A method for recovering platinum group metals from waste automobile exhaust catalyst by pyrometallurgical method and platinum group metal powder

Abstract

The present invention belongs to the field of rare and precious metal smelting, and discloses a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgy and platinum group metal powder. The method comprises the following steps: crushing the waste automobile exhaust catalyst to obtain catalyst powder; uniformly mixing the catalyst powder, a collector and a slag-making agent to obtain a mixture; smelting the mixture at high temperature to obtain a molten liquid; introducing a mixed gas of hydrogen and magnesium vapor into the molten liquid to obtain a reduction desulfurization molten liquid and quenching the molten liquid with water to obtain cement clinker and an iron alloy containing platinum group metals; atomizing and powdering the iron alloy containing platinum group metals to obtain an atomized alloy powder, acid leaching, filtering and drying to obtain platinum group metal powder. The present invention uses magnesium vapor for desulfurization, and after the reaction is completed, the S element enters the cement clinker, so the S element content in the finally obtained platinum group metal powder is extremely low.

Description

Technical Field

[0001] The invention belongs to the field of rare and precious metal smelting, and more specifically, relates to a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method and platinum group metal powder. Background Art

[0002] Platinum group metals have excellent characteristics such as high melting point, strong stability, and good catalytic activity. They are widely used in the automotive industry, precision electronics, aerospace, jewelry and other fields. They are known as "industrial vitamins", "strategic reserve metals", "the first high-tech metals" and "environmentally friendly metals". The average grade of platinum group metal deposits in my country is 0.796g / t, which is only 10% to 20% of that in foreign countries. In addition, most of my country's platinum group metal deposits are concentrated in paragenetic or associated ores, which makes smelting difficult. Waste automobile exhaust catalysts are the most important secondary resource source of platinum group metals. More than 60% of the world's platinum group metals (mainly Pt, Pd and Rh, called PGMs) are used in automobile exhaust catalysts to catalyze the conversion of HC, CO and NOx into H 2 O、CO 2 and N 2 , reducing environmental pollution. At present, there is a large demand for platinum and palladium in automobile catalysts. The grade of PGMs in waste automobile exhaust catalysts is as high as 1000-3000g / t, which is much higher than the average grade of platinum group metal ores of 0.796g / t.

[0003] At present, the recovery processes of PGMs in waste automobile exhaust catalysts mainly include pyrolysis, hydrolysis and biological methods.

[0004] The biological method relies on the metabolism of microorganisms to achieve the enrichment of PGMs. The cultivation and reproduction conditions of microorganisms are harsh, resulting in poor adaptability and low efficiency of biological raw materials.

[0005] The current research direction is mainly focused on the pyrometallurgical method and the hydrometallurgical method. 2 O 3 Often transformed into α-Al 2 O 3 , wrapping the precious metal components, resulting in a low leaching rate of PGMs in the process of using the active component dissolution method. In the process of using the carrier dissolution method, the precious metals will inevitably be dissolved into the solution, reducing the recovery rate of PGMs. The purification and separation efficiency of the precious metal ion solution in the full dissolution method is low and the operation is difficult. At the same time, a large amount of waste liquid will be generated during the wet leaching process.

[0006] The metal capture method is the mainstream method for foreign companies to recover PGMs. It uses the principle that Fe, Pb, Cu, Bi, matte, etc. have similar crystal structures to Pt, Pd and Rh to capture PGMs. When Cu is used as a capture agent, refining is required in the later stage to obtain PGMs, which is costly and complex. The Rh recovery rate is not high when Pb is used as a capture agent, and lead is easy to volatilize during the capture process. When matte is used as a capture agent, PGMs are obtained after the matte phase is blown, which is only suitable for large-scale copper-nickel smelting companies with matte blowing capabilities. Fe is the cheapest and most readily available capture agent. The existing methods using Fe as a capture agent basically use coke as a reducing agent, mainly solid-solid reaction, and the reaction rate is low, resulting in low capture efficiency. In addition, excessive attention is paid to the yield of precious metals in the capture process, and the regulation of impurity elements is ignored, resulting in a high content of impurity S elements in Fe-PGMs alloys, and PGMs cannot be directly recovered by processes such as acid leaching or electrolysis.

[0007] Therefore, it is urgent to propose a new method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method and platinum group metal powder. Summary of the invention

[0008] The purpose of the present invention is to address the deficiencies of the prior art and to provide a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgy and platinum group metal powder. The present invention uses magnesium vapor for desulfurization, and after the reaction is completed, the S element enters the cement clinker, so the S element content in the platinum group metal powder finally obtained is extremely low.

