(125g) Quantifying the Effect of Stripping Factor on Distillation Efficiency Using Cyclohexane/n- Heptane Test System

Distillation is one of the oldest separation processes and the most widely used unit operation in the chemical process industries. About 95% of all separations are accomplished with distillation. Since distillation is also an energy-intensive process, even small improvements in distillation efficiency would have a significant impact on the design and operation of distillation columns.

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, a non-total reflux condition more closely represents the actual operation of a commercial distillation column. Therefore, in this study, we present recent results obtained from an Oldershaw column under non-total reflux conditions. In particular, an Oldershaw column was designed, installed and commissioned that is capable of operating under total as well as non-total reflux conditions. The validation was performed using data for cyclohexane/n-hexane test system from earlier work as well as FRI data on sieve trays.

Since the stripping factor is an important variable for investigating the distillation efficiency under non-total reflux conditions, a systematic study was conducted using the cyclohexane/n-hexane test system over a range of stripping factor values and column pressures from vacuum to atmospheric conditions. Results to date indicate that the point efficiency of the rectifying section was greater than that of the stripping section with the measured point efficiencies falling in the range of 40%-60%. The experimental results were also compared with the L/V ratios and the product concentrations obtained from column simulation in Aspen Plus®, both of which showed close agreement. Important findings from this ongoing study will be discussed.