JP4984123B2 - Method for recovering gold or platinum group elements from SiC-based materials - Google Patents

Description

  The present invention relates to a method for recovering gold or platinum group elements contained in a form such as supported from a SiC-based material such as waste of an exhaust gas purification catalyst.

Recently, an exhaust gas purification system using a catalyst using SiC as a carrier (substrate) material for a gold or platinum group element has been put into practical use. Since SiC is excellent in heat resistance, it is expected to improve the performance and durability of the catalyst, especially when used as a carrier material for PM combustion catalysts in diesel engine exhaust gas. Although various methods have been proposed for recovering the gold or platinum group element contained therein from the catalyst waste of SiC, SiC has a melting point of 2700 ° C. or higher and is chemically inert. In view of this, an appropriate recovery method has not yet been developed.
Japanese Patent Laid-Open No. 06-182214 JP-A-10-076162 JP 2001-349111 A JP 2003-262118 A

Furthermore, there is a problem that SiC is difficult to dissolve in the molten slag of the dry process. According to the experiments by the present inventors, when the SiC-based material was put alone into the molten slag in the electric furnace, the SiC-based material remained solid on the surface of the molten slag, and the SiC-based material was forcibly removed from the molten slag. Unless the operation of immersing in is performed, it is difficult to completely dissolve in the molten slag. Further, even if dissolved, unreacted SiC may remain in the slag, and this makes it impossible to treat the SiC-based material such as a waste catalyst and recover the contained gold or platinum group elements. Therefore, there is an urgent need to establish a method for treating used materials of exhaust gas purification catalysts using SiC, which is expected to be used in the future, as a carrier (substrate) substance and recovering contained gold or platinum group elements. It has become.
In view of such a current situation, the present invention intends to provide a method for recovering gold or platinum group elements contained in SiC-based materials.

  In order to recover the gold or platinum group element contained by treating the SiC-based material, SiC is decomposed into a molten slag component, and the gold or platinum group element contained in the SiC-based material is contained in the metallic copper. It is effective to transfer, and in this case, it is more effective to recover the copper content that has been oxidized and transferred to the slag. As a result of various studies based on these findings, the inventors have found the following invention.

  That is, according to the present invention, first, in a method for recovering a gold or platinum group element from an SiC type material containing gold or a platinum group element, the SiC type material is oxidized in a first furnace together with metallic copper, and Si A first step of separating a molten oxide layer containing an oxide and a copper oxide and a molten residual metal copper layer containing the gold or platinum group element, the separated oxide (molten oxide layer) A second step of reducing in a furnace to separate a new molten metal copper layer and a molten residual oxide layer, and the new metal copper (new molten metal copper layer) is the metal of the first step A method for recovering gold or platinum group elements comprising a third step repeated as a part or all of copper; and second, the gold or platinum group elements from a SiC-based material containing gold or platinum group elements. In the recovery method, the SiC-based material is Oxidation treatment in the first furnace together with molten metal copper, a molten oxide layer mainly composed of Si oxide and copper oxide as the upper molten layer in the furnace, and the gold or platinum as the lower molten layer in the furnace A first step of recovering the gold or platinum group element in the molten residual metal copper layer by forming and separating a molten residual metal copper layer containing a group element, the separated oxide (molten oxide) A second step in which a new molten metal copper layer is formed as a lower molten layer in the furnace, and a molten residual oxide layer is formed as an upper molten layer in the furnace. And a third step of recovering the gold or platinum group element comprising repeating the new molten metal copper (layer) as a part or all of the molten metal copper in the first step; The molten oxide layer contains the unreacted SiC-based material. The collection method according to 1 or 2; fourth, the mass ratio of the SiC-based material charged into the first furnace / the metallic copper is 0.65 or less. Recovery method; Fifth, the oxidation treatment is performed by introducing oxygen gas or an oxygen-containing gas into the first furnace. Sixth, the oxidation treatment includes The recovery method according to any one of 1 to 5 above, wherein the temperature in the first furnace is maintained at 1100 to 1600 ° C .; seventh, the SiC-based material charged into the first furnace is 5 mm The recovery method according to any one of 1 to 6 above, which has a particle size that passes through a sieve of eyes; The recovery method according to any one of 1 to 7 above, which is a product; The molten oxide layer is discharged from the first furnace and then brought into contact with water to form powder, and the obtained oxide powder is used as the oxide in the second step. A recovery method according to any one of the above is provided.

