Retrofit of Distillation Sequences

If the existing shells differ significantly from what is required in the retrofitted sequence, then, in addition to reconfiguring the distillation sequence, the existing shells can also be modified. For example, the number 

The retrofit of more complex distillation sequences can also be considered. Within a larger, more complex sequence, any pair of columns that are together in a sequence can be considered as candidates for the same retrofit modifications as those discussed for two-column retrofit. 

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