve as reducing agents to form a reducing atmosphere. Also, a part of these combustion gases may contain gases that were introduced as combustible gases but did not contribute to the combustion reaction. In order to use the combustion gas as a reducing gas in this way, it is preferable to use a gas containing hydrocarbon gas and / or hydrogen as the gas before ignition. As an example of the gas before ignition, natural gas such as various city gases or acetylene may be used. Also, from the same perspective, it is also preferable to reduce the ratio of oxygen supply compared to normal combustible gases. Note that the combustion gas not only serves as a reducing atmosphere but also as a heat source. From the perspective of the melting point of the refined product, it is preferable to set the inside of the furnace 30 to 200°C to 1500°C according to the metal resource 40 stored in the furnace 30. From the perspective of promoting refining within the heat resistance range of the furnace material, it is preferable to set it to 400°C to 1200°C, and more preferably to 500°C to 1000°C.

[0034] The combustion gas flows in from the gas inlet 10, passes through the metal resource 40, and heads towards the gas outlet 20. Therefore, the metal resource 40 can be fluidized and agitated by the flow of the combustion gas, enabling the overall reaction to proceed more uniformly. In a vertical tubular furnace, the jet behavior of the combustion gas from the bottom to the top of the metal resource 40, the behavior of being spouted up by the jet behavior, and the behavior of the metal resource 40 swirling back to the lower part due to gravity may overlap, sometimes showing jet behavior. In a state showing such jet behavior, by increasing the contact opportunity of the gas and equalizing the difference in reduction intensity depending on location, a more uniform reaction can be achieved.

[0035] <The third step> In the third step, in a reducing atmosphere, pulse discharge is intermittently applied to the metal resource 40 along the flowing direction of the combustion gas. Due to the pulse discharge, a local high-temperature state is realized in the irradiated portion of the metal resource 40 in the furnace 30, or the metal resource 40 itself becomes hot. Further, due to the pulse discharge, the metal resource 40 such as an LED can be destroyed by a thermal shock or a strong electric field. Therefore, although the reaction mechanism varies depending on the metal element constituting the metal compound, in combination with the flowing of the combustion gas in the furnace 30, it is possible to promote the vaporization of the target metal element contained in the metal resource 40 or the reduction by a local strong reducing atmosphere. In particular, the pulse discharge occurs between the downstream side of the upper electrode 81 installed on the side of the gas outlet 20 positioned in the furnace 30 and the upstream side of the lower electrode 82 inserted into the gas inlet 10, and it is preferable to arrange the main discharge path of this pulse discharge so as to pass through the central portion of the stored metal resource 40. In this way, by simultaneously proceeding with the vaporization and reduction effects at the microscopic level and the destruction of the metal resource 40 at the macroscopic level, refining that was impossible with conventional dry refining methods can be efficiently advanced.

[0036] In addition, since refining can be carried out due to the generation of such a local high-temperature portion, etc., in the entire system in the furnace 30, refining can be carried out in a state lower than the melting point of the refined product. From the viewpoint of efficiency with respect to the input energy, it is sufficient that the temperature is at least such that the metal compound of the metal resource 40 melts, reduces, or vaporizes in the discharge portion. It is preferable that the temperature on the gas inlet 10 side is 100 °C or more lower than the melting point of the refined product, more preferably 150 °C or more lower, and even more preferably 200 °C or more lower.

[0037] At this time, the voltage between the electrodes of the pulse discharge unit 80 during pulse discharge is preferably 5 kV or more, more preferably 10 kV or more, even more preferably 15 kV or more, preferably 100 kV or less, more preferably 80 kV or less, and even more preferably 50 kV or less from the viewpoint of generating a discharge between electrodes with an electrode interval of 10 mm to 30 mm. When the electrode interval is increased, it is preferable to increase the voltage between the electrodes as well.

