Heat-integrated Distillation Sequences Based on the Optimization of a Superstructure

8 HEAT-INTEGRATED DISTILLATION SEQUENCES BASED ON THE OPTIMIZATION OF A SUPERSTRUCTURE 

In order to explore distillation sequencing and heat integration simultaneously, a more automated approach to 

If nonlinear capital costs considerations are left out of the formulation, then the problem can be formulated as an MILP problem (see Chapter 3). Once nonlinear costs are included, the problem becomes an MINLP, with all of the problems associated with nonlinear optimizations. As with many such problems, if the required formulation turns out to be an MINLP, then an MILP can be used to provide a good initialization for the MINLP, simplifying its solution. 

The appropriate placement of distillation columns when heat integrated is not across the heat recovery pinch. The grand composite curve can be used as a quantitative tool to assess integration opportunities. The scope for integrating conventional distillation columns into an overall process is often limited. Practical constraints often prevent integration of columns with the rest of the process. If the 

Once the distillation is integrated, the driving forces between the composite curves become smaller. This in turn means that the capital-energy trade-off for the heat exchanger network should be readjusted accordingly. 

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