According to the present invention, the heat energy cost is reduced by the heat generated by the oxidative decomposition of SiC, which is the main component of the raw material to be treated, and the initial heat of oxidation of the molten metal copper in the first furnace. Is burned and discharged as exhaust gas, and Si oxide (SiO ₂ ) generated by oxidizing the Si content of SiC is a flux component, so no new flux is required and the molten oxide layer The amount of generated (also referred to as slag) is reduced, which is advantageous in terms of operation. In addition, gold or platinum group elements contained in the SiC-based material can be efficiently recovered in the molten residual metal copper layer with a high recovery rate.
Further, in the second furnace, the copper content that has been oxidized in the first furnace and transferred into the slag (molten oxide layer) is recovered as new metallic copper by reduction and repeated to the first step. Metal copper can be used repeatedly without any loss, and unreacted SiC mixed in the slag without being oxidized in the first furnace acts as a reducing agent in the second furnace of the second step and is oxidatively decomposed. At the same time, the gold or platinum group element contained in the unreacted SiC is transferred to the new molten metal copper and subsequently used repeatedly in the first step to recover the gold or platinum group element. As a result, the throughput of SiC can be increased.

  The platinum group element in the present invention represents six elements of ruthenium Ru, rhodium Rh, palladium Pd, osmium Os, iridium Ir, and platinum Pt belonging to Group VIII of the periodic table of elements. In the present specification, gold and this platinum group element are sometimes collectively referred to as noble metals.

  In the present invention, the “SiC-based material (containing gold or platinum group element)” is a general term for substances mainly containing SiC (containing various forms such as supporting gold or platinum group element) Preferably, it is a SiC-based material containing SiC in excess of 50% by mass, and may contain other additive substances, PM (particulate matter in exhaust gas from diesel engines), and the like. Examples of the SiC-based material include waste of the exhaust gas purification catalyst of the diesel engine, and electronic component waste.

  The (molten) metallic copper initially used in the first step in the present invention is not limited in purity, and of course, even if it contains gold or platinum group elements, it further contains impurity elements such as iron and chromium. However, it can be used without any inconvenience (in Examples 1 and 2 described later, metallic copper having a purity of substantially 100% by mass was used).

When a converter or rotary furnace is used as the first furnace (sometimes referred to as an oxidation furnace) in the first step of the present invention, the SiC-based material and molten metal copper are contacted and mixed by tilting or rotating as necessary. And can be oxidized by blowing oxygen gas or oxygen-containing gas over the surface with a lance, and further, the molten oxide layer is first extracted by tilting after the oxidation treatment, and then Since the molten residual metal copper layer can be extracted, both layers can be easily separated.
Further, by directly blowing oxygen gas or oxygen-containing gas into the solution in the furnace, stirring of the solution can be promoted, and the oxidation rate of SiC can be increased.
Since the molten oxide after the oxidation treatment has a specific gravity smaller than that of the molten residual metal copper, the mixed melt (liquid phase) of the molten oxide and the molten residual metal copper after the oxidation treatment is allowed to stand in a furnace. The molten oxide becomes an upper layer and the molten residual copper becomes a lower layer and is easily separated from each other.

In addition, in order to oxidize the SiC-based material in the first step, it is also important to control the mixing ratio of the SiC-based material according to the amount of metallic copper initially charged. When the mass ratio of SiC-based material / metal copper charged in the furnace is 0.45 or less, the charged SiC-based material is all oxidized in the first step, but the mass ratio is 0 If it exceeds .45, the charged SiC-based material cannot be completely oxidized in the first step, and unreacted SiC-based material remains and is mixed in the molten oxide layer and brought into the second step. . The unreacted SiC-based material brought in here acts as a reducing agent for the oxide and is oxidatively decomposed in the second step. However, in order to oxidatively decompose the entire amount, the mass ratio is 0.65 or less. It is necessary to be. Therefore, it is preferable that the mass ratio of the SiC-based material / metal copper charged in the first furnace in the first step is more than 0.45 and not more than 0.65.
In addition, in order to transfer gold or platinum group elements to the molten (residual) metal copper layer, it is necessary to end the operation of the oxidation treatment in the first step without oxidizing part of the original molten metal copper. The amount of remaining molten metal copper is preferably 20% by mass or more, more preferably 30 to 50% by mass of the initial amount of molten metal copper.

  The first furnace temperature during the oxidation treatment in the first step is preferably 1100 to 1600 ° C. If it is less than 1100 ° C., the oxidation rate is low, and it becomes difficult to separate the molten phase into an upper layer and a lower layer. On the other hand, if the temperature exceeds 1600 ° C., the refractory in the furnace is damaged, which is not preferable. The furnace temperature is more preferably 1300-1500 ° C.

In order to promote the oxidation treatment reaction in the first step, it is preferable that the SiC-based material charged in the furnace has a particle size that passes through a 5 mm sieve, and the oxidation rate decreases when the particle size exceeds 5 mm. .
In addition, the SiC-based material may be crushed before being charged into the furnace to generate fine particles. In this case, the fine particles are moved out of the furnace by blowing oxygen-containing gas into the furnace (oxidation treatment). Although there is a possibility of scattering, it is possible to prevent scattering by granulating the SiC-based material (or its fine particles) within the range of the particle size passing through the 5 mm sieve.

