Fluidized-bed roasting of molybdenite concentrates

• US 6,190,625 B1
• Filed: 08/07/1997
• Issued: 02/20/2001
• Est. Priority Date: 08/07/1997
• Status: Expired due to Fees

• Current Assignee: Qualchem, Inc.
• Original Assignee: Qualchem, Inc.
• Inventors: May, William A., Jha, Mahesh C.
• Primary Examiner(s): Beck, Shrive
• Assistant Examiner(s): VARCOE JR, FREDERICK T
• Application Number:
  US08/907,373
• Time in Patent Office: 1,293 Days
• Field of Search: 266/172, 266/175, 266/176, 422/146, 423/53, 423/606, 423/659.F
• US Class Current: 423/53
• CPC Class Codes: B01J 2208/00132 Tubes
• CPC Class Codes: B01J 2208/00141 Coils
• CPC Class Codes: B01J 2208/00168 with heat exchange elements outside the bed of solid particles
• CPC Class Codes: B01J 2208/00176 outside the reactor
• CPC Class Codes: B01J 2219/1946 conical
• CPC Class Codes: B01J 8/1836 Heating and cooling the reactor B01J8/42 takes precedence
• CPC Class Codes: B01J 8/34 with stationary packing material in the fluidised bed, e.g. bricks, wire rings, baffles
• CPC Class Codes: B01J 8/36 with fluidised bed through which there is an essentially horizontal flow of particles
• CPC Class Codes: B01J 8/40 with fluidised bed subjected to vibrations or pulsations
• CPC Class Codes: C01G 39/02 Oxides; Hydroxides
• CPC Class Codes: C22B 1/10 in fluidised form
• CPC Class Codes: C22B 34/34 Obtaining molybdenum treatment or purification of solutions by adsorption on solids C22B3/24, by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42; preparation of molybdenum involving liquid-liquid extraction, adsorption or ion-exchange C01G39/003

Abstract

The present invention provides a method for fluidized bed roasting of molybdenite to molybdenum trioxide. A fluid bed reactor separated into separate zones is used to provide plug flow conditions. A cooling tube is submerged in the fluid bed to control temperature. A vibrator is used to enhance fluidization.

Claims

1. A method for converting molybdenum sulfides into molybdenum oxides, comprising:

introducing a feed material comprising molybdenum sulfides into a fluidized bed of particulate solids contained within a fluidized bed reactor, the fluidized bed being separated into a plurality of different zones with adjacent zones being separated by a baffle with an opening between the adjacent zones such that the material flows through the fluidized bed reactor in plug flow mode;

contacting the particulate solids of the fluidized bed, including the feed material, with an oxygen containing fluidizing gas while vibrating the fluidized bed reactor, to convert at least a portion of the molybdenum sulfides into molybdenum oxides and thereby form a product comprising mnolybdenum oxides;

maintaining a fluidized bed temperature in a range of from about 400°

C. to about 580°

C., comprising (i) cooling at least a portion of the particulate solids in at least a first zone of the fluidized bed, during the contacting step, with cooling means for removing heat from the first zone of the fluidized bed to maintain a fluidized bed temperature in the first zone of no more than about 580°

C., the cooling means being submerged in the fluidized bed during the cooling step, an cd (ii) heating at least a portion of the particulate solids in at least a second zone of the fluidized bed to maintain a fluidized bed temperature in the second zone of at least about 400°

C.;

wherein, the particulate solids in the first zone have a higher sulfide content, than the sulfide content of the particulate solids in the second zone, and exothermic reaction of the sulfides in the first zone produces excess heat in the first zone and heat is removed from the first zone by the cooling to maintain the temperature in the first zone within the range;

wherein, the particulate solids of the second zone have a lower sulfide content, than the sulfide content of particulate solids in the first zone, and exothermic reaction of sulfides in the second zone produces insufficient beat in the second zone and heat is added to the second zone by the heating to maintain the temperature in the second zone within the the range; and

removing product comprising the molybdenum oxides from the fluidized bed reactor.

2. The method of claim 1, wherein the feed material has a P₈₀ size of no more than about 100 mesh (Tyler).

3. The method of claim 1, wherein the feed material has a molybdenum sulfide concentration of at least about 50 wt %.

4. The method of claim 1, wherein at least about 95% of the molybdenum sulfides in the feed material are converted into molybdenum oxides during the contacting step.

5. The method of claim 4, wherein the method is conducted substantially in the absence of recycle of the particulate solids.

6. The method of claim 1, wherein the product comprises no more than about 5 wt % molybdenum sulfides.

7. The method of claim 1, wherein the product is in the form of a free-flowing particulate material.

8. The method of claim 1, wherein the amplitude of vibration of the fluidized bed reactor ranges from about {fraction (1/16)} inch to about ½

inch.

9. The method of claim 1, wherein the fluidizing gas comprises at least about 10 vol % oxygen.

10. The method of claim 1, wherein the contacting step comprises:

contacting a first portion of the feed material with a first fluidizing gas in the first zone of the fluidized bed to convert a first portion of the molybdenum sulfides to molybdenum oxides; and

contacting a second portion of the feed material with a second fluidizing gas in the second zone of the fluidized bed to convert a second portion of the molybdenum sulfides to molybdenum oxides.

11. The method of claim 10, wherein the first and second zones are separated by a baffle with a relatively small opening such that the material flows from the first zone to the second zone in a plug flow mode.

12. The method of claim 10, wherein the oxygen content of the first fluidizing gas is greater than the oxygen content of the second fluidizing gas.

13. The method of claim 10, wherein the flow rate of the first fluidizing gas is greater than the flow rate of the second fluidizing gas.

14. The method of claim 10, wherein the fluidized bed depth in the first zone is less than the fluidized bed depth in the second zone and the residence time in the first zone is less than the residence time in the second zone.

15. The method of claim 1, wherein the feed material is comprised substantially entirely of molybdenite concentrate.

16. The method of claim 1, wherein at least a portion of the fluidizing gas is preheated prior to introduction into the fluidized bed.

17. The method of claim 1, wherein the residence time of the particulate solids in the fluidized bed is no longer than about 8 hours.

18. The method of claim 1, wherein the fluidized bed has a top and a bottom and the baffle extends from the top of the fluidized bed to the bottom of the fluidized bed.

19. The method of claim 1, wherein the fluidized bed is located in a lower section of the fluidized bed reactor, the fluidized bed reactor further comprising an upper section located above the fluidized bed, the upper section having a larger width than the lower section, so that the velocity of the fluidizing gas decreases as the fluidizing gas flows from the lower section into the upper section.

20. The method of claim 19, wherein the upper section is in fluid communication with at least one separation device which removes entrained particles from the upper section and returns the entrained particles to the fluidized bed.

21. The method of claim 1, wherein the cooling means comprises a cooling tube submerged in the fluidized bed, the cooling comprising passing a cooling fluid through the cooling tube to remove heat from the fluidized bed.

22. The method of claim 1, wherein the first zone and the second zone are in fluid communication via a space in the fluid bed reactor located above the top of the baffle.

23. The method of claim 1, wherein the fluidized bed includes at least three zones with the second zone being the last in series of the at least three zones.

24. The method of claim 23, wherein delivery of the fluidizing gas to each of the plurality of zones is controlled separately, and the fluidizing gas delivered to at least the second zone is preheated prior to introduction into the second zone.