Quantifying the Point Efficiency of Cyclohexane/n‑heptane in Non-total Reflux Conditions

• Published in: Industrial & engineering chemistry research Vol. 63; no. 16; pp. 7357 - 7367
• Main Authors: Ahmed, Rukhsar, Cai, Tony, Nieuwoudt, Izak, Mohammad, Sayeed, Aichele, Clint
• Format: Journal Article
• Language: English
• Published: American Chemical Society 24.04.2024
• Subjects: Separations
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.4c00556

Distillation is one of the oldest separation processes and the most widely used unit operation in the chemical process industry. Although several experimental variables that affect the distillation tray efficiency have been explored in the past, nearly all of the previous studies were conducted under total reflux conditions. However, non-total reflux conditions more closely represent the actual operation of a commercial distillation column. Therefore, in this study, we present results obtained from an Oldershaw column operated under non-total reflux conditions. An Oldershaw column was designed, installed, and commissioned that can operate under total as well as non-total reflux conditions. The validation was performed using data for the cyclohexane/n-heptane test system from our earlier study as well as from Fractionation Research, Inc. (FRI) (the world’s largest industrial consortium on distillation). We conducted a systematic study using the cyclohexane/n-heptane test system over a range of values for several variables including stripping factor, reflux ratios, and feed compositions for the column operated at vacuum to atmospheric pressure conditions. Results showed an increase in point efficiency with a decrease in the stripping factor for both atmospheric and vacuum conditions. The point efficiency increased as the concentration of the light key in the feed increased. Further, a higher efficiency was observed under atmospheric conditions compared to vacuum.