PROCESS AND APPARATUS FOR THE RECOVERY OF AMMONIA AND CARBON DIOXIDE FROM THE TAIL GAS OF A UREA SYNTHESIS

• US 3,691,729 A
• Filed: 05/26/1971
• Issued: 09/19/1972
• Est. Priority Date: 05/30/1970
• Status: Expired due to Term

• Current Assignee: Henricus A.A. Koenders, Johan D. Logemann, Michael A De Rooy
• Original Assignee: Henricus A.A. Koenders, Johan D. Logemann, Michael A De Rooy
• Inventors: Logemann, Johan D., De Rooy, Michael A., Koenders, Henricus A. A.
• Primary Examiner(s): Friedman, Reuben
• Assistant Examiner(s): Burks, R. W.
• Application Number:
  US05/147,055
• Time in Patent Office: 482 Days
• Field of Search: 55/68,70,227 252/372 260/555A
• US Class Current: 95/211
• CPC Class Codes: C01C 1/12 Separation of ammonia from gases and vapours as part of the ammonia synthesis process C01C1/04
• CPC Class Codes: C07C 273/04 from carbon dioxide and ammonia

Abstract

A process and apparatus for the recovery of ammonia and carbon dioxide from urea synthesis tail gas is disclosed, wherein the tail gas is intensively contacted with an aqueous media in at least one absorption zone, as is known to the art, and thereafter the gas mixture leaving such absorption zone is immediately mixed with a gas which is inert to the constituents of the tail gas. The apparatus involves a gas bubble washer and an intensive gasliquid contactor, with means for supplying inert gas overlying such contactor. By the use of the present invention the possibility of forming an explosive mixture of the gases leaving the absorption zone is eliminated, or at least minimized.

Claims

2. Process as claimed in claim 1, wherein said mixing is conducted substantially at the urea synthesis pressure.

3. Process as claimed in claim 1 wherein said mixing occurs in a mixing zone which is at least partially surrounded by and in contact with a buffer zone filled with said inert gas.

4. Process as claimed in claim 3, wherein said inert gas is carbon dioxide.

5. Process as claimed in claim 1 wherein the amount of said inert gas mixed with said gas mixture is at least 10 percent of that required to form a resulting gas mixture outside the explosive limits.

6. Process as claimed in claim 3, wherein the volume of said buffer zone is at least five times larger than the volume of said mixing zone.

7. Process as claimed in claim 1, wherein said inert gas is incombustible and will not support combustion.

8. Process as claimed in claim 7 wherein said inert gas is carbon dioxide.

9. Process as claimed in claim 1, wherein the amount of said inert gas mixed with said gas mixture is at least sufficient to form a resulting gas mixture outside explosive limits.

10. Apparatus for the recovery of ammonia and carbon dioxide from hydrogen- and oxygen-containing urea synthesis tail gas, said apparatus consisting of a two-part wash column, one part of the said wash column being gas bubble washer means, said means provided with a gas space, a tail gas supply line from the urea synthesis plant, a liquid discharge line installed at a level above said tail gas supply line, and with cooling devices, the other part of said wash column connected to said gas space having means to effect intensive gas-liquid contact, means for supply and distribution of wash liquid overlying said means to effect said contact, a gas discharge line at a higher level than said means to effect said contact, and means for the supply of inert gas overlying said means to effect said contact.

11. Apparatus as claimed in claim 10, wherein said means for intensive gas-liquid contact contains a second gas space therein, is at least partially surrounded by, and is separated, by a wall, from a buffer space, said buffer space provided with means for supplying gas and connected by way of openings in said wall with said second gas space.

12. Apparatus as claimed in claim 11 wherein the volume of said buffer space is at least five times the volume of said second gas space.