Feasibility Analysis An RCM-Based Approach

Residue curve maps provide a powerful tool to represent relevant properties of the system, particularly those aiming to predict feasible design sequences. In addition, analytical material balances may be represented in a RCM, resulting in constraints to feasible product compositions and convenient operating strategies e.g. direct or 

The presence of (non-)reactive singular points i.e. pure components and (non-)reactive azeotropes) in ROMs allows the division of the (transformed) composition diagram into separate (reactive) distillation regions by introducing (reactive) distillation separatrices, which connect two singular points in the composition space. The explanatory note 5.1 gives a brief overview of the concepts of nodes and saddle points, as features of singular points. 

If a separatrice ends at a saddle point, it is commonly referred to as boundary curve. Crossing distillation boundaries has been extensively reported for industrial cases and especially for those with curved distillation boundaries. For those systems, the boundaries can be crossed by simple recycle methods provided an appropriate entrainer. However, conventional design strategies require that the feed and products remain in the same distillation region (Fien and Liu, 1994). 

Saddle point is defined in the stability theory of ODE as the point of a function or surface, which is a stationary point but not an extremum. Let 

In ROM techniqne saddle points are considered to be those intermediate-boiling vertices (pin-e components or (reactive) azeotropes), at which no residue curve has neither its initial nor final point (Fien and Lin, 1994). 

---