Distillate Rate D

Figure 10-3 Variation of the distillate rate D at a fixed reflux rate, I, = 125.

A Continuous Distillation Column at Total Reflux in the Rectifying Section D = 0, B = F, and Lx = Finite Number

In addition to the above specifications, it is also supposed that the following variables and operating conditions are fixed: the number of stages N, the feed plate location f9 the model for the feed plate behavior, the complete definition of the feed (the composition, flow rate, and thermal condition), and the column pressure. Since D = 0, the condenser behaves as a total condenser, and thus

Problems of this type may be solved by use of the 0 method of convergence as demonstrated by Lyster et al.9 However, since (fr,)co is known in advance to be equal to FX,, the 6 method reduces to direct iteration and convergence may become slow. Thus, the application of the 2N Newton-Raphson method to problems of this type is recommended.

The problem may be formulated in terms of either the mole fractions or the component-flow rates. When the component-flow rates are used, the resulting set of equations differ only in minor respects from those presented in Chap. 4 for conventional distillation columns. The problem is formulated in terms of the following set of independent variables x = [02 03 •• eN Qc 7\ T2 ... Tn Qr]t (10-36)

Except for the component-material balance enclosing the condenser-accumulator section

the remaining component-material balances are the same as those shown for conventional distillation columns in Chap. 4. The combined set of component-material balances and equilibrium relationships may be represented again by the matrix equation



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