Method for extracting platinum from invalid alumina-based catalyst

Abstract

The invention belongs to the technical field of precious metal recovery, and particularly discloses a method for extracting platinum from a spent alumina-based catalyst. The method comprises the following steps: adding a sodium hydroxide solution and an invalid alumina-based catalyst into a reaction kettle, stirring and mixing; the mixed reaction kettle is vacuumized, nitrogen is introduced for oxygen removal, and then nitrogen is supplemented to normal pressure; heating the mixed material to 180-200 DEG C and the pressure of 1.4-1.8 MPa within 2 hours, then keeping constant temperature and constant pressure for 1-2 hours, then cooling the mixed material to 100-110 DEG C within 1 hour, then increasing the pressure in the kettle to 0.2-0.4 MPa, and finally conveying the mixed material to a dilution tank; raising the temperature of the mixed material to 100-110 DEG C, introducing a diluent, and stirring and diluting; and filtering the diluted material by using a bag filter, and collecting insoluble substances to obtain platinum-containing metal filter residues. The method has the characteristics of short process flow, low energy consumption, high carrier solubility and platinum enrichment multiple and small platinum metal loss.

Description

Technical Field

[0001] The present invention belongs to the technical field of precious metal recovery, and specifically relates to a method for extracting platinum from a spent alumina-based catalyst, which has the advantages of short process flow, low energy consumption, high carrier solubility and platinum enrichment multiple, and small platinum metal loss. Background Art

[0002] Alumina-supported precious metal catalysts are often used as fixed bed catalysts. Due to factors such as poisoning, carbon deposition, changes in carrier structure, metal grain aggregation or loss, the catalysts lose their activity and become ineffective, so the catalysts need to be replaced frequently. However, after the catalyst fails, the loss of precious metals is relatively small, and because precious metals have high economic value and high catalytic activity, recycling precious metals in alumina-supported precious metal catalysts not only helps to recycle resources, but also reduces environmental pollution, while bringing economic benefits to enterprises.

[0003] At present, the recovery of precious metals in spent catalysts can be divided into pyrometallurgical processes and hydrometallurgical processes according to the process. Among them, the pyrometallurgical processes include smelting enrichment, pyrochlorination and incineration, while the hydrometallurgical processes include acid dissolution methods such as sulfuric acid dissolution carrier method, hydrochloric acid dissolution carrier method and mixed acid dissolution carrier method, as well as alkali dissolution carrier method. For platinum group precious metals in spent catalysts, the hydrometallurgical process is currently mainly used for recovery.

[0004] The acid dissolution method is only suitable for soluble γ-Al 2 O 3 The catalyst is not suitable for treating insoluble θ-Al 2 O 3 ,δ-Al 2 O 3 The alkali dissolution method is rarely used in the recovery of spent alumina-supported precious metal catalysts because it can dissolve both soluble and insoluble Al 2 O 3 The alkaline dissolution method is the mainstream method for extracting platinum from spent alumina-based catalysts. However, the alkaline dissolution method has a low corrosion rate on Al2O3-based catalysts under normal pressure. 2 O 3 The dissolution efficiency of the carrier is low, and the alkali consumption is large, resulting in high production costs. 2 O 3 The dissolution efficiency of the carrier is high and the alkali consumption is small, but there is also Al 2 O 3 The dissolution efficiency of the carrier is still low and the distribution of Al 2 O 3The precious metals on the surface of the carrier are easily oxidized and dissolved in the alkaline solution under high temperature and high pressure environment, resulting in a large loss of precious metals and serious equipment corrosion.