  The oxygen-containing gas in the first step is not particularly limited in terms of oxygen concentration, but an oxygen-containing gas having an oxygen concentration of 40% or more is preferable from the viewpoint of improving the oxidation treatment rate.

  The molten oxide (slag) layer generated in the first step of the present invention is formed by the Si oxide generated by the oxidation of the SiC-based material and the copper oxide generated by the partial oxidation of the metallic copper. Correspondingly, a small amount of fluxes such as Si oxides such as silica, Ca oxides such as lime, F compounds such as fluorite, Al oxides, Fe oxides, Na oxides, improve slag fluidity, Alternatively, the operating slag temperature can be lowered to form a better slag.

  From the molten residual metal copper layer containing the gold or platinum group element obtained in the first step of the present invention, the gold or platinum group element is further fractionated and recovered by a known method such as various melting methods or electrolytic methods. be able to. The copper metal after the gold or platinum group element is separated and recovered can be used as the (original) metallic copper in the first step. In addition, when the copper content after separately collecting the gold or platinum group element is in the form of copper oxide, it is reduced in the second furnace as the oxide of the second step and recovered as new metallic copper, It can be used as one-step metallic copper.

  An electric furnace can be used as the second furnace in the second step (the second furnace may be referred to as an electric furnace). The molten oxide discharged from the first furnace is once cooled and stocked as a solid material is collected, charged into an electric furnace, and melted and reduced by adding a reducing agent and flux as necessary. Since the unreacted SiC-based material brought in mixed with the molten oxide from the first step acts as a reducing agent in the second step and is oxidatively decomposed, in the second furnace, a deficient amount is reduced as necessary. What is necessary is just to add an agent. In the second step, as in the case of the first step, Si oxide such as silica, Ca oxide such as lime, F compound such as fluorite, Al oxide, Fe oxide, It is also possible to add a small amount of flux such as Na oxide to improve the slag fluidity or lower the operation slag temperature to form a better slag.

  When the molten oxide discharged from the first furnace is brought into contact with a large amount of water to form a granular material (that is, granulated), unreacted SiC brought into the molten oxide. Since the system substance is exposed on the surface of the fine particles of the granular material, the reactivity as the reducing agent is significantly accelerated in the second furnace.

In the second step, the copper oxide in the oxide is reduced to metallic copper by melting reduction in an electric furnace and accumulated as molten copper at the bottom of the furnace, and the gold or platinum group element partially remaining in the oxide, and Any gold or platinum group element liberated by oxidative decomposition of the unreacted SiC-based material is transferred into the molten copper pool.
By this smelting reduction in the electric furnace, most of the copper oxide in the oxide can be recovered as metallic copper, and this can be repeated in the first step and reused as metallic copper in the previous first furnace. . In this case, if (new) molten metal copper obtained in the electric furnace is charged into the first furnace as it is, the thermal energy can be greatly reduced. On the other hand, the slag discharged from the electric furnace (residual oxide) no longer contains any gold or platinum group elements, and contains almost no other useful components such as copper, so its economic value is low. Can be sent to disposal.

  On the other hand, as a method of further concentrating the gold or platinum group element from the molten metal (molten residual metal copper) obtained in the first furnace, it is advantageous to adopt the melt oxidation treatment again. In this case, the same first furnace can be used, but another oxidation furnace may be used. As a result, in the furnace, metal copper obtained by further concentrating noble metals such as gold or platinum group elements and copper oxide containing almost no noble metal are obtained in a state of being phase-separated in a molten state. By separating, metallic copper further enriched with noble metals such as gold or platinum group elements can be obtained. Moreover, the copper oxide produced | generated here can be reduce | restored to metallic copper by using for the charging raw material to the said electric furnace (2nd furnace), and can be repeated to a 1st process.

  Examples of the present invention will be described below, but it goes without saying that the technical scope of the present invention is not limited to this description.

  [Example 1] A SiC-based material containing 95% by mass of SiC in which three kinds of noble metals Pt, Pd, and Au were supported on a honeycomb-shaped SiC substrate was used. The precious metal content (% by mass) in this SiC-based material is shown in Table 1 below. First, as shown in Table 2, 501 kg of molten copper and 198 kg of the SiC material passing through a 5 mm sieve obtained by granulation after crushing were charged into a converter as an oxidation furnace. After charging, oxygen enriched air having an oxygen content of 40% is blown from the surface of the charge as an oxygen-containing gas by a lance in the converter, and the charge temperature is maintained at 1400 to 1450 ° C. Blowing (oxidation treatment) was terminated when the amount of the metal was reduced to about half, and then allowed to stand to separate into two layers, a molten oxide layer on the upper side and a molten metal (residual metal copper) layer on the lower side. The converter was tilted, and the upper molten oxide layer was put into a water tank in which a large amount of water flowed to be granulated (that is, granulated), and then dried. The molten metal (residual metal copper) was left in the furnace. Table 3 shows the weight, precious metal content, content, distribution rate, and the like before and after the oxidation treatment. The total amount of the oxide obtained by water granulation and drying was reduced and melted at 1400 ° C. in an electric furnace together with lime of flux and coke of reducing agent to obtain 250 kg of (new) metallic copper. Table 3 shows the respective weights before and after the reduction treatment, the precious metal content, the content, the distribution rate, and the like.

