Can reducing the pressure in an atmospheric distillation tower save energy?

There are several reasons for operating a distillation column under reduced pressure: (1) Reducing the pressure increases the relative volatility between the components; in such cases, the reflux ratio required is necessarily lower than that in normal-pressure operation, and both the heat needed by the reboiler and the cooling capacity required by the condenser are reduced. However, vacuum devices consume electricity, which represents additional energy; therefore, whether they are energy-saving overall depends on a case-by-case analysis. Energy savings are achieved if the relative volatility changes significantly. (2) Pressurizing the operation can increase the temperature at the top of the tower; if cooling water is required as a coolant at atmospheric pressure, it can be used as a coolant after pressurization. The cost of chilled water is much higher than that of cooling water. (3) During multi-column operation, the temperature inside the columns can be adjusted by changing the operating pressure (pressurization or depressurization) of individual columns; thus, heat can be integrated among multiple columns, with the vapor from the top of one column being used as the heating medium for the reboiler of another column. This will inevitably save energy.