The fresh feed of A is constant at 12.6 mol/s in all flowsheets. However, the production rates of the two products and the fresh feed of B change somewhat with the amount of excess used. The reason for this is that less A is lost as more excess B is used. Figure 4.1 shows that

(12.6X0.0326) + (12.6X0.0174) = 0.63 mol/s of A are lost in the one-column neat operation in the two product streams. In the 20% excess case, Figure 4.4 shows that

(13.13X0.0096) + (13.13)(0) = 0.126 mol/s of A are lost, essentially all of which is in distillate Dj. Thus, using more excess of B increases the conversion of A. At the same time, the losses of B increase because the purities of the two products remain at 95 mol%. The flowrates of the two product streams increase slightly from 12.6 to 13.13 mol/s.

Table 4.1 provides equipment and economic results for recovery column C2 with 20% excess for different numbers of trays NT2 in the recovery column. The minimum cost configuration has 20 trays.

Results with a 10% excess of B are given in Figure 4.8. The composition of the bottom from the first column is 6.60 mol% B. The total feed of B to the first column is 13.86 mol/s, and the fresh feed of B is 13.56 mol/s. The recycle flowrate D2 is 0.3056 mol/s. Composition profiles in the reactive column are displayed in Figure 4.9 for the 10% excess case. Figure 4.10 shows the composition profiles in the recovery column, and Figure 4.11 gives the temperature profiles in the two columns.

In the two-column case with 10% excess, Figure 4.8 shows that the loss of A in the two product streams is

This should be compared with losses of 0.63 mol/s in the single neat column case and 0.126 mol/s in the 20% excess case. The conversion of A to products C and D increases as more excess B is used.

118 m2

D1 = 13.08 mol/s *D1(A) = 0.0128 *D1(B)= 0.0372 *D1(C)= 0-9500

118 m2

D1 = 13.08 mol/s *D1(A) = 0.0128 *D1(B)= 0.0372 *D1(C)= 0-9500

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