Constructing Pinch Diagrams without Process MSAs

7 Constructing Pinch Diagrams without Process MSAs 

So far, an MOC solution has been identified through a two-stage process. First, the use of process MSAs is maximized by constructing the pinch diagram with the lean composite stream composed of process MSAs only. In the second stage, the external MSAs are screened to remove the remaining load at minimum cost. 

Suppose that the process does not have any process MSAs. How can a lean composite line be developed The following shortcut method can be employed to construct the pinch diagram for external MSAs. A more rigorous method is presented in Chapter Six. 

If arrow S2 lies completely to the left of arrow Si and cj is less than cj, one can eliminate Si from the problem since it is thermodynamically and economically inferior to S2. On the other hand, if arrow S3 lies completely to the left of arrow S2 but is greater than cj, one should retain bodi MSAs. In order to minimize the operating cost of the network, separation should be staged to use the cheapest MSA 

CHAPTER THREE Synthesis of mass-exchange networks 

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