Asset Integrity
H2S Scavenger
The production of hydrogen sulfide (H2S) gas along with petroleum fluids is a common occurrence in many areas of the world. Other sulfides that can be present include sodium hydro-sulfide, sodium sulfide, and various lower mercaptans and disulfides.
Hydrogen sulfide is corrosive even at low levels and has a toxicity level similar to that of hydrogen cyanide. The occupational exposure limit is set at 10 ppm, and exposure to concentrtions above 150 ppm could be fatal. Gas pipeline requirements often specify the maximum permitted levels of H2S, typically less than 5 ppm.
Corrosion due to hydrogen sulfide can take the form of hydrogen blistering, pitting, cracking and embrittlement (when in contact with high-strength stressed steel). These types of corrosive attacks can lead to catastrophic failures, which may occur without the warnings that might accompany other types of corrosion.
Additionally, hydrogen sulfide can form insoluble salts with many different types of metal ions that might be present in the produced water, causing fouling, filter blocking and injection-well damage.
Hydrogen sulfide can be a natural component of some petroleum reservoirs, or it may arise from bacterial reduction of sulfur compounds in the water. Most produced water that contains hydrogen sulfide is disposed at, or near to, the production site, so safety and corrosion concerns must be considered in these systems.
Sulfide generated by bacteria may form at relatively low levels in water, but when liberated and concentrated in the vapor phase, it has been seen to reach levels in excess of 2,000 ppm.
Forms of hydrogen sulfide
Sulfide can exist in water solution in three different forms:
H2S, the molecular form of the compound, is soluble in water and oil, but, due to its volatility, may be concentrated in the vapor phase in most systems. HS, the hydrosulfide ion, is the result of partial ionization of H2S as the pH of water is increased. This ion can exist in equilibrium concentrations with H2S over the approximate pH range of 5 to 9. S, the sulfide ion, predominates at very high levels of pH.
DESHI Group offers a range of sulfide scavengers based on reaction products of amines and aldehydes.These products have been developed for application in gas, water and oil streams, and they react rapidly with sulfide to form tightly-bound organosulfur compounds. They may be applied as a solution in bubble towers for gas treating, or atomized directly into the gas streams. When used in water systems, rapid sulfide removal is possible and, in many cases, insoluble metallic salts of sulfides can be re-dissolved with these products.
The products designed for water and gas application form water-soluble, low-toxicity, biodegradable compounds which are non-corrosive and which will not release hydrogen sulfide-even over extremes of pH variation.