[0005] In the prior art, in order to solve the problems existing in the existing pressurized alkali dissolution method, a certain amount of reducing agent is added to the alkali solution with a concentration of 28-32% to inhibit the dissolution of precious metals, and then the Al is dissolved by high temperature and pressure in three stages. 2 O 3 The above method further improves the Al 2 O 3 The dissolution efficiency of the carrier is improved, and the problem of the loss of precious metals due to easy oxidation and dissolution is solved. However, the process is complicated and the pressure dissolution time is long, resulting in high energy consumption. To this end, the prior art also fills nitrogen into the reactor to exhaust the air to prevent the precious metals from being oxidized and dissolved in the presence of oxygen and in the strong alkaline solution system, thereby avoiding the loss of precious metals; and a high-concentration sodium hydroxide solution with a concentration of 60-75% is used to dissolve Al 2 O 3 The carrier can not only improve the dissolution efficiency and shorten the dissolution time to reduce energy consumption, but also use the high boiling point of high-concentration sodium hydroxide solution to reduce the pressure in the kettle and lower the reaction temperature, further reducing energy consumption and improving safety. However, due to the strong corrosiveness of high-concentration sodium hydroxide solution, it aggravates the corrosion damage of equipment, seriously affecting the safe production of pressurized alkali dissolution method and increasing the maintenance workload. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention proposes a method for extracting platinum from a spent alumina-based catalyst, which has the advantages of short process flow, low energy consumption, high carrier solubility and platinum enrichment multiple, and low platinum metal loss.

[0007] The method of extracting platinum from spent alumina-based catalysts of the present invention is implemented by including feeding, air replacement, pressurized alkali leaching, dilution, and filtration steps, and the specific contents are as follows: A. Feeding: Add 30-40% sodium hydroxide solution and spent alumina-based catalyst into the reactor respectively, and stir and mix to obtain a mixed material; B. Air replacement: evacuate the reactor after mixing, then introduce nitrogen to discharge the oxygen in the reactor, then continue to add nitrogen to normal pressure, and then close all valves of the reactor; C. Pressurized alkali leaching: The mixed material in the reactor is heated to 180-200°C by electromagnetic heating within 2 hours. As the temperature increases, the pressure in the reactor gradually increases to 1.4-1.8 MPa. Then, the temperature and pressure are kept constant for 1-2 hours. Then, the mixed material in the reactor is cooled to 100-110°C within 1 hour, and the pressure in the reactor is reduced. Then, compressed air is introduced to increase the pressure in the reactor to 0.2-0.4 MPa. Finally, the mixed material in the reactor is transported to the dilution tank by the pressure in the reactor. D. Dilution: Heat the mixture in the dilution tank to 100-110°C, then add the diluent and stir to dilute; E. Filtration: Filter the diluted material in the dilution tank with a bag filter, collect the insoluble matter to obtain the platinum metal-containing filter residue, and recycle the filtrate.

[0008] Furthermore, in step A, the spent alumina-based catalyst is alumina-based catalyst particles with a diameter of 3 to 5 mm, or alumina-based catalyst thin rods with a diameter of 2 to 3 mm and a length of 10 mm; the material true density of the spent alumina-based catalyst is 3.15 g / cm 3 And the bulk density of the material is 1.0g / cm 3 .

[0009] Furthermore, in step A, the mass ratio of the sodium hydroxide solution to the spent alumina-based catalyst is 3-5:1; the sodium hydroxide solution is obtained by mixing industrial water and / or the filtrate of the previous process with caustic soda flakes.

[0010] Furthermore, in the step B, the reactor in which the materials are added and mixed is evacuated to a pressure of ≤-0.09 MPa, and then nitrogen is introduced to reduce the oxygen content in the reactor to ≤100 ppm, and then nitrogen is continuously added to normal pressure.

[0011] Furthermore, in the step C, the mixed material is stirred at a speed of 300-500 prm when the temperature and pressure are constant in the reactor; when the mixed material in the reactor drops to 90-100° C., compressed air is introduced into the reactor to increase the pressure to 0.2-0.4 MPa.

[0012] Furthermore, in the step D, sodium aluminate solution and / or industrial water is introduced into the mixture in the dilution tank at a rate of 1.2 m / s, and stirred at a speed of 300-500 prm for 0.4-0.6 h to complete the dilution of the mixture.

[0013] Furthermore, in the step D, the temperature of the diluent introduced into the mixed material is 80-100° C.; and the concentration of the sodium aluminate solution is 40-50%.

[0014] Furthermore, in the step E, the diluted material in the dilution tank is sent to the bag filter by a pneumatic diaphragm pump and filtered at a temperature of 80-100°C.

[0015] Furthermore, in the step C, the reactor uses Q345R lined N5 nickel plate as the reactor wall, the reactor wall uses rock wool as the insulation material, and the safety valve of the reactor uses TA40Y-64P type and the throat diameter area code is D25.

