Method of removing hydrogen sulfide from gases utilizing a polyvalent metal chelate solution and electrolytically regenerating the solution

• US 4,443,424 A
• Filed: 09/30/1982
• Issued: 04/17/1984
• Est. Priority Date: 09/30/1982
• Status: Expired due to Term

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Olson, Donald C.
• Primary Examiner(s): Thomas, Earl C.
• Application Number:
  US06/430,462
• Time in Patent Office: 565 Days
• Field of Search: 423/224, 423/226, 423/573 G, 423/573 R, 429/17, 429/27, 204/129-131
• US Class Current: 423/576.6
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1468 Removing hydrogen sulfide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: C01B 17/05 by wet processes
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

A process for the removal of H₂ S from sour gas streams is described, the process being characterized by the utilization of washing solutions containing oxidizing polyvalent metal chelates of specified aminocarboxylic acids, and by the electrolytic regeneration of spent solutions. Use of an optional CO₂ -selective absorbent in the washing solution is also disclosed.

Claims

1. A process for the removal of H₂ S from a sour gaseous stream comprising

(a) contacting the sour gaseous stream in a contacting zone with an aqueous reaction solution at a temperature below the melting point of sulfur, the solution containing an effective amount of an oxidizing reactant comprising an oxidizing polyvalent metal chelate of an acid having the formula ##STR3## wherein from two to four of the groups Y are selected from acetic and propionic acid groups;

from zero to two of the groups Y are selected from 2-hydroxy ethyl, 2-hydroxy propyl, and ##STR4## wherein X is selected from acetic acid and propionic acid groups; and

R is ethylene, propylene or isopropylene or alternatively cyclohexane or benzene where the two hydrogen atoms replaced by nitrogen atoms are in the 1,2 position, and mixtures thereof;

and producing a sweet gas stream and an aqueous reaction solution containing crystalline sulfur, hydrogen ions, and reduced polyvalent metal chelate or chelates of said acid;

said contacting zone comprising an anode section of an electrochemical cell, said cell also comprising a separate cathode section containing a cathode connected through an external electrical connection to the anode, the anode section and the cathode section being separated by a hydrogen ion permeable barrier;

(b) oxidizing the reduced polyvalent metal chelate or chelates of said acid in the aqueous reaction solution at the anode by supplying direct current to said cell and allowing hydrogen ions to migrate to the cathode, concomitantly supplying oxygen to the cathode and forming water at the cathode;

(c) removing sulfur from the aqueous reaction solution, and water from the cathode section.

4. The process of claim 1 wherein the aqueous reaction solution comprises a liquid absorbent selective for CO₂.

2. A process for the removal of H₂ S from a sour gaseous stream comprising

(a) contacting the sour gaseous stream in a contacting zone with an aqueous reaction solution at a temperature below the melting point of sulfur, the solution containing an effective amount of an oxidizing reactant comprising an oxidizing polyvalent metal chelate of an acid having the formula ##STR5## wherein from two to four of the groups Y are selected from acetic and propionic acid groups;

from zero to two of the groups Y are selected from 2-hydroxy ethyl, 2-hydroxy propyl, and ##STR6## wherein X is selected from acetic acid and propionic acid groups; and

R is ethylene, propylene or isopropylene or alternatively cyclohexane or benzene where the two hydrogen atoms replaced by nitrogen atoms are in the 1,2 position, and mixtures thereof;

and producing a sweet gas stream and an aqueous admixture containing crystalline sulfur, hydrogen ions, and reduced polyvalent metal chelate or chelates of said acid;

(b) removing sulfur from the admixture;

(c) regenerating aqueous admixture from step (b) electrolytically by passing admixture from step (b) through the anode section of an electrochemical cell and supplying direct current to said cell to oxidize the reduced chelate or chelates in the admixture at the anode and producing a regenerated aqueous admixture containing regenerated oxidizing reactant, the anode section and the cathode section of the electrochemical cell being separated by a hydrogen ion permeable barrier;

concomitantly supplying oxygen to the cathode section of said cell, and allowing hydrogen ions to migrate to the cathode section, and forming water at the cathode;

(d) removing regenerated aqueous admixture from anode section, and water from said cathode section; and

(e) returning regenerated aqueous admixture to the contacting zone.

3. The process of claim 2 wherein the oxidizing reactant is the ferric chelate of N-(2-hydroxyethyl)ethylenediaminetriacetic acid.

5. The process of claim 2 wherein the aqueous reaction solution comprises a liquid absorbent selective for CO₂.

6. The process of claim 3 wherein the aqueous reaction solution comprises a liquid absorbent selective for CO₂.