SulfurUnit Logo

Sulfide Stress Cracking

Hydrogen sulfide has been studied for hundreds of years. In the 19th century, Petrus Johannes Kipp, a Dutch pharmacist invented a device that would generate a variety of gases using liquids and solids as regents. It is called the Kipp Generator and would be quite foreign to lab chemists today. H2S and H20 both contain hydrogen, but that’s where their commonalities end. H2O contains Oxygen and is harmless. H2S contains Sulfur and can kill you.

Hydrogen sulfide is a colorless gas with a distinct, offensive odor at low concentrations and is said to smell like rotten eggs. It is heavier than air and is flammable. H2S has a flash point at approximately 500 degrees. One might think 500 degrees is quite a high temperature. But it’s lower than you think when you consider the end of a cigarette butt is approximately 1400 degrees. H2S is somewhat soluble in water and it reacts with strong oxidizers, nitric acid and metals. Simply put, if you have process with H2S running through the pipes and towers, you’re going to have to pay attention to corrosion issues. One issue Refiners struggle with is the “Wet H2S cracking” problem. It occurs in different concentrations, dependent on the unit process and wherever there is a wet H2S environment, such as fractionators’ overhead drums, absorber and stripper towers and separators.

There is a wide range of damage mechanisms that can occur due to the effect of hydrogen charging in wet H2S environments. One of the more common problems is SSC, Sulfide stress cracking. The H2S causes the Hydrogen to enter the metal structure rather than bubble off from the surface. To protect from SSC, HIC (hydrogen induced cracking) and other damage mechanisms, refiners use a variety of defenses; chemical injection, such as Ammonium Polysulfide, upgraded metal cladding and coating.

Hydrogen Sulfide can cause Iron sulfides (FeS) build up. If Iron sulfides are exposed to oxygen and dry, it can be pyrophoric. When burned, H2S will create S02, Sulfur Dioxide.

Menu Title