Caustic Scrubbing for Acid Gas Removal
Caustic Wash Tower for the removal of CO2 and H2S from cracked gas stream using 8-12 wt% NaOH solution to form irreversibly Na2CO3 and Na2S. In order to maximize the caustic utilization, the tower is divided into either 2 or 3 caustic sections.
Carbonyl contaminants in the cracked gas result in red oil polymer formation by Aldol Condensation in the caustic solution. Highly unsaturated acetylenes and dienes react to form polymeric compounds in the caustic solution promoted by the presence of oxygen and heavy sulfur compounds.
Key features to a superior design of caustic wash tower system is: (1) minimize O2 and heavy metal ingress. (2) efficiently purge and remove the formed polymer. (3) minimize polymer formation by optimizing the operating temperature, caustic strength and caustic utilization.
