Method and apparatus for drying carboxylic acid

Abstract

Disclosed is a method and apparatus for drying a wet cake in a carboxylic acid production process. The method comprises employing a contact dryer for drying solid particles of carboxylic acid, where the solid particles can have a residence time of less than about 7 minutes in the dryer and an exit temperature of less than about 250° C. upon exiting the dryer.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A preferred embodiment of the present invention is described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a process flow diagram illustrating a system for the production, purification, and drying of carboxylic acid constructed in accordance with the present invention, particularly illustrating a configuration where the crude slurry from the oxidation reactor is subjected to purification, the resulting purified slurry is subjected to product isolation, and the wet cake from the product isolation zone is subjected to drying in a drying zone;

FIG. 2 is a side view of a dryer that may be used in one embodiment of the present invention with certain sections being cut away to more clearly illustrate the operation of the dryer;

FIG. 3 is a sectional view of the dryer taken along line 3-3 in FIG. 2, particularly illustrating a rotor having a plurality of radial arms affixed thereto and paddles attached to each individual radial arm;

FIG. 4 is a weight percent vs. time plot depicting the thermal gravimetric analyses of purified terephthalic acid (PTA) in air, PTA in nitrogen, crude terephthalic acid (CTA) in air, and CTA in nitrogen, determined in accordance with the procedure described in Example 5; and

FIG. 4 a is a magnified view of the plot depicted in FIG. 4, particularly illustrating the weight percent range from 95 to 100 and the time range from 185 to 285 of the weight percent vs. time plot depicted in FIG. 4.

Claims

1. A method for drying solid particles comprising a carboxylic acid, said method comprising: (a) introducing a wet cake comprising said solid particles into a drying zone; and(b) drying said wet cake in said drying zone to thereby produce a substantially dry product comprising at least a portion of said solid particles, wherein said solid particles have an average residence time of less than about 7 minutes in said drying zone, and wherein said solid particles have an exit temperature of less than about 250° C. upon exiting said drying zone.

2. The method of claim 1, wherein said carboxylic acid comprises an aromatic dicarboxylic acid.

3. The method of claim 1, wherein said carboxylic acid comprises terephthalic acid.

4. The method of claim 1, wherein said solid particles comprise particles of crude terephthalic acid.

5. The method of claim 1, wherein said solid particles comprise particles of purified terephthalic acid.

6. The method of claim 1, wherein said solid particles have a mean particle size in the range of from about 1 to about 500 microns.

7. The method of claim 1, wherein said substantially dry product comprises less than about 1 weight percent liquid.

8. The method of claim 1, wherein said substantially dry product comprises less than about 0.5 weight percent liquid.

9. The method of claim 1, wherein said solid particles have an average residence time of less than about 5 minutes in said drying zone.

10. The method of claim 1, wherein said solid particles have an average residence time of less than about 3 minutes in said drying zone.

11. The method of claim 1, wherein said exit temperature is in the range of from about 105 to about 240° C.

12. The method of claim 1, wherein said exit temperature is in the range of from about 110 to about 200° C.

13. The method of claim 1, wherein said substantially dry product comprises less than 0.2 weight percent liquid, wherein said solid particles have an average residence time of less than 2 minutes in said drying zone, and wherein said exit temperature is in the range of from 115 to 175° C.

14. The method of claim 1, wherein said wet cake comprises in the range of from about 2 to about 25 weight percent liquid.

15. The method of claim 1, wherein said wet cake further comprises acetic acid, benzoic acid, and/or water.

16. The method of claim 1, wherein said wet cake has a temperature in the range of from about 20 to about 200° C. immediately prior to entering said drying zone.

17. The method of claim 1, wherein said wet cake comprises in the range of from 4 to 20 weight percent liquid, and wherein said wet cake has a temperature in the range of from 65 to 105° C. immediately prior to entering said drying zone.

18. The method of claim 1, wherein said drying zone is defined within a contact dryer.

19. The method of claim 18, wherein said wet cake is fed to said drying zone at a feed rate of at least about 20 lbs/hour per square foot of heated surface area during said drying.

20. The method of claim 18, wherein said wet cake is fed to said drying zone at a feed rate in the range of from about 40 to about 175 lbs/hour per square foot of heated surface area during said drying.

21. The method of claim 18, wherein said dryer comprises at least one jacket, wherein the jacket temperature of said dryer is maintained in the range of from about 120 to about 280° C. during said drying.

22. The method of claim 21, wherein the jacket temperature of said dryer is maintained in the range of from about 200 to about 240° C. during said drying.

23. The method of claim 18, wherein said dryer comprises a paddle rotor comprising a plurality of radially extending paddles.

24. The method of claim 23, wherein said paddle rotor rotates at a speed such that the tips of said paddles travel at a speed of at least about 10 cm/s.

25. The method of claim 23, wherein said dryer further comprises a jacketed cylinder presenting a heated inner surface, wherein said paddle rotor is substantially disposed in said jacketed cylinder.

26. The method of claim 25, wherein during said drying said paddle rotor is operable to facilitate contact of said solid particles with said heated inner surface and to facilitate movement of said solid particles through said jacketed cylinder.

27. The method of claim 18, wherein said dryer is a thin layer contact dryer.

28. The method of claim 18, wherein said dryer is operated under vacuum conditions during said drying.

29. The method of claim 18, wherein the pressure in said dryer is maintained in the range of from about 50 to about 1000 torr during said drying.

