Stabilized chelating agents for removing hydrogen sulfide

• US 4,891,205 A
• Filed: 02/24/1986
• Issued: 01/02/1990
• Est. Priority Date: 02/24/1986
• Status: Expired due to Term

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Bedell, Stephen A.
• Primary Examiner(s): Doll, John
• Assistant Examiner(s): RUSSEL, JEFFREY E
• Application Number:
  US06/831,969
• Time in Patent Office: 1,408 Days
• Field of Search: 423/573 R, 423/220, 423/576.6, 556/2, 556/6, 252/189, 252/190, 252/191, 252/192
• US Class Current: 423/576.6
• CPC Class Codes: B01D 53/52 Hydrogen sulfide
• CPC Class Codes: C01B 17/05 by wet processes
• CPC Class Codes: C10K 1/10 with aqueous liquids alkaline reacting aqueous liquids C10K1/12

Abstract

Soluble chemical compounds having a high affinity for hydroxyl radicals are effective stabilizers for chelating agents used in the hydrogen sulfide removal process. The stabilizers include aromatic compounds, bromide ions, iodide ions, cyanides, nitrites, amino acids, sugars, ascorbates, alcohols, polyols, aliphatic aldehydes, compounds having unsaturated carbon-carbon bonds, dimethyl sulfoxide, organic disulfides, alkyl amines, and formates. The aromatic compounds have the additional benefit of combining with hydroxyl radicals to form chelating agents.

Claims

1. A method for removing hydrogen sulfide from gas streams, comprising the steps of:

passing a gas containing hydrogen sulfide through a stabilized aqueous solution initially comprising;

metal ions in a concentration of at least about 100 ppm;

a chelating agent in an amount of at least equimolar to said metal ions;

a buffering compound in a concentration sufficient to provide a pH between 4 and 11; and

an inhibitor in a concentration sufficient to retard degradation of the chelating agents, the inhibitor being selected from a group consisting of iodide ions, bromide ions, nitrites, amino acids, alkyl amines, and combinations thereof;

continuously oxidizing said sulfide to elemental sulfur while reducing said metal ions, a portion of the inhibitor combining with free hydroxyl radicals formed in the solution;

removing said elemental sulfur from said solution; and

oxidizing said metal ions with oxygen to regenerate the solution.

2. The method of claim 1, wherein the metal ion is iron.

3. A method for removing hydrogen sulfide from gas streams, comprising the steps of:

passing a gas containing hydrogen sulfide through a stabilized aqueous solution initially comprising;

metal ions in a concentration of at least about 100 ppm;

a chelating agent in an amount at least equimolar to said metal ions;

a buffering compound in a concentration sufficient to provide a pH between 4 and 11; and

iodide ions in a molar concentration of at least two times greater than said metal ions;

continuously oxidizing said sulfide to elemental sulfur while reducing said metal ions, a portion of the iodide ions combining with free hydroxyl radicals formed in the solution;

removing said elemental sulfur from said solution; and

oxidizing said metal ions with oxygen to regenerate the solution.

4. The method of claim 3, wherein the iodide ions are presented in the form of potassium iodide, sodium iodide or ammonium iodide.

5. The method of claim 4, wherein the metal ion is iron.

6. A method for removing hydrogen sulfide from gas streams, comprising of:

passing a gas containing hydrogen sulfide through a stabilized aqueous solution initially comprising;

metal ions in a concentration of at least about 100 ppm;

a chelating agent in an amount at least equimolar to said metal ions;

a buffering compound in a concentration sufficient to provide a pH between 4 and 11; and

bromide ions in a molar concentration of at least two times greater than said metal ions;

continuously oxidizing said sulfide to elemental sulfur while reducing said metal ions, a portion of the bromide ions combining with free hydroxyl radicals formed in the solution;

removing said elemental sulfur from said from said solution; and

oxidizing said metal ions with oxygen to regenerate the solution.

7. A method for removing hydrogen sulfide from gas streams, comprising:

passing a gas containing hydrogen sulfide through a stabilized aqueous solution initially comprising;

metal ions in a concentration of at least about 100 ppm;

a chelating agent in an amount at least equimolar to said metal ions;

a buffering compound in a concentration sufficient to provide a pH between 4 and 11; and

bromide ions in a molar concentration of at least two times greater than said metal ions;

wherein the bromide ions are presented in the form of potassium bromide, sodium bromide or ammonium bromide;

continuously oxidizing said sulfide to elemental sulfur while reducing said metal ions, a portion of the bromide ions combining with free hydroxyl radicals formed in solution;

removing said elemental sulfur from said solution; and

oxidizing said metal ions to regenerate the solution.

8. The method of claim 7, wherein the metal ion is iron.

9. A method for removing hydrogen sulfide from gas streams, comprising the steps of:

passing a gas containing hydrogen sulfide through a stabilized aqueous solution initially comprising;

metal ions in a concentration of at least about 100 ppm;

a chelating agent in an amount of at least equimolar to said metal ions;

a buffering compound in a concentration sufficient to provide a pH between 4 and 11; and

an aliphatic aldehyde in a molar concentration of at least 2 times greater than said metal ions;

continuously oxidizing said sulfide to elemental sulfur while reducing said metal ions, a portion of the aliphatic aldehyde combining with free hydroxyl radicals formed in the solution;

removing said elemental sulfur from said solution; and

oxidizing said metal ions to regenerate the solution.