[0038] Also, the frequency during pulse discharge is preferably 50 Hz or more, more preferably 100 Hz or more, still more preferably 150 Hz or more, preferably 10,000 Hz or less, more preferably 5,000 Hz or less, and still more preferably 2,000 Hz or less. When the frequency is increased, the flow of the metal resource 40 by the combustion gas is promoted, and it is considered that the metal refining proceeds more efficiently. This agitation promotion effect can be remarkably seen in the fluidized bed furnace, and the flow is particularly remarkable immediately after the start of discharge. In addition, at the final stage when the separation of the metal progresses, the flow becomes gentle, and depending on the object to be refined, the flow may cease. By involving the destruction of the metal resource 40, the metal resource 40 is exposed with a larger surface area in the reducing atmosphere.

[0039] <Fourth Step> In the fourth step, a purified product is obtained by oxidizing the metal compound vaporized or melted by pulse discharge after reduction or by cooling the vaporized or melted metal compound in the third step. After the second and third steps, the mechanism for obtaining the purified product by this fourth step varies depending on the form of the target metal resource 40 and the resulting purified product, and the following recovery routes 1 to 4 are conceivable.

[0040] <<Recovery Route 1 (When passing through reduction vaporization)>> When the metal resource is a GaN-containing LED element, a GaN power semiconductor, Ga 2 O 3 power semiconductor, a Cu-In-Ga-Se compound semiconductor (CIGS) solar cell, an In-Ga-Zn-O amorphous semiconductor (IGZO) liquid crystal display, or an indium tin oxide (ITO) transparent electrode doped with tin oxide, Ga (as Ga 2 O 3 (s)) and In (as In 2 O 3 (s)) are recovered by the following mechanism. Also, Ge (as GeO 2 (s)) and Te (metallic TeO 2(as) Cs(Ce 2 O 3 (as) is also recovered by the same mechanism. In addition, kaolinite (Al 4 Si 4 O 10 (OH) 8 ) and other ores that could not be reduced by conventional dry refining can also obtain purified products according to this recovery mechanism or the recovery mechanism of Recovery Route 3 described below.

[0041] In this case, inside the dry refining apparatus, oxidation and reduction reactions occur by the reactions of the following chemical formulas (1) to (4), and purified products are recovered.

[0042] Using Chemical Formula (1), the recovery route of Ga 2 O 3 will be specifically described. When pulse discharge is irradiated on metal resources such as LED elements, Ga 2 O 3 existing inside the element is reduced and vaporized to become Ga 2 O(g). Then, the vaporized Ga 2 O(g) is cooled and oxidized inside the furnace to become the purified product Ga 2 O 3 (s), adheres to the inner wall of the furnace, etc., and is recovered. Ga 2 O 3 (s) → Ga 2 O(g) → Ga 2 O 3 (s) ··· (1)

[0043] Similarly, when metal resources containing GaN(s), In 2 O 3 (s) and ZnO(s) are used as raw materials, they are also recovered as purified products after being reduced and vaporized from solids and then oxidized again according to the following Chemical Formulas (2) to (4). Note that the reaction from GaN(s) to Ga 2 O(g) in Chemical Formula (2) can be said to be a reduction reaction considering that the valence of N is -3. GaN(s) → Ga 2 O(g) → Ga 2O 3 (s)···(2) In 2 O 3 (s)→In 2 O(g)→In 2 O 3 (s)···(3) ZnO(s)→Zn(g)→ZnO(s)···(4)

[0044] <<Recovery Route 2 (When there is no redox)>> When using urban ore containing silver as a metal resource, silver metal can be recovered by the following mechanism.

