Process for separating and recovering metals

• US 8,815,184 B2
• Filed: 06/09/2011
• Issued: 08/26/2014
• Est. Priority Date: 08/16/2010
• Status: Expired due to Fees

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Bhaduri, Rahul Shankar, Nordrum, Louis Joseph, Kuperman, Alexander E
• Primary Examiner(s): Mayes, Melvin Curtis
• Assistant Examiner(s): SWAIN, MELISSA STALDER
• Application Number:
  US13/156,589
• Publication Number:
  US 20120039777A1
• Time in Patent Office: 1,174 Days
• Field of Search: 423/56, 423/55, 423/67, 423/68, 423/40
• US Class Current: 423/58
• CPC Class Codes: C22B 23/026 from spent catalysts
• CPC Class Codes: C22B 23/0446 with an ammoniacal liquor or with a hydroxide of an alkali or alkaline-earth metal
• CPC Class Codes: C22B 34/225 from spent catalysts
• CPC Class Codes: C22B 34/345 from spent catalysts
• CPC Class Codes: C22B 7/009 General processes for recovering metals or metallic compounds from spent catalysts for recovering specific metals C22B11/00 - C22B61/00
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

A process for treating spent catalyst containing heavy metals, e.g., Group VIB metals and Group VIII metals is provided. In one embodiment after deoiling, the spent catalyst is treated with an ammonia leach solution under conditions sufficient to dissolve the group VIB metal and the Group VIII metal into the leaching solution, forming a leach slurry. After solid-liquid separation to recover a leach solution, chemical precipitation and solids repulping is carried out to obtain an effluent stream containing ammonium sulfate (Amsul), ammonium sulfamate, Group VB, Group VIB and Group VIII metals. Following sulfidation, the Group VIII metal is fully removed and Group VB and Group VI metals are partially removed from the Amsul stream. In the additional steps of oxydrolysis and iron precipitation, an effective amount of ferric ion at a pre-select pH is added to form insoluble complexes with the Group VB and Group VIB metals, which upon liquid-solid separation produces an effluent ammonium sulfate stream containing less than 10 ppm each of the Group VB and Group VIB metals.

Claims

1. A method for recovering metals from a spent catalyst, the method comprising:

leaching a Group VIB metal, a Group VIII metal, and a Group VB metal, from the spent catalyst with an ammonia containing leach solution at a temperature and a pressure sufficient to form a pressure leach slurry;

separating and removing a solid residue from the pressure leach slurry to form a pressure leach solution comprising a Group VIB soluble metal complex and a Group VIII soluble metal complex;

treating the pressure leach solution by chemical precipitation to precipitate at least a portion of the Group VIB metal and at least a portion of the Group VIII metal as precipitated metal complexes;

recovering the precipitated metal complexes by at least a separation means selected from settling, filtration, decantation, centrifugation and combinations thereof, forming a first effluent stream containing less than 600 ppm of the Group VIB metal and less than 400 ppm of the group VIII metal and a solid residue containing at least 97% of incoming VIB metal and over 80% of incoming Group VIII metal;

sulfiding the first effluent stream with a sulfiding agent to form a sulfided slurry comprising a Group VB metal sulfide and/or oxide, a Group VIB metal sulfide and a Group VIII metal sulfide;

separating and removing the Group VB metal sulfide and/or oxide, the Group VIB metal sulfide and the Group VIII metal sulfide from the sulfided slurry, forming a second effluent stream comprising a Group VB and a Group VIB soluble metal compound;

contacting the second effluent stream with an effective amount of ferric ion at a pre-selected pH for the ferric ion to form a complex with the Group VB and Group VIB metal;

performing a liquid-solid separation to remove the Group VB and Group VIB metal complex as solids, forming a third effluent containing less than 5 ppm of the Group VB metal and less than 5 ppm of the Group VIB metal.

2. The method of claim 1, wherein the contact with ferric ion is carried out at a sufficient temperature and pressure with aeration for oxydrolysis to take place.

3. The method of claim 2, wherein the contact with ferric ion is at a pre-select pH between 4.0 and 8.0.

4. The method of claim 2, wherein the pre-selected pH is between 4.5 and 5.5.

5. The method of claim 2, wherein the contact during oxydrolysis is at a temperature between 150-300°

C.

