RECOVERY OF N-ALKYL LACTAMS EMPLOYED IN STRIPPING OF SULFUR DIOXIDE FROM GAS STREAMS

• US 3,733,781 A
• Filed: 04/17/1972
• Issued: 05/22/1973
• Est. Priority Date: 10/30/1969
• Status: Expired due to Term

• Current Assignee: GAF Chemicals Corp (G Holdings Incorporated)
• Original Assignee: Arthur A. Bellisio, Hippocrates G. Psyras, Marvin M. Fein
• Inventors: Bellisio, Arthur A., Psyras, Hippocrates G., Fein, Marvin M.
• Primary Examiner(s): Hart, Charles N.
• Application Number:
  US05/244,762
• Time in Patent Office: 400 Days
• Field of Search: 55/56,68,73 423/242,243
• US Class Current: 95/179
• CPC Class Codes: B01D 53/1418 Recovery of products
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1481 Removing sulfur dioxide or sulfur trioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: B01D 53/507 by treating the gases with other liquids
• CPC Class Codes: C01B 17/60 Isolation of sulfur dioxide from gases

Abstract

A gas stream from an absorption zone in which sulfur dioxide is stripped therefrom by N-alkyl lactam is passed to a watercontaining scrubber zone at a gas mass flow velocity of 200-3,000 lbs/hr/ft2 in a gas temperature of 0*-75*C, preferably 35*-65*C, wherein at least about 90 percent by weight, advantageously at least about 98 percent, preferably at least about 99 percent, of the lactam vaporized or entrained in the gas stream is recovered. The gas stream leav-ing the scrubber zone, with an SO2 content of less than about 250 ppm and/or at least 90 percent of its SO2 content stripped therefrom, can be discharged to the atmosphere or otherwise disposed of without unacceptable loss of lactam. A water stream having the thus recovered lactam dissolved therein is removed from the scrubber zone and may be passed directly into the absorption zone or to a distillation zone from which a lactam-rich liquid stream can be recycled to the absorption zone. The scrubber zone will generally have a length of from about 2 ft to about 25 ft, typically from about 3 ft to about 15 ft. The water flow rate to the scrubber zone to replace the lactamcontaining stream withdrawn therefrom will generally be from about 0.05 to about 2.0, advantageously about 0.05 to about 0.25, gals of water per MCF of gas passing through the scrubber zone.

Claims

2. The process of claim 1 in which the temperature of the water in said absorption zone is from about 35*C to about 65*C.

3. The process of claim 2 in which the gas stream discharged from the absorption zone has at least about 98 percent by weight of the lactam accompanying the gas stream fed to said absorption zone removed therefrom by the water in said scrubber zone.

4. The process of claim 3 in which the lactam-containing water stream removed from the scrubber zone is passed directly into said absorption zone, water being fed to said scrubber zone at the rate at which said lactam-containing water stream is removed therefrom.

5. The process of claim 3 in which said lactam comprises N-methyl pyrrolidone.

6. The process of claim 3 in which said lactam comprises N-cyclohexyl pyrrolidone.

7. The process of claim 3 in which said gas stream from the absorption zone and said water in the scrubber zone are contacted by counter-current flow of said gas and water.

8. The process of claim 4 in which said water is fed to the scrubber at a rate of from about 0.05 to about 2.05 gal. of water per MCF of gas passing through said scrubber zone, having a length of from about 2 ft. to about 25 ft.

9. The process of claim 8 in which at least about 99 percent by weight of the lactam accompanying the gas stream fed to said absorption zone is removed therefrom by the water in said scrubber zone.

10. The process of claim 3 and including passing the lactam-containing water stream removed from the scrubber zone to a distillation zone in which water is distilled from said stream, a lactam-rich stream being passed from said distillation zone to said absorption zone.

11. The process of claim 10 in which the lactam-rich stream passed from the distillation zone to the absorption zone contains from about 2 percent to about 25 percent water by weight.

12. The process of claim 8 in which said water is fed to the scrubber at a rate of from about 0.05 to about 0.25 gal/MCF of gas being treated.

13. The process of claim 8 in which said lactam comprises an N-lower alkyl pyrrolidone.

14. The process of claim 13 in which said lactam comprises N-methyl pyrrolidone.

15. The process of claim 13 in which water is fed to the scrubber zone and lactam-containing water is removed therefrom to said distillation zone at a rate of from about 0.05 to about 0.25 gal. of water per MCF of gas passing through the scrubber zone, said scrubber zone being from about 3 ft. to about 15 ft. long, at least about 99 percent by weight of the lactam accompanying the gas stream fed to said absorption zone is removed therefrom by the water in mid scrubber zone.