Question 18.3: What is (a) the minimum reflux ratio and (b) the minimum num......

Unit Operations of Chemical Engineering [1581788]

What is (a) the minimum reflux ratio and (b) the minimum number of ideal plates for cases (b)(i), (b)(ii), and (b)(iii) of Example 18.2?

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(a) For minimum reflux ratio use Eq. (18.43). Here $x_{D}=0.974.$ The results are given in Table 18.3.

$R_{D m}=\frac{x_D-y^{\prime}}{y^{\prime}-x^{\prime}}$ (18.43)

(b) For minimum number of plates, the reflux ratio is infinite, the operating
lines coinicide with the diagonal, and there are no differences between the three cases.
The plot is given in Fig. 18.22. A reboiler and eight ideal plates are needed.

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TABLE 18.3
Case	x’	y’	$R_{D m}$
(b)(i)	0.440	0.658	1.45
(b)(ii)	0.521	0.730	1.17
(b)(iii)	0.300	0.513	2.16

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