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How does elemental sulfur form in a water system?

Q: In our Flare Gas Recovery Unit, the liquid ring compressors suction check valve and coolers shell tubes side (cone seal water) get covered with deposits that contain 95%wt elemental sulfur plus iron and carbon. Our question is: How elemental sulfur forms from H₂S or other sulfur compounds in this water system? I have always heard that elemental sulfur indicates that oxygen was present. I have no independent basis to know whether this is true. Assuming that it is true, then logic would suggest that there must have been some H₂S or a similar compound present along with oxygen (in the water that was non-de-aerated, so I suppose that water could have been a source of oxygen). The refinery flare gases contain some H₂S, and some minor amount of oxygen. Initially we used to use reject water from an RO unit as the main water source. That water is no longer used, since it has been change to Stripped Sour water. Water system pH is controlled between 7.3 and 8.3.

A: As a veteran of the chemical processing industry and more specifically the pharmaceutical industry, I am not familiar with petrochemical industry processes so I am not in a position to answer your question. ASM Handbook Volume 13C has a section entitled "Corrosion in Petroleum Production Operations" and discusses hydrogen sulfide, polysulfides, and sulfur. Perhaps that would be a good place to start in getting an answer to your question.

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