Process Simulation and Retrofit Optimization for Cleaner-Fuel Naphtha Distillation

Abstract

This study presents a digital-twin case analysis of a South African refinery’s naphtha splitter, integrating Aspen HYSYS V12 simulation with the plant data. The objective was to balance energy efficiency with benzene control under Clean Fuels II (CF2) regulations. The Aspen HYSYS model, validated against plant data with mean absolute percentage deviations of ≈10% for light- and 14% for heavy-naphtha compositions, was used to identify two successive optimization pathways. First, tuning existing operational variables achieved a 14% reduction in total energy duty, corresponding to about US $1.4 million in annual savings, with zero capital modification. Second, introducing a low-CAPEX midcolumn side-draw to remove benzene-forming precursors further improved performance, delivering a total energy reduction of ≈33% relative to the original baseline. Together, these measures demonstrate how an existing splitter can be retrofitted for lower emissions and cleaner-fuel production. The methodology, plant-calibrated analysis coupled with staged operational and structural optimization, provides a transferable framework for energy-intensive distillation units around the globe seeking rapid, economical decarbonization.