Regenerable process for the selective removal of sulfur dioxide from effluent gases

• US 4,389,383 A
• Filed: 12/02/1981
• Issued: 06/21/1983
• Est. Priority Date: 05/27/1980
• Status: Expired due to Fees

• Current Assignee: UOP Des Plaines IL A NY General Partnership
• Original Assignee: Union Carbide Corporation (Dow, Inc.)
• Inventors: Atwood, Gilbert R., Sokolik, Joseph E. Jr., Kosseim, Alexander J. M.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): HELLER, GREGORY
• Application Number:
  US06/326,915
• Time in Patent Office: 566 Days
• Field of Search: 423/243, 423/242 A, 423/242 R
• US Class Current: 423/242.7
• 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 53/507 by treating the gases with other liquids
• CPC Class Codes: C01B 17/60 Isolation of sulfur dioxide from gases
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

A regenerable process for scrubbing SO₂ from effluent gases using an aqueous alkanolamine and the corresponding sulfite as the solvent, such amine having a boiling point below about 250° C. at one atmosphere pressure and wherein the alkanolamine solutions containing heat stable salts (HSS) is regenerated by alkali addition, crystallization and vacuum distillation of the amine.

Claims

1. In a process for removing sulfur dioxide from a mixture of gases wherein said mixture is contacted in an absorption zone with an amine solvent in aqueous solution to absorb SO₂ to form an SO₂ rich aqueous amine solution which is then passed to a stripping zone where SO₂ is removed from such aqueous amine solution to form a lean aqueous amine solution containing some SO₂ and heat stable salts which is recycled to the absorption zone the improvement comprising:

(a) using as the solvent an amine;

having a boiling point below about 250°

at one atmosphere;

(b) removing a portion of said lean aqueous amine being recycled to said absorption zone and passing said portion to a reaction zone;

(c) admixing said portion of lean aqueous amine with at least one alkali or alkaline earth oxide, hydroxide or carbonate in an amount such that at least one equivalent of metal cation is added per one equivalent of sulfur oxy anions present in said lean aqueous amine solution to form a heat stable solid precipitant;

(d) passing said reacted mixture to a separation zone which is at a temperature of less than about 140°

C. and at a pressure less than 250 mmHg, and maintaining said mixture at said temperature and pressure, removing as an overhead vapor phase a solution containing mainly all water and amine which is recycled back to said absorption zone and collecting a solid bottom residue comprising essentially all sulfur oxy anion salts.

2. Process according to claim 1 wherein the solvent is at least one member of the group consisting of monoethanolamine, dimethylethanolamine diethylethanolamine and benzylamine.

3. Process according to claim 1 wherein the solvent is monoethanolamine.

4. Process according to claim 1 wherein the lean aqueous amine is reacted in step (c) with sodium carbonate.

5. Process according to claim 1 wherein the portion of lean aqueous amine passed to the reaction zone is 2-10% of the stream being recycled the absorption zone.