30. The method of claim 18, wherein said dryer further comprises a vacuum seal device through which said solid particles exit said drying zone.

31. The method of claim 1, step (b) further comprising introducing a drying gas into said drying zone to aid in drying at least a portion of said wet cake, wherein said drying gas has an inlet temperature of at least about 100° C.

32. A method for producing a substantially dry crude terephthalic acid (CTA) particulate product, said method comprising: (a) oxidizing an aromatic compound in an oxidation zone to thereby produce a slurry comprising solid CTA particles;(b) treating at least a portion of said slurry in a product isolation zone to thereby produce a wet cake comprising at least a portion of said solid CTA particles; and(c) drying at least a portion of said wet cake in a drying zone to thereby produce said substantially dry CTA particulate product, wherein said CTA particles have an average residence time of less than about 7 minutes in said drying zone, and wherein said CTA particles have an exit temperature of less than about 250° C. upon exiting said drying zone.

33. The method of claim 32, wherein said substantially dry CTA particulate product comprises less than about 1 weight percent liquid.

34. The method of claim 32, wherein said exit temperature is in the range of from about 110 to about 200° C.

35. The method of claim 32, wherein said wet cake comprises in the range of from about 2 to about 25 weight percent water.

36. The method of claim 32, wherein said aromatic compound comprises para-xylene.

37. The method of claim 32, wherein at least a portion of said product isolation zone is defined within a vacuum filter.

38. The method of claim 32, wherein said drying zone is defined within a contact dryer.

39. The method of claim 38, wherein said wet cake is fed to said drying zone at a feed rate of at least about 20 lbs/hour per square foot of heated surface area during said drying.

40. The method of claim 38, wherein said dryer comprises at least one jacket, wherein the jacket temperature of said dryer is maintained in the range of from about 120 to about 280° C.

41. The method of claim 32, further comprising using a common vacuum source to create a vacuum in said product isolation zone and said drying zone during said treating and said drying.

42. A method for producing a substantially dry purified terephthalic acid (PTA) particulate product, said method comprising: (a) oxidizing an aromatic compound in an oxidation zone to thereby produce a first slurry comprising solid crude terephthalic acid (CTA) particles;(b) subjecting at least a portion of said CTA particles to purification in a purification zone to thereby produce a second slurry comprising solid PTA particles;(c) treating at least a portion of said second slurry in a product isolation zone to thereby produce a wet cake comprising at least a portion of said PTA particles; and(d) drying said wet cake in a drying zone to thereby produce said substantially dry PTA particulate product, wherein said PTA particles have an average residence time of less than about 7 minutes in said drying zone, and wherein said PTA particles have an exit temperature of less than about 250° C. upon exiting said drying zone.

43. The method of claim 42, wherein said substantially dry PTA particulate product comprises less than about 1 weight percent liquid.

44. The method of claim 42, wherein said exit temperature is in the range of from about 110 to about 200° C.

45. The method of claim 42, wherein said wet cake comprises in the range of from about 2 to about 25 weight percent water.

46. The method of claim 42, wherein said purification includes subjecting at least a portion of said CTA particles to further oxidation and/or hydrogenation.

47. The method of claim 42, wherein said drying zone is defined within a contact dryer.

48. The method of claim 47, wherein said wet cake is fed to said drying zone at a feed rate of at least about 20 lbs/hour per square foot of heated surface area during said drying.

49. The method of claim 47, wherein said dryer comprises at least one jacket, wherein the jacket temperature of said dryer is maintained in the range of from about 120 to about 280° C.

50. The method of claim 42, further comprising using a common vacuum source to create a vacuum in said product isolation zone and said drying zone during said treating and said drying.

51. A method for drying a wet cake comprising terephthalic acid (TPA), said method comprising: (a) introducing said wet cake into a dryer; and(b) drying said wet cake in said dryer to thereby produce a dry TPA product, wherein said TPA has an average residence time in said dryer of less than about 7 minutes, and wherein said dry TPA product has a temperature in the range of from about 105 to about 240° C. upon exiting said dryer.

52. The method of claim 51, wherein said TPA has an average residence time in said dryer of less than about 5 minutes.

53. The method of claim 51, wherein said dry TPA product has a temperature in the range of from about 125 to about 200° C. upon exiting said dryer.

54. The method of claim 51, wherein said wet cake comprises in the range of from 1 to about 35 weight percent moisture, and wherein said dry TPA product comprises less than 1 weight percent moisture.

55. The method of claim 51, wherein said terephthalic acid is crude terephthalic acid.

56. The method of claim 51, wherein said terephthalic acid is purified terephthalic acid.

57. The method of claim 51, wherein said dryer comprises a thin layer contact dryer having a heated inner surface.

58. The method of claim 57, wherein said wet cake is fed to said dryer at a feed rate of at least about 35 lbs/hour per square foot of said heated inner surface during said drying.

59. The method of claim 51, wherein said dryer comprises a jacket, and wherein the jacket temperature of said dryer is maintained in the range of from about 120 to about 270° C. during said drying.

60. The method of claim 51, wherein said dryer comprises a paddle rotor comprising a plurality of blades, wherein at least a portion of said blades are angled, shaped, and/or oriented so as to impart centrifugal and axially forward forces on said wet cake.