Method of removing sulfur-containing gases from waste gas

• US 3,883,639 A
• Filed: 12/21/1972
• Issued: 05/13/1975
• Est. Priority Date: 08/12/1971
• Status: Expired due to Term

• Current Assignee: MW Kellogg Limited (KBR Incorporated)
• Original Assignee: Bernard G. Mandelik, Walter A. Cronkright Jr
• Inventors: Cronkright, Walter A. Jr., Mandelik, Bernard G.
• Primary Examiner(s): Thomas, Earl C.
• Assistant Examiner(s): Helby, Gregory A.
• Application Number:
  US05/317,484
• Time in Patent Office: 873 Days
• Field of Search: 423/242-244,166,512
• US Class Current: 423/243.02
• CPC Class Codes: B01D 53/501 by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• CPC Class Codes: C01F 11/48 Sulfites

Abstract

This process involves contacting a waste gas containing an oxide of sulfur with an aqueous medium having a pH below 7.1 in an autoregenerative cyclic process using limestone in combination with carbon dioxide, an added amount of a soluble sulfate of a cation such as potassium, lithium, sodium, magnesium or ammonium or mixtures of these compounds to remove the oxides of sulfur. The soluble sulfates may be added directly to the aqueous medium or may be formed in situ from the known carbonate, bicarbonate, oxide, sulfite, bisulfite, or hydroxide of these cations or ammonia after reaction with the sulfur oxides in the waste gas. Sulfur is removed from the cycle in the form of insoluble calcium sulfite and calcium sulfate.

Claims

1. A PROCESS FOR REMOVING SULFUR DIOXIDE FROM INDUSTRIAL WASTE GAS WHICH COMPRISES:

SCRUBBING WASTE GAS IN A CONTACTING ZONE WITH AN AQUEOUS MEDIUM HAVING A PH BELOW 7.1 CONTAINING CLACIUM CARBONATE, CARBON DIOXIDE AND AT LEAST ABOUT 3 WEIGHT PERCENT OF A SOLUBLE SULFATE SELECTED FROM THE GROUP CONSISTING OF SODIUM, LITHIUM, POTASSIUM, MAGNESIUM, AND AMMONIUM SULFATES, PRECIPITATING SOLIDS SELECTED FROM THE GROUP CONSISTING OF CALCIUM SULFITE AND CALCIUM SULFATE FROM THE AQUEOUS MEDIUM, REMOVING A PORTION OF SAID SOLIDS, AND INTRODUCING A REMAINING PORTION OF THE SOLIDS WITH SAID AQUEOUS MEDIUM TO THE CONTACTING ZONE.

2. The process of claim 1 wherein gas-liquid contact time in said contacting zone is less than 3 seconds.

3. The process of claim 2 wherein said contacting zone is a venturi scrubber.

4. The process of claim 2 wherein said soluble sulfate in the aqueous medium is present in the range from about 5 weight percent to about 27 weight percent.

5. The process of claim 1 wherein said soluble sulfate is generated in the aqueous medium by the addition of ammonia or the oxide, hydroxide, carbonate, bicarbonate, sulfite or bisulfite of sodium, lithium, potassium, magnesium or ammonia or mixtures thereof.

6. The process of claim 4 wherein temperature of the contacting zone is from about 100*F to about 180*F and the pressure is from about 12 psia. to about 18 psia.

7. The process of claim 1 wherein at least part of the aqueous medium is recovered as an aqueous supernatent containing at least about 3 weight percent of a soluble sulfate selected from the group consisting of sodium, lithium, potassium, magnesium, and ammonium sulfates and said aqueous supernatent is separately introduced to the contacting zone.

8. The process of claim 4 wherein at least 5 weight percent of the solids introduced to the contacting zone with said aqueous medium are calcium carbonate and said calcium carbonate is added to the aqueous medium as limestone or dolomite.

9. The process of claim 2 wherein the waste gas contains oxygen, carbon dioxide and from about 0.01 weight percent to about 5 weight percent sulfur dioxide.

10. A process for removing sulfur dioxide from industrial waste gas which comprises:

scrubbing waste gas containing from about 0.01 weight percent to about 5 weight percent sulfur dioxide in a contacting zone wherein gas-liquid contact time is less than 5 seconds with an aqueous medium having a pH below 7.1 containing calcium carbonate, carbon dioxide, and from about 5 weight percent to about 27 weight percent of magnesium sulfate precipitating as solids, calcium sulfite and calcium sulfate from the aqueous medium;

removing a portion of said solids;

introducing a remaining portion of the solids with said aqueous medium to the contacting zone, said solids containing at least 5 weight percent calcium carbonate based on total solids;

recovering at least part of the aqueous medium as an aqueous supernatent containing at least about 5 weight percent of magnesium sulfate; and

introducing said aqueous supernatent separately to the contacting zone.