[0016] Furthermore, in the step D, the dilution tank heats the mixed material by passing steam into the coils provided in the tank, and the coils in the tank use φ32×3 steam pipes; in the step D, two dilution tanks are provided for backup.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts a slightly higher concentration of sodium hydroxide solution to match the corresponding spent alumina-based catalyst, supplemented by appropriate temperature, pressure and alkali leaching time, so as to significantly improve the Al 2 O 3 The solubility of the carrier and the enrichment multiple of platinum metal can achieve efficient recovery of platinum metal, shorten the process flow and alkaline leaching time, and reduce the energy consumption required for extraction.

[0018] 2. The present invention uses nitrogen to replace the air in the kettle before pressurized alkali leaching, which can prevent platinum metal from being oxidized and dissolved into the alkaline solution. It not only effectively reduces the dissolution loss of platinum metal, but also avoids the high cost and difficulty in subsequent waste liquid treatment caused by adding a reducing agent. Moreover, since the composition of the waste liquid in the later stage is simple, part of the waste liquid can be reused for pressurized alkali leaching, further reducing the extraction process cost and the workload of waste liquid treatment.

[0019] 3. The present invention utilizes a slightly higher concentration of sodium hydroxide solution in combination with a suitable temperature and pressure in the kettle to increase the Al 2 O 3 While increasing the solubility of the carrier, it can also reduce the corrosiveness of the sodium hydroxide solution and the pressure in the kettle, thereby improving the safety of the pressurized alkali dissolution method and reducing the equipment maintenance workload. In particular, the use of specific materials for the reactor wall and the reactor safety valve, as well as specific dilution tank coils, can further enhance the corrosion resistance of the reactor and dilution tank, effectively improve production safety and reduce maintenance workload.

[0020] 4. The spent alumina-based catalyst of the present invention is fed in the form of particles or thin rods, without the need for conventional crushing and fine grinding, thereby further shortening the process and reducing process energy consumption.

[0021] In summary, the present invention has the characteristics of short process flow, low energy consumption, high carrier solubility and platinum enrichment multiple, and small platinum metal loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process of the present invention; In the figure: 1-reactor, 2-dilution tank, 3-pneumatic diaphragm pump, 4-filter. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way. Any changes or improvements made based on the teachings of the present invention belong to the protection scope of the present invention.

[0024] like Figure 1 As shown, the method of extracting platinum from spent alumina-based catalysts of the present invention comprises feeding, air replacement, pressurized alkali leaching, dilution, and filtration steps, and the specific contents are as follows: A. Feeding: Add 30-40% sodium hydroxide solution and spent alumina-based catalyst into the reactor respectively, and stir and mix to obtain a mixed material; B. Air replacement: evacuate the reactor after mixing, then introduce nitrogen to discharge the oxygen in the reactor, then continue to add nitrogen to normal pressure, and then close all valves of the reactor; C. Pressurized alkali leaching: The mixed material in the reactor is heated to 180-200°C by electromagnetic heating within 2 hours. As the temperature increases, the pressure in the reactor gradually increases to 1.4-1.8 MPa. Then, the temperature and pressure are kept constant for 1-2 hours. Then, the mixed material in the reactor is cooled to 100-110°C within 1 hour, and the pressure in the reactor is reduced. Then, compressed air is introduced to increase the pressure in the reactor to 0.2-0.4 MPa. Finally, the mixed material in the reactor is transported to the dilution tank by the pressure in the reactor. D. Dilution: Heat the mixture in the dilution tank to 100-110°C, then add the diluent and stir to dilute; E. Filtration: Filter the diluted material in the dilution tank with a bag filter, collect the insoluble matter to obtain the platinum metal filter residue, and recycle the filtrate after filtration.

[0025] In step A, the spent alumina-based catalyst is alumina-based catalyst particles with a diameter of 3 to 5 mm, or alumina-based catalyst thin rods with a diameter of 2 to 3 mm and a length of 10 mm; the material true density of the spent alumina-based catalyst is 3.15 g / cm 3 And the bulk density of the material is 1.0g / cm 3 .

[0026] In the step A, the mass ratio of the sodium hydroxide solution to the spent alumina-based catalyst is 3-5:1; the sodium hydroxide solution is obtained by mixing industrial water and / or the filtrate after filtration in the previous process with caustic soda flakes.

