Modelling and optimal design of a BTX distillation unit using Aspen HYSYS simulator

The present work focuses on the steady-state modelling and design of an industrial distillation process for separating a benzene–toluene–xylene (BTX) mixture into high-purity aromatic products. This study aims to develop an efficient and energy-conscious separation scheme and to evaluate the effectiveness of Aspen HYSYS as a simulation and design tool for BTX distillation systems. The proposed configuration consists of two fractional distillation columns operating in series, designed to sequentially recover benzene, toluene, and xylene. The separation process was simulated using Aspen HYSYS V11, employing the Peng–Robinson equation of state to accurately describe the thermodynamic behavior of the BTX system. The preliminary design of both distillation columns was carried out using the shortcut distillation method to estimate initial key design parameters, including minimum reflux ratios, number of theoretical trays, and initial energy requirements. These results were subsequently refined through the rigorous design approach to provide optimal design parameters that improve separation performance for achieving desired purity with minimum energy consumption. Finally, the mechanical geometry and hydraulic design for both columns were performed using auto section tool, in which each column was divided into two sections to improve hydraulic accuracy and ensure reliable internal column design. Simulation results demonstrate that the proposed configuration successfully achieves high product purities of 99% for benzene, 99.3% for toluene, and 99% for xylene. The auto-section method provided accurate predictions of minimum design and operating parameters, while the shortcut approach proved effective for the preliminary estimation of key requirements. Overall, the simulation results confirm that the designed distillation system is both technically practical and energy-efficient, and that Aspen HYSYS is an effective and reliable tool for the modelling, design, and optimization of BTX distillation processes.