Two novel strategies and their optimized operating modes of batch distillation

i. e. top accumulation under total reflux and varying pressure under combined reflux

are proposed. For the first strategy

the product component is concentrated and collected in a large reflux drum under the condition of total reflux. For the second strategy

the column pressure is varied during operation in order to keep the column temperature below the thermal decomposition point of the residue in reboiler

and a combined reflux is used. The corresponding mathematical models which take into account the holdups in both condenser and column are proposed and solved by using (?) convergency method. The application of these new strategies to the separation of a binary mixture ethanol-isopropanol and a multicomponent mixture n-heptane-n-octane-n-nonane-n-decane show that the present proposals can shorten the operating period by more than 30% and 50% respectively in comparison with the conventional constant reflux operation.