  [Example 2] In the same manner as in Example 1, the SiC-based materials shown in Table 1 were used. As shown in Tables 2 and 4, 502 kg of molten copper and 302 kg of the SiC material passing through a 5 mm sieve obtained by granulation after crushing were charged into a converter as an oxidation furnace. After charging, oxygen enriched air having an oxygen content of 40% is blown from the surface of the charge as an oxygen-containing gas by a lance in the converter, and the charge temperature is maintained at 1400 to 1450 ° C. Blowing (oxidation treatment) was completed when the amount of the metal was reduced to about half, and then allowed to stand to separate into two layers, a molten oxide layer on the top and a molten metal (residual metal copper) layer on the bottom. The physical layer contained unreacted SiC-based material, and the precious metal content in the upper layer was higher than that in Example 1. This is because the unreacted SiC-based material remains because the mass ratio of the SiC-based material / metal copper at the time of charging into the oxidation furnace (first furnace) was 0.6. This molten oxide layer was subjected to water granulation in the same manner as in Example 1, dried, and the entire amount was charged together with the flux into an electric furnace and reduced and melted to obtain 270 kg of (new) metallic copper. The unreacted remaining SiC-based material acted as a reducing agent and was consumed, and the contained noble metal was recovered in the (new) copper metal. Table 4 shows the weight, precious metal content, content, distribution rate, etc. of each of the above.

  As described above, platinum group elements (Pt, Pd) and gold in the SiC-based material are 99.87%, 99.69%, 99.27% in Example 1, and 99.25% in Example 2, respectively. It can be recovered by being transferred to molten metal copper at a high yield and high concentration of 98.81% and 98.47%, and the copper oxide generated in the oxidation reaction of the oxidation furnace (first furnace) It can be seen that almost the entire amount is reduced in the furnace (reduction furnace, second furnace), regenerated to (new) copper, and can be used repeatedly in the first furnace.

Claims (9)

  In the method for recovering the gold or platinum group element from the SiC-based material containing gold or platinum group element, the SiC-based material is oxidized together with metallic copper in the first furnace, and contains Si oxide and copper oxide. A first step of separating the molten oxide layer into a molten residual metal copper layer containing the gold or platinum group element, and a new molten metal copper layer by reducing the separated oxide in a second furnace A gold or platinum group comprising: a second step of separating the molten copper into a molten residual oxide layer; and a third step of repeating the new metallic copper as part or all of the metallic copper in the first step Element recovery method.   In the method for recovering the gold or platinum group element from the SiC-based material containing gold or platinum group element, the SiC-based material is oxidized in the first furnace together with the molten metal copper to form an upper molten layer in the furnace. The molten oxide layer mainly composed of Si oxide and copper oxide is separated by forming a molten residual metal copper layer containing the gold or platinum group element as a lower molten layer in the furnace. A first step of recovering the gold or platinum group element in the residual metal copper layer, the separated oxide is reduced in a second furnace, and a new molten metal copper layer is formed as a lower molten layer in the furnace. A second step of forming and separating a molten residual oxide layer as an upper molten layer in the furnace, and a third step of repeating the new molten metal copper as part or all of the molten metal copper in the first step Gold or white characterized by comprising a process Recovery method of family element.   The recovery method according to claim 1 or 2, wherein the molten oxide layer contains the unreacted SiC-based material.   The recovery method according to any one of claims 1 to 3, wherein a mass ratio of the SiC-based material / the metallic copper charged in the first furnace is 0.65 or less.   The recovery method according to claim 1, wherein the oxidation treatment is performed by introducing oxygen gas or oxygen-containing gas into the first furnace.   The said oxidation process is a collection | recovery method in any one of Claims 1-5 performed by maintaining the temperature in a said 1st furnace at 1100-1600 degreeC.   The recovery method according to claim 1, wherein the SiC-based material charged into the first furnace has a particle size that passes through a 5 mm sieve.   The recovery method according to any one of claims 1 to 7, wherein the SiC-based material is exhaust gas purification catalyst waste mainly composed of SiC supporting gold or a platinum group element.   The molten oxide layer in the first step is discharged from the first furnace and then brought into contact with water to form powder, and the obtained oxide powder is used as the oxide in the second step. The collection method according to any one of claims 1 to 8.