[0009] In order to achieve the above object, the present invention provides a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method, which comprises the following steps:

[0010] S1: crushing the waste automobile exhaust catalyst to obtain catalyst powder;

[0011] S2: uniformly mixing the catalyst powder, the collector and the slag-forming agent to obtain a mixture; and smelting the mixture at a high temperature to obtain a molten liquid;

[0012] S3: introducing a mixed gas of hydrogen and magnesium vapor into the molten liquid to obtain a reduced desulfurized molten liquid and quenching the molten liquid with water to obtain cement clinker and an iron alloy containing platinum group metals;

[0013] S4: atomizing the ferroalloy containing platinum group metals to obtain atomized alloy powder, and performing acid leaching, filtering and drying to obtain platinum group metal powder.

[0014] According to the present invention, preferably, the waste automobile exhaust catalyst is Al 2 O 3 Supported catalyst, SiO 2 Supported catalyst and Al 2 O3 -SiO 2 At least one of the supported catalysts.

[0015] According to the present invention, preferably, the equipment for the crushing process comprises a high-energy ball mill, and the material-ball ratio is (4-6):1.

[0016] According to the present invention, preferably, the particle size of the catalyst powder is less than 500 μm.

[0017] According to the present invention, preferably, the mass ratio of the catalyst powder to the collector is 100:(4-20); the collector is FeO, Fe 2 O 3 and Fe 3 O 4 At least one of .

[0018] According to the present invention, preferably, the slag-making agent is CaO, Na 2 O and K 2 O, the slag-making agent and the catalyst powder form Na 2 O / K 2 O-CaO-Al 2 O 3 、Na 2 O / K 2 O-CaO-SiO 2 and Na 2 O / K 2 O-CaO-Al 2 O 3 -SiO 2 At least one of the slag systems, and at least one of the following conditions is met: (1) the CaO / Al 2 O 3 =0.8-1.2; (2) CaO / SiO in slag system 2 =0.3-0.6; (3) Na in slag system 2 O and / or K 2 O accounts for 1-10% of the total weight of the slag system.

[0019] According to the present invention, preferably, the smelting temperature of the high temperature smelting is 1200-1500° C., and the equipment for the high temperature smelting includes a medium frequency induction furnace.

[0020] According to the present invention, preferably, the time for introducing the mixed gas of hydrogen and magnesium vapor into the molten liquid is 10-60 minutes, and the injection amount of magnesium vapor in the mixed gas is 1.5-2 times the sulfur content in the molten liquid.

[0021] In the present invention, as a preferred embodiment, Figure 2As shown in the figure, magnesium metal generates magnesium vapor in the magnesium vapor generating chamber. The magnesium vapor is composed of H 2 The bottom blowing is carried out into the molten pool containing the molten liquid to carry out the reduction and desulfurization process.

[0022] According to the present invention, preferably, the sulfur content in the ferroalloy containing platinum group metals is less than 0.005%.

[0023] According to the present invention, preferably, the particle size of the atomized alloy powder is 50-800 μm.

[0024] According to the present invention, preferably, the acid leaching solution is a hydrochloric acid solution with a concentration of 0.5-4 mol / L, an acid leaching temperature of 30-50° C., and an acid leaching time of 1-20 min.

[0025] Another aspect of the present invention provides platinum group metal powder obtained by the method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method.

[0026] The beneficial effects of the technical solution of the present invention are as follows:

[0027] 1) The present invention uses magnesium vapor for desulfurization, and after the reaction is completed, the S element enters the cement clinker, so the S element content in the final platinum group metal powder is extremely low. The present invention atomizes the iron alloy containing platinum group metals into powder particles, increases the reaction area, and improves the acid leaching separation rate of iron and platinum group metals.

[0028] 2) At the same time, the present invention uses magnesium vapor for desulfurization to solve the problem of acid leaching polluting water bodies due to the high sulfur content in the alloy containing platinum group metals recovered by the prior art. The iron ion solution obtained after acid leaching in the present invention is relatively pure and can be directly used without purification.

[0029] 3) The present invention uses hydrogen as a clean reducing agent, which has the advantages of small molecular size, large diffusion coefficient and large thermal conductivity, and can replace traditional metallurgical coke, accelerate the mass transfer rate, and hydrogen is a renewable resource. When hydrogen is introduced, stirring of the molten pool is achieved, the collision probability of Fe particles and PGMs particles is increased, and the capture efficiency is improved.

