Process for the removal of acid gases from gas mixtures

• US 4,702,898 A
• Filed: 10/17/1986
• Issued: 10/27/1987
• Est. Priority Date: 10/17/1986
• Status: Expired due to Fees

• Current Assignee: UOP Des Plaines IL A NY General Partnership
• Original Assignee: Union Carbide Corporation (Dow, Inc.)
• Inventors: Grover, Bhadra S.
• Primary Examiner(s): Metz, Andrew H.
• Assistant Examiner(s): MCFARLANE, ANTHONY R
• Application Number:
  US06/920,277
• Time in Patent Office: 375 Days
• Field of Search: 423/220, 423/228, 423/229, 423/232, 423/234, 55/68, 55/73
• US Class Current: 423/220
• CPC Class Codes: B01D 53/14 by absorption
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: C01B 2203/0415 Purification by absorption in liquids
• CPC Class Codes: C01B 2203/0475 the impurity being carbon dioxide
• CPC Class Codes: C01B 3/52 by contacting with liquids; Regeneration of used liquids C01B3/508 takes precedence
• CPC Class Codes: C10K 1/12 alkaline-reacting including the revival of the used wash liquors

Abstract

The present invention is directed to an improved process for the removal of acid gases from gas mixtures which significantly decreases the consumption of heat needed for regenerating the rich alkaline scrubbing solution which is used to remove the acid gases from the gas mixtures. The process comprises passing one portion of the scrubbing solution through a steam stripping section and another portion of the scrubbing solution through a flashing section for regeneration wherein the overhead vapors from the steam stripping section are used to heat and strip the scrubbing solution in the flashing section and heat contained within the regenerated scrubbing solution coming from the steam stripping section is utilized to aid in the regeneration of the scrubbing solution in the flashing section.

Claims

1. In a cyclic process for the removal of acid gases from a feed gas by means of an aqueous alkaline scrubbing solution which is continuously recycled between an absorption zone in which said acid gases are absorbed by said scrubbing solution to form a rich scrubbing solution and a regeneration zone in which said acid gases are desorbed from said rich scrubbing solution to form a lean solution, the improvement which comprises regenerating the rich solution in a regeneration zone which comprises (1) a steam stripping section and (2) and a flashing section containing at least one flashing stage and an acid gas stripping stage wherein:

(a) a first portion of the rich scrubbing solution is passed through the steam stripping section wherein it is regenerated to form a lean solution which is recycled to the absorption zone and a vapor stream containing removed acid gases and steam;

(b) a second portion of the rich scrubbing solution is passed through a flashing stage in which the rich scrubbing solution is flashed to remove acid gases and steam therefrom to form a partially regenerated solution;

(c) the partially regenerated solution is passed through the acid gas stripping stage in which the partially regenerated solution is countercurrently contacted with and stripped by the vapor stream from the steam stripping section to remove acid gases and steam from the partially regenerated solution; and

(d) the lean scrubbing solution leaving the steam stripping section is utilized to heat the partially regenerated solution in the flashing section to thereby form steam which strips additional acid gases from the partially regenerated solution.

2. The process of claim 1, wherein the first portion of rich scrubbing solution is flashed prior to entering the steam stripping section.

3. The process of claim 2, wherein the first portion of rich scrubbing solution is flashed in the flashing stage in which the second portion of rich scrubbing solution is flashed.

4. The process of claim 1, wherein the feed gas is a hot, steam-containing gas.

5. The process of claim 4, wherein the first portion of the rich scrubbing solution is indirectly heated in the steam stripping section with the hot steam-containing feed gas.

6. The process of claim 1, wherein the lean scrubbing solution leaving the steam stripping section is flashed prior to being recycled to the absorption zone to remove low pressure steam, which steam is recycled back to the steam stripping section.

7. The process of claim 1, wherein the absorption zone is comprised of two stages comprising a first stage through which the feed gas is passed and in which the bulk of the acid gases are removed and a second stage through which the feed gas is subsequently passed in which additional acid gases are removed.

8. The process of claim 7, wherein lean solution regenerated in the steam stripping section is recycled to the second stage of the absorption zone and lean solution regenerated in the flashing section is recycled to the first stage of the absorption zone.

9. The process of claim 7, wherein partially rich scrubbing solution from the second stage of the absorption zone is introduced as a scrubbing solution in the first stage of the absorption zone.

10. The process of claim 9, wherein the partially rich scrubbing solution from the second stage of the absorption zone, prior to being introduced as a scrubbing solution in the first stage of the absorption zone, is used to indirectly heat the first portion of rich scrubbing solution which is being introduced into the steam stripping section and which has previously been flashed to remove acid gases.

11. The process of claim 7, wherein the first portion of rich scrubbing solution is taken off from the second stage of the absorption zone and the second poriton of the rich scrubbing solution is taken off from the first stage of the absorption zone and where each portion is a different alkaline scrubbing solution.

12. The process of claim 7, wherein the lean solution leaving the steam stripping section is used as a scrubbing solution in the second stage of the absorption zone and the lean solution leaving the flashing section is used as a scrubbing solution in the first stage of the absorption zone.

13. The process of claim 7, wherein the temperature in the first stage of the absorption zone is in the range of from about 198°

to 213°

F.

14. The process of claim 1, wherein after the partially regenerated solution passed through the acid gas stripping stage, it is then passed through one or more additional flashing stages and where the flashed acid gases and steam from these additional flashing stages are introduced as a stripping medium in the acid gas stripping stage.