Method and apparatus for separating dioxin from fluidizable solids

• US 4,685,220 A
• Filed: 09/02/1983
• Issued: 08/11/1987
• Est. Priority Date: 09/02/1983
• Status: Expired due to Term

• Current Assignee: Recycling Sciences International Incorporated
• Original Assignee: American Toxic Disposal, Inc.
• Inventors: Sullivan, George D., Meenan, William C.
• Primary Examiner(s): Makay, Albert J.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/528,910
• Time in Patent Office: 1,439 Days
• Field of Search: 34/10, 34/27, 34/32, 34/57 R, 34/57 A, 34/57 D, 34/73, 34/79, 34/80, 34/82, 55/71, 55/257 C, 55/406, 159/DIG. 3, 159/4 R, 210/694, 110/227, 110/238, 110/346
• US Class Current: 588/320
• CPC Class Codes: B09C 1/06 thermally
• CPC Class Codes: C02F 11/004 Sludge detoxification
• CPC Class Codes: C02F 11/13 by heating

Abstract

A process and apparatus for treating any fluidizable solid material having a dioxin contaminant absorbed or adsorbed thereon. The method and apparatus includes heating the fluidizable solids, using hot turbulent gas at a temperature in the range of 850° to 2,500° F. to vaporize and thereby separate the dioxin from the fluidizable solids and to fluidize at least a portion of the solids. The dioxin are then further treated to dispose of the dioxins, such as by condensing the liquid and filtering or decanting them from the condensed water.

Claims

1. A method for treating a fluidizable solid material contaminated with a dioxin comprising:

heating said material by exposure to hot gas in a drying vessel at a temperature of from 850°

to 2,500°

F. thereby separating the dioxin from the material; and

conveying said separated dioxin out of said drying means for further treatment.

2. The method of claim 1 including exposing said material to said hot gas for a period of time sufficient to leave 5 parts per million or less of the dioxins in the material.

3. The method of claim 2 wherein the material is exposed to said hot gas for a period of about 1 minute to about 1.5 hours.

4. The method of claim 1 wherein the hot gas vaporizes said dioxin and entrains a portion of the material, as fine particulates, into said vaporized dioxin.

5. The method of claim 4 further including separating the particulates from the dioxins.

6. A method for treating a fluidized solid material contaminated with a dioxin comprising:

contacting the fluidizable solid material in a separator with hot turbulent gas at a temperature of 850°

F. to 2500°

F. to vaporize the dioxin and thereby separate the dioxin from the material and gaseously entrain a portion of the finer fluidizable solid material in particulate form, leaving a dryed particulate mass of fluidized solids having about 5 ppm or less of dioxin; and

conveying the separated dioxin out of said separator.

7. The method of claim 6 further including conveying the entrained particulate fluidizable solids out of said separator and separating the entrained particulate solids from the vaporized dioxin.

8. The method of claim 7 wherein the fluidizable solids is contacted with hot turbulent air and combustion gases at a temperature of 1000°

F. to 1800°

F.

9. The method of claim 7 including directing the fluidizable solids into the separator and onto a first drying surface disposed within said separator, said first surface angled downwardly from a periphery of the separator towards a longitudinal center of the separator for directing the fluidizable solids into a position at the longitudinal center of the separator for contact with the hot turbulent gas and vaporization of the dioxins;

and

dropping the fluidizable solids from said first surface onto a lower, second drying surface disposed within said separator, said second surface angled downwardly from the longitudinal center of the separator towards the periphery of the separator for directing the fluidizable solids toward the periphery of the separator, while vaporizing the dioxin from the fluidizable solids.

10. The method of claim 9 wherein said first and second drying surfaces are frusto-conically shaped.

11. The method of claim 7 including condensing the vaporized dioxin from the vapor conveyed out of the vaporization chamber.

12. The method of claim 8 including condensing a portion of the vapors conveyed out of the vaporization chamber to form a condensate and separating a substantial portion of the condensed dioxin from the remaining condensate.

13. The method of claim 12 wherein the vapors conveyed out of the vaporization chamber are chilled to a temperature below about 200°

F. to form said condensate.

14. The method of claim 13 wherein the vapors conveyed out of the vaporization chamber are chilled to a temperature below about 100°

F. to form said condensate.

15. The method of claim 12 wherein the condensate includes at least 10% by weight water and including separating the water from the dioxin by decanting the water therefrom.

16. The method of claim 8 wherein the vapor and entrained particulates are conveyed through a means for separating solids from gas and the gaseous portion is conveyed to a condenser to condense a major portion of the dioxin from the vapor as a toxic condensate.

17. The method of claim 16 including conveying the toxic condensate through a filter capable of selectively filtering said dioxin from the remaining condensate.

18. The method of claim 8 wherein the fluidizable solids comprises a sludge having 10-90% fluidizable solids and 10-90% liquid, said liquid being predominantly water.

19. The method of claim 18 wherein the fluidizable solids contains at least 20% by weight water so that water vapor formed in the first fluidized bed aids in entraining vaporized dioxin out of the vaporization chamber.