[0030] 4) The equipment used in the present invention is simple, has low maintenance cost, is easy to industrialize, and the total yield of Pt, Pd and Rh in the platinum group metal powder finally obtained is ≥99%.

[0031] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0033] Figure 1 A schematic flow chart of a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method provided by the present invention is shown.

[0034] Figure 2 A schematic diagram showing the introduction of a mixed gas of hydrogen and magnesium vapor in a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgy provided by the present invention.

[0035] The following are the descriptions of the reference numerals:

[0036] 1-Magnesium vapor generating chamber; 2-Molten pool. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0038] In the following examples and comparative examples,

[0039] FeO, Fe 2 O 3 , Fe 3 O 4 , CaO, Na 2 O.K 2 O, Mg, and hydrochloric acid are all industrial grade products;

[0040] The hydrogen in the mixed gas of hydrogen and magnesium vapor is 99.9% high-purity hydrogen.

[0041] The detection equipment and method for the yield and sulfur content of Pt, Pd, and Rh in the following examples and comparative examples include: using an inductively coupled plasma spectrometer to detect the Pt, Pd, and Rh contents in Fe-PGMs, thereby calculating the yield of PGMs. Using a carbon-sulfur analyzer to detect the sulfur content in Fe-PGMs and PGMs mixtures, and using an inductively coupled plasma spectrometer to detect the Fe content in the PGMs mixture.

[0042] Example 1

[0043] This embodiment provides a method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method, such as Figure 1As shown, the method comprises the following steps:

[0044] S1: Al 2 O 3 Supported catalyst (including Al 2 O 3 The catalyst powder with a D50 of 300 μm was obtained by crushing the catalyst in a high-energy ball mill with a material-to-ball ratio of 5:1, a rotation speed of 200 r / min, and a ball milling time of 30 min.

[0045] S2: The catalyst powder, FeO, CaO, Na 2 O are uniformly mixed in a mass ratio of 1000 g: 100 g: 880 g: 100 g to obtain a mixture; the mixture is placed in a medium frequency induction furnace (the induction furnace coil diameter is 200 mm) for high-temperature melting at a melting temperature of 1450° C. to obtain a molten liquid;

[0046] S3: introducing a mixed gas of hydrogen and magnesium vapor into the molten liquid to obtain a reduction desulfurized molten liquid and quenching the molten liquid with water to obtain cement clinker and an iron alloy containing platinum group metals (sulfur content is less than 0.005%);

[0047] The magnesium vapor is generated by 60g of metallic magnesium in a magnesium vapor generating chamber, and the magnesium vapor is generated by H 2 Carry it into the molten pool containing the molten liquid; pass the mixed gas of hydrogen and magnesium vapor into the molten liquid for 40 minutes at a flow rate of 3.5L / min, and let it stand for 10 minutes after the ventilation is completed;

[0048] S4: atomizing the iron alloy containing platinum group metals to obtain atomized alloy powder with a D50 of 600 μm, and performing acid leaching, filtering and drying to obtain platinum group metal powder.

[0049] The acid leaching solution is a hydrochloric acid solution with a concentration of 1 mol / L, an acid leaching temperature of 30° C., and an acid leaching time of 3 min.

[0050] The yield of Pt in the platinum group metal powder is 99.2%; the yield of Pd is 99.4%; the yield of Rh is 99.3%;

[0051] The sulfur content in the platinum group metal powder is below the detection limit (generally 0.005wt.%), and the Fe element content is 0.0001wt.%.

[0052] Example 2

[0053] This embodiment provides a method for recovering platinum group metals from waste automotive exhaust catalysts by pyrometallurgy. The difference between this embodiment and Embodiment 1 is only that: the time for introducing a mixture of hydrogen and magnesium vapor into the molten liquid is 50 min, the flow rate is 3.5 L / min, and after the ventilation ends, it is left standing for 10 min.

[0054] The recovery rate of Pt in the platinum group metal powder is 99.3%; the recovery rate of Pd is 99.4%; the recovery rate of Rh is 99.3%;

[0055] The sulfur content in the platinum group metal powder is lower than the detection limit (generally 0.005 wt.%), and the Fe element content is 0.0001 wt.%.

[0056] Comparative Example 1

[0057] This embodiment provides a method for recovering platinum group metals from waste automotive exhaust catalysts by pyrometallurgy. The difference between this embodiment and Embodiment 2 is only that: when introducing hydrogen into the molten liquid, there is no mixing with magnesium vapor.