[0045] Inside the dry refining apparatus, it is expected to follow the recovery routes of the following chemical formulas (5) and (6). First, when pulsed discharge is irradiated on Ag(s) as a metal resource, Ag(s) sublimates (chemical formula (5)) or evaporates after melting (chemical formula (6)) to become gaseous Ag(g). Then, the vaporized Ag(g) is cooled inside the furnace to directly (chemical formula (5)) or condense through the liquid phase (chemical formula (6)) to become purified Ag(s), which adheres to the inner wall of the furnace, etc., and is recovered. When Ag exists as a compound such as an oxide or sulfide, after a reduction reaction occurs, the recovery of the following chemical formulas (5) and (6) is carried out. Ag(s)→Ag(g)→Ag(s)···(5) Ag(s)→Ag(l)→Ag(g)→Ag(l)→Ag(s)···(6)

[0046] <<Recovery Route 3 (Reduction · Gravity Separation)>> As metal resources, cassiterite (SnO 2 ), iron ore (Fe 2 O 3 , Fe 3 O 4 , FeO(OH)), chalcopyrite (CuFeS 2The case of using common ores such as (oxides, sulfides, hydroxides, etc.) will be described. As refined products, Sn (metal), Fe (metal), and Cu (metal) are recovered as refined products by following the mechanisms of the recovery routes of the following chemical formulas (7) to (9) and undergoing reduction and coarsening inside the dry refining apparatus.

[0047] As an example, the recovery route of SnO(s) will be described in detail using Chemical Formula (7). First, when pulsed discharge is irradiated onto SnO(s) as a metal resource, SnO(s) is reduced to become powdered solid Sn(s: powder). Then, the powdered Sn(s: powder) continues to be irradiated with pulsed discharge, and a part of it melts, and the melted parts adhere to each other and coarsen to form agglomerated Sn(s: agglomerate), and in the flowing metal resource, it is separated by specific gravity and recovered at the bottom of the furnace. SnO(s) → Sn(s: powder) → Sn(s: agglomerate) ··· (7)

[0048] Similarly for Fe 2 O 3 (s), when using a metal resource containing CuS(s) as a raw material, it is also reduced from a solid to a powder state according to the following Chemical Formulas (8) and (9), and then further aggregated and separated by specific gravity to be recovered as a refined product. Also, by this mechanism, V can be obtained from other vanadium-containing ores, Pb from galena (PbS), Zn from sphalerite (ZnS), Bi from bismuthinite (Bi 2 S 3 ), Mo from molybdenite (MoS 2 ), Ca and W from scheelite (CaWO 4 ), Fe, Mn, and W from ferberite ((Fe,Mn)WO 4 ), Fe and Cr from chromite (FeCr 2 O 4 ), Mg and Cr from magnesiochromite (MgCr 2 O 4 ), Fe and Ni from pentlandite ((Fe,Ni) 9 S 8 ), Fe and Ni from linnaeite (Co 3 S 4) Co can be recovered as a purified product from it. Fe 2 O 3 (s) → Fe(s: powder) → Fe(s: agglomerate) ··· (8) CuS(s) → Cu(s: powder) → Cu(s: agglomerate) ··· (9)

[0049] <<Recovery Route 4 (Gravity Separation)>> When using urban ores such as electronic devices, automotive exhaust gas purification devices, and anode slime as metal resources, Au (metal), Ru (metal), Rh (metal), Pd (metal), Os (metal), Ir (metal), and Pt (metal) are recovered as purified products by following the recovery routes of the following chemical formulas (10) to (12) inside a dry refining device, melting, and coarsening.

[0050] As an example, the recovery route of Au(s) will be described in detail using chemical formula (10). First, when pulsed discharge is irradiated onto Au(s) as a metal resource, a part of Au(s) melts, and the melted parts adhere to each other and coarsen to form agglomerated Au(s: agglomerate). In the flowing metal resource, it is separated by gravity and recovered at the bottom of the furnace. Au(s) → Au(s: agglomerate) ··· (10)

[0051] Similarly, when using metal resources containing Pt(s) and Pd(s) as raw materials, they are also agglomerated and separated by gravity as shown in the following chemical formulas (11) and (12) and recovered as purified products. Pt(s) → Pt(s: agglomerate) ··· (11) Pd(s) → Pd(s: agglomerate) ··· (12)

[0052] As described above, by passing through the first to fourth steps of the present invention, it is possible to efficiently recover a desired metal from various metal resources and realize a dry refining method of metal resources with a small environmental load. In particular, even with a small energy input, it is possible to easily concentrate and recover precious metals to a certain concentration from a mixture containing trace amounts of precious metals, such as ores mined from mines, used electronic components, and anode slime, which is advantageous compared to conventional methods. Furthermore, the method of the present invention is also useful in that it can suppress the generation amount of exhaust gas and surplus heat not involved in the reaction.

