WO1999041417B1

WO1999041417B1 - Method for producing high-purity molybdenum chemicals from molybdenum sulfides

Info

Publication number: WO1999041417B1
Application number: PCT/US1999/001435
Authority: WO
Inventors: Mahesh C Jha; William A May
Original assignee: Qualchem Inc
Priority date: 1998-02-11
Filing date: 1999-01-22
Publication date: 1999-12-16
Also published as: PE20000252A1; WO1999041417A2; WO1999041417A3

Abstract

The integrated process of the subject invention is directed to the production of high purity molybdenum chemical products from molybdenum sulfide containing materials by a series of steps, including roasting, sulfuric acid leaching of the calcine to remove impurities from the calcine, ammonia digesting of the calcine to form a pregnant molybdate solution containing dissolved molybdenum, and recovery of the dissolved molybdenum by crystallization and/or molybdic acid precipitation. The process is a 'zero discharge' process in that all process waste streams are combined to produce a ferrous ammonium sulfate fertilizer byproduct.

Claims

AMENDED CLAIMS[received by the International Bureau on 2 November 1999 (02.11.99); original claims 1-24 replaced by new claims 1-19 (3 pages)]

1. A method for recovering molybdenum from a molybdenum sulfide-containing material, comprising: fluidized bed roasting the molybdenum sulfide-containing material in the presence of oxygen to form a calcined material comprising molybdenum oxide and metal impurities; leaching the calcined material with sulfuric acid to solubilize the metal impurities while maintaining a substantial portion of the molybdenum oxide in the material; contacting the leached calcined material with ammonia solution to form an ammonium molybdate solution comprising molybdenum from the leached material; and lowering the pH of the molybdate solution to precipitate ammonium polymolybdate.

2. The method of Claim 1 , wherein the pH of the molybdate solution after the pH lowering step is no more than about pH 4.

3. The method of Claim 1 or Claim 2, wherein the temperature of the molybdate solution during the pH lowering step is maintained in the range of about 30 °C to about 80 °C.

4. The method of any one of the preceding claims, wherein the pH lowering step comprises: contacting the molybdate solution with sulfuric acid.

5. The method of any one of the preceding claims, wherein at least about 95 % of the molybdenum in the molybdate solution is converted into a polymolybdate.

6. The method of any one of the preceding claims, further comprising: filtering the molybdate solution, after the pH lowering step, to separate the polymolybdate from the molybdate solution to form a recovered polymolybdate precipitate and a filtrate.

7. The method of Claim 6, wherein the filtrate comprises dissolved molybdenum, and further comprising: recovering the dissolved molybdenum from the filtrate by contacting the filtrate with a sulfide under conditions sufficient to precipitate molybdenum sulfide.

8. The method of any one of the preceding claims, further comprising before the pH lowering step: converting only a portion of the molybdenum in the molybdate solution into molybdenum-containing crystals including at least one of ammonium heptamolybdate and ammonium dimolybdate and 36 removing the molybdenum-containing crystals from the molybdate solution.

9. The method of Claim 8, wherein the molybdate solution comprises a dissolved metal besides the dissolved molybdenum and further comprising before the pH lowering step: precipitating the dissolved metal as a sulfide from the molybdate solution.

10. The method of any one of the preceding claims, wherein the metal impurities solubilized during the leaching step are selected from the group consisting of aluminum, cadmium, calcium, cobalt, copper, iron, lead, magnesium, nickel, potassium, sodium, tin, zinc, and mixtures thereof.

11. The method of any one of the preceding claims, wherein the pH during the leaching step is no more than about pH 2.

12. The method of any one of the preceding claims, wherein the temperature during the leaching step ranges from about 60 °C to about 100°C.

13. The method of any one of the preceding claims, wherein, after the leaching step, the calcined material comprises from about 96 to about 99% of the molybdenum contained in the calcined material before the leaching step.

14. The method of any one of the preceding claims, wherein, after the leaching step, the pregnant leach solution comprises no more than about 7 g/1 molybdenum-containing compounds.

15. The method of any one of the preceding claims, wherein the method comprises recovering a roaster off-gas including sulfur dioxide at a concentration of from about 5% percent to about 10% by volume, and converting at least a portion of the sulfur dioxide to sulfuric acid.

16. The method of Claim 15, wherein the sulfuric acid used in the leaching step includes sulfuric acid converted from the sulfur dioxide.

17. The method of Claim 15, wherein the pH lowering step comprises adding to the molybdate solution sulfuric acid converted from the sulfur dioxide.

18. The method of Claim 15, wherein the method comprises preparing a ferrous ammonium sulfate product, comprising: converting at least a portion of the sulfuric acid converted from the sulfur dioxide to a ferrous sulfate solution; and combining at least a portion of the ferrous sulfate solution with ammonium sulfate solution resulting from the precipitating step. 37

19. The method of any one of the preceding claims, wherein the fluidized bed roasting is at a temperature of from about 450 °C to about 600 °C.

38

STATEMENT UNDER ARTICLE 19

Original Claim 24 is being amended to be the sole independent claim and is renumbered as new Claim 1. Included in the changes to Claim 24 is the specification of

fluidized bed roasting to prepare the calcined material, which finds support in the application as originally filed at page 8, lines 9-20. The phrase "in a pregnant leach solution" has been

deleted in reference to leaching of the calcined material as being unnecessary to definition of

the claimed subject matter. "Ammonia" has been changed to "ammonia solution" and

"primary pregnant leach solution" has been changed to "ammonium molybdate solution"

consistent with the disclosure at page 12, lines 4-9.

Original Claims 2-6, 9-11, 16, 17, and 19-21 are amended for consistency with the changes made to Claim 24 as well as to place those claims in multiple dependent form and to renumber those claims as new Claims 2-14.

New Claims 15-19 are added to further define aspects of the invention, and all depend from the new independent Claim 1. Claim 15 requires recovery of a roaster off-gas including certain levels of sulfur dioxide and converting at least a portion of the sulfur dioxide to

sulfuric acid, and finds support in the application as originally filed in process flow diagram

shown in Figs. 2A-2C and in the description at page 8, lines 21-26 and page 10, lines 5-16.

Claim 16 requires that sulfuric acid converted from the sulfur dioxide is used in the leaching

step to leach the calcined material, and finds support as noted for Claim 15 and additionally at page 10, lines 23-28. New Claim 17 requires that sulfuric acid converted from the sulfur dioxide be used during the pH lowering step and finds support as noted for Claim 15 and at

page 17, lines 2-4. New Claim 18 requires preparation of a ferrous ammonium sulfate

product, and finds support in the application as noted for Claim 15 and at page 19, line 27 through page 20, line 24. New Claim 19 requires that the fluidized bed roasting be at a 39 temperature from about 450°C to about 600°C and finds support in the application as filed at page 8, lines 27-31.