[0058] The sulfur content in the ferroalloy containing platinum group metals is 16.5%.

[0059] The recovery rate of Pt in the platinum group metal powder is 99%; the recovery rate of Pd is 99.2%; the recovery rate of Rh is 99.1%.

[0060] The sulfur content in the platinum group metal powder is 0.52 wt.%. This is because in this comparative example, desulfurization is not carried out in the early stage, and platinum group metals are sulfurophilic elements. Therefore, in addition to existing in the form of iron sulfide in the ferroalloy containing platinum group metals, sulfur also combines with platinum group metals and exists in the ferroalloy containing platinum group metals. Therefore, in the acid leaching stage, part of the sulfur enters the acid solution in the acid leaching stage, while part of the sulfur still remains in the platinum group metal powder. The Fe element content is 0.023 wt.%.

[0061] Comparative Example 2

[0062] This comparative example provides a method for recovering platinum group metals from waste automotive exhaust catalysts by pyrometallurgy. The difference between this embodiment and Embodiment 2 is only that: the ferroalloy containing platinum group metals obtained in step S3 is directly subjected to acid leaching treatment without atomization.

[0063] The solution for acid leaching is a hydrochloric acid solution with a concentration of 1 mol / L, the acid leaching temperature is 30 °C, and the acid leaching time is 45 min, which is significantly longer than that in Embodiment 2.

[0064] The recovery rate of Pt in the platinum group metal powder is 99%; the recovery rate of Pd is 99.2%; the recovery rate of Rh is 99.1%.

[0065] The sulfur content in the platinum group metal powder is 0.65wt.%, and the Fe content is 0.56wt.%. It can be seen that without atomization, there is still a trace amount of iron remaining after leaching for 45in.

[0066] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method, It is characterized in that The method comprises the following steps: S1: crushing the waste automobile exhaust catalyst to obtain catalyst powder; S2: uniformly mixing the catalyst powder, the collector and the slag-forming agent to obtain a mixture; and smelting the mixture at a high temperature to obtain a molten liquid; S3: introducing a mixed gas of hydrogen and magnesium vapor into the molten liquid to obtain a reduced desulfurized molten liquid and quenching the molten liquid with water to obtain cement clinker and an iron alloy containing platinum group metals; S4: atomizing the ferroalloy containing platinum group metals to obtain atomized alloy powder, and performing acid leaching, filtering and drying to obtain platinum group metal powder.

2. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The waste automotive exhaust catalyst is at least one of Al 2 O 3 supported catalyst, SiO 2 supported catalyst, and Al 2 O 3 -SiO 2 supported catalyst.

3. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The equipment for the crushing process includes a high-energy ball mill, and the material-to-ball ratio is (4-6):1; The particle size of the catalyst powder is less than 500 μm.

4. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The mass ratio of the catalyst powder to the collector is 100:(4-20), and the collector is FeO, Fe 2 O 3 and Fe 3 O 4 At least one of; The slag-making agent is Na 2 O or K 2 O, and CaO, the slag-making agent and the catalyst powder form Na 2 O / K 2 O-CaO-Al 2 O 3 、Na 2 O / K 2 O-CaO-SiO 2 and Na 2 O / K 2 O-CaO-Al 2 O 3 -SiO 2 At least one of the slag systems, and at least one of the following conditions is met: (1) the CaO / Al 2 O 3 =0.8-1.2; (2) CaO / SiO in slag system 2 =0.3-0.6; (3) Na in slag system 2 O or K 2 O accounts for 1-10% of the total weight of the slag system.

5. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The smelting temperature of the high temperature smelting is 1200-1500° C., and the equipment for the high temperature smelting includes a medium frequency induction furnace.

6. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The time for introducing the mixed gas of hydrogen and magnesium vapor into the molten liquid is 10-60 minutes, and the injection amount of magnesium vapor in the mixed gas is 1.5-2 times the sulfur content in the molten liquid.

7. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The ferroalloy containing platinum group metals has a sulfur content of less than 0.005%.

8. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The particle size of the atomized alloy powder is 50-800 μm.

9. The method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to claim 1, in, The acid leaching solution is a hydrochloric acid solution with a concentration of 0.5-4 mol / L, an acid leaching temperature of 30-50° C., and an acid leaching time of 1-20 min.

10. Platinum group metal powder obtained by the method for recovering platinum group metals from waste automobile exhaust catalysts by pyrometallurgical method according to any one of claims 1 to 9.

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