[0053] The dry refining method described so far can be carried out using the vertical reduction furnace described in FIG. 1, but the apparatus mode may be appropriately changed to correspond to each mode of the dry refining method.

[0054] For example, in addition to the above-described configuration for purifying metal resources, the dry refining apparatus may have a heat exchanger for heating the inflowing gas, a heating unit for heating the tubular furnace, a recovery unit for recovering the refined product, a purification unit for purifying the exhaust gas, and the like.

[0055] The recovery unit that can be provided in the dry refining apparatus may be, for example, a dust collector, and the purification unit may be, for example, activated carbon. One or more catalysts for converting carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NO X ) and the like in the by-product gas generated by dry refining into harmless substances may be provided.

Example

[0056] Hereinafter, the dry refining method of metal according to the present invention will be described in detail using examples.

[0057] (Example 1) In Example 1, refining was carried out using a vertical dry refining apparatus having the same configuration as that shown in FIG. 1, and a quartz tube was used for the furnace. First, city gas was introduced into the gas inlet of the furnace at a flow rate of 0.03 L / min. Next, waste LEDs were stored in the furnace as a metal resource containing Ga. Then, the city gas flowing in from the gas inlet was ignited to obtain combustion gas.

[0058] Next, following ignition of the town gas, using the pulse discharge unit, with a frequency of 250 Hz and a voltage of 13 kV, the main discharge path of the generated pulse discharge was arranged to pass through the center of the stored metal resources (waste LEDs), and pulse discharge was performed for 10 minutes. Then, after waiting for the entire apparatus to cool sufficiently, the deposits adhering to the inner wall of the furnace were collected, and the purified product according to Example 1 was recovered.

[0059] (Example 2) In Example 2, dry refining was carried out under the same conditions as in Example 1, except that the frequency of the pulse discharge was 120 Hz and the voltage was 32 kV, and the purified product according to Example 2 was recovered. Here, the reason for setting the frequency of the pulse discharge to 120 Hz and the voltage to 32 kV is to make the energy applied to the entire system equivalent to the conditions of Example 1 with different frequency conditions.

[0060] For the purified products recovered in Examples 1 and 2, the recovery amount and composition were analyzed by high-frequency inductively coupled plasma atomic emission spectrometry (ICP-AES) by dividing them into the lower, middle, and upper parts of the inner wall of the furnace. The external appearances of the furnaces after recovering the purified products of Examples 1 and 2 are shown in FIGS. 2(a) and (b), respectively, and the conditions of dry refining and the analysis results of the recovered purified products are shown in Table 1. [Table 1]

[0061] From the results of Examples 1 and 2, it was found that in the dry refining method using pulse discharge, even when the input energy is the same, more purified products can be recovered when the frequency of the pulse discharge is higher. This is presumably because reduction and the like for generating the purified product occur the number of discharge times at the location where the pulse discharge occurs. Also, from the external appearance of the furnace after recovering the purified product in FIG. 2, it was found that the amount of the recovered purified product differs depending on the location of the furnace (lower part, center, upper part), and this result also agrees with the result of the recovery amount in Table 1. Further, from the analysis results for each element of Ga, Ag, and Zn, it was found that the purified product can be obtained with different element mixing ratios between the upstream side and the downstream side.

[0062] (Example 3) In Example 3, dry refining was carried out under the same conditions as in Example 1 except that the frequency of the pulsed discharge was set to 150 Hz, and the refined product according to Example 3 was recovered.

