(350a) Optimum Batch Distillation of Multicomponent Mixtures

Batch distillation is still widely used in numerous chemical plants that make multiple products at a relatively small scale. As in continuous distillation, various combinatorial sequences of batch separations can be derived. Each of these sequences can be optimized using commercial simulator and compared with the other sequences. The objective function in optimization of batch distillation is usually the cycle time that needs to be minimized. It corresponds to the minimum energy of separation in continuous distillation, because batch distillation columns operate usually at maximum boilup. Therefore, the shorter the cycle time, the lower the energy of separation. Optimization procedure has to take into account sizes of existing tanks and other available equipment, which may lead sometimes to a classical scheduling problem.

An example of selecting the optimum batch distillation sequence will be presented. The components in the feed may be lumped into five groups, ordered according to their volatilities: 1. Lights (L), 2. Product A, 3. Intermediates (I) , 4. Product B, 5. Heavies (H). Combining optimization with batch column model available in commercial simulator provides a useful tool for developing optimum batch distillation recipes.