H2S abatement with stabilized chelates in geothermal drilling

This patent describes a method for removing hydrogen sulfide from a gas stream. It comprises contacting a gas containing hydrogen sulfide with an aqueous chelating solution to form elemental sulfur, the solution comprising: ferric ions in a concentration of at least about 100 ppm; an aminocarboxylic acid chelating agent in an amount of at least an equivalent weight relative to the ferric ions; a buffering compound for maintaining a pH between about 4 and about 11; and a water-soluble inhibitor having a hydroxyl reaction rate constant of at least about 1 x 109 dm3mol-1s-1 effective as a hydroxyl radical scavenger in an amount substantially in excess of an equivalent weight relative to the ferric ions, the inhibitor selected from the group consisting of iodide and bromide ions, nitrites, amino acids, aliphatic aldehydes, aryl sulfonic acids, and combinations thereof; wherein at least a portion of the ferric ions are reduced to ferrous ions; removing the sulfur from the solution; and oxidizing the ferric ions to regenerate the solution for reuse