[0063] (Example 4) In Example 4, dry refining was carried out under the same conditions as in Example 1 except that the frequency of the pulsed discharge was set to 100 Hz, and the refined product according to Example 4 was recovered.

[0064] Table 2 shows the conditions of dry refining in Examples 1, 3, and 4 and the recovery amount of Ga among the recovered refined products. For the recovered refined products, compositional analysis was carried out using high-frequency inductively coupled plasma optical emission spectrometry (ICP-AES) by dividing them into the lower, middle, and upper parts of the inner wall of the furnace, and the recovery amount of the Ga component was measured. In addition, the temperature of the metal resources during pulsed discharge was measured, and the maximum value, minimum value, and average value were obtained respectively. For the temperature measurement, the temperature in the region where pulsed discharge occurred was measured with a modified radiation thermometer, and a value of ε = 0.9 was used for the emissivity. For comparison, Example 1 is also reproduced and the evaluation results are described.

[0065]

Table 2

[0066] From the results in Table 2, it was found that the higher the frequency, the larger the recovery amount of Ga. Especially in the lower part, the recovery amount of Ga in Example 1 (250 Hz) was about 30 times that in Example 4 (100 Hz).

[0067] (Example 5) Next, in Example 5, as the metal resource, a power semiconductor containing GaN was stored in the furnace, and the time of pulsed discharge was set to 30 minutes. Otherwise, dry refining was carried out in the same manner as in Example 1, and the refined product according to Example 5 was recovered.

[0068] (Comparative Example 1) In Comparative Example 1, the same power semiconductor as that used in Example 5 was used as the metal resource. However, dry refining was performed using a fluidized bed reduction furnace as a conventional method, and the refined product according to Comparative Example 1 was recovered. The dry refining method by this conventional method is a method of heating the metal resource with a heater outside the furnace without using pulse discharge.

[0069] Table 3 shows the conditions of dry refining and the composition of the recovered refined products in Example 5 and Comparative Example 1. In addition, the X-ray photoelectron spectroscopy (XPS) of Example 5 and Comparative Example 1 are shown in FIGS. 3 and 4, respectively.

[0070]

Table 3

[0071] From the comparison between Example 5 and Comparative Example 1 in Table 3, when the power semiconductor was used as the metal resource, in the conventional reduction fluidized bed method, although peaks indicating the Pb component could be confirmed as shown in FIG. 4, no significant peak indicating the Ga component could be confirmed. However, in the method using pulse discharge, a peak derived from Ga was observed as shown in FIG. 3, and it was found that Ga could be recovered. This is considered to be because the power semiconductor has a layer containing Ga inside the component, and the Ga component is exposed to the outside for the first time by a method involving physical destruction such as pulse discharge, and separation by vaporization or the like proceeds. 2 O 3 Next, in Examples 6 to 9, powdered tin oxide was used as the metal resource, and dry refining by pulse discharge was carried out. The dry refining apparatus used was the same as that used in Example 1.

[0072] Next, in Examples 6 to 9, powdered tin oxide was used as the metal resource, and dry refining by pulse discharge was performed. The dry refining apparatus used was the same as that used in Example 1.

[0073] (Example 6) First, in Example 6, the frequency of the pulse discharge unit was set to 150 Hz and the voltage was set to 22.1 kV. The main discharge path of the generated pulse discharge was arranged to pass through the center of the stored metal resource (tin oxide), and pulse discharge was intermittently performed for 10 minutes. At that time, the temperature around the discharge part was measured with a radiation thermometer. Otherwise, dry refining was carried out in the same manner as in Example 1, and the refined product according to Example 6 was recovered.

[0074] (Example 7) In Example 7, refining and temperature measurement were carried out under the same conditions as in Example 6, except that the pulse discharge time was set to 15 minutes, and the refined product according to Example 7 was recovered.

[0075] (Example 8) In Example 8, refining and temperature measurement were carried out under the same conditions as in Example 6, except that the pulse discharge time was set to 20 minutes, and the refined product according to Example 8 was recovered.

