An aqueous solution of a volatile component A containing 7.94 mol % A preheated to its boiling point is to be fed to the top of a continuous stripping column operated at atmospheric pressure. Vapor from the top of the column is to contain 11.25 mol % A. No reflux is to be returned. Two methods are under consideration, both calling for the same expenditure of heat, namely, a vaporization of 0.562 mole per mole feed in each case. Method 1 is to use a still at the bottom of a plate column, generating vapor by use of steam condensing inside a closed coil in the still. In method 2 the still and heating coil are omitted, and live steam is injected directly below the bottom plate Equilibrium data are given in Table 21.7. The usual simplifying assumptions may be made. What are the advantages of each method?

Table 21.7

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TABLE 21.7 Equilibrium I 0.0035 0.0100 data in mole fraction A 0.0125 0.0077 0.0200 0.0300 0.0177 0.0400 0.0292 0.0600 0.0429 0.0590 0.0800 0.1000 0.01784 0.1200