TH31373A - Methods and systems of separation and purification of perfluoro compounds. - Google Patents

Abstract

DC60 (05/03/44) will provide a novel method and system for the separation and purification of perfluorocarbon compounds (PFCs). The method consists of the following steps: (a) introducing the perfluorocarbon-containing gas into the first distillation column; (b) removing the light product from the first column and removing the heavy product from the first column; (c) introducing the light product from the first column into the second distillation column; (d) removing the light product from the second column and removing the heavy product from the second column; (e) introducing the light product from the second column into the third distillation column; and (f) removing the light product from the third column and removing the heavy product from the third column. The method and system can be advantageously applied in the treatment of gases discharged from semiconductor manufacturing equipment and will result in highly purified PFCs that can be recycled, thus avoiding the release of PFCs into the atmosphere. A novel methodology and system will be provided for the separation and purification of perfluorocarbon compounds (PFCs). The methodology consists of the following steps: (a) introducing the perfluorocarbon-containing gas into the first distillation column; (b) removing the light product from the first column and removing the heavy product from the first column; (c) introducing the light product from the first column into the second distillation column; (d) removing the light product from the second column and removing the heavy product from the second column; (e) introducing the light product from the second column into the third distillation column; and (f) removing the light product from the third column and removing the heavy product from the third column. The method and system can be advantageously applied in the treatment of gases discharged from semiconductor manufacturing equipment and will result in highly purified PFCs that can be recycled, thus avoiding the release of PFCs into the atmosphere.

Claims (37)

1. The method for purifying perfluorocarbons consists of the following steps: (a) introducing a stream of gas containing perfluorocarbons into the first distillation column; (b) removing light products from the first column and heavy products from the first column; (c) introducing the light products from the first column into the second distillation column; (d) removing light products from the second column and heavy products from the second column; (e) introducing the light products from the second column into the third distillation column; and (f) removing light products from the third column and heavy products from the third column. Thus, pure perfluorocarbons are obtained. 2. Method according to claim 1, where a stream of gas containing perfluorocarbons composed of C2F6 and CF4. 3. Method according to claim 1, where C2F6 is removed as a heavy product exiting the second column and CF4 is removed as a heavy product exiting the third column. 4. Method under claim 3, whereby the heavy product of the second column is packed with C2F6 containing less than approximately 10 ppm of impurities. 5. Method under claim 3, whereby the heavy product of the third column is packed with CF4 containing less than approximately 10 ppm of impurities. 6. Method according to claim 3, where the heavy product of the second column is packed with C2F6 with approximately 10 ppm less impurities, and the heavy product of the third column is packed with CF4 with approximately 10 ppm less impurities. 7. Method under claim 2, where the gas stream contains perfluorocarbon compounds further comprising N2 and SF6. 8. Method according to claim 7, where N2 is removed as a light product exiting the third column and SF6 is removed as a heavy product exiting the first column. 9. Method under claim 1, where the second and third columns are thermally connected. 10. The method according to claim 9, where the second and third columns are stacked layer upon layer. 11. Method according to claim 10, where the third column is superimposed on the second column. 12. Method according to claim 9, where the second and third columns are enclosed in a single shell. 13. The method under claim 9, where the liquid in the lower part of the third column condenses the vapors coming from the upper part of the second column. 14. Method according to claim 1, where columns one, second and third are thermally connected. 15. Method according to claim 1, where the first column operates at a pressure range from approximately 5 to 15 bar and at a temperature range from approximately 0° to -99°C. 16. The method under claim 1, where the second column operates at a pressure range of approximately 5 to 12 bar and at a temperature range of approximately 0° to -120°C, and the third column operates at a pressure range of approximately 1 to 10 bar and at a temperature range of approximately -50° to -200°C. 17. Method pursuant to claim 16, whereby the second column operates at temperatures in the range of approximately -25° to -100°C. 18. Method pursuant to claim 16, where the third column operates at temperatures ranging from approximately -90° to -180°C. 19. The procedure under claim 1, which is further comprising the introduction of the heavy product from the second column into the fourth distillation column. 20. Method according to claim 1, where a stream of gas containing perfluorocarbon compounds is fed to the adsorption unit before being introduced into the first column. 21. Method under claim 20 where the gas stream containing the perfluorocarbon compound is cooled to a temperature range of approximately -120° to -30°C at or before being fed to the cooled absorption unit. 22. The method under claim 1, which includes the recycling of at least a portion of one or more product streams to the point of origin of the product stream. 23. The method pursuant to claim 22, which includes the recycling of at least a portion of one or more streams of the product into a stream of gas containing perfluorocarbon compounds. 24. The procedure under claim 1, where the first column operates in the approximate range of 0° to -120°C and the third column operates at temperatures in the approximate range of -50° to -200°C. 25. The method for purifying perfluorocarbon compounds involves the following steps: (a) introducing a stream of gas containing perfluorocarbon compounds composed of C2F6, CF4, N2, and SF6 into the first distillation column; (b) removing the light product containing C2F6, CF4, and N2 from the first column and removing the heavy product containing SF6 from the first column; (c) transferring the light product from the first column to the second distillation column; (d) removing the light product containing CF4 and N2 from the second column and removing the heavy product containing C2F6 from the second column; (c) removing the light product from the third distillation column; and (f) removing the light product containing N2 from the third column and removing the heavy product containing CF4 from the third column. 26. The system for the purification of perfluorocarbons consists of: (a) a pipe connected to the source containing the perfluorocarbons, which is connected to the first column for conducting the perfluorocarbons and a pipe for removing heavy products from the first column; (b) a second distillation column and pipes connecting the first and second columns for conveying light products from the first to the second column and for removing heavy products from the second column; and (c) a third distillation column and pipes connecting the second and third columns for conveying light products from the second to the third column, a pipe for removing heavy products from the third column, and a pipe for removing light products from the third column. 27. A system pursuant to claim 26 where the second and third columns are thermally connected. 28. The system pursuant to claim 27, where the second and third columns are stacked one on top of the other. 29. The system pursuant to claim 28, whereby the third column is superimposed on the second column. 30. The system pursuant to claim 28, whereby the liquid from the bottom of the third column is provided to perform condensation in the second column, and the vapor in the second column is provided to perform re-boiling in the third column. 31. A system pursuant to claim 27 where the second and third columns are enclosed in a single shell. 32. A system pursuant to claim 27 where the first, second and third columns are thermally connected. 33. The system under claim 26, which includes a piping system for bringing the heavy product from the second column into the fourth distillation column. 34. The system under claim 26, which includes an upstream cold absorption unit in contact with the first column. 35. The system under claim 34, which includes equipment for cooling the feed to the absorption unit to a temperature ranging from approximately -120°C to -30°C. 36. A system under claim 26, which includes a pipeline for recycling one or more streams of product to the point of origin of the product stream. 37. A system as per claim 36, which includes a pipeline for recycling one or more streams of product to semiconductor manufacturing equipment (Clause 37, drawing - diagram).