As seen, the column operates at lowest possible reflux ratio in the
first time interval to remove methanol as much as possible. The
reflux ratio gradually increases in the 2nd and 3rd time intervals
to retain the reactants (especially water) in the reaction zone and
to have further reaction and to meet the product specifications.
The overall batch time gradually increases with product purity of
the product, which is obvious. Increasing batch time also increases
conversion of limiting reactant.