Fractionation Mode Cut Strategy

In cut strategy II the products are collected consecutively, that is, the next fraction collection starts immediately after the previous fraction. High purity demand can therefore only be satisfied by reducing the feed throughput. Furthermore, purity 

Cut strategy I allows a waste fraction between the product fractions, which can be either discarded or processed further (e.g., by recycling the waste fraction or by application of other separation steps, such as crystallization, to purify it). Due to the introduction of a waste fraction the optimization problem gains additional degrees of freedom, that is, times for the beginning and the end of waste collection. These additional degrees of freedom, however, will not increase the complexity of the optimization, because they are pinpointed automatically by the purity demand, which serves as a boundary condition for the optimization problem. 

Since cut strategy II is only the marginal case of cut strategy I and since the application of cut strategy I provides more flexibility and often leads to a better global optimum, only cut strategy I will be used for model-based optimization in this chapter. 

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