I[dlHiTul bilhiTNl QCi

Also, the component-material balance enclosing column 1 must be altered in order to account for the return of B2 to column 1. Thus, instead of Eq. (7-9), one obtains

When the condition that QKl = Qc2 is imposed on the system, the capital 0 method again consists of 14 functions in 14 unknowns; see specification set 1 of Table 7-2.

Figure 7-2 A system of two columns with mass recycle and energy recycle; the condenser of column 2 is the reboiler of column 1.

Example 7-2 This example is a minor variation of Example 7-1 in that the bottoms from column 2 are recycled to column 1 as shown in Fig. 7-2. Again the overhead condenser of column 2 is to serve as the reboiler for column 1, and the problem is to be solved subject to the condition that QRl = QC1. The statement of the example is given in Table 7-3, the initial values in Table 7-4, the final temperatures, the total flow rates, and the final product flow rates are given in Table 7-7, and the convergence characteristics are given in Table 7-8.

Table 7-7 Solution values of the temperatures and vapor rates for Example 7-2 (see Fig. 7-2)

I. Temperature and vapor rate profiles Column 1 Column 2

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