[0076] (Example 9) In Example 9, refining and temperature measurement were carried out under the same conditions as in Example 6, except that the pulse discharge time was set to 30 minutes, and the refined product according to Example 9 was recovered.

[0077] (Comparative Example 2) In Comparative Example 2, while using the same tin oxide as the metal resource used in Examples 6 to 9, dry refining of the furnace temperature was carried out using a fluidized bed reduction furnace according to the conventional method, and the refined product according to Comparative Example 2 was recovered. Note that, as described in Comparative Example 1, this dry refining method according to the conventional method is a method of heating the metal resource with a heater outside the furnace without using pulse discharge.

[0078] The dry refining conditions and evaluation results of Examples 6 to 9 and Comparative Example 2 are shown together in Table 4. Also, the profiles during X-ray diffraction (XRD) measurement of the refined product masses according to Examples 6 to 9 are shown in FIG. 5, and the profile of Comparative Example 2 is shown in FIG. 6, respectively.

[0079]

Table 4

[0080] From the results of Table 4 and FIGS. 5 and 6, it was found that tin oxide was not reduced to tin (Sn) by the conventional reduction fluidized bed method, while in the refining method using a reduction fluidized bed by pulse discharge, tin metal could be recovered in both cases. Further, from the results of FIG. 5, it was found that the peak of elemental Sn became sharper as the discharge time was longer, and the Sn particles were coarsened by the fluidized bed.

Industrial Applicability

[0081] According to the present invention, it is possible to provide a dry refining method for efficiently recovering a desired metal from a metal resource and having a small environmental load, and a dry refining apparatus using the method.

Explanation of Symbols

[0082] 100 Dry refining apparatus 10 Gas inlet 20 Gas outlet 30 Furnace 35 Lid 40 Metal resource 50 Combustion device 80 Pulse discharge unit 81 Upper electrode 82 Lower electrode

Claims

1. A first step of storing a metal resource containing a metal compound in a furnace having a gas inlet and a gas outlet; A second step of flowing combustion gas into the gas inlet and exhausting the combustion gas from the gas outlet to maintain a reducing atmosphere inside the furnace; A third step of intermittently irradiating the metal resource with pulsed discharge in the reducing atmosphere; A fourth step of recovering the metal compound decomposed in the third step as a purified product, and A dry refining method of a metal resource, wherein in the third step, the pulsed discharge is performed along the flow direction of the combustion gas.

2. The dry refining method according to claim 1, wherein the combustion gas is generated by combustion of a gas containing a hydrocarbon gas and / or hydrogen.

3. The dry refining method according to claim 1, wherein in the fourth step, the purified product is obtained with different element mixing ratios on the upstream side and the downstream side in the flow direction of the combustion gas.

4. The dry refining method according to claim 1, wherein in the third step, the temperature on the gas inlet side in the furnace is 100 °C or more lower than the melting point of the purified product.

5. The dry refining method according to claim 1, wherein the frequency of the pulsed discharge is 50 Hz or more.

6. The dry refining method according to claim 1, wherein the furnace is a vertical tubular furnace.

7. The dry refining method of a metal resource according to claim 1, wherein the metal resource is urban ore.

8. The dry refining method according to claim 1, wherein the metal resource is powdered ore.

9. The purified product recovered in the fourth step is in particulate form, and The dry refining method according to claim 1, wherein the furnace is a vertical tubular furnace, and the purified product accumulates at the lower part of the furnace.

10. A dry refining apparatus comprising: a furnace having a gas inlet and a gas outlet and storing a metal resource containing a metal compound; A combustion device located upstream of the gas inlet and flowing combustion gas into the furnace from the gas inlet; An electrode inserted into the gas inlet and an electrode installed on the side of the gas outlet, and a pulsed discharge unit in which the path between the downstream side of the electrode inserted into the gas inlet and the upstream side of the electrode installed on the side of the gas outlet is along the central axis direction of the furnace. ​

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