(9b) Novel Configurations Using Fewer Columns for Multicomponent Distillation

The synthesis of optimal distillation sequences for a given application is a challenging problem in process design. Several researchers have provided solutions for the problem of synthesizing the complete search space of distillation configurations that use exactly (n-1) distillation columns to separate a zeotropic feed mixture into n product streams. However, the search space of all possible distillation configurations that use less than (n-1) distillation columns for an n-component separation has not been completely explored. We have developed a mathematical framework to synthesize the complete set of distillation configurations that use less than (n-1) columns for an n-component separation.

While several configurations with less than (n-1) columns cannot make arbitrarily high purity product streams, there exist a few distillation configurations that use less than (n-1) columns while still retaining the ability to make products with any pre-specified purity. Such fewer column configurations deserve special attention and are derived from the set of configurations that use exactly (n-1) distillation columns by simultaneous heat and mass integration between two or more distillation columns. The Brugma and Kaibel configurations are probably the most well known among such configurations. We present a systematic procedure to synthesize the complete set of fewer column distillation configurations obtained by simultaneous heat and mass integration of columns from the set of configurations with exactly (n-1) distillation columns.

Furthermore, we have found that these heat and mass integrated configurations lead to an entire class of hitherto unknown distillation configurations. These novel configurations show great promise for reducing the energy consumption. A synthesis procedure for these novel configurations will also be described.