Overlaying Preventative Versus Mitigative Controls in the Control Hierarchy

Economical removal of trace impurities is a big challenge in today’s refining and petrochemical complexes. One such challenge in today’s scenario is the CS2 contamination which is limiting the feed stock flexibility of petrochemical naphtha (PCN). Presence of CS2 in PCN causes corrosion in downstream units of cracker and also reduces activity of hydrogenation catalysts.

This article provides an insight of how dividing wall column (DWC) technology was implemented in meeting CS2 limit of 2ppm is PCN product at one of the largest refineries in Asia. The DWC was retrofitted in existing depentanizer column. Besides meeting specifications for CS2 removal, the revamped column produced premium gasoline products to boost the revamp profitability.

DWC design required validation of thermodynamic model with plant data and a robust control scheme to maintain high level of product purities.