Effect of Purging Time during Distillation Column Startups

This work evaluates the relationship between the purging start time and its effects during the startup of an extractive distillation system. According to the literature, only a few papers have considered the purging step during the system startup. The objective of this paper is to report the effects of purging start time as a startup optimization variable, contributing to a more realistic dynamic approach. The extractive distillation process to produce anhydrous ethanol using ethylene glycol as solvent was chosen as a case study due to its complexity. In order to evaluate the effect of the purging step during the column startup, the opening of the purge valve was varied in different scenarios. It was verified that an increase in the purge step runtime favors the time undertaken for the extractive column. However, this same increase did not favor the time spent for the recovery column, contributing to a greater amount of time spent overall. The results also showed that an increase in time to execute the purging step provides a reduction in the amount of heating utility up to 1.48% for the system. However, this gain implies a momentary increase in system pressure, which could compromise the equipment and jeopardize the integrity of the operators.