[0027] In the step B, the reactor in which the materials are added and mixed is evacuated to a pressure of ≤-0.09 MPa, and then nitrogen is introduced to reduce the oxygen content in the reactor to ≤100 ppm, and then nitrogen is continuously added to normal pressure.

[0028] In the step C, the mixed material is stirred at a speed of 300-500 prm when the temperature and pressure in the reactor are constant; when the mixed material in the reactor drops to 90-100° C., compressed air is introduced into the reactor to increase the pressure to 0.2-0.4 MPa.

[0029] In the step D, sodium aluminate solution and / or industrial water are introduced into the mixture in the dilution tank at a rate of 1.2 m / s, and stirred at a speed of 300-500 prm for 0.4-0.6 h to complete the dilution of the mixture.

[0030] In the step D, the temperature of the diluent introduced into the mixed material is 80-100° C.; the concentration of the sodium aluminate solution is 40-50%.

[0031] In the step E, the diluted material in the dilution tank is sent to the bag filter by a pneumatic diaphragm pump and filtered at a temperature of 80-100°C.

[0032] In the step C, the reactor uses Q345R lined N5 nickel plate as the reactor wall, the reactor wall uses rock wool as the insulation material, and the safety valve of the reactor uses TA40Y-64P type and the throat diameter area code is D25.

[0033] In the step D, the dilution tank heats the mixed material by passing steam into the coils arranged in the tank, and the coils in the tank use φ32×3 steam pipes; in the step D, two dilution tanks are arranged to back up each other.

[0034] Example 1 S100: Add 815 kg of 98% caustic soda flakes into the reactor 1, then introduce 1200 kg of industrial water, and stir to prepare a 40% sodium hydroxide solution; then add 500 kg of spent alumina-based catalyst particles with a diameter of 3 to 5 mm into the reactor 1, stir and mix to obtain a mixed material.

[0035] S200: Turn on the vacuum pump to evacuate the reactor 1 after mixing, and when the pressure in the reactor is ≤-0.09MPa, slowly open the nitrogen inlet valve on the reactor to introduce nitrogen to control the discharge of oxygen in the reactor 1; when the oxygen content in the reactor 1 drops to ≤100ppm, turn off the vacuum pump, and then continue to add nitrogen to the reactor 1 to normal pressure, and then close the valves of the reactor 1.

[0036] S300: Heat the mixture in reactor 1 to 180°C within 2 hours. As the temperature in the reactor rises, the pressure in the reactor gradually increases. Slowly open the vent valve on the reactor to appropriately reduce the pressure in the reactor to 1.6MPa. Then, keep the temperature and pressure constant while stirring at a speed of 300prm for 2 hours. Then, gradually cool the mixture in reactor 1 to 110°C within 1 hour. When the temperature of the mixture naturally drops to 100°C, open the compressed air valve to supplement the pressure in the reactor to 0.3MPa. Finally, open the discharge valve of reactor 1 to press the mixture in the reactor into dilution tank 2.

[0037] S400: Open the steam regulating valve of the coil in dilution tank 2, control the steam intake, heat the mixed material in dilution tank 2 to 110°C, and then introduce a sodium aluminate solution with a concentration of 50% and a temperature of 90°C into dilution tank 2 at a rate of 1.2m / s, and stir and dilute at a speed of 300prm for 0.5h to complete the dilution of the mixed material.

[0038] S500: The pneumatic diaphragm pump 3 is used to send the diluted material in the dilution tank 2 to the bag metal filter (i.e., filter 4) for temperature control at 80°C and filtration. The insoluble platinum-containing metal filter residue adheres to the filter bag. The collected filter residue is used to extract platinum (about 5 kg of filter residue is collected, accounting for 1% of the amount of failed alumina-based catalyst particles fed), and the filtrate is recycled.

[0039] Example 2 S100: Add caustic soda flakes with a concentration of 98% into the reactor 1, then introduce industrial water and the filtrate of the previous process, and stir to prepare about 2000 kg of a 30% sodium hydroxide solution; then put 400 kg of alumina-based catalyst thin rods with a diameter of 2 to 3 mm and a length of 10 mm into the reactor 1, stir and mix to obtain a mixed material.