6. The method of claim 2, wherein the contact during oxydrolysis is at a pressure of 300-600 psig.

7. The method of claim 1, wherein the precipitated metal complexes are recovered by filtration and water washed, and wherein the wash water comprises at least a chelating agent.

8. The method of claim 7, wherein the wash water has pH ranging from 1.5 to 5.0, and wherein the wash water contains 1-20 wt. % of a chelating agent.

9. The method of claim 7, wherein the chelating agent is selected from the group consisting of formic acid, acetic acid, propionic acid, maleic acid, fumaric acid, succinic acid, tartaric acid, citric acid, oxalic acid, glyoxylic acid, aspartic acid, alkane sulfonic acids, aryl sulfonic acids, arylcarboxylic acids and mixtures thereof.

10. The method of claim 1, further comprising repulping the solid residue with acidic wash water.

11. The method of claim 10, wherein the solid residue is repulped with acidic wash water having a pH in the range of 2.0 to 3.0.

12. The method of claim 10, wherein the solid residue is repulped with a sufficient amount of water for a slurry density of 20-40 wt. % solids.

13. The method of claim 10, further comprising separating and removing the solid residue to recover the wash water as a filtrate.

14. The method of claim 13, further comprising adding the wash water filtrate to the first effluent stream for sulfidation with the sulfiding agent to form the sulfided slurry.

15. The method of claim 1, wherein the second effluent stream is brought in contact with an effective amount of ferric ion for at least 50% of the Group VB metal and at least 50% of the Group VIB metal to be removed by forming an insoluble complex with the ferric ion.

16. The method of claim 15, wherein the second effluent stream is brought in contact with an effective amount of ferric ion for at least 75% of the Group VB metal and at least 75% of the Group VIB metal to be removed by forming an insoluble complex with the ferric ion.

17. The method of claim 16, wherein the second effluent stream is brought in contact with an effective amount of ferric ion for at least 90% of the Group VB metal and at least 90% of the Group VIB metal to be removed by forming an insoluble complex with the ferric ion.

18. The method of claim 1, wherein the second effluent stream is brought in contact with an effective amount of ferric ion for the ferric ion to form insoluble complexes with the Group VB and Group VIB metal and for the Group VB and Group VIB metal in solution to be 5 ppm or less.

19. The method of claim 1, wherein the effective amount of ferric ion ranges from 6 to 50 ppm of metal cation to each ppm of the Group VB and Group VIB soluble metal compounds in the second effluent stream.

20. The method of claim 1, wherein the ferric ion is selected from ferric sulfate, ferrous sulfate and ferric chloride.

21. The method of claim 1, wherein the second effluent stream is set to a pre-selected pH prior to contact with ferric ion by adding sulfuric acid or ammonium hydroxide to the second effluent stream.

22. The method of claim 1, further comprising subjecting the second effluent stream to aeration at a sufficient temperature and pressure for oxydrolysis to take place prior to contacting the second effluent with an effective amount of ferric ion.

23. The method of claim 22, wherein the second effluent stream after oxydrolysis is cooled down to a temperature of less than 100°

C. prior to contacting the second effluent stream with an effective amount of ferric ion.

24. The method of claim 23, wherein the second effluent stream after oxydrolysis is cooled down to a temperature of 60-70°

C. prior to contacting the second effluent stream with ferric ion.

25. The method of claim 1, wherein the contact with the ferric ion is for a sufficient amount of time for at least 50% of the Group VIB soluble metal to form an insoluble complex with the ferric ion.

26. The method of claim 1, further comprising aerating the second effluent stream while it is in contact with the ferric ion.

27. The method of claim 1, wherein the liquid-solid separation to remove the Group VB and Group VIB insoluble metal complexes is via an inclined plate settler.

28. The method of claim 1, wherein the solids containing the Group VB and Group VIB metal complexes is body fed with at least one of calcium silicate, diatomaceous earth, and cellulose.

29. The method of claim 1, wherein the first effluent stream is sulfided with a sulfiding agent selected from the group consisting of hydrogen sulfide, ammonium sulfide, NaHS, Na₂S, and mixtures thereof.