If you’re not familiar with how natural gas is processed, you may be tempted to believe it can simply be captured from the earth, moved through pipelines, and directed to your home or business. However, just like oil, numerous processes must occur to ensure the final product is clean and safe for use. One such vital process is “sweetening,” the removal of excess carbon dioxide (CO₂) and hydrogen sulfide (H₂S) from acidic or sour gas. If not removed, toxic buildup and stress cracking occurs, particularly in pipes where water molecules are present.

Numerous technologies are employed in sweetening, depending on factors such as CO₂ and H₂S levels, energy efficiency requirements, and budget. Commercial gas plants often turn to amine sweetening units, systems with compliant stainless and carbon steel that can resist the corrosive forces of solvents like amines, which chemically bond with acidic gases to form unstable salts that eventually break down. The natural gas is then captured in its cleaner state. However, other removal systems exist, including membrane (for bulk CO₂ removal) and molecular sieve (for small-scale, low-quantity removal) systems.

Some entities are working to extend the technology of gas sweetening even further. For example, Energy Recovery announced in June 2014 that it experimented with the high-pressure flows inherent to gas sweetening, converting waste pressure energy into useable electrical energy using a hydraulic turbogenerator. In the fall of 2014, Members of The Petroleum Institute gave several talks about their research into optimizing the sweetening process, including how lowering amine temperatures and optimizing amine strength leads to “potential savings in operating costs without increasing the risk of corrosion and fouling.” Through this type of technological innovation and process research, sour gas processors continue to adapt their strategies to remain competitive in the market.