Chemical Engineering Science, Vol.55, No.16, 3187-3194, 2000
Batch distillation column low-order models for quality program control
For batch distillation, the dynamic composition behaviour can be described by the dominant time constant and the bottom exhaustion. Its magnitude is determined by the change of the composition distribution and is maximal when the inflection point of the molar fraction profile is located in the middle of the column. Then, the tray interactions are minimal. The distribution change during the batch run strongly depends on the applied control strategy. Under constant quality control, the dominant time constant proved to be nearly constant whereas under constant reflux control the dominant time constant can vary by more than a factor of four. To calculate the dominant time constant from static design calculations, two different methods are discussed: the retention time and the "change of inventory" time method. These methods are experimentally verified.