Sour Gas

Natural gas that contains hydrogen sulfide (H2S) in any amount is termed sour gas.  Sour gas has an unpleasant odor and is a hazard to human health and is corrosive to carbon steel when water is present.

Sour gas is sweetened by removing the hydrogen sulfide with a variety of processes, most of which involve regenerative solvent processes.  This technology is well established within traditional limits of hydrogen sulfide.  The specific choice of solvent depends on the amount of hydrogen sulfide, carbon dioxide and condensable hydrocarbons in the sour gas.  The most common processes involve the circulation of amines, which dissolve hydrogen sulfide and carbon dioxide into the amine solution.  The hydrogen sulfide and carbon dioxide are released from the amine solution when the solution is heated.  The resulting gas is known as acid gas, and contains a high percentage of hydrogen sulfide and carbon dioxide. 

The hydrogen sulfide component of acid gas has fuel value, and can be burned, creating sulfur dioxide as a combustion product.  Increasingly stringent regulations limiting the emission of sulfur dioxide are eliminating direct flaring or combustion of acid gas.  Sulfur recovery technology that converts the hydrogen sulfide into elemental sulfur is well known and utilized broadly, however, elemental sulfur is becoming increasingly more difficult to sell or give away.