Heat exchangers, condensers variation with flow

Example 7-3 This example is a minor variation of Example 7-2 in that the streams and B2 are passed through a heat exchanger as shown in Fig. 7-3, and columns 1 and 2 are to be provided with independent reboilers and condensers. The statement of this example is given in Table 7-3, the initial values in Table 7-4, the final temperatures, vapor rates, and product flow rates are given in Table 7-9. The convergence characteristics are given in Tables 7-10 and 7-11. 

Condensate heat flow is essentially in the same direction as vapor flow. First, steam condensate and evaporator vapor condensate (the latter also variously referred to as secondary condensate and process condensate) are kept separate. Steam condensate returns to the boilers after exchanging some of its heat with process liquor. Process condensate is used as described in Section 12.4.3.2. In the drawing, condensate from each of the first three effects first passes through exchangers that heat the liquor (not shown) moving from one effect to the next higher. Variations include the use of condensate to preheat evaporator feed and the diversion of some condensate to overhead desuperheaters. As an example, the drawing shows the use of second-effect condensate to desuperheat steam and first-effect vapor. 

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