[0040] S200: Turn on the vacuum pump to evacuate the reactor 1 after mixing, and when the pressure in the reactor is ≤-0.09MPa, slowly open the nitrogen inlet valve on the reactor to introduce nitrogen to control the discharge of oxygen in the reactor 1; when the oxygen content in the reactor 1 drops to ≤100ppm, turn off the vacuum pump, and then continue to add nitrogen to the reactor 1 to normal pressure, and then close the valves of the reactor 1.

[0041] S300: Heat the mixture in reactor 1 to 190°C within 2 hours. As the temperature in the reactor rises, the pressure in the reactor gradually increases. Slowly open the vent valve on the reactor to appropriately reduce the pressure in the reactor to 1.4MPa. Then, keep the temperature and pressure constant for 1 hour while stirring at a speed of 400prm. Then, gradually cool the mixture in reactor 1 to 100°C within 1 hour, open the compressed air valve to supplement the pressure in the reactor to 0.2MPa, and finally open the discharge valve of reactor 1 to pressurize the mixture in the reactor into dilution tank 2.

[0042] S400: Open the steam regulating valve of the coil in dilution tank 2, control the steam intake, heat the mixed material in dilution tank 2 to 100°C, and then introduce a sodium aluminate solution with a concentration of 40% and a temperature of 80°C into dilution tank 2 at a rate of 1.2m / s, and stir and dilute at a speed of 400prm for 0.4h to complete the dilution of the mixed material.

[0043] S500: The diluted material in the dilution tank 2 is sent to the bag-type metal filter (i.e., filter 4) by using a pneumatic diaphragm pump 3, and the temperature is controlled at 100°C and filtered. The insoluble platinum-containing metal filter residue adheres to the filter bag, and the collected filter residue is used to extract platinum (about 4 kg of filter residue is collected, accounting for 1% of the amount of failed alumina-based catalyst particles fed), and the filtrate is recycled.

[0044] Example 3 S100: Add 715 kg of 98% flake caustic soda into the reactor 1, then introduce 1285 kg of industrial water, and stir to prepare a 35% sodium hydroxide solution; then add 667 kg of spent alumina-based catalyst particles with a diameter of 3 to 5 mm into the reactor 1, stir and mix to obtain a mixed material.

[0045] S200: Turn on the vacuum pump to evacuate the reactor 1 after mixing, and when the pressure in the reactor is ≤-0.09MPa, slowly open the nitrogen inlet valve on the reactor to introduce nitrogen to control the discharge of oxygen in the reactor 1; when the oxygen content in the reactor 1 drops to ≤100ppm, turn off the vacuum pump, and then continue to add nitrogen to the reactor 1 to normal pressure, and then close the valves of the reactor 1.

[0046] S300: Heat the mixture in reactor 1 to 200°C within 2 hours. As the temperature in the reactor rises, the pressure in the reactor gradually increases. Slowly open the vent valve on the reactor to appropriately reduce the pressure in the reactor to 1.8MPa. Then, keep the temperature and pressure constant while stirring at a speed of 500prm for 1.5 hours. Then, gradually cool the mixture in reactor 1 to 110°C within 1 hour. When the temperature of the mixture naturally drops to 100°C, open the compressed air valve to supplement the pressure in the reactor to 0.4MPa. Finally, open the discharge valve of reactor 1 to press the mixture in the reactor into dilution tank 2.

[0047] S400: Open the steam regulating valve of the coil in dilution tank 2, control the steam intake, raise the temperature of the mixed material in dilution tank 2 to 100°C, and then introduce industrial water with a temperature of 100°C into dilution tank 2 at a rate of 1.2m / s, and stir and dilute at a speed of 500prm for 0.6h to complete the dilution of the mixed material.

[0048] S500: The diluted material in the dilution tank 2 is sent to the bag-type metal filter (i.e., filter 4) by using a pneumatic diaphragm pump 3, and the temperature is controlled at 90°C and filtered. The insoluble platinum-containing metal filter residue adheres to the filter bag. The collected filter residue is used to extract platinum (about 7 kg of filter residue is collected, accounting for 1% of the amount of failed alumina-based catalyst particles fed), and the filtrate is recycled.

