(145a) Optimization of the Vapor Flow Distribution in a Distillation Column Using Computational Fluid Dynamics

Chemical separations account for approximately half of the U.S.’s industrial energy use and 10-15% of the U.S.’s total energy consumption. More energy-efficiency chemical separation processes could save 100 million metric tons of CO₂ emissions annually. Specifically, distillation is the most widely used chemical separation technology, which accounts for approximately 40% of total energy consumption in petrochemical and chemical plants. Unfortunately, the overall efficiency is just around 11%. Therefore, it is necessary to improve the distillation efficiency, of which optimization of the spatio-temporal vapor distribution inside the column is essential. In this study, a computational fluid dynamics (CFD) model has been developed and employed to predict the vapor velocity distributions in a virtual 3-dimensional (3D) distillation column, with multiple inlet diameters (12 inches and 15 inches) and vapor flow rates (from 7929 lb/h to 27,750 lb/h) as the two key design parameters. The column height is approximately 8 feet, and the column diameter is 4 feet. Mellapak 250Y (M250Y) is used as the packing bed. Velocity contours and secondary flows at the top of the packed bed were compared to find the optimal design, with the minimum velocity variations across the plane. Coefficients of variation on the velocity distributions were also calculated and compared. Results indicate that with the increase of inlet Reynolds number, either due to the increase in inlet flow rate or the decrease in inlet diameter, the flow distributions become more uneven at the cross-section when the vapor flow exit the porous media region. Therefore, a low inlet Reynolds number is recommended for achieving a more evenly distributed vapor flow velocity.