Hydrogen Sulfide

Craig Spears

December 19, 2006

Hydrogen Sulfide (H 2 S) is an interesting species. 

It has the characteristic odor of rotten eggs that I am sure you have smelled.  What’s interesting, though, is that this smell is only apparent in low concentrations.  Some people can smell this in as low of a concentration as about 4 ppb (parts per billion).  Once the concentration gets over approximately 200 ppm (parts per million) the olfactory nerve is overwhelmed, and you can no longer smell the danger.

Danger?  Even though the human body constantly has small amounts of H 2 S either inhaled or created internally, our enzymes can only handle small amounts. Soon they can no longer keep up with converting the H 2 S into sulfates, and unconsciousness will occur.  The H 2 S interferes with oxygen flow and the central nervous system, and at concentrations above 1000 ppm death can be immediate after inhalation of just one breath of air.

So having concentrated H 2 S is a bad thing.

Now, if you work in a typical amine plant, a high concentration of H 2 S is expected in the regenerator off-gas (assuming your feed is sour in hydrogen sulfide).  If you have a Claus train, high concentrations of H 2 S are not only expected, but required for decent operation.

So having concentrated H 2 S is a good thing.  Well, it’s really more of a necessary evil; just be careful in parts of plants that have concentrated H 2 S gases.

Authored by Craig Spears - BR&E Technical Support