Caustic Scrubbing in Refinery Fuel Gas Treatment

Caustic scrubbing lowers fuel gas sulfur.

Why It Matters

Refineries must remove sulfur from produced fuel gasses before they are used as fuel. Amine treatment removes hydrogen sulfide, but cannot effectively remove mercaptans. Caustic scrubbing can remove both hydrogen sulfide and mercaptans, but the most common application is for mercaptan removal.

What Is Caustic?

NaOH is known in most industries as sodium hydroxide. In refineries, solutions of water and NaOH are called "caustic". Caustic solutions are basic. The caustic reacts with mercaptans and forms sodium sulfide. Spent caustic is formed and it is not easily regenerated.

Caustic vs. Amine

Amine is easily regenerated. Therefore, amine is often used as a first treatment for hydrogen sulfide removal, followed by caustic scrubbing to remove mercaptans.

Spent Caustic Treatment

Oxidation is a common treatment method for spent caustic. The oxidation of the spent caustic makes it easier for treatment in wastewater facilities.