Minimum Number of Mass Exchangers

Minimum number of mass exchanger units. Combinatorics determines the minimum number of mass exchanger units required in the network. This objective attempts to minimize indirectly the fixed cost of the network, since the cost of each mass exchanger is usually a concave function of the unit size. FuithetTnore, in a practical context it is desirable to minimize the number of separators so as to reduce pipework, foundations, maintenance, and instrumentation. Normally, the minimum number of units is related to the total number of streams by the following expression (El-Halwagi and Manousiouthakis, 1989). 

Using mixed-integer programming, find the minimum number of mass exchangers the benzene recovery example described in Section 3.7 (Example 3.1). 

Figure 11.10 MEN having minimum number of mass exchangers, while satisfying the minimum ust e of external MSA.

By analogy to HENs, the minimum number of mass exchangers in a HEN is... 

The MEN in Figure 11.10 contains the minimum number of mass exchangers with the minimum usage of external MSA, assumed equivalent to the minimum operating costs (MOC), given by ... 

The minimum number of mass exchangers is shown in Figure E15.10(c). The method exacdy parallels that for the minimum number of heat exchangers. In this example, there are three mass-exchange devices... 

Figure E15.10(c) Minimum Number of Mass Exchangers for Example 15.10...

Using the cascade diagram, solve Problem 3.3. Also, synthesize an MEN which h the minimum number of units satisfying the MOC solution. Employ the mass-load paths to reduce the number of mass exchangers at the expense of increasing operating cost. 

The number of mass exchangers is reduced toward the minimum, possibly at the expense of increasing the consumption of MSAs. 

Hentify any mass loops in the solution to part b. Break these Hss loops to design a MEN that has the minimum number of Hss exchangers. 

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