20. A method of removing a dioxins from a fluidizable solid material comprising:

conveying said fluidizable solids and a hot, turbulent gas at a temperature of about 850°

-2500°

F. into a vaporization chamber;

contacting said fluidizable solids with said hot turbulent gas in a hot gas-fluidizable solids first fluidized bed contacting zone in a lower portion of said vaporization chamber to fluidize at least a portion of said fluidizable solids in said lower portion of said vaporization chamber, to vaporize a majority of said dioxin from said fluidizable solids in said lower portion; and

to cool said hot gases;

conveying said cooled hot gas upwardly through said vaporization chamber at a rate sufficient to propel a finer particulate portion of the fluidizable solids above the first fluidized bed contacting zone to a second fluidized bed contacting zone at a lower temperature than, and disposed above, said first fluidized bed contacting zone, whereby a finer particulate portion of the fluidizable solids is fluidized by said cooled hot gases and additional dioxin are vaporized from said fluidized finer particulates in said second fluidized bed contact zone;

recycling a portion of the fluidizable solids particulates from the second fluidized bed down to the first fluidized bed for further vaporization of dioxin from said recycled particulates; and

conveying said gases and vaporized dioxins out of the vaporization chamber for further treatment.

21. The method of claim 20 wherein the second fluidized bed has a temperature of 250°

to 500°

F.

22. The method of claim 21 wherein the second fluidized bed has a temperature of 300°

to 350°

F.

23. The method of claim 20 including separating the fluidizable solids particulates from the vapor conveyed out of the vaporization chamber.

24. The method of claim 20 including grinding the fluidizable solids in the vaporization chamber while contacting said fluidizable solids with said hot gas.

25. The method of claim 24 wherein said first fluidized bed is disposed below an area in said vaporization chamber where said fluidizable solids is ground and including conveying a coarser portion of the ground fluidizable solids down to said first fluidized bed and agitating the coarser fluidizable solids in said first fluidized bed to achieve more efficient vaporization of said dioxins.

26. The method of claim 20 wherein the vaporization chamber includes a rotating member having radially extending blades disposed in an upper portion of the vaporization chamber whereby a portion of the particulates entrained in the rising gas is mechanically pushed downwardly by said blades for recycling to said first fluidized bed.

27. An apparatus for treating dioxin contaminated sludge comprising:

separating means for separating the dioxin and water from the sludge, said separating means including means for exposing the sludge to a hot gas stream to vaporize the dioxin; and

means for separating the vaporized dioxin from said water.

28. An apparatus for treating dioxin contaminated sludge comprising:

separating means for separating the dioxin and water from the sludge, said separating means including means for exposing the sludge to a hot gas stream for a period of time sufficient to vaporize a substantial portion of the dioxin from the sludge, leaving 10 PPM or less of the dioxin in the sludge; and

means for conveying said separated dioxin and water out of said drying means for further treatment.

29. An apparatus for treating dioxin contaminated sludge comprising:

separating means for separating the dioxin and water from the sludge thereby leaving 5 PPM or less of the dioxin in the sludge, said separating means including means for exposing the sludge to a hot gas stream to dry the sludge and convey water vapor, gaseously entrained dioxin and sludge particulates away from said separating means; and

means for separating the particulates from the water and dioxin.

30. Apparatus as defined in claim 29 further including means for separating a substantial portion of said water from said dioxin.

31. Apparatus for removing dioxin from a fluidizable solid containing material comprising:

a vessel for vaporizing said dioxin from said fluidizable solids, said vessel including means for contacting said fluidizable solids with a hot gas in a lower portion of the vessel to form a first fluidized bed of said fluidizable solids in said lower portion of said vessel;

means for conveying hot turbulent gas into said lower portion of said vessel at a rate sufficient to form said fluidized bed upon contact with said fluidizable solids in said lower portion of said vessel and to propel a portion of said fluidizable solids upwardly, above said fluidized bed, said gas having a temperature sufficient to vaporize said dioxin from said fluidizable solids and to dry said fluidizable solids;

means for recycling a portion of said upwardly propelled fluidizable solids back to said lower portion of said vessel for additional contact with said hot gas and additional vaporization of dioxin therefrom; and

means for conveying vapors, including vaporized dioxin, out of said vessel for further treatment.

32. The apparatus of claim 31 including means for separating solids from the vapors conveyed out of said vessel.

33. The apparatus of claim 31 including means for condensing a major portion of the vapors conveyed out of the vessel to form a toxic condensate.

34. The apparatus of claim 33 including means for separating the dioxin from the remainder of the condensate.

35. The apparatus of claim 33 including filter means having a positive charge for selectively removing a major portion of the dioxin from said condensate when said condensate is conveyed through said filter, and means for conveying said condensate through said filter.

36. The apparatus of claim 33 including means disposed within said vessel for grinding the fluidizable solids to a smaller particle size while said fluidizable solids is in contact with hot gas.

37. The apparatus of claim 36 wherein said fluidized bed is disposed below said grinding means.

38. The apparatus of claim 37 including means for agitating the fluidizable solids in the fluidized bed.

39. The apparatus of claim 38 wherein said agitating means comprises a rotating impeller disposed in a lower portion of the vessel.

40. The apparatus of claim 31 wherein said recycling means includes a rotating impeller including a plurality of impeller blades disposed in an upper portion of the vessel so that contact of fluidizable solid particulates against said impeller blades forces a portion of the particulates downwardly in said vessel for further contact of hot gas.