[0049] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for extracting platinum from spent alumina-based catalysts, comprising feeding, air replacement, pressurized alkali leaching, dilution, and filtration steps, the specific contents of which are as follows: A. Feeding: Add 30-40% sodium hydroxide solution and spent alumina-based catalyst into the reactor respectively, and stir and mix to obtain a mixed material; B. Air replacement: evacuate the reactor after mixing, then introduce nitrogen to discharge the oxygen in the reactor, then continue to add nitrogen to normal pressure, and then close all valves of the reactor; C. Pressurized alkali leaching: The mixed material in the reactor is heated to 180-200°C by electromagnetic heating within 2 hours. As the temperature increases, the pressure in the reactor gradually increases to 1.4-1.8 MPa. Then, the temperature and pressure are kept constant for 1-2 hours. Then, the mixed material in the reactor is cooled to 100-110°C within 1 hour, and the pressure in the reactor is reduced. Then, compressed air is introduced to increase the pressure in the reactor to 0.2-0.4 MPa. Finally, the mixed material in the reactor is transported to the dilution tank by the pressure in the reactor. D. Dilution: Heat the mixture in the dilution tank to 100-110°C, then add the diluent and stir to dilute; E. Filtration: Filter the diluted material in the dilution tank with a bag filter, collect the insoluble matter to obtain the platinum metal filter residue, and recycle the filtrate.

2. The method for extracting platinum from spent alumina-based catalysts according to claim 1, characterized in that: In step A, the spent alumina-based catalyst is alumina-based catalyst particles with a diameter of 3 to 5 mm, or alumina-based catalyst thin rods with a diameter of 2 to 3 mm and a length of 10 mm; the material true density of the spent alumina-based catalyst is 3.15 g / cm 3 And the bulk density of the material is 1.0g / cm 3 .

3. The method for extracting platinum from spent alumina-based catalysts according to claim 2, characterized in that: In the step A, the mass ratio of the sodium hydroxide solution to the spent alumina-based catalyst is 3-5:1; the sodium hydroxide solution is obtained by mixing industrial water and / or the filtrate of the previous process with caustic soda flakes.

4. The method for extracting platinum from spent alumina-based catalysts according to claim 1, characterized in that: In the step B, the reactor in which the materials are added and mixed is evacuated to a pressure of ≤-0.09 MPa, and then nitrogen is introduced to reduce the oxygen content in the reactor to ≤100 ppm, and then nitrogen is continuously added to normal pressure.

5. The method for extracting platinum from spent alumina-based catalyst according to claim 1, characterized in that: In the step C, the mixed material is stirred at a speed of 300-500 prm when the temperature and pressure in the reactor are constant; when the mixed material in the reactor drops to 90-100° C., compressed air is introduced into the reactor to increase the pressure to 0.2-0.4 MPa.

6. The method for extracting platinum from spent alumina-based catalyst according to claim 1, characterized in that: In the step D, sodium aluminate solution and / or industrial water are introduced into the mixed material in the dilution tank at a rate of 1.2 m / s, and stirred at a speed of 300-500 prm for 0.4-0.6 h to complete the dilution of the mixed material.

7. The method for extracting platinum from spent alumina-based catalysts according to claim 6, characterized in that: In the step D, the temperature of the diluent introduced into the mixed material is 80-100° C.; the concentration of the sodium aluminate solution is 40-50%.

8. The method for extracting platinum from spent alumina-based catalysts according to claim 1, characterized in that: In the step E, the diluted material in the dilution tank is sent to the bag filter by a pneumatic diaphragm pump and filtered at a temperature of 80-100°C.

9. The method for extracting platinum from spent alumina-based catalyst according to any one of claims 1 to 8, characterized in that: In the step C, the reactor uses Q345R lined N5 nickel plate as the reactor wall, the reactor wall uses rock wool as the insulation material, and the safety valve of the reactor uses TA40Y-64P type and the throat diameter area code is D25.

10. The method for extracting platinum from spent alumina-based catalysts according to claim 9, characterized in that: In the step D, the dilution tank heats the mixed material by passing steam into the coils arranged in the tank, and the coils in the tank use φ32×3 steam pipes; in the step D, two dilution tanks are arranged to back up each other.

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